[sdiy] Re: About this LC filter formula questions

[harrybissell]

You might try that... but the speed of sound is MUCH faster in copper than in
air...
so if the sound couples to the inside of the tube, or directly into the tube
from the
transducer, you might have trouble.  The foam is probably a good idea, but I'd
consider
some elastic joints (rubber tubing over a cut section of pipe) to try and
decouple the
direct path as well.

I found that my audio frequency unit made a lot of noise (source) and received a
lot
of noise...  I considered it a failure and moved on.  I suppose the idea could
be made to
work better, but its a far cry from tape, bbd, or digital solutions.

Maybe we should turn the project over to the Electric Peasant, who excels in
such
low-tech enterprises.  (see the slinky reverb for example).  ;^P

H^) harry

John L Marshall wrote:

> Harry,
>
> I was considering using ultasonic transducers. It seems that 8kHz of flat
> bandpass could be obtained. Just hetrodyne up at the sending end and
> hetrodyne down at the receiving end. There should be a lot less outside
> acoustic interference (except for the bats). Quarter inch copper pipe in a
> coil with sponge separators between turns could function as a waveguide.
>
> Take care,
> John
> ------------------------------------------------------------------
> Pacific Northwest Synthesizer Meeting
> August 9, 2003
> www.sound-photo.com
> ------------------------------------------------------------------
>
> ----- Original Message -----
> From: "harrybissell" <harrybissell at prodigy.net>
> To: "Ken Stone" <sasami at hotkey.net.au>
> Cc: "Glen" <mclilith at charter.net>; <synth-diy at dropmix.xs4all.nl>
> Sent: Saturday, May 31, 2003 7:02 PM
> Subject: Re: [sdiy] Re: About this LC filter formula questions
>
> > The biggest problem is keeping the main audio path in the hose... not
> through the
> > walls of the hose. I had a lot of trouble with the coils of hose touching
> each
> > other...
> > forming a sneak path.  It was big and it was sensitive to external noise
> as well...
> >
> > not too practical.  Easy to see why the idea is abandoned.  My hose was
> 3/8" ID
> > (garden hose)... I used a compression driver and a dynamic microphone
> (electrets
> > were not 'invented' yet :^)
> >
> > BTW I heartily recommend the BBD as a better DIY vehicle for delay,
> compared with
> > the coiled hose method...   H^)
> >
> > I was thinking of a 4" PVC sewer pipe buried the length of my property...
> with a
> > small
> > electric train moving a microphone into various positions....   :^P
> >
> > H^) harry
> >
> > Ken Stone wrote:
> >
> > > There is a half built one in my workshop at the moment. For a workable
> echo,
> > > you need 20 metres of hose. I ahve 40, with multiple taps using
> electrets
> > > set in T-pieces. To top it off, there is also a set of reeds being
> excited
> > > by the same speaker, which should produce some interesting "resonant
> responses"
> > >
> > > This method has been around for ages. Shcober Organs tried it before
> > > settling on tape loops. The Time Cube is a commercial example, and
> numerous
> > > experimentors have built their own.
> > >
> > > Ken
> > >
> > > >
> > > >Here's a freaky idea:
> > > >
> > > >Build a "tube echo" with a large length of flexible plastic pipe, which
> has
> > > >been rolled into a coil. Connect one end to a small box which contains
> a
> > > >speaker. At several points along the pipe, drill a small hole and
> insert an
> > > >electret microphone into the hole. Connect preamps (probably with some
> EQ)
> > > >to each microphone. Then use your scanning circuitry to sweep back and
> > > >forth among the various microphone signals. In other words, do the
> whole
> > > >delay line with sound instead of an electrical transmission line
> simulation.
> > > >
> > > >How's that for an unusual vibrato-chorus design?
> > > >
> > > >One thing's for certain, it's sure to have an "analog" character to it.
> > > >
> > > >
> > > >later,
> > > >Glen Berry
> > > >
> > > _______________________________________________________________________
> > > Ken Stone   sasami at hotkey.net.au
> > > Modular Synth PCBs for sale <http://www.blaze.net.au/~sasami/synth/>
> > > Australian Miniature Horses & Ponies <http://www.blaze.net.au/~sasami/>
> >