The MKH 8090 (centre) with its siblings, left to right: MKH 8020 (omni), MKH 8030 (fig 8), MKH 8040 (cardioid) and MKH 8050 (supercardioid).
Introduction
It’s funny how reluctant some are to try an omni as the mid mic in a mid-side pair (seemingly afraid that this will make for a mono recording) despite it often being the best tool for the job. But I have had many queries now about whether a wide cardioid will strike a sweet spot between an omni and a cardioid when paired up with an MKH 8030 for mid-side recording. Normally, I swap between omni, cardioid and supercardioid mid mics, but recently, thanks to the good folks at Sennheiser, I have extended my available mid-mic options to include the wide cardioid MKH 8090. And so has begun my exploration as to whether – and this is said only partly tongue-in-cheek – it is something of a Goldilocks mic, hitting the perfect balance between omni (MKH 8020) and cardioid (MKH 8040) options, or, alternatively, whether – in practical use – for many it represents too fine a mid-point between these polar patterns, if, indeed, it can be described as a ‘mid-point’.
These things are personal, of course, reflecting both taste and subject matter, but in this blog post I will focus on a series of recordings made with the different mid-side pairs at the same time, so hopefully it will be of some use to a few readers – especially those who cannot try the different polar patterns before buying. And, although I have demonstrated the supercardioid (MKH 8050) mid-mic options previously, in comparison to the MKH 8020 and MKH 8040, I have included it again here for completeness. I have omitted the Sennheiser shotgun mid-mic options (MKH 8060 and MKH 8070) for three good reasons: first, mid-side recording with an interference tube mid mic is a very different beast and usually, though not always, for very different purposes than field recording or music recording; second, it is very hard to think of a set-up that could adequately cope with simultaneous recordings or such differently sized mid mics (well, not one that doesn’t involve at least four fig 8s); and, third and most conclusively, I don’t have either! Likewise, it would be rather tricky to include a fig 8 as the mid mic in a typical windshield, given the required orientation of the mic.
The specs
I don’t want to repeat what can be read in detail on Sennheiser’s website, but, nonetheless, a quick comparison of the polar and frequency response charts is a useful starting point, not least as they are rarely seen grouped together for these four mics.
Polar patterns of the omni MKH 8020, wide cardioid MKH 8090, cardioid MKH 8040 and supercardioid MKH 8050.
The most obvious feature of the polar pattern of a wide cardioid such as the MKH 8090 is the absence of a null, with the pattern looking rather that of an omni, albeit consistently reduced at the rear by around 7dB.
Frequency response graphs of the omni MKH 8020, wide cardioid MKH 8090, cardioid MKH 8040 and supercardioid MKH 8050.
In contrast to the situation with polar plots, the frequency response graphs see the MKH 8090 wide cardioid look much more like its cardioid sibling than the omni. The two most noticeable differences from the cardioid are the earlier high-frequency peak and the slightly flatter curve below 100Hz: this is still a long way from the MKH 8020 omni with its almost flat response down to 10Hz.
Test rig for the MKH 8090 comparisons as a mid mic for mid-side: two clusters of three mics, each comprising an MKH 8030 with two SDC siblings (MKH 8020, MKH 8040, MKH 8050 and MKH 8090), on a custom 3d-printed bar (with Radius Windshield hoops for the shock-mounts) in a Mega-Blimp.
Test rig
Even rigging four alternative mid mics is no doddle, especially for outdoor field recording, so I have done some thinking and, inevitably, a bit of 3d printing to make a suitable mount. Although, as readers of this blog will know, I am not overly concerned about the often rather theoretical (or at least often imperceptible) issues of shadowing, even I think a cluster of four mics around a single fig 8 seems a bit too congested, so I split the mics into two pairs each with its own MKH 8030 side mic, spacing the two groups of mics 170mm apart on a 3d-printed bar I made up, and mounted within my roomy Mega-Blimp. It is not perfect, of course, but each MS pair can’t occupy exactly the same space at the same time and be free of other mics nearby, so its is a reasonable compromise, and one, I feel, that doesn’t obscure or misrepresent the differences between the various pairs.
Village street
Although the garden has changed dramatically here over recent months (much of the reason why blog posts have been a little thin on the ground of late!), the nominally quiet village street – used as a frequent test bed for me – seems as noisy as ever, with a ripe mixture of sounds. In the recordings below, you can hear the curious thumps from inside a Waitrose van delivering to a neighbour, followed by its departure, along with passing vehicles and birdsong.
First up, we have MS with the omni MKH 8020 mid mic:
Second, we have MS with the wide cardioid MKH 8090 mid mic:
Third, we have MS with the cardioid MKH 8040 mid mic:
And finally we have MS with the supercardioid MKH 8050 mid mic:
Test recording down at the North Norfolk Railway: always a good test to have a rumbling and hissing locomotive passing, followed by the rattling carriages, even if anyone about assumes I am something of an uber-trainspotter!
Down at the station
Risking large crowds on a bank holiday Monday, I tootled off to Holt station on the North Norfolk Railway, which is another familiar haunt of mine for mic tests, positioning myself a little way from the platforms, opposite the signal box and right next to a signal (I do like the double clunk the latter makes). Funnily enough, it was unexpectedly quiet in terms of people, although the distant hum of traffic and the more disturbing near continuous thunder of aeroplanes overhead were ever present. Here is a snippet, with the signal changing and then a small 0-6-0ST saddle tank setting off, pulling a short train of three Victorian carriages and leaving another train (pulled by an xxxx) hissing steam at the platform:
Following the same sequence as before, first up we have MS with the omni MKH 8020 mid mic:
Second, we have MS with the wide cardioid MKH 8090 mid mic:
Third, we have MS with the cardioid MKH 8040 mid mic:
And finally we have MS with the supercardioid MKH 8050 mid mic:
Conclusions
In the strict sense there are no universal conclusions to be drawn from these tests, with their purpose being simply to illustrate the differences in the polar patterns of the MKH 8090 and its MKH 8020, MKH 8040 and MKH 8050 siblings when used as the mid mic in a mid-side pair. Inevitably, to some these tests will serve to show how the less directional MKH 8090 and MKH 8020 mid mics work well and are viable alternatives to the more commonly used cardioid and supercardioid mid mics. To others, these tests will show how radically different the four mid mics are. Such is the nature of listening tests even without confirmation bias rearing its ugly head. From a personal view, and drawing on wider use than the few test clips presented here, I have been very impressed by the stereo image presented in mid-side with the MKH 8090 mic. Unless more rear rejection is needed from the null of a cardioid or the deeper bass response of an omni is required (and often the bottom end of the MKH 8020 needs rolling off in field recordings), the MKH 8090 is a compelling option, and one I have been using increasingly in my field recordings. In short I am so glad to have it in my arsenal of mics. Now making such finely gradated choices between polar patterns can be hard when field recording compared, say, to setting up mics for an acoustic music recording in a more controlled indoor space, due to the fact that outdoors sound sources can be unpredictable and constantly swapping mics can become impractical, so, in that sense, having an option between a cardioid and an omni can just make life more complex. But, equally, field recording can involve frequent recordings of the same sound source, or similar sound sources, in familiar or similar locations, and for many an experienced recordist having more finally gradated choices in polar patterns can be useful. And if you are just kicking off with mid-side recording and are uncertain as to which initial mid-mic polar pattern to choose, then, just possibly, this post might provide some food for thought.
A chilly but, for once, dry day down at the station for some omni MS tests. OK, I’ll be honest, I was down there to test some shotgun mics, and just brought the omni and twin mics along on a whim!
Introduction
In my previous blog post on the Nevaton MC59-8 (fig 8) and new MC59 Twin mics, I touched briefly – as an aside – on the question of using the MC59 Twin or, indeed, any similar twin mic (such as the Sennheiser MKH 800 Twin) for mid-side (MS) recording on its own: i.e. without a second mid mic. This means using the combined output of the two (cardioid) capsules with the rear (or right) out of phase to create the fig 8,and simultaneously using the two outputs combined in phase to create the omni. Evidently this allows the single mic to be used for omni MS, although no other variation of MS (i.e. with a different polar pattern for the mid mic) is possible with such usage: only the omni pattern will create a mid mic at 90 degrees to the side (fig 8) mic. Of itself this isn’t a problem since, while many assume a cardioid or, perhaps, a supercardioid mid mic only is necessary for satisfactory results for MS, an omni mid mic is eminently usable, even desirable, in many situations. Indeed, in a previous post I provided (simultaneously recorded) comparisons of MS rigs with different polar patterns – the MKH 8020 (omni), MKH 8090 (wide cardioid), MKH 8040 (cardioid) and MKH 8050 (supercardioid) – so you can hear how they compare. Rather, assuming omni MS is appropriate for the recording, the issue with using a twin mic on its own for MS is to do with the fact that the polar pattern of an omni created by the two diaphragms is imperfect: whereas most SDC omni mics are also imperfect, typically becoming more directional from, say, around 8kHz (I am thinking here of the polar pattern of my MKH 8020 mic), the frequency response on axis remains consistent, while the omni polar pattern of a dual-diaphragm mic is best at the front and rear (i.e. on axis to the individual diaphragms) but sees significant high-frequency fall off at 90 degrees, as illustrated in my previous post. This isn’t a particular issue if using a twin mic as an infinitely variably patterned mid mic in MS in conjunction with a separate fig 8 mic, since the mid mic is facing forward to the assumed focus of the sound source. However, when using a twin mic on its own for MS, the two diaphragms are necessarily facing sidewards for the fig 8, so the omni mic (created from the same two capsules) is aimed poorly for sounds directly in front of the mic. On the positive side, though, the fig 8 and omni mic are truly coincidental, having none of the vertical separation of the two mics in a normal MS pair.
