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I have gotten back into messing around with piezo pickups after rejecting them a couple of years ago because I was unable to sufficiently isolate them -- they were too sensitive, picking up fingering and handling noise, etc. You know the story... Anyways, recently I built 2 instruments using the 20mm (2cm) diameter piezos that CB Gitty sells. To isolate them, I filled half a coke bottle cap with hot glue, letting it pool. After is cooled, I put the piezo pup in the middle of the bottle cap, and filled the rest with hot glue, making sure the piezo did not touch the edge of the bottle cap. Once that cooled, I applied a liberal dab of hot glue to the top side of the bottle cap and stuck that to the underside of the soundboard near where the bridge is located. I then added the jack, and finished up the two instruments. The result was two instruments (a CBG and a paddle box dulcimer) that have minimal sensitivity to fingering and handling (a BIG improvement over by earlier attempts), but the resulting instrument seems to favor the Bass side of the spectrum. So, I'm thinking that my method of isolating the pickup is causing the treble side to be attenuated (decreased like I was using a low pass filter). Have any of you experienced this? Do you have a work around (one that also allows me to minimize sensitivity to finger and handling noise)? By the way, my piezo pup isolation technique using the bottle cap is something I read elsewhere on CBN. I don't really want to have to pass it through an external preamp with equalizer to filter the lower (bass) frequencies and, in so doing, boost the high (treble) frequencies. I do have a guitar amp with 3 band equalizer. Turning down the bass, turning mid range part way up and turning treble way up only helps a little, but adds a lot of electric buzz to the sound coming out the speakers, so I usually turn it down. I'm not very knowledgeable when it comes to electric guitars, so any productive suggestions would be appreciated.
Thanks for bringing this subject to the forefront, Rand. I've just begun to experiment with pickups and piezos and will post my observations of attempts here. My own goal would be to include some degree of percussive capability, and not lose the high end of the scale, as you mentioned. A piezo should be 'brite', yet not over-sensitive, IMO.
Sounds like ETB has an idea, with the piezo placed in a thickened section of wood within the soundbox.
Natural cork is great. Cork under piezo kills screaming and screeching high frequencies. Brings more low frequencies.
Thanks for the suggestions.
I have no problem with low frequencies. With the bottle cap and hot glue approach I get plenty (too much) bass. What I'm looking for are ways to get the isolation but without loosing much high (treble) and mid-range frequencies. I think for canjos, cookie tin banjos and similar instruments, the bottle cap and hot glue approach would be good, since those instruments have too much treble to begin with, But with an instrument designed around a wooden box, this type of piezo isolation results in an instrument that's too bass-y IMHO. If I can find some cork, I'll see if it is any better than the bottle cap and hot glue approach.
I'm also going to give Ellwood T. Bear's approach a try. I've used wood isolation before, with foam rubber, but the sensitivity was not isolated that well. But maybe following Elwood's construction method and using silicon seal, it might prove the right approach. I need to score a few more piezos pups, first. I'll need to find a source here in China. Wonder how you say "piezo" in Chinese...
I use a source in Thailand. If you want me to send you that info let me know and I'll send you the info. They are cheap, but the shipping is very slow - three weeks to a month.
I use two piezos with two volumn controls so I control each pick up separately. I place one under the bass and one under the treble. The bass is further away from the bridge and the treble as close to under the bridge as I can get it. Both encased in Balsa sandwiches and glued to the underside of the top of the box. Both piezos are soldered to the jack. I adjust the volumn of the pickups before they are sent to the amp. I have thought of using tone controls as well but have heard this does not have much effect on piezos?
Are you centering the piezo between the strings? Moving the pup to the treble side of the box might compensate for the loss you're describing. Also, I've had good success (is that an oxymoron?) using dual piezos wired in parallel, widely spaced apart and buried in hot glue, Your bottle top method might work even better doing that.
Hi Habanera Hal.
