Plugging Holes to Change Polar Pattern?

[yikelu]

Hey all, I was reading this thread about the CM012 capsule: New-ish electret capsule

It mentions plugging the holes to change the polar pattern. How is this done? More specifically, with what materials? I've been searching for anything on this and haven't found anything. Does it not matter? Somehow I doubt using porous foam would be the same as e.g. a small cutout of wood.

Thanks in advance!

 

[gyraf]

.. Just something that stops air movement and - pressure.?

 

[yikelu]

.. Just something that stops air movement and - pressure.?

Thanks for the reply. I guess I'm overthinking it. Sure the frequency response/permeability is going to vary by material, but the cardioid isn't frequency perfect to begin with. I guess I'll just try a few different things.

 

[neowalla]

Bumping this as I have been looking around for a pair of omni electret capsules for a binaural yoga block head-thing I built. If I can plug the holes and effectively turn these into omni capsules, they might be a good choice for the dummy head.

 

[kingkorg]

You can do that, and it will turn the capsule into an omni, but the result frequency response might be unpredictable, most probably significantly boosted high end. Which is something you might, or might not like.

 

[yikelu]

Bumping this as I have been looking around for a pair of omni electret capsules for a binaural yoga block head-thing I built. If I can plug the holes and effectively turn these into omni capsules, they might be a good choice for the dummy head.

Probably be easier to start with an omni capsule. They're not hard to source. JLI has some IIRC, or Mouser for that matter.

 

[mhelin]

Josephson C715 has capsule with adjustable shutter in backplate to adjust the pattern between cardioid and omni:
http://www.josephson.com/pdf/c715ds.pdf
Not an electret capsule but anyway, it's possible. Some back-electret capsules have omni and cardioid versions where the only difference is the outermost piece which either have the holes or not (can't remind myself where I saw that though).

 

[neowalla]

I posted asking for an electret omni capsule recommendation on the microphone "groups.io" group and was recommended the PUI-5024 and the P48 circuit. I will go that route, but it is good to know that a cardioid capsule can be modified to be an omni if you have to.

 

[Icantthinkofaname]

I posted asking for an electret omni capsule recommendation on the microphone "groups.io" group and was recommended the PUI-5024 and the P48 circuit. I will go that route, but it is good to know that a cardioid capsule can be modified to be an omni if you have to.

The Primo EM272 (or 273) would be my recommendation. The Clippy lav mics using it are fantastic. You can get a matched pair for £34 (approx $40). You'll be spending 5x what you'd spend on the PUI capsules, but I'd say it's worth it when it's this cheap.

 

[yikelu]

I posted asking for an electret omni capsule recommendation on the microphone "groups.io" group and was recommended the PUI-5024 and the P48 circuit. I will go that route, but it is good to know that a cardioid capsule can be modified to be an omni if you have to.

Simple P48 circuit is pretty easy to build, and cheap. I built a couple of the 5024 and they came out well. The most annoying part of the build is just making sure the parts are held in place physically and stable.