The diminutive size (48.5mm overall length) of the MC59 Twin (shown here in comparison to an MKH 8030 fig 8) makes in particularly tempting for those who fancy a miniscule omni MS rig with just the one mic!
Field testing
The introduction above is just an amplification of my cautionary aside on use of twin mics in their own for omni MS in my previous post. But so much for theory: the point of this short present post is to provide an example of a simultaneous field recording so that others can download and scrutinize the files, compare and analyse short snippets in a DAW etc. as they wish and draw their own conclusions. I have deliberately chosen a field recording since it is hard to imagine anyone would accept the very high-frequency loss in, say, a classical music recording, and it is the most likely scenario – due to compact rigs – where someone might be tempted to make an MS recording with a single twin mic. And I have gone for one of my, perhaps all too frequent, railway loco recordings as it is good to have a varied sound source crossing the stereo field. So here we go with the two sample recordings, one using the MC59 Twin only and one using the MC59 Twin with the omni MC59/O as the mid mic:
Just as with the pinknoise test in my previous post, this field recording reveals the fall off in high frequencies at 90 degrees to the omni mic created from the MC59 Twin, which, in this MS use, becomes on-axis for frontal sound sources. You can see this in the spectrum analyzer visualization below, which is a snapshot of the sound as the steam loco passes directly in front of the mics. Whether or not you can hear a significant difference is another matter as the drop in sensitivity to high frequencies really only kicks off in this example around 15kHz.
MC59 Twin in omni mode off axis (red) overlaid on MC59/O omni mic on axis (green): that is, both mics set up for MS use, with the main sound coming from directly in front of the mics.
Conclusions
The main purpose of this short blog post is to provide an example comparing the all-in-one omni MS recording with a twin mic vs the more normal approach taken with separate mid and side mics. Take from it what you will! From my own perspective, while it sounded better to my ageing ears than I suspected, I can’t really think of circumstances where I would find it helpful to use the MC59 Twin on its own and accept the pay-off of high-frequency loss on axis. I would much rather use the twin more flexibly as the infinitely variable mid mic of an MS pair, along with an MC59-8 fig 8, in which set up, of course, it can also function as a DMS rig, with all the choices made in post: and, as we have seen before, this is still a very compact pairing, capable of use in the field in a small windshield such as the Mini-ALTO.
The MKH 418-S stereo shotgun mic was introduced in 2003, creating – by addition of a fig 8 capsule – what was essentially a mid-side (MS) version of the popular mono MKH 416 shotgun mic. The new MKH 8018 does something similar for the MKH 8000 family of mics, although its mid mic is less directional than the MKH 8060 short shotgun and, of course, a lot less so than the longer MKH 8070. While the specs are significantly improved on the MKH 418-S, the MKH 8018 is aimed squarely at a similar market – most obviously outside sports broadcast. A few reviews have begun to appear on the mic and, rather than repeat ground covered in them, the focus on the tests for this blog post is a bit different: as usual I explore the basics (self-noise, handling noise, frequency response, resistance to RFI etc.), but the field tests focus on the performance of the MKH 8018 as a stereo mic. Above all, I am interested in how this latest take on a stereo shotgun compares to a non-shotgun mid-side pair and, for this, it seems most appropriate to test it in parallel to an MS pair of its MKH 8050 (supercardioid) and MKH 8030 (fig 8) siblings. How can the useful side rejection of a mono shotgun be reconciled with the addition of a fig 8 to create a stereo signal? Likewise, the tight focus of a shotgun mic for some sound effects can be useful, but how does a stereo version work for this? Does the inevitably more erratic (lobar) polar pattern of the shotgun mic at higher frequencies render it very much a poor cousin, or is it eminently usable? Is this mic about having that tight mono shotgun perspective, but with instant flexibility (without changing rig, or, even, making the call in the field) to have that stereo image when useful? If any of these or related questions are of interest to you too, then read on!
PS I should add that the good folks at Sennheiser sent me this MKH 8018 gratis for my unfiltered scrutiny. As usual, I play a straight bat and do my best to be objective (and, if anything, my starting point is a little scepticism about MS and, consequently, DMS with shotguns, as readers may have noticed!), and, with plenty of test WAV files to download, you can pore over my tests and draw your own conclusions. Right: onwards!
PPS It’s not the shortest blog post ever, so if you are after sound samples, stick with it: mostly they are further down.
A look at the mic and its specifications
Well, first to the mic itself. There is no great value in repeating the specifications provided on the Sennheiser website, but a few key ones jump out and merit some discussion. First, of course, is the self-noise, for which figures of 12 dBA are given for the mid (shotgun) mic capsule and 14.5 dBA for the side (fig 8) capsule. These are lower than for the MKH 418-S, for which the mid channel is 14 dBA and the side channel 22 dBA. The fig 8 self-noise improvement is very substantial, but, interestingly, the value is not the same as that for the recently introduced MKH 8030 (13 dBA). The polar pattern of the MKH 8018’s fig 8 is also much less regular than that of the MKH 8030 above 4kHz, which, with the self-noise difference, suggests a different capsule, which Sennheiser have confirmed. The shotgun mic capsule appears to be different from the MKH 8060, and, again, I have had this confirmed…
The MKH 8018 is also a lot more sensitive than the MKH 418-S: for the mid (shotgun) capsule -25 dBV vs -32 dBV; and for the fig 8 capsule -32 dBV vs -40dBV. In both cases, in actual use the substantial difference between the sensitivity of the mid and side channels is then amplified by the fact that the side channel usually gets a much lower signal. In practice I have run 7dB more gain on the side channel in the field with the MKH 8018, to get the capsules up to matching sensitivity, but that’s not always easy with some mixer/recorders with MS linking. And while the MKH 8018 shotgun capsule has quite a hot output, it isn’t unusually so: for example, the MKH 8060 is 1 dBV hotter at -24 dBV.
Thinking about the sensititivies of the two channels leads to another key difference between the MKH 8018 and the MKH 418-S: while the latter outputs the M and S signals only, the MKH 8018 can switch between this option, ‘narrow-XY’ and ‘wide-XY’. No information is given as to the ratio of M to S in the two decoded LR stereo outputs and, while I am sure that they will prove useful to some not familiar or unable to work with the M and S outputs, for all my testing and use I have had the mic set in its MS output mode: I like to know what I am doing!
Turning to the physical appearance of the mic itself, all is exactly described and illustrated on the Sennheiser website. The one thing that wasn’t clear from that was the position of the capsules within the mic, so the first thing I did on opening the box was to hold the mic up to the light to try to see what is going on.
Back-lit view of the slotted tube part of the MKH 8018, showing the three sections: that on the right (i.e. rear) contains the fig 8 capsule with the mid mic capsule then adjoining (to its left); and the two left-hand slotted sections are the actual interference tube of the (shotgun) mid mic, which measures 82mm in length. The internal circular openings can be seen – along with the tight mesh – behind the slots.
Capsules and polar patterns
Polar patterns vary much more across the broad category of shotgun mics than across the individual types of first-order mics (omni, cardioid, supercardioid, hypercardioid, fig 8 etc.). Shotgun mics also have a much more variable polar plot at different frequencies than mics with no interference tube. For example, a shotgun mic might have a similar acceptance angle (signal no more than 3dB down on the on-axis signal) as a hypercardioid (i.e. 105°) up until 1-2kHz, before narrowing (i.e. getting more directional) above that to, say, 25° at 16kHz. So the simple distance factor (i.e. the distance at which the mics get the same direct-to-diffuse field ratio) that can be described for omni mics through to fig 8s has no immediate application to shotgun mics: you will read of ‘typical’ distance factors for shotgun mics of 2 to 3 (with an omni being 1.00, a cardioid being 1.73 and a supercardioid being 1.90), but, clearly, this is a crude approximation given the change in directivity with frequency. Adding to the variables in design (inc. length) of the interference tube and capsule, multi-capsule shotguns also change how the mics reject off-axis sound. The polar pattern (with its particular frequency dependent variation), therefore, has a much more significant role in determining which model of shotgun mic a sound recordist will choose for any given type of recording situation. That doesn’t mean, of course, that the published polar patterns are what a recordist uses to make such choices: an experienced sound recordist will usually base that on how they have heard different microphones perform in use in a range of situations.
