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Windshield tests

October 6, 2022

Decent wind protection is essential outdoors (and sometimes indoors), but quite what to use for different conditions isn’t always clear. Is a massive full blimp overkill for more benign conditions and, as well as size and weight, is it having an effect on the mic’s frequency response? Are simpler windshields, such as foams and softies, better in lower wind? Is one full blimp better than another in high wind? Is a cheap Rode blimp terrible compared to an expensive Rycote Cyclone? When choosing windshields I often grab what I think will be best for the conditions and use, but this involves a combination of experience together with some untested assumptions. Having acquired quite a few windshields along the way, it is high time I tested those assumptions. My collection of windshields doesn’t cover all brands, but it covers several types and, therefore, these (admittedly unscientific!) tests may have value beyond personal musing: I hope so.

LOW/MEDIUM WIND

For the first set of tests, I took a pair of Rycote HC-22 shotgun mics into the garden on a day with light wind, up to around 8 mph (13 kmh), with some stronger gusting: by no means what I would describe as a calm day, but not what anyone would say was a blusterous day. I used shotgun mics throughout all the tests as these are geared to the outside for film and TV sound, and even have some use in other types of field recording. Obviously other polar patterns – most noticeably omni mics – have a much lower sensitivity to wind noise. Since I’ve used shotgun mics that means I haven’t included some of the windshields I own that don’t fit these mics, such as the Rycote Baby Ball Gags or the Rode WS8.

For the low wind tests I recorded tests in pairs, working my way up from a bare mic to the most sophisticated windshield that I have (a Rycote Cyclone). The sounds recorded are the garden ambience, plus a bit of key jangling to get those high frequencies: I’m not certain I always got the keys equidistant from the mics, so don’t be misled by any volume differences arising. In all the tests there was no low-cut/high-pass filtering and the HC-22 mic has a better bass response than many a (dialogue-focused) shotgun mic, so all these tests emphasize the effect of wind: the WAV files will allow you to play around with EQ to try to remove the low-frequency wind in a DAW should you wish. Anyway, here are the first batch of tests:

Test 1: bare mic vs foam

The results are entirely as expected: massive (unusable) wind rumble with the bare mic and, while the foam improves things in the second test, it hardly represents a solution in such light winds. I wouldn’t use any mic outside with just a foam windshield.

Test 2: foam vs Classic Softie

Again, as expected, there is a significant difference between the foam and the Rycote Classic-Softie Kit (18cm), with such softie windshields evidently designed for outdoor use. There is significant wind noise with the softie, however, despite the light wind: a high-pass filter in post at 100Hz removes most of it. I guess softies are a viable solution if a) you are in light winds; b) are recording sources where heavy EQ of the bass doesn’t matter; and c) where size is critical (e.g. ENG work). Cost might come into play too (this softie, without the grip, costs around £80, and cheaper alternatives can be had), though it is highly questionable as to whether anyone recording outside with any degree of seriousness wouldn’t have a full blimp: and, of course, softie-styled windshields will only cover similar mics in your collection (e.g. in this case, medium-sized shotgun mics).

Test 3: Classic Softie vs Rode Blimp without fur

With the first full blimp in the tests – the Rode Blimp mk1 here used without its fur/dead wombat – there is a distinct reduction in wind noise and certainly no loss of high frequencies compared to the Rycote Classic Softie.

Test 4: Classic Softie vs Rode Blimp with fur

And now with its fur on, the Rode Blimp is, effectively, the first recording without wind noise. Looking at it in Reaper there is some essentially inaudible low-frequency rumble (e.g. starting at 17 seconds into the clip), that is easily removed with a high-pass filter; the rumble is very audible on the softie windshield and not fully removed by the same high-pass filtering (100 Hz, 2 octave). Which is reassuring: for the level of wind, degree of exposure, and mic pattern, a Rode Blimp with fur on is the minimum wind protection I would have used for such a recording. Perhaps experience has some value!

