want to build PZM

Hi,

I've asked this already before but, since this board has grown so much in the last months, i like to refrain my question...

Have you build a PZM and did you get good results with it?
I'm looking for a few to build myself as i really like em in kickdrums and for miking up rooms.

Cheers,

Tony

PS edited to detautologise

[quote author="tony dB"]PZM mike[/quote]

The "M" in PZM stands for microphone... What do you call it when you say something twice like that? I know there's a name for it :?...

Anyway, I'm pretty sure that the nice folks over at the micbuilders group have done this. Do a search over there.

Peace,
Al.

[quote author="alk509"]What do you call it when you say something twice like that?[/quote]

Tautology! That's what it is :grin:.

Peace,
Al.

PZM stands for pressure zone microphone, aka boundary microphone.

Tony,

You can use any omni microphone as a PZM. I was using my tube mics based on C4 capsules, and also my modified ECM8000, with good results. Make sure that physically, capsule is as close to the boundary as it is possible, to avoid LF loss. As a boundary you can use any surface--floor, plate, tape the mic to a wall, etc. If need more uniform omni polar response, mount it perpendicular to the boundary, facing its surface. In this case you will need to experiment a little bit with the distance to avoid resonant chamber created by air volume between diaphragm and boundary surface.

The Crown PZM, with the capsule mounted in a little arm over the surface, is supposedly a flawed design. The correct method is just to flush-mount a capsule in the surface, ideally with the membrane exactly flush with the surface.

In other words, take a little Panasonic omni capsule, drill a hole in a sheet of plexiglass, and stick the capsule in from the back. That's basically the concept.

tautology is my middlename, name.

[quote author="Marik"]PZM stands for pressure zone microphone, aka boundary microphone.
[/quote]

Yeah, I am really slow today.... or always?

Maybe interesting for you.

Here is some small info about PZM:
http://web.telia.com/~u31617585/

--Bo

> Make sure that physically, capsule is as close to the boundary as it is possible, to avoid LF loss.

HF comb-filtering, not LF loss.

LF loss is caused by too-small boundary. The 4-inch plate nomrally supplied is a boundary and "pressure zone" only above 3KHz. For full PZM effect to 50Hz, use a 10-foot plate (in practice, always a wall or floor). Since we can often use PZM effect just above 250Hz, a 2-foot plate is popular for overhead hanging; less if we want crisp highs with blended lows.

You can use a fat old EV-635A as a PZM. EV even made foam "mice" for the purpose. With a 1" capsule 1/2" off the table, it comb-filtered above 6KHz, but gave really nice speech response. I'm not sure the Crown design is "wrong": it gives a compact layout (1/8" error) and they had to do something about the severe ringing in the capsules they used (significantly modified hearing-aid mikes). Yes, a P-Sonic face-up in a hole, or set sideways in a groove, works fine too.

You can see the PZM effect. Record an impulse source (rim-shot) with an omni mike to a waveform editor. Try with the mike out in the room, then 2 feet, 1 foot, 6 inches, etc from a hard wall. As you get near the wall the echo off the wall will appear and rise in level. When you get close-enough to the wall, the echo and the direct sound merge, echo gone, double the peak level.

Hi,
the PZM system is a wrong boundary layer mic system.

With the Crown PZM type the sound cannot reach the Mic directly, because the mic is directed toward the sound-hard boundary surface.

Here is a pdf where you can see on the left pictures the wrong System (crown PZM) and on the right pictures the correct system. Its in german but you can try to put it in "altavista translation" or similar...

http://www.sengpielaudio.com/ZweiVerschiedeneGrenzflaechenmikrofone.pdf

Thanks for participating;
very interesting reading so far.
Any hints on the electronics behind the P-sonic capsule?

Tony

[quote author="tony dB"]Thanks for participating;
very interesting reading so far.
Any hints on the electronics behind the P-sonic capsule?

Tony[/quote]

How fancy do you want to get? A phantom-powered circuit isn't too hard, or you can just do it with a capacitor, a resistor, and a 9v battery.

i would like to be in the same ballpark as Crown, Shure, Tandy...
or better :grin:

Cheers,

Tony

and phantompowered of course, i hate batteries that always run out of power when you need them most + batteries are getting very expensive overhere (dangerous to the environment),

hail to the sansbatterie studio :wink:

Tony.

Here's a circuit I use to phantom-power those electret capsules:



This circuit assumes the "Linkwitz mod" to the capsule, which rearranges the hookup to the internal FET for lower distortion.

I need to update that note on the resistor values on the bottom, basically higher resistances (say 5.6K) give better SPL handling, lower (say 2.2K) give a bit lower noise.

Any hints on the electronics behind the P-sonic capsule?

Click to expand...

Hi Tony,

The ESP #93 circuit might just what you're looking for:
http://sound.westhost.com/project93.htm

I've build these circuits with the ESP-PCBs, these are good value for money. I hope it's OK to link the follwing pics:


I'm using them with the current Radio Shack boundary-mics (33-3022)
but have the feeling those mics are the weakest link now and could use a better capsule and/or the 'L-mod' for more signal handling.

A simpler method is like Joel did but you can't use long cables (as also mentioned in the ESP-article):
http://prosoundweb.com/recording/tapeop/buildmic/buildmic_16_1.shtml

The hardest part of this all is perhaps how to get Panasonic capsules - as I understood these are now hard to get.

Bye,

Peter

Thanks Peter

[quote author="clintrubber"]

The hardest part of this all is perhaps how to get Panasonic capsules - as I understood these are now hard to get.

Click to expand...

Hence my next question, anyone knows a good source to get these Panasonics?

[quote author="tony dB"]Hence my next question, anyone knows a good source to get these Panasonics?[/quote]

They have been discontinued. There's some people selling Transound capsules, which they claim sound just as good.

Again: you really, really need to check out the micbuilders group. Go to http://groups.yahoo.com/ and do a search for "micbuilders".

Peace,
Al.

Only some of the Panasonic capsules have been discontinued. The most useful ones, the WM-61A (omni) and the WM-55A103 (cardioid) are still going strong.

The Transsound capsules are a mixed bag. The real winners are the TSB-140A and TSB-165A which are larger (but not large) diaphragm models. The 165s require an external FET and those pesky gigohm resistors but sound pretty darn good.

Mark Strong brought in a bunch of Transsound capsules and is selling them. You can reach him at

mstrong@*not*jlielectronics.com (remove the *not*)

for a price list and ordering info.

Panasonic has been discontinuing some models of capsule to comply with "lead free" requirements. But you can still get both omni and cardioid at Digi-Key. No problem at all.