Nonetheless, a polar plot, especially if not overly smoothed, contains useful information for a shotgun mic, and it certainly gives an immediate insight into the MKH 8018. This shows that at lower frequencies, up to 1kHz, the MKH 8018 mid mic has a very slightly wider pattern than the MKH 8060, and, indeed, fractionally more so than the supercardioid MKH 8050, but with a much smaller rear lobe than either. Above that there is more divergence: by 2kHz the MKH 8060 has a significantly tighter pattern and this increases with frequency, along with a less noticeable rear lobe. The MKH 8018 and MKH 8050 remain very similar up to 4kHz, but, thereafter, the MKH 8018 gets more directional, as you would expect. As with all polar plots for interference tube mics, by 8kHz that for the MKH 8018 shows erratic, or lobar, form, but the response from a sine wave at a specific frequency is very hard to translate to use: this is where listening to the mic is critical. Hopefully the various test files in this blog post will help, but there’s no substitute to testing for yourself, especially when comparing to a mic known to you.
Composite image to show the MKH 8018’s fig 8 capsule behind the fairly opaque fine mesh: it was a little tricky, but some lighting from above and then below, coupled with careful focusing, reveals something of the fig 8 capsule within the mic.
Turning to the fig 8 capsule, as I said in the introduction, its specs are similar but not identical to that of the new MKH 8030. I am loathe to take the new MKH 8018 apart, but, despite the fine mesh of the mic, careful lighting shows the position and appearance of the capsule. It is positioned (to the rear of the shotgun mid mic capsule, obviously) so that it is centred on the seventh slot from the end of the interference tube (so 12.5mm from the solid part of the mic body), and its appearance is very close to that of the MKH 8030, with a similar stainless-steel filter over the usual MKH symmetrical push-pull single diaphragm, and a brass tensioning ring around it that looks identical to that of the MKH 8030 apart from the mount detail, which, in this case, widens for the fixings at both ends (one end joining to the mid mic capsule). Unlike the MKH 418-S the fig 8 capsule (KS-16-3) does not sit in an oblong block, but, rather, has a rounded tension ring. It appears that, like the MKH 8030, the fig 8 in the MKH 8018 has a16mm-diameter diaphragm, but that is based on a visual estimate compared to the overall mic diameter (22mm). It is a little surprising, given the visual similarity of the MKH 8030 and MKH 8018 fig 8 capsules, that they don’t have identical specs, although in the case of the difference in polar patterns it is unclear whether this relates at all to, in the case of the MKH 8018, the mounting between the preamp and the mid mic capsule (given the nulls it is hard to imagine why this should be so), or indeed the less open slotted tube and close mesh that continues across the fig 8 part of the MKH 8018 vs the more open design and open weave mesh of the MKH 8030. Here are the comparative polar patterns:
The different presentation (90-degree rotation and split vs continuous circles) of the two polar patterns doesn’t disguise the fact that they are quite different, with significant irregularities from 2-4kHz upward in the MKH 8018.
Frequency response
The frequency response curves and sensitivity measurements supplied with (and for) the MKH 8018 example tested here.
Like the MKH 8060 and MKH 8070 shotgun mics the MKH 8018 also has a more limited frequency range than the rest of the MKH 8000 mics. The published figures for the latter are all 30 Hz to 50 kHz, apart from the omni MKH 8020, which has a published range of 10 Hz to 60 kHz. The frequency range given for the MKH 8018 is 40 Hz to 20 kHz, but looking at the plots above you can see that the fig 8 side mic is shown as having much less low end: fig 8 mics are often a little bass-shy compared to other polar patterns, although this shows a steeper fall-off than with the MKH 8030. As discussed in previous posts, an extended high-frequency response might seem entirely academic outside those recording at high sample rates and pitching down in post (e.g. for bat recordings, or for sound effects), but there are those that argue frequency response over 20kHz is important for high-resolution recording (such as David Blackmer of Earthworks mics in this article). But quoted figures of themselves do not tell the whole story (for example the extended high-frequency capabilities of the first-order MKH 8000 mics comes with a sharp rise in self-noise, which can be problematic for very quiet sounds), so for a field test, I again thought the overtones of some church bells would be an interesting sample, so up I clambered to the belfry at Norwich Cathedral.
Up in the massive early 12th-century cathedral belfry, where the the bells and bell frame seem small by comparison.
For the recording I set up the MKH 8018 and an MKH 8050 + MKH 8030 MS pair in separate Mini-ALTO windshields (there was a breeze inside the belfry) facing the bell-frame. Such a loud sound really brings home the sensitivity of the mid (shotgun) capsule: 20 dB gain was pushing my luck! Here are the 96 kHz sound files:
And here is a spectrogram of part of the recording, showing the chimes. The higher-frequency capability of the MKH 8030 and MKH 8050 are evident with much stronger signals up to 48kHz (the limit on this spectrogram), but, equally, so is the much greater self-noise of these mics from just below 20 kHz and upwards compared to the MKH 8018 (see below for more on self-noise). And while the latter might only be quoted as having a frequency-range up to 20 kHz, like many similarly specified mics there is no abrupt cut-off at this point and there is plenty of signal above this frequency.
Spectrogram of the bells tolling midday, from left to right: MKH 8018 mid mic, MKH 8018 side mic, MKH 8050 mid mic, and MKH 8030 side mic. The vertical axis extends to 48kHz.
Turning to the other end of the spectrum, I set up the MKH 8018 and the MKH 8050 + MKH 8030 pair aimed at the exhaust pipe of the rear of a parked car (with the engine running needless to say!). Here are short clips from the recording, which include a little gentle revving:
And here are the spectrum analyzer visualizations:
MKH 8018 mid (shotgun) mic capsule.MKH 8050 supercardioid.MKH 8018 side (fig 8) mic capsule.MKH 8030 fig 8.
The tracks show all four capsules capable of rendering the lowest fundamental, which was around 26.5Hz, although, of course, the fig 8s show a lot less of the low-end of the engine: this is partly since the exhaust pipe itself was centred on their nulls and partly since fig 8s inherently have a poorer low-frequency response. What is more interesting is that, compared to their MKH 8050 + MKH 8030 counterparts, both MKH 8018 capsules have a greater low-frequency output down to around 50Hz, but a lower output at the 26.5Hz fundamental and then fall away quickly below that. It is comparable to using an MZF 8000 ii filter module on the modular MKH 8000 mics, with its permanent low-cut filter of –3 dB @ 16 Hz, 18 dB/oct: indeed, the comparison is especially valid (and I assume a design intention) since both the MZF 8000 ii filter module and the MKH 8018 have a switchable low-cut filter of -3 dB @ 70 Hz. So without use of the switchable low-cut filter, the MKH 8018 seems to have a steep roll-off of the very low frequencies likely to arise from handling noise (and the inevitable resonant frequency of a mic suspension); and then the option to roll-off more (often not optional in many shotgun mics) at a higher frequency to reduce wind noise, traffic rumble and, even, higher-frequency handling issues. In short, the design allows the MKH 8018 to be used where many a shotgun mic would struggle for lack of low-frequency response, yet is designed with handling in mind and has the option to roll off more low-end in keeping with many a shotgun mic: and the response of the two capsules is consistent in this regard.
Self-noise
The 12 dB-A self-noise figure for the MKH 8018 shotgun mic capsule is respectable for a shotgun mic and as we have seen it is an improvement on the mid mic in the MKH 418-S stereo shotgun (14 dB-A), and only a little higher than the figure for the MKH 8060 shotgun mic (11 db-A). And, while the side mic capsule of the MKH 8018 might have a little more self -noise than the MKH 8030 fig 8 (14.5 dB-A vs 13 dB-A) that is still very good for an SDC fig 8 and radically better than that in the MKH 418-S. But specs of self-noise are one thing and how they sound can be quite another: a single figure doesn’t tell the whole story. So on to some tests…
First off, I checked that the manufacturer’s sensitivity figures were broadly correct, recording a 1kHz tone and measuring that with a tight band-pass filter applied at 1kHz: all was evidently in order at least in relative terms (I compared the two MKH 8018 capsules to an MKH 8030 and an MKH 8050 [also 13dB-A], getting a maximum deviation of 0.8 dBV from the published specs). So, in the absence of an anechoic chamber, I then did my usual recording the sound of nothing with the mics buried deep in duvets in the airing cupboard, with all doors and windows closed and the mains electricity turned off, recording with each mic at 76dB gain (the max of a Sound Devices 788T). Also as usual, to remove any low-frequency sound still permeating, I applied a 100Hz high-pass filter, and, in my DAW, added further gain to match the three less sensitive capsules with the sensitivity of the MKH 8018’s mid mic (the hottest of the four capsules). Normally, I wouldn’t bother including the sound of madly cranked-up mic hiss in a test/review (total gain for the MKH 8050, for example, being 85 dB), but in this case it is quite interesting to compare the different capsules. And, as I have cautioned in the past, don’t panic: all the mics are very quiet in normal use!