On my CBG with the bottle cap & hot glue piezo pup, the piezo is placed on the treble-side of the sound board because that instrument was a neck-thru design w/o any special cutout for a neck-mounted (or neck-clearing) pup. Compared to my paddle-box dulcimer with its center-mounted piezo (located under the soundboard below where the bridge is located), there is not much noticeable difference in terms of treble response. It's a good idea, though. Maybe I need to reduce the amount of hot glue I use and try placing it on the treble side to see if that helps. That will have to wait until my next build with a piezo pup.
Also, if anyone is interested, "piezo pickup" in Chinese is "压电拾音器" ("yādiàn shíyīn qì") and it literally means "pressure-electricity pick up device"). This will come in handy when I search Taobao.com for piezo pups in earnest. And "Electric guitar single coil pickups" translates to "电吉他 单线圈 拾音器" ("diàn jítā dānxiànquān shíyīnqì"). They can also be had pretty cheaply on Taobao.com.
Howdy Rand -
I have had similar experiences with Hot Glue = too much bass.
I made two very similar CBGs.
On both of them I placed the Piezo on top of the box directly under the strings and just in front of the Bridge.
(I then drilled a hole into the box for the wires to connect with the Jack wires.)
On one of the CBGs, I glued the Piezo to the box with Hot-glue 'only' on the bottom of the Piezo, i.e. to stick the Piezo to the box. No glue was placed on top of the Piezo. I hid the Piezo by super-gluing a concave metal disk over it. This disk was twice as large in diameter as the Piezo, so the Piezo did not touch the disk. The sound on this CBG is very good with no unwanted extraneous finger sounds. And no excessive bass.
On the second CBG, I again glued the Piezo to the box with Hot-glue....but on this CBG, I used Hot-Glue to glue the concave metal disk over it. So basically, the Piezo was completely encased with Hot-Glue. Again, this CBG had no unwanted extraneous finger sounds. But........it indeed had excessive bass. The only way to compensate for that extra bass was with the amp controls.
It'll be November before I can get back to making some more CBGs, but at that time I'll do some more experimenting and report back to y'all.
Thanks for the feedback. It seems to confirm my findings. So, I'll have to try your "minimal hot glue approach" and super-glue some kind of cover/casing over it. Maybe a larger bottle top like one of those off a fruit juice bottle. I'll let you all know how this works. Will have to wait for my next build.
Many thanks to Rand and KS ! Really valuable information to have in advance when contemplating a more advanced build than I am presently fabricating !
It might seem to me that the soundboard is transferring the harmonic vibration to the piezo transducer.
Any excess flexible adhesive must be dampening the higher level tones.
Perhaps the transducer might perform acceptably if placed upon the underside of the soundboard, in that same location, where it might not be necessary to place a cover over it ?
I'm still learning about diddley bow and canjo construction, but look forward to building the more complicated instruments.
Yes, Rusty, I would recomend that the Piezo be Hot-Glued to the underside of the SoundBoard, (i.e. place it inside the CigarBox). That way, it is hidden and no need to place any type of cover over the Piezo to hide it.
My purpose of putting the Piezo on the top of the CigarBox was that I was trying to place the Piezo directly under the strings and directly in front of the Bridge. That would be difficult to accomplish when the Piezo is placed inside the CigarBox, as the CBG Neck extends down the middle of the inside of the CigarBox. Hence, the Piezo would need to be placed just to the side of the Neck, and would not be under the strings and not in front of the Bridge.
Just to throw another concept into the discussion here, I understand that some folks glue the Piezo to the Neck instead of the CigarBox. I wonder how that works out for them?
Great discussion here on this topic....I hope others will share their experiences on "Piezo Location Placement", and results.
I guess a good option here would be to enlist a geek with a sillyscope and see what the picture says with the piezo mounted in a number of different positions, and using varying methods, along with trying multiple piezos... to cover all the angles! :-)