Date: Sat, 02 Dec 2000 03:48:06

Author: "Brad Shue"

Subject: Shattering glasses

Post:

>From: "Stephen Skinner"
>Can anyone recommend a good brand of glasses to use. I have a set up >that
>I inherited that uses a 100W horn and a nice amp. But I am not >having any
>success breaking glasses. I know that I am finding the >right frequency
>for the glasses and using a strobe light I can tell >that the glasses are
>really flexing but no luck. Any suggestions?

Inherited? Inherited? ... you are making me feel old Steve.

You helped me set that up 3 years ago! Remember, you, me and Miguel tuned
all the glasses in the basement so we wouldn't annoy the hell out of
everyone with the volume. You are not going to find resonance with the
strobe, the strobe comes later on when all is tuned. It is strictly a
visual tool to show what is going on with the glass. Audio feedback with an
O-scope is the only way to tune those suckers.

You know how to tune it. Use the scope and wait until the signal from the
mic goes off the screen. And keep in mind that 0.5 Hz will make a
difference... so warm up the equipment first to prevent drift. And get the
glass as close to the horn as possible and make sure it is clean. All of
the clear glasses I left you with should still have the resonant frequencies
written on the bottom of them. Find resonance and then CRANK THE VOLUME.
Oh, and make sure you have the "bridge" jumper in place so you use both
channels of the amp for the output instead of running stereo.

Those green Arby's glasses still seem to work the best and they are a
holiday item so see if you can get more this time of year. You should still
have a 1/2 case of them in the first floor demo closet. Don't get them if
they are engraved... just the plain ones with gold rims. I got them for
cost because they were for "educational purposes"... and a happy meal to
boot.

Let me know if you have any more questions.

Brad Shue

P.S. Secret trick: To ease the breaking, use a "micro file" on the lip of
the glass and just put a small nick. It's not enough to disturb the
resonance frequency but it will give the fracture a place to start if you
have a stubborn glass. Makes it more forgiving.

I did this in Lincoln at the demo workshop.

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