And here are the spectrum analyzer visualizations of the noise:
MKH 8018 mid (shotgun) mic capsule.MKH 8050 supercardioid.MKH 8018 side (fig 8) mic capsule.MKH 8030 fig 8.
The sound files and the spectrum analyzer visualizations show that the two MKH 8018 capsules are quite different in terms of self-noise from the MKH 8050 and MKH 8030. The more limited ultra-sonic capabilities mean that the MKH 8018 is not tuned like its first-order siblings, where steeply rising self-noise towards 20kHz continues to rise to 48kHz. With the MKH 8018, the rise in self-noise in both capsules starts lower and is less steep, and then flattens off after 20kHz. This lower and more gradual rise in self-noise means that the character of the self-noise is quite different in the audible spectrum: self-noise in the MKH 8018 capsules is characterized by more of a high-frequency hiss (say in the 6-12kHz region) very evident to my ageing ears and, obviously, much more so to younger ears. Thinking of younger ears, extreme high-frequency hiss in the MKH 8030 and MKH 8050 will become more discernible to them in the 12-20kHz region as the self-noise in these mics rises to match or exceed that of the MKH 8018 capsules. But, I must reiterate, while interesting to compare and to note for reference, these tests are at extreme gains and so unless recording a watch ticking or other very quiet sound effects, self-noise will not be an issue with any of these mics in most use case. And for an extreme example – relevant to sound design and effects – I slowed down the cathedral bells recording included above to a quarter of its speed, bringing down the pitch accordingly (i.e. by two octaves), and yet no hiss is discernible even in the quiet sections unless gain is cranked up to levels that mean the chimes would destroy your speakers and ears! If interested, do have a play with the downloadable files yourself.
RFI
Looking at radio frequency interference (RFI) on the MKH 8018 is nothing to do with its RF design (which, in the words of the MKH designer Manfred Hibbing in his The MKH Story white paper), means the mic essentially has ‘a transmitter and receiver that are directly wired together’), but is about its resistance to external RFI. As I’ve said in posts on other tests, I am interested in the impact of RFI on mics since, as living in rural Norfolk, much of my life is outside or on the edge of mobile phone reception, where some models of phones transmitting at full power can cause notable interference on mics at up to, say 1m/3ft: not a problem with mics on a stand, but I’ve had this become a real issue with handheld shotgun mics and a phone in my jacket pocket (on those rare occasions when I forget to turn my phone off). And this could be a problem with ENG work too (not least from the phone of an interviewee). So I was glad to find that in testing, as before, with several different phones on the absolute fringe of reception (i.e. working at highest power) the MKH 8018, like its MKH 8000 siblings, showed no sign of RFI even at close distances (100mm): for control I recorded the mic alongside a known problem mic (to check that the intermittent issue was occurring: it was) .
Handling noise
While the MKH 8018 might well see much use mounted on stands (e.g. for line-side recording of sports), it will become a regular fixture in windshields on boom poles or on a pistol grip, whether being used as a mono mic for dialogue or ENG, or in stereo for those times when a bit of ambience is required during production sound recording, or perhaps to get closer to a difficult to access source during field recording. So with that in mind, I put the mic through some boom-pole handling tests, mounting them in Radius Windhsields RAD-2 mounts on a short stereo bar on the end of the boom pole to allow comparison. Gain levels were adjusted for relative sensitivities.
When holding the boom pole statically (extended and horizontally) all four capsules mics showed some handling noise, with the MKH 8050 and MKH 8030 being the most significant, both peaking around 24dB higher than the two MKH 8018 capsules: admittedly the MKH 8050 and MKH 8030 were peaking below 20Hz. This pattern applied across other boom-pole handling tests: rough handling and tapping/thumping the end. To a significant degree – not least given the apparent similarity of the two fig 8 capsule designs – this is doubtless a consequence of the EQ built into the different mics with, as we have seen, the MKH 8018 bass response being very much rolled-off below, say, 50Hz and, especially, below 25Hz. But, equally, there is no denying that the MKH 8018 has handling noise extremely well controlled even without the use of its switchable 70Hz high-pass filter or any such additional, or alternative, filtering in the recorder/mixer or in post.
MKH 8018 mid (shotgun) mic capsule: handling noise test. Note 2kHz upper limit for the spectrum analyzer visualizations showing handling noise.MKH 8018 side (fig 8) mic capsule: handling noise test.MKH 8050 supercardioid: handling noise test.MKH 8030 fig 8: handling noise test.
Wind noise
To get a base line I used a double rig of the MKH 8018 and MKH 8050 + MKH 8030 on a stereo bar and boom pole. Fast boom swings were made to generate wind noise in a controlled fashion. Swinging the bare mics produced overwhelming rumble, as would be expected. The two fig 8s were fairly similar, although the MKH 8030 naturally showed a little more noise at low frequencies (say, below 30Hz). The shotgun mid mic was by far the least susceptible to what was a laminar stream of wind, and the MKH 8050, perhaps surprisingly for some, was by far the most susceptible to wind noise in these conditions. Of course, such use is unrealistic: even with a modest amount of boom movement indoors (or the gentlest air movement around a static mic indoors) at the very least a foam windshield would be used. Matching foams between the mics isn’t that easy, so for the next test I stepped up to bare windshields (i.e. sans fur), using Radius Windshields Mini-ALTOs for both. In tests with the windshields side on and into the wind (again, wide arcs from a boom swing), both capsules in the MKH 8018 performed about 3dB better than their MKH 8050 and MKH 8030 counterparts, and, as expected, lacked the very low-end (sub 30Hz) component: given the testing with a boom, this may well have been as much to do with handling noise as wind. I think another round of spectrum analyzer visualization or even WAV files wouldn’t add anything much to this description, so I will spare you those. Suffice it to say, such limited bare and windshield tests, show that the MKH 8018 is not oddly susceptible to wind (and, goodness, you wouldn’t expect it to be!) and, as you will hear from the samples below, this is further borne out by use in the field.
The MKH 8018 and an MKH 8050 + MKH 8050 MS pair on the beach on a grey English summer’s day in a pair of Mini-ALTOs.
Out in the field
A shotgun mic, of course, is primarily designed for outdoor use (OK, for large movie sound stages too), given that reflections are the enemy of interference tube designs. So to test the mic in its natural habitat, I put it through its paces recording a fairly wide range of sources outside. Many of these require it to be compared to something else, naturally, or we have no reference, and for most of the tests I have compared the MKH 8018 to an MKH 8050 and MKH 8030 MS pair: the supercardioid MKH 8050 being the most directional MKH 8000 non-shotgun mic (i.e. without an interference tube). Of course a supercardioid mid mic might well not be ideal for MS either in many situations, but you can refer to my recent tests of the MS pairs with the whole range of MKH 8000 SDC mics (i.e. MKH 8020 omni, MKH 8090 wide cardioid, MKH 8040 cardioid and the MKH 8050) if you are unsure of the differences.
First off, I headed to the beach on what I thought was a calm August day, but which turned out to be a brisk on-shore wind. Here are the two recordings facing straight out to sea:
Retreating a bit from the shoreline and the incoming tide to shelter behind the fishermen’s gear, I recorded myself walking on the shingle in a 360 circle around the mics, starting and finishing directly on axis:
Finally, for the seaside recordings, here’s a closer-up effect, recording the scooping up and dropping of shingle right by the mics:
Back to the same spot I have often been for test recordings, lineside at Holt station, as, yet again, a visiting Grange class locomotive pulls the train towards Sheringham.
