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| Date: |
July 26, 2010 at 12:53:12 |
| From: |
Dan, [97-117-104-144.slkc.qwest.net] |
| Subject: |
Advice needed - using sub as microphone |
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The question I have is quite unusual and I really hope to connect with
someone who can advise me about the project I am attempting.
First of all, I am a didgeridoo maker and player. If you haven't already heard of it, a didgeridoo is a wind instrument coming from the Aboriginal people of Northern Australia. It is a hollowed log, basically.
What I want to do is use a subwoofer in reverse as a microphone in order to add bass to a 45hz didgeridoo that would be played in front of the subwoofer. I've already done this with a sub mounted on the back of a sympathetically-tuned kick drum. It works great for recording
(unbelievably nice bass, actually) but the feedback loop is severely reinforced by the drumhead and live performances are not really feasible.
What I would like to do as an alternative to the kick drum, is to create the added bass by taking advantage of Helmholtz resonance. My idea is
to mount the subwoofer on the top of a djembe drum (the goblet shaped drum from Africa). The bass tone on a djembe is created by Helmholtz
resonance because of the port on the bottom of the goblet, like a subwoofer enclosure. For this project, the djembe would have no drumhead, just the subwoofer and it would have the right volume and port size to create
Helmholtz bass at 45hz (how to calculate?).
When the 45hz didgeridoo is played against the subwoofer, the vibrations of the woofer should go through the port and oscillate from the
Helmholtz effect.
My main question is whether the Helmholtz oscillations would bounce back up through the drum to the speaker membrane and cause it to vibrate in such a way as to add the right kind of bass going to the input. Normally, if you
wanted to capture the bass tone of a djembe, you would place a regular microphone under the bottom of the drum, so I'm not sure if the sub
mounted on the top is going to receive a boost from the Helmholtz oscillations. And, if it does receive a boost, would it be out of phase or have
some other effect that would make the project unworkable?
More generally, I welcome any suggestions on alternative ways to do this.
I would appreciate any advice.
If anyone is interested, I would love to send an mp3 of a recording I made with the 45hz didgeridoo played against the kick-drum-sympathetic-resonator-sub-mic!
Cheers.
Moderated By: brian@diysubwoofers.org
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