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-   -   piezo transducers as contact microphones (http://www.diyaudio.com/forums/instruments-amps/7805-piezo-transducers-contact-microphones.html)

lohk 19th November 2002 08:55 PM

piezo transducers as contact microphones
 
Maybe you all know, but the small piezo transducer disks (sometimes found in the strangest places, for making "beep" occasionally) can make up quit good contact microphones. Ok, it is not hifi stuff, but here is the instruments page...


The output level is sufficient and luckily quite noise-free, and with a little eq-ing at your mixing desk you are done.
The cables are soldered to the backside of the discs (symmetric or non symmetric) and this side is sealed with hotglue or silicon. I use discs with about 3 cm diameter.
I usually fix this little things with Gaffa tape for a non-vibrating contact (one strip for the "transducer" and one for the cable to secure it).

I used them now in many occasions (working with children in musical composition and improvisation workshops) for making things "sound" or just amplifying sounds.
This "transducers" can provide very good input for further processing or as a trigger for other sound events.

This is a VERY cheap "instrument". Just try it.

good luck - and happy sounding

Klaus

Havoc 20th November 2002 05:53 AM

Take care if you do so. Piezo buzzers can output a high voltage if hit hard and if the input is not sufficiently protected may damage it. If not sure put 2 back to back zeners of 5.6V over it.

Such a transducer works better with a high impedance input. A I-V convertor would be best and give the flattest response.

gyraf 20th November 2002 01:42 PM

Cutting the disc into smaller pieces gets rid of a lot of the inherent "sound" in this kind of piezo pickups.

It is really hard to cut though, it breaks easily. But if you manage to get a ~2x5mm piece and solder wires to it, it sounds much more neutral..

Jakob E

bob4 20th November 2002 08:29 PM

Yeah,

Piezos are a nice thing to play around, and fit perfectly in situations as described by lohk, especially regarding the cheap price.

I know some other material that transforms vibration or pressure into a usable signal. THe company that manufactures it describes it as an "elecret film". They claim that their material gives a more flat freq response and a natural sound compared to piezos.

www.b-band.com


another word on piezos:
Quote:

It is really hard to cut though, it breaks easily.
You could perhaps dremel it (here in germany they sell a multi-purpose-tool called "Dremel", don't know if it's also sold elsewhere in the world......)

dice45 22nd November 2002 01:55 PM

All,
cutting works best with a diamond cutting disc and a Dremel.

Diamond cutting disc is 10-15 Euro.

lohk 22nd November 2002 07:31 PM

Jakob,

you must be joking !
How can you cut a piezo disc "into smaller pieces ?
There are definite parts at the backside for connections, but cutting it into pieces means destroy it - maybe you can make it a bit smaller, but this will not work without nending it, which also means destruction.
:whazzat:

Klaus

haldor 22nd November 2002 09:43 PM

Bass players and acoustic guitar players have been using piezo pickups for years. They are also used for drum triggers.

Checkout your local music store, they probably have them in stock. Stewart McDonald's sells piezo pickups for guitar builders.

http://www.stewmac.com/cgi-bin/hazel...catalog/s.html

Here's a fun website with about DIY pickups for the DoubleBass.

http://www.jazzpages.com/Doublebass/pickups_h_GB.html

Phil

bob4 22nd November 2002 10:56 PM

I don't want to step on anybodys toes, but for applications such as acoustic guitar pickup etc. piezos can be a pain in the are!

1. They don't sound too well (uneven freq response)

2. In live situations they tend to resonate in a veeery ugly way, I've experienced that several times

But of course not everybody can afford an expensive condenser mic for better results, and there are certainly some people around that are fully content with a piezo system.

I've already posted above about a company that manufactures a material that seems to represent a real alternative to piezos.

www.b-band.com

Unfortunately, I haven't compared piezos directly to that stuff yet.

Anyway, it's at least a interesting read........

lohk 22nd November 2002 11:02 PM

Yesterday I was in a concert here in Linz/Austria where two experimental electronic musicians were playing.

It may interest you that the main sound they used as a material for their transformations was the creaking sound of the wooden floor picked up with piezo disks fixed on the ground.
So the audience made the music somehow without knowing it...

Klaus

Havoc 23rd November 2002 11:00 AM

If you need large piezo sensors, you could try to get a piece of PVDF foil. Easier to work, flexible and cheaper.

Easiest way to connect to piezo is with conductive glue or self-adhesive copper tape (with conductive glue). Both can be found in electronics shops.


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