Moving inland, I headed for one of my old test haunts at the North Norfolk Railway. Sadly, both the stationmaster and the signalmen recognized me so I had to take the assumption that I am an uber trainspotter on the chin: to deny it would have seemed as if I doth protest too much and, besides, testing mics is arguably an even more suspect activity! Next thing I will be calling a drink a ‘beverage’: it’s a slippery slope… Anyway, here is a three-clip recording of a steam train pulling into Holt station, then after a momentary gap, the signal box bell ringing and then, after another brief silence, the train pulling out. No editing other than the obvious cutting to produce the three parts to the recording:
Scything a rather overgrown field. Easier watching the hard work…
Back outside again, I popped over to my friend Rob’s new field (yes. that’s the same Rob who TIG welds the Mega-Blimps!), where he was sycthing or, as he put it, hacking away with a scythe to return the meadow to some order. Doubtless he will crack and get a tractor on it, but in the meantime here’s a pair of recordings of him sharpening the scythe:
And then a bit of scything/hacking at the nettles. I stood rather behind Rob and to the right so as to avoid him slicing through my rather nice and expensive MS cables.
A little bit of music
After all that fresh air I thought I would head inside for an indoor music test, slightly inspired by the well-known use of the Sennheiser MKH 4018-S for the NPR Tiny Desk concerts (although it has been increasingly supplemented by other mics over the years). So I popped down to woodcarver Luke Chapman’s workshop, which I often use: it has a surprisingly good acoustic. Luke obliged yet again (he must be sick of all these tests!) with guitar, working away on a new composition. Here is a video showing the recording with the MKH 8018 compared to an MS pair (again the MKH 8050 and MKH 8030):
Conclusions
This brief introduction to stereo use of the MKH 8018 has covered a bit of ground, from some discussion and tests of the salient aspects of interest from the specs to some tests in use. There are many uses I haven’t included here, partly reflecting my own interests (for example, I’m not in the business of recording sports events, so that’s for someone else to test!) and partly what is practical within a single blog post. One aspect I haven’t addressed is how the MKH 8018 compares to alternatives as a mono shotgun. For some this may well be a determining consideration for buying the mic: in other words, would the MKH 8018 meet their main needs as a mono shotgun mic, whilst providing a stereo option at all times for those occasions where it might prove useful? That is really hard to address, since comparing mono shotguns is not easy, as different sound recordists – especially experienced production sound mixers – will usually need to compare mics directly in use to see whether the nuances of any particular mic means that it suits their use. And, of course, there are many shotgun mics out there. But, that said, I may return to the MKH 8018 to explore the mono shotgun capability in a comparison with its nearest sibling – the MKH 8060: but don’t hold me to it! At the other end of the spectrum, I did think of including results of testing the MKH 8018 as part of a DMS rig here, but haven’t done so for reasons of not wanting to make an overly long post any longer and, also, since the efficacy of any mid mic in a DMS rig is very much apparent from its use in an MS pair. But, again, I may well return to this in a specific post: not least it might be helpful for some to hear the results of using different polar patterns for the rear-facing mid mic (e.g. just what balances a shotgun mic forward facing mid mic best: an MKH 8090 wide cardioid or an MKH 8040 cardioid?).
Anyway, returning to the ground that is covered in this post, drawing conclusions is as much something for the reader as it is for me: my aim was to explore the different in performance between the MKH 8018 in stereo use and an MS pair comprising its most directional non-shotgun sibling – the MKH 8050 supercardioid – and the MKH 8030. Given the better polar pattern and placement (i.e. above, not behind the mid mic capsule) of the fig 8 in the latter, and the more consistent off-axis performance of the supercardioid, its better performance for stereo is entirely expected and is evident in the various recordings. My aim wasn’t to demonstrate this and, as Basil Fawlty would say, get myself on Mastermind with the ‘special subject of the bleedin’ obvious’, but, rather to try and get a sense of the degree of difference. For some users and, indeed, for some uses, it may be vast: for others, and for other uses, the sonic differences may be too subtle and outweighed by other features of the MKH 8018: its usefulness as a mono-shotgun, its simplicity as a single mic vs rigging an MS pair, its ability to be both a shotgun mic and, say, an ambient pair without changing to (let alone buying) a second MS pair, its resilience to handling noise, its inbuilt pad and high-pass filters, and, even, its cost (less than the combined cost of an MKH 8050 supercardioid, or other mid mic, and the MKH 8030). Hopefully this blog post will help some when balancing all these factors. One major obstacle – the significant self-noise of the MKH 418-S – has been removed with Sennheiser’s new stereo mic, and this is hugely welcome. And if you have been humming and hawing about a stereo shotgun mic (including, the slightly noisier and sans RF technology, Sanken CSM 50, Neumann RSM 191, and the Audio Technica BP4027 and BP4029, as well as Sennheiser’s own MKH 418-S), the MKH 8018 is definitely one to get hold of (if you can!) and test for yourself. I’ve been very pleasantly surprised!
Postscript: wind protection for the MKH 8018
There’s nothing difficult in terms of rigging the MKH 8018 for outdoors (the supplied foam, of course, only being suitable for indoor use): it will fit many a windshield from the usual suspects. I note that Cinela have already got a Pianissimo model to fit (and do remember that the Cinela mono models can often be less expensive than you might expect), and a Rycote Modular 4 or a Rode Blimp would work fine. Here, I have tested the mic in a Rycote Cyclone medium, and much of my concern about using the Cyclones for MS rigs is allayed in this instance: the side lobes of the fig 8 capsule do not aim squarely at the thick plastic ring of this windshield, with evident colouration problems, as I have found with MKH 8030-based MS and DMS rigs in the small Cyclone. But the result is far from compact, so for my field tests with the mic I used the new Mini-ALTO 250 from Radius Windshields: they have been expanding their range of Mini-ALTO sizes and this fits perfectly, and I had no problems with wind noise in the admittedly not overly windy conditions of this English summer. And when not lugging two rigs for comparative purposes, I’ve enjoyed the fact that I can fit the MKH 8018 in the Mini-ALTO 250 in its fur, along with a field recorder, headphones, cable, camera etc. all in my little Think Tank Retrospective 7 bag that I like to use for field recording (yes, I know, I know: this is ironic from the creator of the Mega-Blimp!). For the cable I used an excellent low-profile XLR5F to XLR5M stereo cable, made with super-light and flexible Mogami 2739, which really keeps cable-borne noise to a minimum: critical if booming or use the mic on a pistol grip. This was made by Ed at ETK Cables.
Following on from part 1, where the design of fitting an ORTF pair into the diminutive Mini-ALTO was covered (using a pair of Sennheiser MKH 8040 mics with modified MZL connectors), this second part of the blog post concerns testing the compact rig. There are two main aspects that I wanted to test to see if such an ORTF rig is usable: transparency (i.e. how much does the windshield colour the sound) and wind protection.
Composite view of ORTF in a Radius Windshields Mini-ALTO showing the position of the mics with two 90mm pods.Composite view of ORTF in a Radius Windshields Mini-ALTO showing the position of the mics with two 136mm pods.
Transparency
My main concern with colouration was not just the basket structure in general, but the thicker plastic rings that mark the join of the end caps to the cylindrical part of the windshield basket. The impact of such rings can be quite discernible with set ups in some windshields: others have noted the impact of the large rear plastic ring in the Rycote ORTF windshield, and I have noted and measured the impact of the still chunkier ring in the Rycote Cyclone on the sideward-facing lobes of the fig 8 mic when used for mid-side recording. The rings in the Mini-ALTO are much less substantial than in these examples, but, given the 80mm diameter of the basket, they are closer to the mics, so the key questions are: i) is the impact measurable?; ii) is there a difference between the impact in the two different pod sizes? and, iii) if there is a measurable impact, does this matter – i.e. does it translate to noticeable issues when making field recordings?
Without an anechoic chamber it is difficult to get an exact read on the transparency of any windshield, but, as I did with my original Mini-ALTO 115 test, for a reasonable quick and dirty test I placed a bare mic on the windshield ORTF shock-mount in front of a speaker (in my treated studio) playing pink noise, then carefully added the windshield pods without moving the mic for a second recording. I did this with the ORTF bar oriented square-on to the speaker (0 degrees), at 45 degrees and side-on to the speaker (90 degrees). I repeated the exercise for both the 90mm and 136mm pod sizes. The results for each pair of recording were compared using a spectrum analyzer and overlaid as follows:
Pink noise test with Mini-ALTO with ORTF bar square-on to the speaker (0 degrees), using one of the two mics only: green is the bare mic on the shock-mount and the red overlay is the recording with the 90mm basket pods added.Pink noise test with Mini-ALTO with ORTF bar square-on to the speaker (0 degrees), using one of the two mics only: green is the bare mic on the shock-mount and the red overlay is the recording with the 136mm basket pods added.
In these tests with the ORTF bar square-on to the speaker the sound is arriving at the cardioid mic about 63 degrees off-axis. In the case of the 90mm pods the plastic ring for the end caps is directly between source and capsule, whereas with the longer 136mm pods the ring sits beyond the direct line. Given this, it is not surprising to see a greater impact when the 90mm pods are used, in addition to some generally increasing attenuation of high frequencies, although the significant colouration only kicks in at 15.2kHz and above.
