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I'm working on an electric body, and I had a thought. First, a brief background on the application. I'm building this guitar primarily for taking to lessons, most of which are 30 minutes (in the student's home). It will have a built in amp to speed setup time, as 30 minutes is just so short. It will also have a 4X6 coaxial speaker built into the back of the guitar. It will be a hollow body (2" thick, poplar, "nut bowl" design) for the sake of the speaker. And it will have a thin, flat top.

As I was looking at my work yesterday, trying to decide what I wanted to use for the top, it occurred to me that I have a hollow body with something close to a soundboard. So I'm thinking about using an acoustic bridge with a piezo strip beneath the saddle. Am I crazy? Here's the basic design:



I definitely have application for an acoustic sound in lessons. It would be very useful. And I know people have done stuff like this before. The goal is not to produce a good true acoustic sound. It's to produce a passable piezo sound (through an external sound system or even through the built in speaker). So here are some specific questions:

1. Is that big pickguard likely to ruin my chances of success? I like the look of it, and I've known some acoustics to have fairly big pickguards.
2. Are the weight of the pickups and controls likely to ruin my chances of success?
3. Given that the top will be flat, should I make it any thinner or thicker than one might expect of a radiused top? Are there other special concerns there I'm not thinking of?
4. I'm thinking of using two simple braces running from the neck end to the end pin, like in some archtops. Good idea? Bad idea? Should I even be using braces?
3. Have I devised an abomination against the art of luthiery? Should I just throw a strat bridge on there and be done with it?

Here's what it looks like without the pickguard:



I appreciate any help you guys might offer. This is clearly an experimental build, but I think it could work. Besides, I'm using cheap materials anyway.

Thanks,
David

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David Morris

Good idea but this will not work, it will have a TON of feedback. Feedback happens when the guitar pickup up the sound that the amp is making, then the signal is sent to the amp again where it is picked up again by the guitar (and the process continues). Since the speaker will be build into the guitar, the guitar will definately pick up EVERYTHING that the speaker puts out, and even more so because the guitar will be hollow. The second you turn this on there will be absolutely nothing but feedback. Its a great idea, but unfortunately it wont work, sorry dude -Alex

Alex, I appreciate your reply, but I've installed an amp and a speaker in a guitar before, and you're not correct. Here's a production model guitar that does the same thing:

http://www.amazon.com/Pignose-PGG-200-E ... B002JCSTE6

In my case, the speaker will actually be facing toward my body, away from the soundboard, reducing feedback. I certainly realize the chance of feedback with any sort of acoustic pickup is much greater than with an electric guitar, but the low volume produced, combined with the relative thickness of the back and sides should keep feedback in check. My concern is not that that piezo element will pick up too much. To the contrary, I'm concerned it will pick up too little.

Thanks for your input, nonetheless.

David

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David Morris

There are successful hybrids out there, definitely.
The biggest thing is grounding the strings for the electric guitar portion.
EMG's solve that problem.

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Old growth, shmold growth!

Anyone who has shopped in enough music stores or looked on eBay will tell you that you are in the wrong - big time. I owned one like this in the past, and built one for a client. It's not a great idea - but it DOES work.
Therefore - to the OP I say "ROCK ON!", and document everything in order to post it here.

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"Act your age, not your shoe size" - Prince

Run a strip of conductive metal beneath the bridge plate where it will touch the ends of the strings. That's your string ground.

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David Morris

Is there a bridge plate in this hybrid?

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Old growth, shmold growth!

I suppose it makes sense to have one, doesn't it? Probably a thin one. I think I've got an old scrap of Brazilian Rosewood that would work well. Any thoughts on how that top will work as a soundboard?

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David Morris

Yo, David,

Ya, your crazy alright, but you ain't stupid...big difference.

build the sucker and post pics please.

Parallel braces eh...might wanna do parallel ladder brace with a bridge plate or go thicker top and and or heavier braces since the sound is comeing from the vibes entering the piezo and not form a top plate thats pushing air. But still you may wanna add a sound hole.

It looks like a strat with too many knobs...whats with all the knobs? Me thought this was a teaching aid...besides when you start looking at on board amps for that piezo me think you may have to do a rethink about all them knobs. Me thinking says you only need a volume pot for to hear the sucker. Yup, me would work out all the electronics first and then design the body accordingly.

blessings
Padma

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Audiences and dispensations on Thursdays ~ by appointment only.


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Padma, I'm so glad you saw this thread! You're the king of crazy builds. I mean that in a good way.