Test 5: Rode Blimp with fur vs Rycote Nano Shield with fur

With two blimps with fur unsurprisingly in this wind level there is no discernible rumble: this tests serves to show that the smaller Rycote Nano Shield NS4-DB is effective, and that there is no discernible difference (at least to my ears!) in the high frequency performance/acoustic transparency. The elliptical shape of the Nano Shield may have some benefits in some situations, but it’s not evident in this field test.

Test 6: Rycote Nano Shield without fur vs Rycote Cyclone without fur

Rycote makes quite a bit of the 3D-Tex material covering their Cyclone windshields, saying it ‘provides enormous benefits in terms of surface turbulence and acoustic impedance, resulting in wind-noise reduction comparable to the combined modular-style windshield/fur cover performance’, so I thought it worth testing the medium Cyclone without its fur, and, by comparison, the Rycote Nano Shield NS4-DB without its fur too (and just the basic grey sock). Both struggled with the relatively modest wind (OK a little breezier than in the previous test a few minutes earlier) and while the Cyclone fared rather better, wind rumble is pretty evident. That windier section from 25 seconds onward isn’t easily removed by modest high-pass filtering (100 Hz, 2 octave) even on the Cyclone: in these far from extreme conditions I would’t use either without its fur.

Test 7: Rycote Nano Shield with fur vs Rycote Cyclone with fur

Putting the fur on both the Rycote Nano Shield NS4-DB and the Rycote Cyclone medium removes the wind noise entirely, as expected. I can’t hear any difference in the high frequency performance/acoustic transparency between the two in this test, or, indeed, listening back to the previous test. I would expect that more scientific testing would reveal some attenuation of high frequencies with any fur added to a windshield, but it is a small price to pay vs wind rumble. Again, in anything but the very lightest of breezes, I would add the fur to a blimp, and these field tests have confirmed that as a reasonable modus operandi.

HIGH WIND

Moving on from the tests in more benign conditions, this part of the post focuses on tests in high wind. Accordingly I have ruled out the smaller and cheaper solutions: I know from experience that a Classic Softie won’t cut out the wind rumble and that even a full blimp with fur will need a low-cut filter somewhere along the chain to get an acceptable sound. So this test is simply between three full blimps I own and, given that the wind was gusting strongly, each was fitted with its fur.

The three windshields are:

Rode Blimp mk1: no longer in production this has the same basket and fur as the updated mk2 version that is in current production, although the latter is lighter and has lyre suspensions. This is an improvement for use with a single mic, especially if booming, but I prefer the mk1 version for its more adaptable suspension: I can fit two or even three SDC mics in it, still centralized and well away from the basket (it is 100mm diameter), for mid-side and double mid-side recording. The current version of the blimp sells for a street price of around £200.

Inside the Rode Blimp mk1, showing how it can be easily adapted for a mid-side mic pair. For the windshield test it was reverted to its normal mono mic suspension.

Rycote Nano Shield: this is the newest of Rycote’s long line of windshields, and is distinguished by its small size, light weight, tool-free adjustment, eliptical profile (internally the basket is about 105mm wide and 85mm high) and inbuilt (external) low-cut filter. It has other attributes, such as being flexible, that have less obvious benefits to me. I have two of the Nano Shields: a diminutive NS2-CA for short shotgun and hypercardioid mics, and the larger NS4-DB for medium shotgun mics. I have used the larger NS4-DB for these tests, given that I used the Rycote HC-22 shotgun mic. The NS4-DB has a street price of around £600.

Inside the Rycote Nano Shield NS4-DB: rear part of basket removed. The low-cut filter (not used in the tests, though these were the conditions where you might well use it normally), can be seen in the foreground.

Rycote Cyclone: this is the most expensive of Rycote’s windshields and, with its size and design, this very much suggests it is their most capable model. It comes in three basket sizes, and with a mono and a range of stereo and double mid-side internal mounts. My version is the mono medium Cyclone. The street price (including the separately sold fur) for this is around £720.

Inside the Rycote Cyclone Medium, showing the mono suspension fitted with the HC-22 shotgun mic used in the tests.