Pink noise test with Mini-ALTO with ORTF bar at 45 degrees to the speaker, using one of the two mics only: green is the bare mic on the shock-mount and the red overlay is the recording with the 90mm basket pods added.Pink noise test with Mini-ALTO with ORTF bar at 45 degrees to the speaker, using one of the two mics only: green is the bare mic on the shock-mount and the red overlay is the recording with the 136mm basket pods added.
In these tests with the ORTF bar at 45 degrees to the speaker the sound is arriving at the cardioid mic about 16 degrees off-axis. In the case of the 90mm pods the direct line between source and capsule is through the end cap of the windshield, whereas with the longer 136mm pods the direct line is through the cylindrical part of the basket and near to the end cap ring. It is interesting to see that, despite the seeming greater significance of the plastic ring to the 136mm pods at this angle, the colouration arising from the basket is a little less than with the 90mm pods.
Pink noise test with Mini-ALTO with ORTF bar at 90 degrees to the speaker, using one of the two mics only: green is the bare mic on the shock-mount and the red overlay is the recording with the 90mm basket pods added.Pink noise test with Mini-ALTO with ORTF bar at 90 degrees to the speaker, using one of the two mics only: green is the bare mic on the shock-mount and the red overlay is the recording with the 136mm basket pods added.
In these tests with the ORTF bar at 90 degrees to the speaker the sound is arriving at the cardioid mic at 35 degrees off-axis. In the case of both the 90mm and 136mm pods the direct line between source and capsule is along the longitudinal axis of the windshield and, thus, through the centre of the end cap of the windshield: in short, the mic position relative to the sound source, apart from being angled, is very much in accordance with a mono directional mic in the windshield as per the original design intention. As a result, the impact of the basket is minimal (and comparable to my previous tests of the Mini-ALTO 115 with a supercardioid mic), although a couple of troughs at high frequencies – at 15.2kHz and 17kHz – are visible with the 90mm pods.
For the purposes of comparison, here is my previous test of an MKH 8030 with the Min-ALTO basket turned side-on to the speaker source so that the fig 8 mic is on axis to the sound source:
Pink noise test with Mini-ALTO 115 with MKH8030 fig 8 mic aimed at speaker: green is the bare mic on the shock-mount and the red overlay is the recording with the basket added.
This is useful, since it shows that – within the limitations of this testing methodology – that the ORTF pair in the Mini-ALTO with 90mm and 136mm pods is less affected by the basket than the fig 8 mic in the Mini-ALTO 115. And for another comparison, here is the same fig 8 test repeated with a Rycote Cyclone.
Pink noise test with Cyclone (small) with MKH8030 fig 8 mic aimed at speaker: green is the bare mic on the shock-mount and the red overlay is the recording with the basket added.
The more significant impact of the Cyclone basket is doubtless largely due to the substantial plastic ring for its end cap.
The pink noise testing evidently shows some impact of the Mini-ALTO basket on the ORTF set up, much of which is a general and modest loss of high frequencies, with a few more obvious anomalies over 15kHz. The colouration, however, looks better than feared, not radically different between the two pod sizes, and, above all, less significant than that with a fig 8 in the Mini-ALTO 115 and far less than with a fig 8 in a Rycote Cyclone.
As I noted when I tested the Mini-ALTO 115, there is one thing demonstrating differences with this pink noise test or, indeed, more exhaustive and expert tests in an anechoic chamber, but how does the colouration actually sound? It is hard to come up with a perfect test, especially with limited resources, but I have settled on an approach that some at least may find informative. Eschewing the variability of successive live recordings, I placed the ORTF rig in front of a pair of speaker (Vivid S12s) in my studio and played back a short section of a recent recording of mine of a singer-guitarist (Luke Chapman), angling the ORTF bar square-on to the speaker, and with the mic aligned to the speaker so that it was 55 degrees off-axis. This positioning ensured that the plastic ring for the end cap was exactly on the line between the speaker and the mic with the 90mm pod, so very much the worse case positioning. Here are the resulting mono sound files:
If really keen, you can download the files and set them up in a DAW and flip between short repeated sections of each pair, which is what I have done. In both the recordings with the windshield you can hear the expected slight change to the high frequencies when the basket is added, as anticipated following the pink noise tests, but I would suggest that it is subtle and, therefore, unlikely to be of great significance to the majority of those making sound recordings in the field. Perhaps more importantly, there seems little practical reason to favour the longer 136mm pods over the more compact 90mm pods in terms of transparency: of course, there may be differences in wind protection, which is what we will explore next.
Wind protection
The laws of physics dictate that the small 80mm diameter of the Mini-ALTO cannot offer the wind protection of larger basket designs, and that was never the intention behind its compact design. That said, the small windshield performs reasonably well outdoors, and I was surprised in my original tests in breezy conditions to note that it outperformed the Rycote Nano Shield, which, although another smaller basket windshield design, has a larger cross-section (measuring internally 86mm high and, with its elliptical form, 107mm wide), although testing confirmed that larger windshields did provide better wind reduction. The questions I have for ORTF in a Mini-ALTO, therefore, are not how it compares to the same in much larger baskets, but the following: i) is there a noticeable difference in the wind reduction performance between the two different (i.e. 90mm and 136mm) pod sizes; and ii) how does the wind protection for an ORTF pair compare to that afforded to other rigs in a Mini-ALTO? With the last, I was particularly interested to see how the ORTF pair compares to a mid-side pair in a Mini-ALTO: if performance was similar to the last, then, given that I have been happy to use MS pairs in the Mini-ALTO where wind conditions allow and where compactness is paramount, this would mean that the ORTF design is similarly viable from a functional point of view.
First off, the matching front and rear pods provided by Radius Windshields for this whole experiment mean that the two Mini-ALTOs are non-standard lengths, so a couple of bespoke furs had to be made by the sewing department in Stroud. These are of the same, longer pile, grey fur that Radius provides as an option for the existing Mini-ALTOs and I have matching ones for my Mini-ALTO 115s. It might seem trivial or obvious, but it is important to have identical furs when testing the wind performance of the different rigs and pod sizes. Wind tests in the real world, where wind is turbulent and not laminar, are never quite as easy as you might think: simultaneous recordings are essential, of course, but the windshields have to be placed a bit apart to avoid one protecting or otherwise affecting the other, so wind gusts can vary a bit in terms of impact and timing. The other difficulty is matching mics: despite my growing mic locker I don’t have a stash of multiple MKH 8040 mics, but just one pair. My solution to this problem has been to record a single channel in each of the two Mini-ALTO ORTF rigs, which is fine: we are after a comparison of the wind performance of the two different sized pods not making beautiful stereo recordings, and this serves the purpose just as effectively. And for the comparison between ORTF and mid-side, where single-channel recording could be a bit misleading (i.e. comparing one channel of ORTF to, say, just the side mic of an MS pair seems like apples to oranges), I used the pair of MKH 8040s in ORTF in one of the test Mini-ALTOs and a MS pair of MKH 8030 and MKH 8090 in the Mini-ALTO 115 I use for MS: I’ve noted very little difference in wind performance with the wide cardioid vs the cardioid mics in MS.
Starting off with the windshields with no fur, here is an excerpt of a windy gust on a pretty breezy day, with the ORTF rig using 90mm pods compared to the Mini-ALTO 115 with an MS pair (MKH 8090 and MKH 8030).
And then compared using a spectrum analyzer and overlaid as follows:
Wind gust test with Mini-ALTO 115 with MS pair (MKH 8090 and MKH 8030) in green, with Mini-ALTO 90+90mm ORTF (MKH 8040) in red.
Both listening to the sound file and viewing the spectrum analyzer show that the ORTF pair in a Mini-ALTO with 90mm pods more than holds its own against the MS pair in the Mini-ALTO 115, each with the bare basket. But it is equally clear from the audio that the the differences are not constant. Moreover, we need to think about the impact of wind direction on performance, given that the two stereo pairs sit at 90 degrees to each other in relation to their windshields: in this example both mic pairs were side on to the wind direction, so that the ORTF windshield presented its small end-on form to the wind while the MS pair’s windshield presented its side to the wind. Changing this around by rotating the mic stand 90 degrees, here is a second set of recordings with the mics facing directly into the wind, so that the windshield housing the MS pair was end-on and the windshield housing the ORTF pair was side on.
The impact of wind on the MS pair is less in this second test compared to that on the ORTF pair. What we can draw from these comparisons, however, is that overall the ORTF pair in the 90mm pods seems to hold its own compared to the the Mini-ALTO 115 with an MS pair, with both baskets being bare.
