These piezo disk options - Mouser list

[Guitarist]

On this page piezo Speakers & Transducers | Mouser
there are a few normal piezo disks.But I see a few have different frequencies listed are these upper MHz limit? Which do you figure be the best choice for acoustic guitar (or even bass or drums)?
I've used up the dozen I bought on eBay last time and figured I'd try Mouser this time. I found that I don't like the treble spike I get from putting (whatever model I had?) a disk under the e and b strings —so would move it past the bridge and down a bit if the 3rd in a set of three paralleled.

1) 6.3k @ 350Ω, 2 cm
2) 3.6k @ 500Ω, 2 cm
3) 6K @ 800Ω, 1.5 cm
4) 9K @ 1000Ω, 1.2 cm 7BB-12-9 Murata Speakers & Transducers

There are lots of other potential goodies there too including new products, but these disks seem the most standard.

Attached is a quick pickup test: first was a cheap acoustic w. one disk under the bridge someplace, second is a LR Baggs stacked M1a I think (could use a piezo paralleled if the impedance played fair. Tom Petty does this), and last take was the three disks in an old Framus classical.

[Steve Conner]

The frequency they list is the mechanical resonant frequency of the first normal mode.

http://commons.wikimedia.org/wiki/Ca...ion_animations

In other words, the frequency to drive it at for the loudest beeps. It's not really relevant any more if you fix the disc to a surface, because this will damp and shift the resonance.

[rjb]

In other words, the frequency to drive it at for the loudest beeps. It's not really relevant any more if you fix the disc to a surface, because this will damp and shift the resonance.

Steve, does that mean the frequency is totally irrelevant if you want to use the disc as a pickup?

Restating the OP's question in other words, which disc would you select, and why?

Would one be better for bass than for guitar? Would one be better for guitar than for mandolin?

I apologize for the thickness of my skull.

Later,
-rb

[David King]

Listen, these discs are dirt cheap so buy a stack of the different sizes and see what gives. You can also find them for pennies each at many of the surplus electronics places.

[Guitarist]

It appears that that mode-bump correlates with the diameter: smaller nets higher KHz. Thus attaching to a surface, which could be a ft square, makes the peak moot. This may not be Gospel truth, but close enough for rock and roll.
The smaller ones can be easier to work with in tight spaces. So sensitive are they that, in an acoustic they capture sleeve noise and your finger nails strumming onto the flat top.

I tried a piezo film but it put out a tiny fraction that these disks do.

Another brainwave, is to mount these via modelling clay unto the inside curve of drum shells, maybe cymbals too with NakTac putty, then have a bank of DI transformers going into a 8 channel stage snake that would plug into the stage breakout box. Though the sound would be "direct" that could be a good thing live.

Anyone tried gluing them into a guitar cab?
Maybe temporally onto tubes to test for microphonics.
Put into a small, flat piece of wood with a 500K pot and a .02uF cap for a foot drum.
Glued to the trem block of an electric, I haven't tried this yet.
Taped to the announcers window at the raceway for sound capture.

The piezo disk kinda rules, don't you think?

[defaced]

Another brainwave, is to mount these via modelling clay unto the inside curve of drum shells

DIY drum triggers are done more/less this way.

[Steve Conner]

As I suggested above: When you attach the disk to a surface, the surface and the method of attachment affects the sound more than the disk's natural frequency. IME, it varies from trashy to dreadful.

To give an extreme example, the most interesting sound I ever got from a piezo disk was as a body pickup on an electric bass. After a lot of experimentation, I settled on using it in bending mode like a diving board, with one edge clamped to the body and a large steel nut glued to the other edge as a seismic mass. The resonant frequency in that arrangement was maybe 20Hz, and it gave several volts of output with a thunderous bottom end.