The high wind tests

The tests were pretty simple: the three windshields were mounted on a bar on a stand and faced straight into the wind, which was gusting to around 45mph (72kmh). Recordings of the Rycote shotgun mics (each at 26dB gain) were made simultaneously into a Sound Devices Mixpre-3, with no low-cut filter applied. I only have two Rycote HC-22 mics, so for these three-way high wind tests the third mic was a Rycote HC-15 (used in the Rode Blimp): I don’t think this invalidates the tests as it is such a close match to the HC-22, as demonstrated in my other tests/posts. The two Rycote windshields, however, did use matching HC-22 mics. The location was a garden in a quiet Norfolk village, so the wind can be heard hitting trees and hedges, as well as the mics themselves. I read a short piece of text to give some dialogue too (sorry: I am no voice actor!), and then afterwards in Reaper just spliced a few bits of the recordings together (to capture the reading and some wind gusting) and trimmed the length: no other processing (again, no low-cut/high-pass filter applied). Here are the three recordings:

Rode Blimp:

Rycote Nano Shield:

Rycote Cyclone:

All three WAV files here will allow readers to listen and play around with them themselves and draw their own conclusions. In terms of coping with high wind, there isn’t a vast difference: without a low-cut/high-pass filter and no attempt to seek a more sheltered spot all three are affected by the strong gusts as, indeed, I would have expected. The Rode does have a little more noise, again as I would have expected: this is evident by listening and by analysis, which shows its peak at-12.5dB vs -15.1dB for the Nano Shield and -16.6.dB for the Cyclone. Applying a high-pass filter in Reaper shows up the distinction a bit more, as it is much easier to cut out most of the low frequency wind energy with the Cyclone than with the other two windshields.

So where does this leave me? All three full windshields are effective, with the performance differences between them, while noticeable, much smaller than between them and the next tier down of windshields (i.e. softie types). The Cyclone is clearly the best in terms of pure wind noise reduction, so I’ll continue to use that where practical. If booming for dialogue (and that isn’t very likely in such high wind) or if travelling minimally, however, I’ll continue to use the lightweight and compact Nano Shield (and very possibly my still smaller NS2-CA for short shotgun and hypercardioid mics) instead. But if wanting mid-side or double mid-side flexibility, I won’t be worried about using my wonderfully adaptable old Rode Blimp. So no real change to what I do anyway!

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Audio Gear

EarSight microphones

June 5, 2022

Budget omni mics using the same very affordable 10mm capsules have been made for some years by small manufacturers, most notably  FEL Communications Ltd (Micboosters) in the UK and LOM in Slovakia. As I discussed in a previous post these use the Primo EM172 and, more latterly, the EM272 capsules: FEL/Micboostsers make this clear (and sell the bare capsules too), while LOM are rather more coy about what is inside their mics.

Intriguingly, a very similar looking – and similarly low-priced – mic has been introduced by another of these small-scale makers, again using a pre-made electret capsule: like LOM, Immersive Soundscapes in France (a one-man band – or autoentrepreneur) is equally reticent about what capsule is inside the mic, although the website is at pains to say it is equivalent to an EM272, but is not one! The specs match those of the AOM-5024L-HD-R capsule used especially in the US, but let’s hope that Immersive Soundscapes clarify the matter in due course. Certainly the specs, while close to the Primo capsule (including the respectable self-noise of 14 dBA), are different in one significant regard: the sensitivity is -24dB vs the EM272’s -28dB (with the maximum sound pressure level, or SPL, reduced from 122dB to 110dB). The full specs are given on the Immersive Soundscapes website.

