[sdiy] Percussion MIDI controller - again

[drheqx]

I'm getting a bit confused here. We want the thing to ring, but not too
much. Spurious signals are getting in the way, but dampening them out
would remove the ring to the point where the thing will not work.

My two cents,
Suspend the piezo disks in an oil( or other viscous fluid )filled rigid
metal cylinder ( as per Harry ) so that the high frequency shell
resonance would not come into play. The main pulse would be transmitted
through the oil which would act as a filter to remove any low level HF
ringing. No air bubbles please. 


heqx


-----Original Message-----
From: owner-synth-diy at dropmix.xs4all.nl
[mailto:owner-synth-diy at dropmix.xs4all.nl] On Behalf Of Magnus Danielson
Sent: Tuesday, March 29, 2005 1:20 PM
To: harrybissell at prodigy.net
Cc: ijfritz at earthlink.net; pfperry at melbpc.org.au;
synth-diy at dropmix.xs4all.nl
Subject: Re: [sdiy] Percussion MIDI controller - again

From: harrybissell <harrybissell at prodigy.net>
Subject: Re: [sdiy] Percussion MIDI controller - again
Date: Tue, 29 Mar 2005 00:05:54 -0800
Message-ID: <42490C60.9CB9BDFE at prodigy.net>

> I'd try a bar of something quite rigid (so that all the resonances are
> high in the audio range) and then support it from each end in a can
> of jelly (like RTV) so that any waves that get to the end are heavily
damped.
> 
> Wonder if there is a way to pick up just a surface acoustic wave and
not even
> see main resonances ?
> 
> OTOH if you use a bar of steel (which would probably work real good)
it would
> suck to hit it with a stick.  Early Simmons pads anyone ???

The trouble is that you need to terminate the steel bar so that all the
energy
is swamped up, or else it will ring like hell, and you've got yourself a
single
rod of glockenspiel or something. PVC tubing is good since it is cheap,
can
handle some abuse and rings out fairly quickly due to the fortunate
losses.
It is also easy to help it on the way with loses which just improves the
response if done properly.

Cheers,
Magnus - just home from work where I played with the new network
analyser, yum!



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