a question for all you wood knowledgable forumites...

[dain]

so i'm working on my electric sitar tele, talked about here index.php?topic=6112.0

and i've got it strung up and everything, but i'm noticing the sympathetic strings are not resonating as well as they were on the original cheap plywood rogue.  now i realize that a solid block of tonewood is not going to have the sympathetic vibes a thin top will, so i'm thinking about making the tele semi hollow.  if i do it i'll do it rickenbacker style where you route out the body till its a shell then glue on a thin top.  i'll leave the body solid where the 12 zither tuners are because i doubt the thin top would support that much tension.  ditto where the string anchors are.

i'm wondering this
A will this method of construction give me the sympathetic vibration i need to drive the extra strings? or will it be too dampened by the thick sides of the body?

B will i lose the sustain that i have now on the main strings when i don't have the body mass i do now?

C  what kind of top do i need?  i'm assuming it has to be a solid piece of wood, not bookmatched pairs if i want to get good transmission...

anyway, any help would be great!

[djetz]

I'm loving semi solid guitars right now - and I've never found them to lack sustain. An ES335 style semi has a solid centre block and hollow sides, and the wood that makes up the front and back - the arched bits - is usually a laminate. In other words, upmarket plywood.

I think having an f-hole (or whatever) under the sympathetic strings would be a great idea. It will definitely increase the resonance of the sympathetic strings, and probably make the regular strings sound slightly fatter. Most of the effect would be localised under the drone strings, though.

So, no, you won't "loose" any sustain. One O in lose, BTW. "Loose" means "not tight".

Since you're not making an archtop, you don't need to worry about covering the entire front of the guitar, just the hollow section. It won't make a difference. One piece or twelve, no-one on earth can actually hear a difference, no matter what they claim.

It's probably not that hard (or expensive) to find a smaller thin piece of maple, birch, spruce, whatever seems best - any tone wood that's used on semis or acoustics.

[dain]

thanks for the info...so an f hole actually increases resonance?  interesting.. i don't have a whole lot of real estate left with that guitar but that is an idea...

i'm just bugged by the huge difference between the two bodies, the rogue was zero sustain/excellent sympathetics and the tele is just the reverse!  i'm wondering if i can split the difference.

[djetz]

so an f hole actually increases resonance?

That's why acoustic stringed instruments are hollow and have soundholes. Makes the sound project more - it's actually a kind of acoustic feedback. The vibration of the strings goes into the hole and bounces back, making the strings (and the wooden top) vibrate even more.

It's a good thing Sir Isaac Newton invented physics and prevented the conservation of energy, otherwise acoustic instruments would sustain forever and we'd never get any sleep.

Anyway, acoustic feedback is exactly what you want for sympathetic strings, so a sound chamber with a hole in it under the strings is ideal. I'd suggest experimenting with the shape and size of the hole for best results, but that would require considerable fucking around so I'd just suggest a hole (doesn't have to be round or "f" shaped) under the middle of the strings. Not too big or it'll defeat the purpose.

As to why the original guitar didn't sustain - I expect the "sitar" bridge is the main cause. It's dampening the vibration of the strings, soaking up energy (Newton again), so it will never have as much sustain as a regular guitar bridge.

[djetz]

This topic is interesting me, plus I'm an insomniac, so I'm going to write more...

Les Paul didn't invent solid bodied guitars to increase sustain, he invented them to reduce it. Or to reduce acoustic resonance, anyway, which is what creates sustain. The whole point of a solid body is to prevent everything except the strings from vibrating. To minimise acoustic feedback. Check out what Les has said about it - I'm paraphrasing from memory, but you can check the accuracy of what I'm saying.

Think about an acoustic guitar with a pickup mounted on it. Plug it into an amp, and what happens? Feedback.

Feedback isn't an electrical phenomenon, it's just vibrating air (aka "sound") causing the strings to vibrate, which produces - you guessed it - more sound. Which makes the strings vibrate more. And so on. At a certain volume, it causes a loop - your actual feedback loop.

All acoustic stringed instruments need a certain amount of acoustic feedback, otherwise... well, play a solid body electric without plugging it in. It's quiet and bland. That's why acoustic instruments are hollow. Guitars, violins, cellos, pianos - wooden boxes for vibrating air.

