contact mic fun

[DaveX]

I am interested in making some contact mics. I know that you can make them from piezo buzzer things, but I am not very certain of how to do it properly. I'll also admit that I plan on using Radio Shack piezos for three reasons:

1) I am cheap.

2) Radio Shack is cheap.

3) I do weird music that people think sounds like ass anyway.

So... can anyone help me out with a good step-by-step on this problem (without blasting me over the Radio Shack business)???

Always in contact,
DaveX

 

[The Axis]

Karma being what it is and all...
I am an acoustic engineer for a piezoelectric ceramic manufacturer. We don't supply the Radio Shack piezos (they come from Japan, Malaysia, China..), but we do supply the piezos for many major pickup brands.

Your idea is a good one, and in fact, that is all that a major brand-name piezo contact mike is: a piece of piezoelectric ceramic with leads soldered to it.

Here are the tricks:
1. The bare ceramic is very fragile and brittle. Buy a few, because you are likely to break some during experimentation.
2. Use a very thin adhesive and fixture it so it is very flat at the installation location until the adhesive cures.
3. It will sound different depending on where you mount it, but you know that !
4. Get a preamp mounted as close to the piezo as possible. They put out very low voltage and will pickup noise. Apparently 8-10" of wire is commonly used, but I would stress keeping it as short as possible...1" if possible !
5. The lead on the side touching the mounting surface should be VERY flat. We sometimes use .001" silver foil on those surfaces, instead of creating a bump for a wire solder-dot. it will still work with a solder dot, but the high frequency response will be dulled.

I think they have the potential to sound VERY good, but the trial-and-error locating process, and the need to use adhesives and preamps is what puts most people off. I don't even use them myself, for these same reasons. I just use mikes !


Peace,
Rick

 

[regebro]

I had this idea of gluing a contact mic to a piece of thin magnet. Then you could attach it on metals and move it around...

One thing I was thinking of trying this with is making a plate reverb...

What do you gyus think? Bad idea, or good idea? And where the heck to I get hold of contact mics ( in Stockholm or via Web)?

 

[DaveX]

thanks, sorta

The information and ideas you both have given me so far are excellent, but I still need to know how to actually make the darned things. I kinda have the idea, but it has never been explained properly.

DaveX

 

[The Axis]

When you open up a radio shack buzzer, you will see a flat disk of brass, with a disk of thin ceramic bonded to it. It will probably already have leads soldered to it. If it does, glue it to your instrument. If it doesn't, solder leads to it then glue it to your instrument. Hook it to a preamp and listen !

I have obviously glossed over a lot of subtlety here. The whole art of building and installing piezoelectric transducers can become as finely detailed and subtle as you want to make it.

The first refinement would be to get rid of the brass layer, which serves no purpose in your application. But since I don't know how they constructed theirs, I don't know what solvents would safely eat away the adhesive. Methylene Chloride will probably work, but DO NOT mess with that stuff unless you have hazardous chemical handling experience !

Peace,
Rick


Peace,
Rick