I fear that using multiple capsules in parallel for ultrasounds might have
problems with the receving beam lobes, as the short wavelengths captured by
separate transducers might not add in phase ....
on the contrary, if you want to have a directional mic for ultrasounds the
multi capsules configuration gives you a good frontal lobe and - difficult
to control - lower sidelobes.
2018-02-26 7:52 GMT+01:00 Gregory O'Drobinak
> The idea of clustering the capsules close together is a good one.
> But I would run separate wires for the EM-258s because of their worse S/N
> ratio and also since 4 capsules won't work with PIP.
> However, I am not sure how ultrasonic mics would perform in a SASS-type
> You need to try it and see if it gives good imaging at very high
> David Dunn has made some ultrasonic mic boundary arrays that claim to
> have unidirectional response, but it is more likely hemispherical in
> Here is a link:
> He uses an extended range MEMS mic facing a boundary plate about 1 -2 mm
> I can't find the build doc online right now, but I have the data somewher=
> I'll post it when I find it.
> Good luck!
> - Gregory
> *From:* " [naturerecordists]" <
> *Sent:* Sunday, February 25, 2018 2:50 PM
> *Subject:* [Nature Recordists] Esoteric Mic Builds: Multi-style Capsule
> It's looking like I might have a chance to travel to Austin, Texas, some
> time this summer. There are some great opportunities to record Mexican
> freetail bats while I'm there (Congress St. Bridge, Bee Caves, etc.) but =
> don't have much in the way of ultrasonic-capable microphones.
> We only have one very rare species of bat where I live here in Hawaii, so
> I haven't had much of a need for ultrasonic mics. I'm more than willing t=
> build some, but I don't want to pour a lot of effort into a mic I'm going
> to use for a week, and then not need again for years, if ever.
> While I was looking at some of the capsules Nick Roast has on
> micbooster.com, a thought occurred to me: I've got all the bits and
> pieces to build a dual-capsule EM-172 SASS similar to the one Vicki Powys
> describes on her web site: https://caperteebirder.com/?page_id=3D284
> If I picked up four EM-258 capsules and either wired them in with the
> EM-172 caps, or ran a completely separate set of wires, I could potential=
> build a dual-range SASS (20Hz-20kHz on the EM-172s and ???-96kHz on the
> EM-258s). The EM-258 capsules wouldn't raise the cost of the build by tha=
> much, and in the end I'd still have an SASS I could use in my largely
> bat-free environment here once I'm back from Austin. This would also help
> solve the issue of luggage space since I'm going to Austin for a conferen=
> and really can't pack gobs of recording gear for the trip.
> My thought is to cluster four capsules for each of the two wings on the
> SASS: two EM-172s and two EM-258s. I haven't worked through the packing
> densities in CAD, but I should be able to keep everything pretty close
> Does this seem reasonable? Or am I barking up the wrong tree with this
Centro Interdisciplinare di Bioacustica e Ricerche Ambientali
Universit=E0 degli Studi di Pavia
Via Taramelli 24, 27100 Pavia