DIY mic has a lot of subsonics...

So, a while back I made a semi-DIY mic: http://groupdiy.com/index.php?topic=55958.0

It has the board from a CAD Equitek E-350, the capsule polarization circuit from Zapnspark at Yahoo MicBuilders, a microphone-parts.com capsule (RK-47), and a body I made myself. (All thanks to groupdiy user Ricardo's guidance... i would have been lost on my own.)

It works great, I love it, etc.

But I notice that it is incredibly sensitive to low-frequencies. The E-350 and the related CAD VX-2 were both known for a very extended low-end, but I regularly see stuff down around 4Hz or lower on this mic. I can wave my hand back and forth a few inches, at about a foot from the mic, and the ~4-8Hz signal is very loud and clear in the result. The slightest movement or foot tapping seems to trigger slow deep sinusoids in the recorded signal.

It's easy to filter out, of course, but I'm just curious if this might point to some flaw in my DIY hack job? Would an incorrect capsule polarization voltage contribute to something like this?

Thanks for any thoughts!

Here are some pics... not that they'll be useful for the thread; just because i want to share.

http://lacinato.com/pub/L350/L350_front.jpg
http://lacinato.com/pub/L350/L350_capsule_front.jpg
http://lacinato.com/pub/L350/L350_pol_circ.jpg
http://lacinato.com/pub/L350/L350_basket.jpg

I'm baseing my response on my experience with the CAD E300 original circuit mic. NO! That is not out of the ordinary at all for these Mics. The demo I saw at The AES convention included the closing of the door to the iso booth CAD had set up and watching the meters on the Mic Pre while the guy doing the demo said "want to see low end response watch this"! So no that circuit goes way down there. I own two E300 mics I love 'em.

Nice build by the way well done.

Pip said:

That is not out of the ordinary at all for these Mics.

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Good to hear, thanks.

I own two E300 mics I love 'em.

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Me too -- I have an E-350 and this hacked 350. I do love them both. I have a few more of these boards and i'm excited to try an RK-12 capsule on one... gotta raise the cash first, though.

Nice build by the way well done.

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Thanks! My first one, and it amazes me how well it worked out. Every other audio project i've done has been a slog (aka "learning process") to get working, and this thing just fired right up. Only issue was that the pattern selector switch was bad (i have a feeling the board might have been a factory second). Amazingly (to me) the exact same switch was still available... so satisfying. Good to know maybe if your 300's switches ever go bad.

Only thing is that I made the basket so damn tall for some unknown reason. Not usually a problem, but when I want to do a mid-side I can't get the mid mic all that close to the capsule.