Piezo Buzzer characteristics?

[Sandu]

I read around the site about using the piezo elements from piezo buzzers to create a pickup. However, somebody mentioned that they would be quite harsh and lacking low end. What are the specs of a suitable buzzer? For example, I found this one: PT 2040PQ
Piezo-Element 22.0X7.0mm 90Db 4.0Khz Max.30VDC. Should the ideal one have lower/higher values (Db, Hz)?

[Koeda]

Hey hey,
I think the problem with buzzers is the placement under the bridge is not ideal rather than the material. Was just being discussed - some good info here:
Under bridge piezos - Best grounding method?
David

[GregDunn]

My concern with using a buzzer instead of a generic piezo transducer is that it's probably built to resonate at a particular frequency, and would be very "peaky". Maybe they tune it with an attached capacitor (which might be removable), but I wouldn't spend a lot of money on one till I'd experimented a bit first.

[bassbenj]

Originally Posted by GregDunn

My concern with using a buzzer instead of a generic piezo transducer is that it's probably built to resonate at a particular frequency, and would be very "peaky". Maybe they tune it with an attached capacitor (which might be removable), but I wouldn't spend a lot of money on one till I'd experimented a bit first.

First you really don't want a "buzzer" but just the piezo element inside the buzzer. Apparently these things were so popular that Radio Shack had to stop carrying them. They are hard to find now. The "buzzer" you would really want is the one that has no drive circuitry in it. It's just a piezo disk in a plastic housing with wires. You crunch the housing away and extract the disk with wires attached.They used to cost $1.50 or so at RS. VERY popular for drum triggers. I put one on my 12 string Carlo Robelli guitar by gluing to the wood under the bridge. Not bad. The problem with the buzzers is first crunching them out of the plastic case without damaging them. Plus the lack of availablity and finally the fact that the piezo element is glued to a brass disk to make the buzzer. Still not bad for experiments if you glue them onto things with silcone bathtub seal. Just glue them in brass disk and all.

But FAR better than these and the hassle and the brass disk are these:

http://windworld.com/products-page/electronic-hardware/

They are piezo film transducers perfect for under a bridge. They come in different sizes. They are NOT totally shielded so under a bridge you'd want the hot side toward the grounded bridge with the ground side out to act as a shield.

Note that to get a piezo to respond at bass frequencies requires a preamp with a VERY high input impedance (10 megs!) Fishman makes some of these. Feeding to a normal guitar amp will roll off all the bass.

Even more interesting, is the piezo coaxial cable they sell. It's automatically shielded! Works great under a saddle on a ABG or guitar. May work under a normal bridge. Dirt cheap and worthy of some experiments. Again be aware of the Hi Z needed for bass use. I love the Fishman "powerchip" which is a volume control and circuit for combining magnetic and piezo pickups. Not cheap but GREAT! The stereo (magnetic and piezo to separate channels) feature really KILLS! Try it!

Good luck!

[Pbassred]

I went down this route with my TRB1005.

Firstly piezo is a crystal. There is no such thing as a buzzer piezo. The only thing that changes is the frequency response - bigger is lower, but its still high.

Secondly mounting a piezo under the bridge makes it into a pressure transducer. It needs to be flat or else only a small portion (one edge) is working. However in order to do that you need to shim your bridge - which takes away some of the energy that you wanted going through your pickup.

Thirdly the contacts on the piezo are soldered so they sit raised from the contact face, so you need to carve out some body or some bridge material to make it fit. So its not just a case of unscrewing you bridge a bit and sliding them in.

Anyway I went down this route and the result was rubbish. It sounded ok as a blend to the overall sound but the huge drawback was the extra sound coming off the body. By placing a transducer in the middle of your woodwork you turn the whole thing into a microphone. Every movement of your hand on the back of the neck is amplified. Imagine the potential for feedback.

A better alternative is to buy piezo saddles. They work really well, and unless you are doing it purly as a learning excercise with a bass you don't intend to play, its better not to cheap out.

I hate to be a thread killer