Interested in hearing the different capsule, I asked Philippe at Immersive Soundscapes to send me a pair to test and review, which he was kind enough to do: in this case it was a pair of the P48/XLR mics (which retail for 85,00 €), but he also sells a PIP version with a 3.5mm stereo plug (75,00 €). The mics are well put together, within what looks to be the barrel of a 1/4″ (6.35mm) phono plug: an unbranded equivalent to the Neutrik NPX3. The slightly tapered barrel (around 13mm diameter) is rather small for off-the-peg shock mounts and windshields, so Philippe provides a push-on plastic collar that beefs up the diameter to 18.25mm. The mics are wired with about 1.5m of Sommer’s diminutive starquad (SC-Cicada 4) cable, and a Neutrik XLR plug. Physically then the mics are rather like the LOM Uši Pro mics, and are in contrast with the smaller housing of the Micbooster Clippy mics (which are smaller and lighter, effectively over-sized lav mics). The EarSight mics lack the mini-XLR connectors of the LOM Uši Pro mics, although I’m not certain how much use these are with such small mics.

So much for the look and feel of the mics: on to tests!

Interference

One of the annoying features of the Primo EM272 capsule is its susceptibility to interference. Indeed, Nick Roast at Micboosters even publishes a caveat to that effect: I have seen no such info on the LOM website and am not certain how their mics perform in this regard. Certainly, the problem is not one of the Clippy mics, but, rather, the capsule itself: making up mics from the bare EM272 capsules, I have found the problem with wifi interference, most obviously with the Rode Wireless GO ii. Given that this is the sort of thing recordists will plug a small mic into, this is a real problem. The EM172 (no longer in production) doesn’t have the issue and I’m very pleased to note that the EarSight mic is also immune to the Rode Wireless GO ii (and, indeed, mobile phone-based RFI). Good news indeed!

Even close up to the EarSight mic (left), there is no interference from the handy Rode Wireless GO ii: not so with the EM272 mic on the right.

Sound tests

And, finally, plugging in the EarSight mics to Sound Devices MixPre-3, for some field tests. Needless to say, all the test recordings are without any effects, processing etc. First off, it was good to hear how the stereo pair handled some typical ambience – very much the target use of the mics.

EarSight mics as stereo spaced pair: 30cm spacing, in Rode WS8 windshields and on Rycote Invision 7 shockmounts.

So here’s an initial test of a supposedly quiet village street ambience. The 80Hz low-cut filter was enabled on the MixPre-3 to remove the excessive bass (for which, read on).

Comparing the mics, clustered together inside a Rode blimp (outer parts removed for the photo, obviously!)

Exploring the low frequency response of the mics rather more, here are some comparative (mono) tests, with three mics (the EarSight, an EM272 mic in the form of a Micbooster Clippy, and a Rode NT55 with the omni NT45-O capsule). I recorded various tracks, but this one, with a background engine (I think a tractor or JCB several hundred meters/yards away) and then an aeroplane is quite instructive.

The extended bass of the two 10mm capsules (i.e. the EarSight and the EM272 in the Clippy mic) is rather overwhelming compared to the NT55 omni capsule. Just to be sure that the latter wasn’t bass-shy for some reason, I swapped it for an AKG CK92 omni (with a very flat response) and it was very similar to the Rode mic in this regard. In short, the low-frequency response of the two 10mm capsules appears extended or exaggerated. Either way, it isn’t something normally wanted for ambience recording, so I subsequently used the MixPre-3’s low-cut filter, setting it at 80Hz. With the lowest frequencies reduced, the recordings were more comparable and useful:

Certainly, the EarSight and the EM172 Clippy mic sounded fairly similar: the AKG CK92 rather different, as would be expected. Matching levels between the mics involved using a 1kHz tone and pinknoise sources, which saw gain on the MixPre-3 set as follows: EarSight 20dB; Clippy 33dB; and AKG CK92 41dB. There was some fine tweaking in Reaper afterwards to match these more exactly in terms of LUFs, but that is a rough guide to the different outputs of the mics: the sensitivity of the EarSight mic was unexpectedly high.

Of course, high sensitivity means low maximum sound-pressure level (SPL), and the EarSight mic’s spec certainly shows that with its 110 dB max SPL. For much in the way of nature or ambient recording that shouldn’t be a problem (save thunderstorms, whales or an elephant’s trumpet close up!). But it does limit things for some recording activities: loud sound effects or some musical instruments (e.g. percussion or brass close up). You can certainly hear the distortion kicking in on this spot miking of some (poor, I know!) playing of a cajon (initially with the mics to the rear, then at the front): and that’s mic distortion, not overloading of the preamp input. Again, the EarSight mics is compared to the Clippy (EM172) and AKG CK92 mics: no high pass/low cut filters.

