Sticking piezo discs inside acoustics

[Albatross]

Hi all, I'm hoping you might help with ideas.

I want to glue or attach in some way a pair of piezo dics to the underside of the bridge plate on my 12-string.

This is a renewal job actually, I've had a pair of discs in there before, superglued.

In fact I've tried many ways over the years... double sided tape (pretty useless), blu-tack (like the tape, they fall off) and Superglue.

Superglue has been the most successful to date and has lasted ages but its messy to install and one runs the risk of gluing a guitar to ones arm for a couple of days. Its also a bugger when its time to get them off.

What do you use? I've been reading about commercial units being supplied with a magic putty (but what is that) and also superglue gel which seems like a good idea as it wont run al over the fingers while getting the disc positioned.

I've also read 'hot glue' might be a way to go, and some have suggested silicon glue? Is this just the same 100% white silicon that you can use a caulk in the bathroom around baths and windows?

I'm wondering if there is a definitive good way to attach piezo discs covered in copper tape to the wood of my bridge plate.

Any thoughts would be much appreciated.

[simedgoose]

Silicone sealant? I use silicone sealant for attaching piezos to drum related items (pads etc). It lasts ages, has a good amount of 'give' in it, but can be easily pealed when required. It does mark some surfaces though.

[Wonks]

I've used the suggested superglue gel to stick some K&K pure sound mini piezos to the underside of a bridge. Their little alignment gadget helps to get them in place and hold them there whilst the superglue gel sets and avoids getting any on your hands.

Worth reading their installation guide (link below) as it should give you some ideas. It was very easy to do with their little jig and you could easily make your own. A bit of blu-tak to hold the disk to the jig, CA gel on the top of the disk, post up through a bridge hole, use the golf tee to align the other end, hold in place for 30 seconds and you're done for one disk.

https://kksound.com/pdf/puremini.pdf

[shufflebeat]

I like superglue. If you're worried about the mess then the techniques described above covers most eventualities.

(TL;DR - what Wonks said)

I like to make a jig out of the top of a plastic takeaway box lid cut in the shape of a "T", the stem if which will make a handy handle. Lay it over the bridge and mark off the outermost bridge pin holes, punch them out.

Lay the lid, I mean the jig, in place and poke some chopsticks through to locate and hold it, mark your saddle if preferred, I do.

Put the discs onto the top bar of the "T" where you want them to be located underneath, fasten with blu-tac onto the jig with the "to be glued" side facing up (stretch and pull blu-tac repeatedly to make it extra sticky first). Take care that cables are pointing where you will want them to be later.

Glue 'em. Don't be shy.

Pull out your chopsticks, remove the jig, replace the chopsticks and carefully manoeuvre the jig into the guitar, usually cable first. This is where you find it was a good idea to be robust with the blu-tac.

Once the jig is inside, put your hand inside, locate the chopsticks and push the holes onto them, carefully offer up to the bridge plate so that the glued faces make contact, press with confidence, the jig is between your fingers and the glue.

Hold in place with one hand while you eat the Chinese ffood with the other. Remove jig and blu-tac.

[Albatross]

Cheers gents.

[Tomás Mulcahy]

Very interesting. Is this sonically equal to an under-saddle pickup? I mean those long thin ones. It's a helluva lot more convenient!

[Sam Spoons]

They are different to USTs, they usually sound better (no 'quack') but are a little more feedback prone. They must be securely and permanently fixed to the soundboard/bridge plate, putty doesn't work (whatever the claims). The best known are K&K but these are pretty much identical and around 1/3rd the price http://jjb-electronics.com/prestige-220.html

[Wonks]

It is a similar sound, if not identical. You tend to get less of a piezo 'quack' to the sound, and you pick up a bit more of the soundboard vibration, so it can sound fairly natural. The response depends on the size and positionioning of the disks.

Bigger disks mean a larger signal output, though they sense over a wider area, so high frequencies can be less accurate due to partial phase cancellations.

Also a bit more prone to acoustic feedback than an UST, but not by a lot.

[shufflebeat]

I have a James May Ultra Tonic sat on the shelf waiting to go into a Crafter Dread when I can be A'd. All the tone/dynamics, none of the feedback (by all accounts). The guitar already has a Fishman UST in it but I think that will be re-homed.

On that point, SBTs can't really be re-homed once they're fitted.

[Tomás Mulcahy]

Great, thanks for the info. Some experimentation this weekend so