So when Les Paul attached pickups to a solid chunk of wood, he did it because he realised that if you're amplifying the strings electrically, you want to keep the acoustic feedback to a minimum. Otherwise: amp feedback. Not popular in jazz.

The famous Les Paul guitar sustain doesn't come from the wood itself, the wood is meant to be inert. The sustain comes from powerful pickups picking up (yes!) every bit of vibration from the strings. And nothing else.

The wood is never quite inert, of course, so it does have some influence on the overall sound, but compared to scale length, bridge design, and PICKUPS, it's pretty slight.

So anyway - hollow = more resonance, solid = less. If you want strings to resonate more, add a sound chamber. But if the bridge is designed to soak up some of the string's energy - like the electric sitar bridge is, by making the strings buzz - the price is less sustain. Which would be why the original electric sitars are hollow. Going to a solid body won't increase sustain, if anything it will decrease it.

Really, Newton explained most of this 300 years ago, and Einstein tided up most of the loose ends. Energy - in this case a vibrating string - will dissipate. It's absorbed, and everything returns to a state of inertia. You can't have free energy, it's impossible. So if you put energy in - by making a string vibrate - eventually the energy will dissipate and the string will stop vibrating. If you speed up the process, by making the string buzz, you dissipate the energy faster and that means the string returns to an inert state faster. In other words, less sustain.

Now, I wouldn't say that transferring the sitar parts to a solidbody is a bad idea, because you're going to crank your amp, and when you do, everything will come alive. But at low volumes, it'll sound crap. Trust me on this, Newton and Einstein will back me up. So my advice is: play loud. If anyone complains, tell them it's justified by solid scientific principles.

[dain]

As to why the original guitar didn't sustain - I expect the "sitar" bridge is the main cause. It's dampening the vibration of the strings, soaking up energy (Newton again), so it will never have as much sustain as a regular guitar bridge.

nope,  the sitar "buzz" bridge has been the constant in both guitars.  it is of course still "soaking up energy" but on the solid tele body i can let the bass notes drone.  that was really hard on the original setup.

the strange thing is i'm not really talking about "resonance"  i'm really concerned with "transmission" i wonder if they are separate enough functions to need different techniques .  the main difference between the electric sitar and a real one (among many things) is the fact that on a real sitar the sympathetics are running through the same bridge as the main strings.  this is awesome because it couples the two sets of strings.  unfortunately, i don't have that so i'm wondering if i need to concentrate more on transmission issues.  i.e. linking the bridges versus linking the string anchors.

i'll have to work on the soundhole placement...here's what i'm working with now...

http://i165.photobucket.com/albums/u47/ ... IM0713.jpg

[djetz]

nope,  the sitar "buzz" bridge has been the constant in both guitars.  it is of course still "soaking up energy" but on the solid tele body i can let the bass notes drone.  that was really hard on the original setup.

Well, it's entirely possible that a badly designed/made guitar will actually dampen string vibrations in unpleasant ways, so putting the buzz bridge on a different body - moving it from a crappy semi-solid to a decent solid - will increase sustain if that's the case.

[soundhack]

hi dain & djetz

i don't know if i can add anything here - but i think you have it backwards djetz. a solid body guitar will sustain more because the wood vibrates less. if the wood vibrates more (the case with a hollow body), it soaks up energy from the strings, and the sustain goes down.

sustain and resonance go in opposite directions. lets define sustain as the length of time that the string vibrates, and resonance as the amount of vibration in the guitar body. as more energy is transferred from the string to the body, the resonance goes up and the sustain decreases.

as far as transmission. the solid body vibrates very little, so very little gets transmitted from bridge to bridge. like you suggest, you could increase the transmission by making a thin top (like a danelectro) which is driven by the bridge, but your sustain will go down. so yes, its a balancing act, how much buzz sustain do you want versus how much sympathetic vibration.

myself - i'd go for the long buzz.....

[dain]

i DO like the loooong buzz....i've been dreaming about adding a sustainer pickup with the pickup on the main strings and the driver on the symps...

but then you'd need TWO pickups on the sypathetics! and i don't know if i have any more room...

well, if i still want it to look like a guitar and not a jackson pollack...