But there’s no such issue when recording an acoustic guitar close up (25cm from 12th fret). Again, apologies for lack of musicianship, but hopefully it is sufficient to make the point!

And, for light relief as much as anything, here’s a stereo recording of a melodeon played by Rob Moore, using the EarSight mics. Well, I say stereo, but it’s that classic melodeon/accordion technique of one mic either side.

Rob Moore getting to grips with a new melodeon with an additional key (more buttons!)…

Conclusions

It’s not that easy from some fairly quick and dirty samples to draw too much in the way of conclusions. For example, the AKG CK92 doesn’t sound too great on the guitar, but, from much wider experience, I’d rather tackle music recording with the CK92 than either the EarSight or the Clippy mics: it was a poor (small) room, mediocre instrument, and less than ideal placement. But what can be drawn from these tests is that the EarSight mic is sonically very close to the Primo EM172/272-based mics; in this case Micboosters Clippy, but, equally, the LOM Uši Pro and other mics with the same capsule. It doesn’t have the issue with wifi RFI that can affect the EM272 capsule, and is much more sensitive. For those recording all but the loudest nature/ambient sounds then this is a real positive, especially – as is so often the case – if recording with less than stellar preamps: with the excellent MixPre-3 this was not significant, but with a handheld recorder this would really tip things in favour of the EarSight mics (or any made with the same capsules). So it is a useful addition to the ranks of small, cottage-industry assembled mics from pre-existing capsules. Given that the Clippy P48 mics are currently £125.94 a pair and the (seemingly always sold out) LOM Uši Pro mics are €130.00 a pair, it looks as if the EarSight mics are something of a bargain.

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Audio Gear

Rycote HC-22 vs Rode NTG5

December 19, 2021
Rode NTG5 (bottom) and Rycote HC-22 (top), mounted with capsules aligned.

As I said in my original review and tests of Rycote’s new shotgun mics pricewise they sit in rather unpopulated territory, above the equivalent mics made by, say Rode, and below the professional shotgun mics made by Sennheiser, Schoeps, DPA etc. Since comparisons with other mics are few and far between, this weekend I spent some time comparing the Rycote HC15 and HC-22 mics with the newest and arguably most comparable of Rode’s shotgun mics – the NTG5. With prices of £672 and £690 for the HC-15 and HC-22 vs £495 for the NTG5, there is quite a gap: more so, when discounts of Rode’s more established 2019 mic are taken into account (though, I have noticed some discounts already on the Rycote mics). So this is more a case of seeing what more do you get for the extra £200 than really expecting the Rode to match the Rycotes: though good to keep an open mind as, of course, Rode have a lot more experience at making mics.

First off, I compared the self-noise in the real world. Both the HC-15/22 and the NTG5 have low self-noise specs, at 8.5dBA and 10dBA respectively. As I pointed out in my original review, the low-self noise of the Rycote mics seems borne out in real-life (being pretty much indistinguishable from that of the LDC Rode NT2-A, with its 7dBA self-noise): measuring self-noise of the HC-15/22 and the NTG5 showed a difference of 2.5dB, which is rather more than the expected 1.5dBA from the specs. Given the previous test against the NT2-A, it seems that the Rycotes are in fact a little quieter than the specs suggest. In this vein, it is interesting to note that on Rycote’s Facebook page for 26 Sept they note the following: ‘Updated spec sheet available on our website. Please note an update we made to the self noise. Our pre-production batches were all clocking in right at 6 dB. Now that we have moved to full production the mics are clocking in at 8.5 dB. This is not unusual given that we now have larger batches of components that don’t always line up to perform the exact same. So rather than keep the self noise at 6 dB (+/- 3 dB) and claim to be “within tolerances” … we adjusted it to 8.5 dB so you know that’s what you can expect when get one of these mics.’ It seems then, that 8.5dBA is conservative and that some mics at least, such as my pair, are noticeably better. Of course, not all self-noise sounds the same, so here are the unedifying sounds of both for comparison, with the mics buried deep under duvets etc. in a quiet house with the faintest sound of a loud clock ticking:

So there is a little bit of a difference in the tone, or spectrum, of the self-noise as well as the level, but nothing hugely significant: both the Rycotes and the Rode shotgun mics are extremely good in this regard.

