advice on wiring electric marimba?

Here's the story. A group that I play with uses zimbabwean style marimbas. These are nothing like their western counterparts as the keys are very thick and yield very minimal sustain. Also, the resonators (pvc pipe) generally have a 1" diameter hole at the bottom with plastic covering the hole to give a "buzzing" sound when struck.

The group uses four marimbas on stage as well as drum-set, electric mbira, and four vocals. The bass marimba is 7 feet high and keys are around 12" wide, 2" thick and up to 2.5' long.

We have been miking the bass marimbas. I am generally happy with that, but that ends up having over 16 open mics on stage often, and we play on very small stages (for us). I still think the mic trick is the best solution, but the other guy in the band (the one who builds the marimbas) is constantly searching for ways to complicate-I mean improve things. He has installed peizo pickups in each individual bass key (in the nodes) and then wants to wire them all up and plug the bass marimba straight into the board.

Do you guys have any thoughts on how best to do this? I have found peizo's inconsistant at best and the gain of one seems much greater that the gain of another. I was thinking of maybe trying to wire each one in parallel and running into a summing box where we check the impedence of each peizo and put in a resistor for each to get a level signal and then run out of the box into the board.

As a person who likes simplicity though, I still feel like a couple of mics may be a better solution.

Any thoughts?

Joel

> The bass marimba is 7 feet high and keys are around 12" wide, 2" thick and up to 2.5' long.

Pictures! Pictures!

> the other guy in the band.... has installed piezo pickups in each individual bass key (in the nodes)

Maybe a terminology mix-up, but I thought "node" was the place they did NOT vibrate?

And:

> the resonators (pvc pipe) generally have a 1" diameter hole at the bottom with plastic covering the hole to give a "buzzing" sound when struck.

If I understand the pickup technique: you won't get ANY pipe resonance or port buzz this way.

> check the impedance of each piezo

They will show infinite DC ohms. Anyway I suspect that the level variation is mounting position. In the extreme case you might just need 88 faders (or however many pickups you have) which probably means 88 preamps. Even if this is just a 16-bar instrument: Ugh.

Pictures! Pictures! I know "my" marimbas well (like Lionel Hampton except wood) but am not picturing how you play 7 feet tall. But in general, for maximum usable acoustic gain with some pipe/buzz effect, I would think of a Panasonic omni capsule centered between two bars and two pipes. If the bar and pipe proportion were anything like this:

That would give good gain. If you have 12"-wide bars on narrower pipe resonators, you may need one capsule per resonator. If the bars and resonators are well matched one to the next, you can just wire all the capsules parallel. If they are not matched you are back to many faders to set balance.

Thanks PRR,
Here's some pics. These aren't our marimbas, but this gives you the idea.


That is pretty much like our bass. You can see that these don't have a large range. Our bass has 11 keys. You stand on a platform to play it. Our frame is much stronger.

Maybe a terminology mix-up, but I thought "node" was the place they did NOT vibrate?

Click to expand...

Correct. The keys don't vibrate on the node as much, but the sound is still there-perhaps from the mass of the keys. The bass is played with big mallets (the ball is usuall about the size of a tennis-ball:


Thisn't light touch stuff. The vibrations of the keys seem to destroy the electronics of any mounted pick-ups over time. That may be why he chose to put the pups on the nodes. The piezos are mounted with epoxy.

you won't get ANY pipe resonance or port buzz this way.

Click to expand...

True. That's no concern, as the buzz doesn't translate well through the PA anyway.

I know that the "classical" marimba players sometimes use little condensor mics that clip between each bar down by the tubes. That would be crazy expensive though. Classical marimbas can be up to $100,000 value, but we play in bars, etc.

Joel

How about a magnetic pickup system? All you need is a small coil (or two, for humbucking) under each bar, and a bit of metal glued to the bar.

Well, piezos are about $.25 each. That is probably the biggest incentive. To wind 11 coils-matched doesn't sound very fun to me.

Joel

Have you tried the Kynar piezo plastic materal. IIRC AMP made and sold it. I think another company does now. It comes in sheets and coax wire shapes IIRC.

Have you tried the Kynar piezo plastic materal

Click to expand...

Not trying to be a smart-ass, but why would this be a better solution than the metal discs?

I'll go do a search, and see if I can answer my own question...

Joel

hmm,
interesting looking stuff. I wonder what kind of frequency response it would give? It looks like it is mainly used as a sort of "buzzer" indicator for movement or pressure, etc.

more info:

? Wide frequency range?0.001 Hz to 109 Hz.
? Vast dynamic range (10-8 to 106 psi or µ torr to Mbar).
? Low acoustic impedance?close match to water, human tissue and adhesive systems.
? High elastic compliance
? High voltage output?10 times higher than piezo ceramics for the same force input.
? High dielectric strength?withstanding strong fields (75V/µm) where most piezo ceramics depolarize.
? High mechanical strength and impact resistance (109?1010 Pascal modulus).
? High stability?resisting moisture (<0.02% moisture absorption), most chemicals, oxidants, and intense ultraviolet and nuclear radiation.
? Can be fabricated into unusual designs.
? Can be glued with commercial adhesives.

Joel

Thats cool you found the info fast.

I am one of the people who believe that giving some answers is not as good as the person finding the information with a hint.

The main reason I posted was

"The vibrations of the keys seem to destroy the electronics of any mounted pick-ups over time."

I think the same kynar stuff is used in kids blinking light sneakers to trigger the gate of a fet to turn on the LEDS. If the stuff in kids sneakers can handle the impact maybe the stuff can work well in the zimbabwean style marimbas.

If the stuff in kids sneakers can handle the impact maybe the stuff can work well in the zimbabwean style marimbas.

Click to expand...

Very true.

Certainly teaching to fish is the way to go. It's just a difficult situation as the costs involved of the keys etc, doesn't lend itself well to constant experimintation.

Joel