[djetz]

hi dain & djetz

i don't know if i can add anything here - but i think you have it backwards djetz. a solid body guitar will sustain more because the wood vibrates less. if the wood vibrates more (the case with a hollow body), it soaks up energy from the strings, and the sustain goes down.

sustain and resonance go in opposite directions. lets define sustain as the length of time that the string vibrates, and resonance as the amount of vibration in the guitar body. as more energy is transferred from the string to the body, the resonance goes up and the sustain decreases.

as far as transmission. the solid body vibrates very little, so very little gets transmitted from bridge to bridge. like you suggest, you could increase the transmission by making a thin top (like a danelectro) which is driven by the bridge, but your sustain will go down. so yes, its a balancing act, how much buzz sustain do you want versus how much sympathetic vibration.

I was talking about what I called acoustic feedback. Let's call that good resonance. When an acoustic instrument resonates well, it actually drives the vibration of the strings, making notes louder and sustaining them longer. When it resonates badly, it can absorb the vibration of the strings, muffling the instrument. Which was what I was talking about in my last post. Phase cancellation. A dead sounding guitar.

But if you think semi-solid guitars don't sustain: bzzt! Wrong. Go play a decent one. Play a good acoustic guitar: You can play a note, mute it, and hear the "bloom" hanging in the air for a moment as the body continues to resonate in sympathy with the note. Seriously, try it. Acoustic players get all hung up on the design of the internal bracing of a guitar - but unlike electric players worrying about multi-part bodies, it does make a difference.

The idea that solid dense wood creates sustain is completely wrong. It can prevent bad resonances from muffling sound, true, but the primary goal in solid body electric design was to prevent acoustic feedback (good resonance) from causing amp feedback. Solid body guitars, as invented by Les Paul and designed by Gibson, were meant to keep all vibrations except the strings to a minimum so that the amp - not the guitar body - was amplifying the strings. 

Later it was realised that some acoustic resonance can be a good thing, which is why semi-acoustic guitars were invented in 1958, ten years after solid bodies. Before 1958, the choice was either a hollowbody or a solid body. (Before anyone starts talking about Charlie Christian and Gibson ES150s and so on - they're archtop acoustic hollowbodies. All of them. Jazz guitars with pickups attached. The first semi-solid was the ES335, in 1958.)

Anyway, if you pluck a string on an acoustic, then pluck the same note on a solid body, it's easy to hear that the acoustic note lasts longer. (Unless the instrument in question is a POS.) Once you plug into an amp, you create sustain electronically by a couple of methods, the best one being gain. We all know that you need a certain amount of volume for an electric to "come alive" properly - solid body guitars don't sound as good without a certain amount of interaction with the physical properties of vibrating air coming from an amp. In an acoustic guitar, the same process is is caused by the vibration of the body of the guitar itself. Vibrating bodies make strings louder, not quieter. Duh.

Try this simple experiment: fill your acoustic guitar with towels, stopping it from vibrating. Is it louder or quieter? Do notes sustain more, or less?

Sustain in a solid body electric comes from the pickups and the amp. Not the guitar body. If the amp is loud, it will excite the guitar's strings in the same way the vibration of a good acoustic guitar body will. Feedback. Not amp feedback, not the sound we all love and hate, but feedback in the sense that the strings are excited enough to vibrate more, without it being uncontrollable or creating unwanted notes. It just means the notes will "bloom", and you'll have more sustain.

I'm not expressing an opinion here, it's basic audio physics. Solid bodies do not create sustain. Hollow bodies do. Bad design and/or bad build quality means that some hollow bodied (or semi solid) guitars don't sustain well, and can even end up being acoustically dead. But solid bodied guitars were originally designed to be as acoustically dead as possible so that all the sound came from the amp. Since solid bodies were invented, people have found that there will always be some acoustic resonance, and it can be a good thing, but the whole point of solid bodied guitars was for nothing but the strings to vibrate. Not to create resonance, but to prevent it.

The amount of string energy lost by sympathetic vibration of the guitar is trivial, and it's offset (ha) by the feedback loop created by the vibration of the guitar feeding back into the strings. Yes, the energy is dissipated eventually, but it's dissipated into the air as vibrations: sound. It's not absorbed by the guitar body. That would be getting things backwards.

Guitarists are incredibly superstitious, and Mythbusters would have a year's worth of material to work with if they took on that challenge, and at the end of it you'd still have guitar players coming up with stuff that's got no basis in reality and believing it with every fibre of their being - so I've tried to explain as much as I can here. If you want to believe something different, fine, whatever, have fun with that. I'm no scientist, I'm barely educated at all in the formal sense, but I do try to understand how things really work.