Next test was outside booming of dialogue – obviously the main use of such mics. With the mics mounted closely together (see top pic) in a Rode blimp, and with the boom pole held static by use of a lightstand and Boombuddy, I recorded on-axis and off-axis sound. In the samples here, you hear the on-axis sound followed by a brief silence then the sound at 90 degrees:

Some significance difference here then: the HC-22 (and I am using this one in the blog post to compare to the NTG5 as nearer to it than the HC-15) sounds much clearer to my ears both on and off-axis. As per my original review of the Rycotes, the off-axis performance of the mics seems pretty good in terms of low colouration (which, though hard to achieve with an interference tube, is what we all want).

On now to a test of the mics indoors, in tough conditions for a shotgun mic: a small living room with a very low ceiling. What isn’t apparent from the tests below is that the mics were never still, but were on a swinging boom continuously moving with the subject, about 300mm from the talent’s mouth. This was to avoid the problem with many static indoor mic shotgun tests where the mic can happen to be placed well, with no problems from comb filtering. Neither recording sounds very good, but neither sounds as bad as you might fear in such a space. Most would use a hypercardioid in such a situation.

Rycote HC-22 and Rode NTG with AKG CK94 (fig 8) in Rode blimp suspension for mid-side recordings

Then, finally, for stereo ambience recording it was back outside to hear how the HC-22 and NTG5 compare being the mid mic in a mid-side stereo pair, with the fig 8 side mic being provided by an AKG CK94. The ambience is another recording of the street in this small Norfolk village, with cars passing and, given the murky weather this weekend, dripping of water from fine rain and mist condensing on trees. Horrible! But both mics did a good job.

So, what to conclude? Well, while both mics seem fine, personally I much prefer the Rycote mics. The most telling tests were those I did of outside dialogue and the example I posted above reveals the difference more than the other tests: the Rycote mic has a much clearer, more open sound than the Rode. Given that outdoor dialogue is the primary use for such mics, that is pretty telling. Whether it is worth £200 for the improvement is, of course, up to others, but I would suggest that the Rycotes happily play in more exhalted – and expensive – company. Worth a good listen and test, or even adding to your Christmas list (if you have anything so mercenary)!

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Audio Gear

A windy weekend with the Rycotes

November 8, 2021
Rycote HC-15 and HC-22 shotgun mics in Rycote Nano Shields: furry windjammers needed too in 34 mph wind.

Last weekend was blowy and autumnal here in Norfolk, so I had a bit of fun out in the wind with the Rycote shotgun mics that I have been testing, in this case with the new Rycote Nano Shield kits: the NS2-CA for the HC-15 short shotgun and the NS4-DB for the HC-22 medium shotgun. The Nano Shields are impressively light and small, even if the deliberately bendy (but resilient) structure seems a bit unfamiliar to start with.

First up, I simply stuck the mics in the garden of this quiet village, facing the road, so you can hear the sounds of wind in the trees, passing cars, and the odd actual shotgun going off. With no low-cut switches on either mic, the 80 Hz switchable low-cut filter on the XLR connector seemed useful so here is the HC-15 with no low-cut (or high-pass) filter:

And here is a recording made at the same time, but with the HC-22 and its low-cut filter switched on:

OK, there could be a difference between the two mics or the effect of the different sizes of their Nano Shields, so here’s the test reversed. First, the HC-15 with its low-cut filter switched on:

And then the HC-22 with no low-cut filter:

