Building a combination bridge piezo unit?

I like the idea of building a bridge with a piezo in it, and was wondering how others do it. What size "diameter" piezo would you use for that? How recessed should the gap for the piezo be, and is it glued in place with a flexible glue, or a hard glue, or would it be glued at all? Is it better to mount the piezo in the bridge, or in a recessed hole in the bottom? Would the bridge need to be glued to the box, or would the string tention hold it in place... so on and so forth...... 

This discussion is for anyone interested, or knowledgeable on the subject. I'm in the interested category. Feel free to post pictures, and links to your piezo/bridge's. I made this discussion becuase I wasn't able to find any other discussions on the topic, but mabe I didn't look hard enough. If so please post a link to the other discussion.

Thanks!

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Replies

  • I'd probably use brass because I have some, and I like the looks a little better, but I do see how it would make spacing the strings easy with a bolt. Thats the great thing about CBG's you can build them how ever the hell you want to as you can still play it when it's done.

    Naz Nomad said:
    Glenn Reither said:
    A 6mm bolt with the head cut off and filed flat on one side works well too - especially if your string anchors in tailpiece don't line up with your neck string spacing exactly. You do the same for a nut and you've got a really easy way of changing your spacings whenever you want.
    Well obviously I would file slots in the brass rod to maintain string spacing ... I guess it all depends how 'DIY' you want it to look. I know a lot of people use a bolt, and I'm sure it works reasonably well, but I use brass/bone/steel/whatever purely because it DOESN'T look like a bolt . :-))
  • Glenn Reither said:
    A 6mm bolt with the head cut off and filed flat on one side works well too - especially if your string anchors in tailpiece don't line up with your neck string spacing exactly. You do the same for a nut and you've got a really easy way of changing your spacings whenever you want.
    Well obviously I would file slots in the brass rod to maintain string spacing ... I guess it all depends how 'DIY' you want it to look. I know a lot of people use a bolt, and I'm sure it works reasonably well, but I use brass/bone/steel/whatever purely because it DOESN'T look like a bolt . :-))
  • A 6mm bolt with the head cut off and filed flat on one side works well too - especially if your string anchors in tailpiece don't line up with your neck string spacing exactly. You do the same for a nut and you've got a really easy way of changing your spacings whenever you want.

    Naz Nomad said:
    I used 2 x 20mm piezos (unwired ones from CB Gitty) in this bridge.

    Using a 20mm Forstner bit with the point ground off, I cut two recesses under the bridge. A small channel for the connecting wire was cut between the recesses with a Dremel bit.
    The piezos were stuck into the recesses with a little spot of hot-glue.
    I then wired the piezos in parallel, bringing just one pair of wires out from the bottom of the bridge. You don't need 4 wires unless you think it'll sound better in stereo, or you can't solder a couple of simple wires.
    PLEASE don't heat piezos twice for every wire you solder on, despite what ''experts (hah) on some sites might tell you, this is bad workmanship and could result in you destroying the transducer. If your wire is tinned correctly, you don't need a huge blob of solder on the piezo ceramic to hold it on.

    Once the wires were soldered on, I tested the connections by plugging it into an amp, then filled the rest of the recesses with epoxy (you could use more hot-glue).

    For the saddle, I used a piece of 6mm brass rod, with a flat ground on it. Once I was happy with the intonation, I put a couple of drops of superglue under the brass rod to stop it moving about. (I believe Diane also uses the half-round saddle method, it works well and saves having to cut a round channel in the top of your bridge).

    piezobridge.jpg

  • There is a long-standing debate over the differences of wiring piezos in series or parallel.

    People have had great success with both methods ... http://www.cigarboxnation.com/forum/topics/wiring-2-piezo-in-series

    Performance does seem to be based entirely on where, and how, you mount them, and how many you use. The series/parallel wiring debate will go on forever so it's best to experiment, I would say.