Moving onto tests with furs added, which, of course, reflects more typical usage of the Mini-ALTOs outdoors, here we have a pair of ORTF and MS recordings with the wind coming from the side:
And then with the mic stand rotated 90 degree so that the two pairs are aimed into the wind, albeit with the ORTF pair’s windshield side-on to the wind and the MS pair’s windshield end-on to the wind:
So, the fur (while, of course, reducing wind noise) does not change the situation: the broadside offered by the windshield when an ORTF pair faces into it and the broadside of the windshield offered when an MS pair faces at 90 degrees to the wind are what creates the most windnoise. With this caveat, which has implications for usage (in any given situation one array may outperform the other: equally it could be argued that wind direction and sound source direction – if not negotiable by moving the mic position – might influence choice of mic array), there is no obvious difference in the overall wind performance and, to some extent, this is predictable given the mic capsule locations and orientations in the two arrays.
So now we should turn to the matter of the two pod sizes for the prototype ORTF rig: does the increased volume of the 136mm pod windshield offer an advantage in wind reduction over its shorter counterpart with the 90mm pods? For this, of course, I was able to orient the two windshields identically, and recorded a single cardioid in the ORTF rig in each simultaneously.
First up we have the 90mm pods (with fur) facing so that the wind direction was end-on to windshield:
And then the simultaneous recording using a Mini-ALTO with 136mm pods (with fur):
And then the mic stand was rotated 90 degrees so that wind direction was side-on to the windshields:
There is again some gust to gust variability between the two windshields, doubtless reflecting the highly localized differences in the turbulent wind you get in the real world, but there is nothing in these short clips (or, indeed, the much longer recordings I made) to suggest that the longer version of the ORTF Mini-ALTO with its 136mm-long pods outperforms the shorter 90mm version. This applies in both orientations into and at 90 degrees to the wind.
Conclusions
So what’s the verdict? Is an ORTF pair viable in the diminutive Mini-ALTO? If so, is a short symmetrical Mini-ALTO with two 90mm pods as effective as a longer version? My short answer is, yes, an ORTF pair is viable in a Mini-ALTO and that the advantages of pods longer than 90mm are so small as to be insignificant: so you might as well use the more compact 90mm pod version. Moreover, I would suggest that an ORTF pair is just as viable in a Mini-ALTO as a mid-side pair, although the number of cardioid mics that are short enough to make use of the 80mm diameter windshield for ORTF are few and far between: so far I have identified the MKH 8040 used here, the Schoeps CMC1 KV + Mk4, the Nevaton MC59S(C) and the upcoming DPA MMP-GS with the existing 4011 capsule as suitable candidates, and, in a third blog post, will be testing at least some of these. And there well be other mics that would fit without resulting in capsules close to the windshield basket. There are other caveats to add to this, but these are very much the same as with the Mini-ALTO for use with a mono directional mic: above all, a small diameter windshield will – all other things being equal – perform less well at reducing wind noise than a larger windshield; and, second, the structure of a basket, especially with significantly chunky plastic components, will provide colouration of sound above and beyond the curtailing of high-frequencies that is inherent to any fabric covering of a mic. So, of course, a Cinela Albert is a better bet for ORTF in terms of acoustic transparency and wind performance (as, indeed, is my own TIG-welded Mega-Blimp), but that’s not really the point: the Mini-ALTO is designed – above all – to be compact, to offer modest wind protection, and to allow rapid changing between bare mics and full basket. Now the latter, which is so relevant to production sound recording with a supercardioid or shotgun mic, may not be quite so relevant to an ORTF pair, but compactness is relevant to many recording in the field. Many people do seem to love dinky little recording rigs with miniscule recorders and lightweight stands (if a stand at all). For them, moving from a pair of furry slip-on covers for an ORTF pair on a stereo bar to a Mini-ALTO containing an ORTF pair would offer better wind performance and a more practical, transportable and robust form for the setup. For those already using ORTF in larger blimps, then a Mini-ALTO ORTF rig offers more compactness for those times when (small) size really matters, just as is the case for using the Mini-ALTO instead of larger windshields for MS or even DMS. Given that many windshields – I am thinking especially of traditional cylinder types such as the Rode, Rycote Modular and Rycote ORTF windshields – don’t have noticeably less colouration than a Mini-ALTO, for many it just comes down to size vs wind reduction: just as it would for a mono supercardioid or shotgun mic. So, yes, ORTF in a Mini-ALTO is usable and will appeal to many. Whether or not that translates to commercial viability is beyond me, not least given the small number of mics that are short enough: that is one for Simon Davies and the team at Radius Windshields to ponder. If the two blog posts on this experiment have piqued your interest, do get in touch with them (they are eminently approachable and responsive) and let them know as feedback will doubtless influence where they go with this!
Members of the City of Norwich Pipe Band arranged in two arcs, in the rather wonderful setting of Wymondham Abbey.
Introduction
In part 1 of the blog posts on recording test sessions with the City of Norwich Pipe Band (a prelude to a CD recording, with the tests focused on establishing whether recording indoors or outdoors is preferable), I covered the rationale and detail behind the microphone choices. To recap, with the band formed in both a circle and a near circle, I decided to go with a native B-format array of two fig 8s (Sennheiser MKH 8030) and an omni (Sennheiser MKH 8020), which, in terms of the required stereo end product, gave me options of mid-side with two fig 8s (i.e. decoding to a Blumlein pair), omni mid-side, and double mid-side (the latter with any polar pattern for the mid mics). And just to cover all bases, I also elected to add a spaced pair of omni mics (Rycote OM-08s). This second blog post is concerned with the recording and the results.
Location
Recording a pipe band indoors requires a large space. In the absence of a massive purpose-built recording studio (ruled out due to cost and because this was always intended as a location recording of a non-competition pipe band), I was glad to be able to arrange for use of Wymondham Abbey (many thanks especially are due to Brian Randall, churchwarden, for his help and support). The early 12th-century nave that survived the demolition of the rest of the abbey at the Dissolution (to function thereafter as the parish church for the town) is substantial, being twice the size of Abbey Road Studio One: if a small pipe band (the recording involved some members only – we had five pipes, one tenor drum, one side (or snare) drum and a bass drum) was to overwhelm the abbey church, then indoor recording would evidently be a non-starter outside a studio or concert hall.
Arranging the band
The regular formation used by pipe bands is a circle, and I could see no reason to, say, go for a more linear concert-style arrangement for recording. On the one side, recording a band in a circle is a challenge, but, as we have seen in the previous post on mic array selection, one that is solvable. But aside from the easy benefit of intervisibility for band members, this arrangement offers an additional benefit for loud acoustic instruments such as bagpipes and drums: direct sound will predominate over reflected sound from all directions. That is certainly the case if an unbroken circle is adopted, but balancing this with the array options (which included mid-side with two fig 8s) meant that these tests comprised both a full circle and a very broken circle – i.e. two opposing arcs each just under 90 degrees. With a modest contingent of the band for the test session, for the full-circle version we had the pipers occupying a little more than half the circle, which had a radius of around 2 metres. For the two opposing arcs, the pipers were all on one side facing the three drummers on the other side, with a radius of 3 metres for both arcs. We will replicate the arrangements for the outdoor test session in due course, but, evidently, any CD recording with a larger number of band members is likely to require some tweaking of the radius to accommodate everyone. That said, the band members were far from squashed together on this initial session.
Recording
Prior to the recording test session, I dropped into one the regular practices to meet the band. They hold these in the former Regal Cinema (now part of the Wymondham & District Ex-Services Social Club), so, while not a remote glen, it is far from a small room with a low ceiling. The sound of the band, however, came bouncing back from all directions and, given the reputation of bagpipes, I was a little concerned about levels before the test session. With only one pad on one of the mics (courtesy of the single MZF 8000ii filter I have – more on that soon) I was crossing fingers that I would be OK in terms of volume: with healthy max SPLs of 139dB for the MKH 8030s and 138dB for the MKH 8020, I was happy with the Sennheisers, but the Rycote OM-08 with its max of 127dB was an order lower. And then, what about levels into the recorder? Well at least with the Sound Devices 788T I had the option of using line inputs, which can still supply 48v phantom power, if things got overly hot. Needless to say, such slightly nagging concerns were entirely unfounded: with the more distant 3 metres of the two arcs I was able to set all the mic input trim/gains at 20dB, and with the shorter 2 metre radius of the full circle, I was fine with 15dB. Perhaps more reassuring too, the reflected sound in the aisled abbey church seemed much less overwhelming than the practice rooms: or was I just acclimatising!
Set up in the south aisle with the Sound Devices 788T. No overloading of mics or recorder, and I didn’t even resort to the earplugs I brought along!
