Cardioid capsule, question.

Welcome all.
I have a 1 "cardioid capsule for experimentation.
Can the directional pattern of the capsule change if I remove the posterior "inactive" membrane?

I'm pretty sure it will - couldn't tell you how, though. I'll let the wiser members here chime in on that part

Perhaps in addition, it will increase the bass response as well?

vmanj said:

Welcome all.
I have a 1 "cardioid capsule for experimentation.
Can the directional pattern of the capsule change if I remove the posterior "inactive" membrane?

Click to expand...

How would you remove it?
Whatever way you do it, the changes would be minimal, unless you significantly alter the backplate and the rear acoustic path.

  Perhaps in addition, it will increase the bass response as well? 

Click to expand...

Closing the rear path tends to modify the directivity pattern towards omni, which also tends to minimize the proximity effect, so less apparent bass in close-micing, but the response would not be correct. For an omni mic, the diaphragm tension must be increased significantly, actually almost impossibly for a LDC.
I think you know a dual-diaphragm capsule can be wired in two different ways for cardioid operation; one is to use only the front diaphragm and ignore the rear one, the other uses both diaphragms in parallels but only the front one is biased. There are differences in directivity and bass response, that are well documented in Shure and Neumann publications.
Altogether removing the rear diaphragm is a major change in acoustic tuning, that would probably result in making the pattern hypercardioid, but would also decrease the damping, resulting in a more midrangey response.
Now, if you're looking for effects, why not try and see if it suits you?

Of course, I will try to do this, but I wanted to ask a preliminary question.
Maybe after the answers, this capsule will remain untouched ..

My capsule has one "active" diaphragm (in the image), so you can turn it on only in one way.
I thought the change could be towards Bi-directional and not Omni-directional.

Thanks for answers.

vmanj said:

Of course, I will try to do this, but I wanted to ask a preliminary question.
Maybe after the answers, this capsule will remain untouched ..

My capsule has one "active" diaphragm (in the image), so you can turn it on only in one way.
I thought the change could be towards Bi-directional and not Omni-directional.

Thanks for answers.

Click to expand...

What you call the "inactive membrane" has three purposes:
It acts a s a filter that prevents dust penetrating between the diaphragm and the backplate. If dust is allowed to penetrate, it retains atmospheric humidity, which results in crackling noise and ultimately a non-working capsule.
It is also part of the acoustic delay that creates the cardioid effect. Removing it certainly produces a modification of the directivity pattern, probably towards hypercardioid, but with large frequency dependancy..
It adds some damping, so removing it would probably make the response less linear.
As I said earlier, you may try it, at your risk; what's certain is this capsule would probably have no re-sell value after that.

Her "inactive" purpose was something I imagined, except for a dust filter.
This may be a decisive factor for me to leave the capsule alone ..  ;D

Thanks.