    Spacing ... hmm. I suppose for a 6-stringer you should make the centres of the 2 piezos under strings 2 & 4 for the best result. Again, your mileage may vary. Remember, it's all about transferring the vibrations from the strings, through the bridge, to the piezos. So if you can visualise what's vibrating and where, you can kinda see where the piezos might need to be. Yet again, you're personal preference can only be found by experimentation.

    Drilling the hole for the wires might be best left until the end, but you'd probably know beforehand the scale length, the neck length and the box length, so you could pre-drill it if you kinda stick to one type of build/scale/etc.

    This will also depend on your piezo size, of course. I've used 2 x 20mm piezos, or one 50mm monster.

    Now, I'm not affiliated in any way, but you'll get a great deal on piezos from CBGitty http://www.cbgitty.com/cubecart/index.php?act=viewCat&catId=9
  • I wasn't expecting such detailed replies so fast.
    "The twin piezos wired in series seem to work better electrically with the amplifier than a single piezo too." does having two make it pickup more vibrations? How far do they need to be spaced apart in the bridge? Oh, and a diagram would be great Kevin! Also about the hole you'll need to drill in the top of the box for the wires, would it be one of the last things done when building a cigar box guitar, so you can get your desired length between the nut at the head stock, and the bridge?
    Thank's for all the replies!
  • I used 2 x 20mm piezos (unwired ones from CB Gitty) in this bridge.

    Using a 20mm Forstner bit with the point ground off, I cut two recesses under the bridge. A small channel for the connecting wire was cut between the recesses with a Dremel bit.
    The piezos were stuck into the recesses with a little spot of hot-glue.
    I then wired the piezos in parallel, bringing just one pair of wires out from the bottom of the bridge. You don't need 4 wires unless you think it'll sound better in stereo, or you can't solder a couple of simple wires.
    PLEASE don't heat piezos twice for every wire you solder on, despite what ''experts (hah) on some sites might tell you, this is bad workmanship and could result in you destroying the transducer. If your wire is tinned correctly, you don't need a huge blob of solder on the piezo ceramic to hold it on.

    Once the wires were soldered on, I tested the connections by plugging it into an amp, then filled the rest of the recesses with epoxy (you could use more hot-glue).

    For the saddle, I used a piece of 6mm brass rod, with a flat ground on it. Once I was happy with the intonation, I put a couple of drops of superglue under the brass rod to stop it moving about. (I believe Diane also uses the half-round saddle method, it works well and saves having to cut a round channel in the top of your bridge).

    piezobridge.jpg

  • Jim Farris used to have a diagram and instructions up on his Flicker site. Very good instructions on how to do it.
  • I am try to work out how to draw a diagram and post it here. What seems to be particularly effective is to make the bridge in two parts - top and bottom. I believe that Ted Crocker does them this way.
    The idea is that the larger bottom part be recessed to take the top part so it fits fits loosely and is free to vibrate independantly.
    Then Inside the upwards-facing recess on the base, you carve slight depressions to hold an identical pair of piezos side-by-side - which you wire in series. You want these recesses just deep enough to stop them moving around, but not so deep that the piezos are buried. It is important that the piezos stand fractionally proud of the bottom of the recess so that, when the top part of the bridge is fitted, it rests on the piezos them selves.
    The reason this will work so well is that it makes the string vibrations travel straight through the piezos going from the top part of the bridge to the bottom part. This gives you a nice strong a clear signal and thus, as a result, very little feedback and much less handling noise. The twin piezos wired in series seem to work better electrically with the amplifier than a single piezo too. Like I say, the important thing is to arrange for the vibrations to actually travel through the piezos so that they are slightly deflected as this gives the best signal.
    Try it - it is surprisingly effective and dispels much of the criticisms hurled at piezos.
  • not sure on the ideal size of piezo and i never actually measure the gap that i leave but u want to deep enough my guesse is about 1/8 inch and as foar as the ideal glue goes ..Hot Glue is ur best way to go I myself and i kno severall ither folks havehad nothing but good results using
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