DIY Projects

ORTF: working towards a minimalist approach

November 15, 2024

The near-coincident ORTF stereo pair has a huge following that extends way beyond the remit of the body for which it was invented – the Office de Radiodiffusion-Télévision Française – and long after its demise in 1975. The required 110 degrees angling of the mics and diaphragm centres at 170mm spacing can be set up with any stereo bar. Or you can always use the Schoeps MSTC 74 ORTF mic (or its predecessor, the MSTC 64), where the spacing and angles are built in. And if you don’t have nearly £3k to spare, there’s the similarly designed Superlux S502 at around £100. But, evidently, there are many that find setting the angles and spacings on a stereo bar too fiddly by far (it’s certainly harder to eyeball 110 degrees than a right-angle); many who don’t want to splash out on a dedicated (but inflexible) Schoeps solution; and many who want something of higher quality than the Superlux. As a result there are many dedicated ORTF mounts available for SDC mics. These include offerings by major mic companies, such as DPA’s CXO4000 (which can also mount an XY pair) and, more recently, commercially available 3d-printed options. Ostensibly neat solutions, these dedicated mounts hold the mics directly, and can then be fixed directly to a mic stand: attempts to introduce shock-mounts then become clumsy, typically using Rycote lyres for the whole rig (fixed on a stem protruding from the bottom of the ORTF mic holder, and at 90 degrees to the intended use: a real shot in the foot). Come to think of it, an effective shock-mount or suspension for the Schoeps MSTC 64/74 or Superlux S502 isn’t immediately obvious: a Shure donut perhaps?

ORTF using a standard stereo bar (the small K&M 23550) and the smallest lyre/hoop mounts that I know: the Radius Windshields RAD field edition mounts. Rycote InVision INV 6s would be a larger alternative. The red hoops are a test run of softer 55D shore ones, and will go into production soon in a more subtle dark green. This is a fairly minimalistic ORTF rig with properly set up shock-mounts, but there is no denying that setting angles and spacing is a bit fiddly.

With a 3d-printer to hand, I wondered about a neater solution, using mics mounted correctly in suspensions (as if, for example, using a pair of Rycote InVision INV 6s or, smaller, Radius Windshields RAD field edition mounts on a standard stereo bar), which would then be fixed to a dedicated ORTF bar: the best of both worlds. First off, I designed a simple mount with size slots to fit both Rycote lyres and Radius Windshield hoops. The latter can fit Rycote mounts, but not vice versa. The three slots to each channel allow a bit of flexibility in the placement of the lyres/hoops for different mic models. I added a cable grip at the rear to help isolate the mics from cable-borne vibrations and, for my personal usage, designed this to perfectly grip a Sennheiser MZL cable: in my usage the ORTF mount will be used for MKH 8040 mics with MZLs. Taking a more minimalist route with MZLs made me think a bit more about the suspensions and clips, so I ordered a pair of 19/20mm clips from Radius (much more minimal than their chunky universal clips) and a pair of their 8mm clips (designed to hold the rear of a Sennheiser MZL or a Schoeps Lemo connector). This works fine although there is a mildly disconcerting slope to the mics as a result of the centres of the two clips being slightly different (they didn’t originate as such a pair), but the ORTF mount can be angled freely anyway: for this the bar makes use of a Gravity Quick-Tilt Microphone Adapter (MS QT 1 B).

With the same hoops mounted on the 3d-printed ORTF bar.
And angled a bit to show the construction of the ORTF bar more clearly.

So far so good, but when talking to Simon Davies at Radius about the different centres of the clips, he suggested that I try the two clips individually: that is, use one hoop only (the curved profile giving the new hoops more stability when used singly than the flat lyres from his Rycote days), and suggested I try the 8mm clip only. That was food for thought, so with the ORTF mount I tested the following:

8mm clip with single RAD-2 (21b) hoop x 2 (the control)

8mm clip with single hoop 21b vs two 21b hoops with 19/20mm + 8mm clips

8mm clip with single hoop 21b vs 19/20mm clip with single hoop 21b

8mm clip with single hoop 21b vs 8mm clip with single RAD-1 (21a) hoop

8mm clip with single hoop 21b vs single Rycote lyre 72 shore

8mm clip with single hoop 21b vs no shock-mount (another sort of control!)