My wife tends to agree with you on keeping it simple. I think you guys are right. No pickguard, and only a single P90 in the neck position (and the piezo). Controls will be side mounted. I plan to build a "Noisy Cricket" amp that will require three knobs for the electric. I'd planned a master volume for the piezo and a 5 position rotary pickup selector. I just don't have much experience with acoustic soundboards, so that's where I'm feeling shaky.

I just ordered an Englemann top from LMI that's advertised as being between 0.120-0.125" thick. Think that would be alright, or still to thick? I could certainly do ladder bracing. I was just drawing some inspiration from Taylor's T5 bracing, which from what I remember was just two parallel braces down the length of the body. Ladder bracing would give me a chance to play around with chisels and spokeshaves though, and that's fun. I was trying to decide whether a soundhole would be necessary just for the Helmholtz resonance. If it has one, I'm putting it in the back or the side (or both).

Here's what we've got so far. Not bad for Poplar!



EDIT: Thanks also for your response, Chris. I missed it. You're right in what you say about hybrids. They're a compromise. But for this project, I think it's appropriate.

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David Morris

My apologies for the incorrect response, if this really does work then I certainly know what my next project is

Before you read, this, keep in mind that Padma is more experienced than me. I kinda dig all the knobs, definately go without a pickguard since your making in semi-hollw (we dont want to interfere with that beautiful face resonating as much as it can). I think a pair of f-holes would be absolutely gorgeous on this thing. Personally, I like having alot of knobs to let me hone in on the sound that Im looking for. In this situation, I would go with f-holes, one tone knob and one volume knob for the pickup, and a set of these http://www.stewmac.com/shop/Electronics ... trols.html mounted in one of the f- hole to control the tone and volume of the piezo if not a pre-amp. Just my little Ideas!

F-holes instead of a soundhole would lessen feedback IMO, also, .125-.130 is not too thick, I would think maybe too thin, for this type of instrument.

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Old growth, shmold growth!

Good to know. Thick braces then? What should I be trying to achieve? Tone? Structure?

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David Morris

Ummm, dude tanx for the compliment....
but the truth be known, I, me, Padma really don't know diddly squat about loofierism,
although me real good at shootin me mouth off and me can make great sawdust.

Yes me function on dis site is to lead all you up and coming loofiers down the garden path with me satirical B.S. Please don't be takin any thing me say cereally.



blessings
Padma

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Audiences and dispensations on Thursdays ~ by appointment only.


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You gotta be kidding me...

may me most humbly suggest you don't be bother messing with any of that B.S* tone and structure stuff...naw...you wanna achieve something, well then why not go for the Great Perfection...you know, the Gold Ring, Enlightenment, the Rainbow Body, Buddha Hood or perhaps try and pull of the Ascension or maybe Cosmic Union with the Nothingness of the What. Ya thats it Comsic Union with a sexy consort from the 23rd dimension. Now theres something to be achieving so they say. Messing with all that tone and resonance loofier stuff, it just be a waist of time.


blessings
Padma

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Audiences and dispensations on Thursdays ~ by appointment only.


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Hmm...

I could try writing ancient incantations on the braces with a virgin's blood. Of course I'd have to find a virgin first. I'll have to think on that one.

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David Morris

Not sure I know what I'm doing, but here's the bracing...



I sort of went my own way on this. I took Padma's suggestion of ladder bracing, and then just added in a couple extra bars in an attempt to distribute vibration across the soundboard. The general concept was very thick bracing in the upper bout (where the electric surface-mounted pickup will be), and thin bracing in the lower bout, to try and compensate for the rigid sides. I used an old scrap of Brazilian Rosewood for the bridge plate, because that's what I had lying around. The top is Englemann and the braces are 2nd grade Sitka.

Incidentally, I've decided that shaping braces is the most fun thing I've done in any guitar build. I don't know if I did anything right, but I had a lot of fun. And it does seem to have a pretty good tone, from my limited experience. You can hear the BRW when you tap there, which was my goal. The two primary lessons I learned in this step were to make sure you keep notches really tight where braces intersect, and not to buy 2nd grade bracewood unless you really know what you're doing. That said, I'm thus far pleased with the outcome.

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David Morris

Looking good, David.
You might think about another brace in the upper bout,
because of the stress from the neck.
Just my initial thought.
Maybe somebody else will chime in about that.
You could go to the acoustic section of the forum,
and see what they think.

Looking good, David.
You might think about another brace in the upper bout,
because of the stress from the neck.
Just my initial thought.
Maybe somebody else will chime in about that.
You could go to the acoustic section of the forum,
and see what they think.

Thanks Alan. Where would you put it? Side to side it's really stiff, but I could see why it might not be as stiff along the length. The sides in the upper bout are something like 3/8" thick, so I'm not worried about structural stability, but I certainly wouldn't want the top to warp over time.

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David Morris