So the verdict: in high winds the Nano Shield 80Hz low-cut filter is effective, especially with mics such as Rycote’s own ones with no in-built filters. Evidently the new windshields and mics were considered together. There’s no sense that the wind is overloading the mic to the degree that the low-cut filter is too far down the chain to be effective. Of course, this means that you can apply a low-cut filter at the preamp stage: how good this is will depend on your preamp/recorder, but I found no discernible difference when using my Sound Devices MixPre-3 80Hz low-cut filter. This doesn’t mean that there is no value in having a low-cut filter at the Nano Shield stage since in severe wind conditions you can double up: e.g. set the MixPre-3 low-cut filter (perhaps to say 40Hz) and apply the Rycote 80Hz low-cut filter too.

While doing various tests in the garden, out of idle curiosity I also set the two shotgun mics up as a NOS pair (capsules at 30cm spacing, angled out to 90 degrees between the mics). Despite being manifestly different mics, the identical capsule and preamps mean that it works surprisingly well. If nothing else, it’s a demonstration of how well the two mics match if cutting from one to the other. Sorry about the rather theatrical footsteps stamping past at one point!

Out in the woods on a windy day with Rattlebox for some mic tests…

Off then to the woods to test the mics in wind on something different. Perhaps it’s just me, but the woods around north Norfolk in early November seem pretty dead in terms of sound apart from wind (maybe I simply lack the patience to lurk about for hours like a real wildlife sound recordist?), so for a bit of acoustic interest I persuaded Norfolk’s raucous folk band, Rattlebox, to do some unaccompanied singing (Dick Shannon’s ‘The Auld Triangle’): this was also for my tests on double mid-side recording with two forward-facing mics, for which see my separate post. Anyway, in terms of the Rycote mics, here’s a rather unfair test of the HC-15, pointing into a semicircle of singers – fine for the lead vocalist, but, as intended with a shotgun mic, rejecting much of the other singers in the choruses that were more side-on to the mic:

Combining with an AKG CK94 for a mid-side pair changes things rather, as you’d expect. The HC-15 works rather well in this manner:

Finally, returning to the stereo experiment in the garden (above), I set up the HC-15 and HC-22 as a NOS pair (as shown in the photo above – which also shows a double mid-side rig in a Rode blimp), with the following result:

Again, I’m not recommending mixing a short and a medium shotgun as a stereo pair, but it’s not bad.

So the final word on the wind tests? Well, needless to say these were much more extensive than shown in this short post, but it is clear that the Rycote mics handle themselves fine in windy conditions. The Nano Shields – which I haven’t reviewed as such – are a good match and their performance belies their small size and light weight. Finally, and rather incidentally, those slightly tongue-in-cheek NOS stereo pair tests with the two different mics confirm both that the off-axis sound is rather good, and that the two different mics match very well.

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Audio Gear

Variation on double mid-side recording

November 7, 2021
AKG Blueline mics used for these tests, top to bottom: CK93 (hypercardioid), CK94 (fig 8) and CK92 (omni): initial rig.
Second setup, bringing the three mics closer together (5mm apart): physically more stable, mics further from edge of the blimp, and fewer phasing issues.

Mid-side recording is a familiar technique to most sound recordists: a coincident stereo pair that is flexible and handy (not least as it can fit in a blimp or windjammer more easily than most pairs). I’ve written previous posts about my mid-side rigs, both for LDC mics and SDC mics. Double mid-side, where the fig 8 side mic is used by two mid mics – one facing forward and one facing backwards – is less used, but still well known, mainly by those recording surround sound. But, of course, the fig 8 side mic can also be shared with two (roughly) forward-facing mid mics: say one pointing up to the mouth of a singer-songwriter and one down to their guitar. Matrix the two mid-side pairs and you have stereo for both vocal and guitar, with reasonably little spill, and – with all three mics coincident – no phasing issues. Hugh Robjohns wrote an article for Sound On Sound about this use a few years back.