The results
With the native B-format array, the options are endlessly variable, but what follows are some short clips (around 30 seconds long) from the beginning of Scotland The Brave (my request, as familiar to many: but we did record a couple of other tunes too), covering the main options.
Another view of the band set up in two opposing arcs.
Starting off, here are clips from the recordings of the band arranged in two opposing arcs:
First, we have fig 8 mid-side with the two MKH 8030 mics, which, of course, decodes to a Blumlein pair:
The stereo imaging is good for this, but the bass drum is very light. Looking at this in an FFT frequency spectrum analyser (Voxengo SPAN), the fundamental of the drum is around 35Hz, so the lack of low end in the MKH 8030 (whilst unusually good for a fig 8) is rather exposed. With a coincident omni in the array we can add this in a variety of ways, but just to keep things straightforward here is the same clip above with the bottom end of the omni MKH 8020 mixed in (with a 100Hz low-pass filter) at -6dB.
So now moving on to the omni mid-side pair itself, which, of course, has no problem with the bottom end of the bass drum. As you would expect, the drums have swapped sides (most obviously the snare is now on the left as it was in reality) as this and the subsequent clips don’t have the flipped LR stereo of the rear side of fig 8 MS and Blumlein pairs:
Leaving the various outputs of the native B-format array for the moment to compare omni-based recordings, here is the omni AB (spaced pair) of Rycote OM-08 mics at 840mm spacing (the spacing chosen to match the stereo recording angle of the Blumlein pair, decoded from the fig 8 mid-side pair, which lay behind the two opposing arcs formation):
Next up we have double mid-side. This uses forward and backward cardioid mid mics (created by mixing the omni and forward-facing fig 8 in the native B-format array) with the two resultant cardioid mid-side arrays mixed at the same level:
This might well be fine with the full band (and the low end is certainly present, due in no small part to the fact that the cardioids are created from a mix of the forward-facing fig 8 MKH 8030 and the MKH 8020 omni, so, as my preparatory tests demonstrated, have a better bass response than the MKH 8040 cardioid), but the level of the very small drum section is a bit low. Of course, we can change independently both the polar pattern of the two mid-side arrays that make up a double mid-side array and, more relevant here, can change the relative levels between the front and the rear. So here is more of the same, but with the rearward-facing component of the double mid-side array 6dB louder than the front:
And to demonstrate this flexibility a bit further, here is the double mid-side array again, but with the rearward-facing component of the double mid-side array 12dB louder than the front:
And then in a full circle, with a tighter radius.
Moving on, here are clips from the recordings of the band arranged in a full circle. Again the clips comprise the opening part of Scotland The Brave.
As before, first off we have fig 8 mid-side with the two MKH 8030 mics:
This still lacks the bottom end of the bass drum as with the fig 8 mid-side recording of the two arcs, but I must admit that the effect of the full circle (i.e. not avoiding direct sound from the side, with the consequent phasing issues arising from the fact that such sound is picked up by the front of one capsule and the rear of the other) is much less noticeable than I thought it would be. Perhaps that’s just my ears (I have been listening to a lot of bagpipe recordings over the last few days)! Anyway, I think it might still be one to steer away from and, accordingly, I haven’t included a version of this clip with added low end from a low-pass filtered omni mic.
On then to the omni mid-side pair, which, as before, has no problem with the bottom end of the bass drum. Again note that the drums have swapped sides (most obviously the single snare is now on the left as it was in reality) as this and the subsequent clips don’t have the flipped LR stereo of the rear side of fig 8 MS and Blumlein pairs:
Here is the omni AB (spaced pair) of Rycote OM-08 mics at 460mm spacing (i.e. narrowed from the previous 840mm spacing to give the wider stereo recording angle required for the full circle: 180 degrees):
Next up we have double mid-side. This uses forward and backward cardioid mid mics (created by mixing the omni and forward-facing fig 8 in the native B-format array) with the two resultant cardioid mid-side arrays mixed at the same level:
As noted in the two opposing arcs set up, the drums in the double mid-side recording here are a bit on the quiet side, reflecting the lack of tenor and side/snare drums, although, perhaps counter intuitively, they are clearer than in the equivalent recording with the two arcs, despite the pipers spreading into the rear half of the full circle. As noted before, we can change, independently, both the polar pattern of the two mid-side arrays that make up a double mid-side array and, more relevant here, the relative levels between the front and the rear. So here is the same as before, but with the rearward-facing component of the double mid-side array 6dB louder than the front:
And to demonstrate this flexibility a bit further, here is the double mid-side array again, but with the rearward-facing component 12dB louder than the front:
High-frequency loss with vertical omni
As mentioned in part 1 of the blog post, omni mics are increasingly directional with high frequencies, which is the main reason to orient the mic vertically in the native B-format array if dealing with a sound source in a circle rather than, more typically, largely in front of the mics: that is, to ensure an even response in the horizontal plane round the full 360 degrees. But, of course, it also means that this approach reduces the high-frequency response (albeit equally) in the horizontal plane. As I said in the section on mic arrays, I didn’t expect that the high-frequency losses would be hugely significant with a pipe band: indeed, it could be useful given the nature of bagpipes and snare drums. I certainly don’t feel that results are weak in that regard, but, for the sake of completeness, here is a clip of the omni mid-side recording of the band in the full circle, with the omni mic given EQ to compensate as per Sennheiser’s polar plot for the MH 8020:
Using a plugin for processing the native B-format recording: in this case the (free) Soundfield by Rode plugin.
Processing
The native B-format array offers a lot of flexibility, which is only partly explored in the already rather numerous clips provided above. These have all been produced manually in Reaper, albeit using a mid-side plug in for the MS processing. Further tools can aid the process, be that Schoeps’s double mid-side plugin or, more usefully, plugins that can use the WXY tracks of the native B-format directly. So finally, here are the WXY clips (for both the opposing arc and the full circle set ups) for anyone who wants to play with them in an ambiosonic audio processor such as the Soundfield by Rode plugin, with which I have had fun dabbling.
The verdict?
Well this may be too early to call, given that this recording session was designed to be the first of two tests to compare indoors vs outdoors recording of the pipe band. The outdoor session will probably have to wait until September, due to holidays and a flurry of summertime engagements for the band, and then we will have to juggle the vagaries of the weather. But, even before this second test, I must confess I am much happier with recording the pipe band indoors than I was beforehand: I was very much in the ‘record a pipe band outside’ camp (indeed, perhaps the only voice in this case!). The set up in the abbey worked extremely well from my perspective: OK, the part-band was imbalanced in terms of pipes vs drums (and, indeed, imbalanced within the drum line with just one tenor and one side/snare), and there are some tweaks that I would like to make when we have a fuller drum line (e.g. bringing the tenor drums forward of the snare/side drums), but the acoustic was excellent and vastly different to the practice room.
And, beyond that, this first session has been extremely useful for assessing the different means of recording the band in a circle or in a broken circle of two arcs: I am happy with both formations although, of course, the different mic arrays performed differently in the two configurations of the band. The omni AB, or spaced pairs, worked reasonably, but lacked clarity on the snare drum so would require extremely careful placement of band members to get the (baked-in) balance right, if possible: in the context of a loud pipe band with members understandably not used to protracted setting up for recording and the lack of really good (and isolated) monitoring on location, I would be loathe to go down this route. This isn’t unexpected, as I included the spaced omnis as something of a control in this test. The native B-format array was a great success in giving so many options from a three mic set-up, and producing what I think is the better sound. Using the two fig 8 MKH 8030s alone, as a fig 8 mid-side pair, underplayed the low frequencies of the bass drum, understandably, but, as we have seen (or, rather, heard), this can be supplemented by a bit of bass from the omni MKH 8020 mic. Again using just two mics, the omni mid-side (MKH 8020 and MKH 8030) pair gave a good result in both the opposing arcs and full circle arrangements. The (virtual) double mid-side array from the three mics, however, is my preference: while sharing the ability to vary the levels of front and rear with a conventional double mid-side array (say made with two cardioids and a fig 8), the fact that in this case it was derived from the native B-format array gives it additional advantages. First, it keeps the low end intact (by virtue of the increased low-frequency response of the two virtual cardioids made by combining the MKH 8020 and forward-facing MKH 8030). And, second, it has complete flexibility in post in terms of the polar patterns of the mid mics. Playing around with all this is certainly easier in something such as the Soundfield by Rode or Harpex-X plugins, and they make steering the mic arrays (not that useful in this instance) easier too. In short, I’m really impressed by the MKH 8030 and MKH 8020 native B-format array for recording musicians in a circle: I suggest that it is worth giving something similar a go if you have a comparable challenge and suitable mics to hand.