With structure-borne noise transmitted from a suspended floor via the stand, the 8mm clip with a single hoop 21b sounded the best: in my test it offers less transmission of the lower frequencies than the 19/20mm hoop (or the latter with two hoops and an 8mm clip in the rear hoop), which I suspect is due to the fact that the 8mm clip is holding the rubber element at the rear of the MZL rather than the mic body direct. I couldn’t really hear/see any difference between the RAD-2 (21b) and RAD-1 (21a) hoops with the single 8mm clip. The single Rycote lyre worked OK on its own with such a light mic, but, connecting to the mic body, again transmitted much more than the 8mm clip. The absence of any shock-mount was definitely much worse than any of the clip/hoop/lyre combinations, as one would expect! So the conclusion is that the single-hoop and 8mm clip is an excellent idea for an ORTF mount for static mics with MZLs (sans windshield: or, indeed, inside a large windshield).

So with these useful tests in mind, I quickly modeled and printed a shorter version of the ORTF mount, this time with just with two slots – for one hoop for each mic. With the RAD hoops set with the concave side forward (orientation of the hoops is irrelevant as long as opposing if in a pair), the MKH 8040 sits nicely forward of any suspension or mount that could have an acoustic effect, and the whole arrangement has a certain minimalistic elegance (though I say it as shouldn’t, as my great grandmother would say).

Here’s the 3d model of the mini ORTF mount/bar.
A view of the single-hoop ORTF mount, this time with the 62D-shore hoops.
The view from the rear: the cable grips are important to both stop transmission of vibrations along the cables, and also to set the angle of the mics. I was a little sceptical that the cable clips would do both, but testing very much shows they do. Obviously differently sized cables than the Sennheiser MZLs used here would need different cable clips in the 3d-printed mount, but that’s part of the beauty of 3d-printing: you can design something that works for you!

It was only yesterday, after having modeled and printed these different ORTF mounts, that I received the 55D test hoops from Radius Windshields, in their ‘Evil Red’ colour. I had suggested the idea to Simon Davies as with Rycote lyres I felt that many end up using too stiff a suspension for a lightweight static mic with no windshields – be that for indoor effects or for music recording. Both Rycote and Radius are primarily geared to production sound markets, and those using mics statically often forget this and that there is a substantial difference between the needs of a mic that is moving – often quite quickly – on a boom-pole or in a pistol grip (think of the momentum involved) and a mic that is completely static, and where the aim of the suspension is to reduce the impact of structure-borne noise transmitted from, or through, the floor and then through the stand. So today I tested the 55D shore hoops on the mini ORTF bar, and they reduced low-frequency transmitted sound significantly, which can be useful on those occasions where you do not want to roll-off the low end of the mic. The MKH 8040 mics with MZLs mounted in 55D hoops (in the eventual production colour of dark green) and the mini ORTF bar (which I will now 3d print in black) will make a very minimalistic, discreet and well-suspended pair that are quick to set to the ORTF configuration on those occasions when I steer away from my favoured MS pairs. Sorted, as they say!

Just for completeness, here’s my comparison of the effectiveness of the 55D hoops vs the 62D hoops:a useful reduction in low-frequency structure-borne noise for those occasions (particularly when recording music: think of organ recordings, or even a standard piano where the lowest note is 27.5Hz) where you don’t want to use a high-pass filter.

Obviously the ORTF mounts shown here are very much tailored to my use, with MKH 8040 mics with MZL cables, but just in case anybody else wants to 3d-print these ORTF bars (free of course!), here is a link to the larger version for two Radius hoops/Rycote lyres per mic and here is the link for the more minimal one for a single Radius hoop. For others with very different mics and different cables, perhaps this DIY project will give a bit of inspiration!

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