But there is another use for double mid-side with the two mid mics facing forward, and one that is rarely used or described: that’s where the two mid mics are pointing the same way but have different polar patterns. Using, say, omni and hypercardioid mid mics, you can matrix either with the side mic and get omni or hypercardioid mid side or matrix both and mix and you can get all the polar patterns in between for your mid mic: say, wide cardioid or cardioid as well as the omni and hypercardioid. This flexibility in polar pattern is quite separate from the familiar aspect of mid-side recordings, where you can vary the width of the stereo image by changing the proportion of mid to side mic: with this arrangement you get both stereo width and polar pattern flexibility in post, and – if using SDC mics – all with a very compact three-channel rig. As you can see, with a few Rycote back-to-back clips you can even fit it in a fairly standard 100mm diameter blimp.

Here’s a vocal test with a group (Norfolk’s raucous folk band, Rattlebox) arranged in a semi-circle around the mics outside on a very windy day (about 20 mph wind), singing Dick Shannon’s ‘The Auld Triangle’: the test was in part to see if the mics would be OK stacked in a standard (in this case Rode) blimp in reasonable wind (the top and bottom mics were nearer to the edge of the blimp than is ideal: at this stage I hadn’t come up with the more compact triangular array). The configuration needs the fig 8 centrally, which is good as fig 8 mics are the most sensitive to wind. The three mics had their 75Hz low-cut filters engaged to counter the wind noise. I matrixed, or decoded, each mid-side pair, so in the video you hear these on their own and then mixed 50:50. In the video, I call this mix of the two pairs a ‘virtual cardioid mid mic’) as it isn’t far off mid side with a cardioid mid mic: of course, a seamless range of possibilities from omni to hypercardioid is possible.

And here’s another test, this time with a guitarist (Luke Chapman) in his workshop (by day Luke is a woodcarver), with the same matrixing/decoding options. With no wind to contend with, the three mics have no low-cut filters engaged. Of course, the smaller sound source of a guitar means the changes in mid-mic polar pattern are fairly subtle.

How best then to process the three channels of audio in post? Well there might appear to be three options: 1) mix the two mid mics first, then decode to LR stereo as per normal mid-side; 2) decode each mid-side pair then mix the resultant LR stereo files; and 3) decode one mid-side pair then mix in the additional mid mic.

A bit of maths shows the first two are identical:

Mixing the mid mics first:
M = μM1 + λM2
L= μM1 + λM2+S
R= μM1 + λM2-S

Decoding each mid-side pair then mixing:
L1=M1+S L2=M2+S
R1=M1-S R2=M2-S
L=μL1+λL2
= μ(M1+S)+ λ(M2+S)
= μM1 + λM2+S

Decoding one mid-side pair then adding the M2 mic (centrally) to the stereo pair, however, gives a different result (as, indeed, you might conclude intuitively when thinking about it):
L = μ(M1+S)+ λM2
= μM1 + λM2+μS

So avoid this third option.

[NB I’ve just done the L channels in the second and third examples, to reduce the off-putting maths…]

In my case, I’ve gone for the second option as it is difficult to determine what mix of mid mics you might want – i.e. what mid-mic virtual polar pattern – without hearing the stereo sound. I must now set up my DAW (Reaper) so that raising one stereo channel reduces the other by the same amount to make assessing the balance/mix easier.

In terms of monitoring when recording you can either just listen to the channels in mono or, with any reasonable recorder, send two of the channels (the fig 8 and, say, the hypercardioid) to be decoded in the headphone monitoring or in the LR mix (either are possible on my Sound Devices MixPre-3): in this way you get confirmation that at least one of the stereo pairs sounds as you want it. With time on your hands, you can, of course, check the other pair in LR stereo too.

UPDATE (9.11.2021). By request I’ve recorded some ambiences (just my quiet Norfolk village street from my garden) with this rig and have uploaded the iso tracks (AKG CK92 omni; AKG CK93 hypercardioid; and AKG CK94 fig 8), the two separate MS recordings (as LR stereo) and the combined MMS recording (giving something akin to cardioid MS). These recordings were made with my modified array (i.e. the mics set in a more compact triangular arrangement, each only 5mm apart from the others).

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