Why are guitar cavities not "filled"?

The Dali

The Dali

MeltedClockologist
I've often wondered about this... and I'm sure I'm just not an acoustically-attuned person... but is there a reason that control cavities and pickup routings are not filled with material, like a speaker? Just curious, since I have a fender strat with a single-humbucker in the pickguard and was considering "filling" the other parts of the top-route with some form of acoustic material. Which got me thinking about some of these guitars with large control cavities and the "dead space". Has anyone tried packing in stuff in those spaces to see if there are acoustic differences?

Another reason I posted this is I was reading the "single humbucker" guitar thread and Frank had mentioned that guitar that only have a bridge humbucker routing (with wood in the neck/middle) have a stronger/aggressive sound... which I wonder if it could be replicated with some form of "packing"...

Any ideas, or am I totally nuts?
 
Re: Why are guitar cavities not "filled"?

To keep the electronics accessible and, hence, possible to service.
 
Re: Why are guitar cavities not "filled"?

Probably won't know unless you try..
I'd be afraid throwing a bunch of foam or whatever in the cavity would wind up wearing the wires or solder joints and potentially short something out.. Guitars have worked fine for 50+ years with the cavities, I don't think it'd make a huge difference either way...
 
Re: Why are guitar cavities not "filled"?

Fill 'em up with packing peanuts. Expect gorgeous tone.





















Not.
 
Re: Why are guitar cavities not "filled"?

The Dali said:
Another reason I posted this is I was reading the "single humbucker" guitar thread and Frank had mentioned that guitar that only have a bridge humbucker routing (with wood in the neck/middle) have a stronger/aggressive sound... which I wonder if it could be replicated with some form of "packing"...
Click to expand...

In this case, it's not the presence of substance that makes the difference, it would be the way the neck relates to the body, shape wise, transferring vibration through a thick block of wood, instead of a body that's gutted out close to the neck joint. Filler material wouldn't do the job of actual wood being present and ingrained. I didn't think it would make that big of a difference, but I'm not surprised that it does.

What I wonder is if you could win back some rigidity and transference of vibration by putting something like a truss rod between the neck joint and the tail end of the guitar. And if you can't make it a straight line, what about a cable truss that rounds a corner?
 
Re: Why are guitar cavities not "filled"?

Also, the reason there is batting/dampening material in a hi-fi speaker is to dampen the back waves from the drivers, the idea being that it helps you hear the front wave (coming from the front of the speaker) more clearly. The goal of the speaker, as a system, is to reproduce with a high degree of accuracy a musical signal that has already been created. We tend to like linearity and neutrality for this kind of task, so we usually take design approaches that seek to minimize interference from cabinet vibrations, feedback into crossover elements, phase non-linearities, etc.

With an electric guitar, the vibrations of the strings -- as interpreted by the pickups -- are really the source of the musical signal. The guitar, as a system, doesn't have to reproduce a signal so much as create a new one. It doesn't have to sound exactly like anything, really. If you like the sound that's coming out of it, it's doing its job. Aside from tightening things down so that they don't rattle, we usually don't inhibit vibrations in guitars. But if you happen to find a practical way of dampening the air volume inside a control cavity, and you like the result, well there you go.
 
Re: Why are guitar cavities not "filled"?

Control cavities in electric guitars are not producing sound, so packing them will do nothing. The most likely difference to occur is you'll push a positive wire against a ground plane on the back of a pot and ground out part of your guitar. For a 'filled' cavity to contribute to the guitar's sound and resonance, it would have to be filled with the original wood.
 
Re: Why are guitar cavities not "filled"?

beaubrummels said:
Control cavities in electric guitars are not producing sound, so packing them will do nothing. The most likely difference to occur is you'll push a positive wire against a ground plane on the back of a pot and ground out part of your guitar. For a 'filled' cavity to contribute to the guitar's sound and resonance, it would have to be filled with the original wood.
Click to expand...

Well, it's a chamber. There's probably a difference between a chamber "covered" with wood that's never been missing, vs. a chamber covered with plastic or aluminum. How big a difference would it make, sonically? No idea. But I think you're right that more people would inadvertently cause wiring issues than would report a noteworthy sonic difference.
 
Re: Why are guitar cavities not "filled"?

The Dali said:
Another reason I posted this is I was reading the "single humbucker" guitar thread and Frank had mentioned that guitar that only have a bridge humbucker routing (with wood in the neck/middle) have a stronger/aggressive sound.
Click to expand...

I've read some about this, & a lot of it has to do with the fact that there is no neck pup magnetically pulling on the strings.
I've seen guitarists (though I can't name any right now) who purposely remove the neck pup for just this reason.
Maybe phil x ?
 
Re: Why are guitar cavities not "filled"?

I think having a cavity (ex - swimming pool route) has a slight difference - something you're not going to hear in a mix, but might have a quality you like or dislike. Filling cavities would be a good bit of work for probably not a lot of benefit.
 
Re: Why are guitar cavities not "filled"?

You want resonance. In a guitar. Not in a speaker cabinet.

I'm pretty such that e.g. putting epoxy into all cavities will make a big difference in sound.
 
Re: Why are guitar cavities not "filled"?

925SS said:
I've read some about this, & a lot of it has to do with the fact that there is no neck pup magnetically pulling on the strings.
I've seen guitarists (though I can't name any right now) who purposely remove the neck pup for just this reason.
Maybe phil x ?
Click to expand...

Frank Falbo says it's half magnetic pull and half the lackof a cavity https://forum.seymourduncan.com/sho...cker-guitars&p=3645314&viewfull=1#post3645314

It would be nice to know what the measurable difference is though, I think the significance of magnetic pull is often overestated.
 
Re: Why are guitar cavities not "filled"?

I always build wood cavity covers for my custom guitars for this sort of reason. I figure, it is an open cavity (just like a semi-hollow or chambered guitar, so I might as well cover it with wood that vibrates. That and I've got to cover that cavity with something: plastic or wood, so......
 
Re: Why are guitar cavities not "filled"?

The only example I can think of where something like this makes a difference is stuffing the body of a hollowbody or semi-hollow with foam or similar material to prevent feedback. That's how Izzy Stradlin was able to play an ES-175 on stage with Gun 'N Roses and not have feedback issues with their insane stage volume.
 
Re: Why are guitar cavities not "filled"?

I've always wondered if strat routes work as a miniature sound box. They seem to have a slightly livelier acoustic sound. I don't know how well that comes out amplified.
 
Re: Why are guitar cavities not "filled"?

Because it would make no tonal difference whatsoever, but would add plenty of hassle and expense.
 
Re: Why are guitar cavities not "filled"?

Dr. Vegetable said:
Because they wouldn't be cavities if they were filled!
Click to expand...

Hmm - doesn't your dentist still call them cavities after they are filled?

I subscribe to this school of thought, tho:
Pic+C+-+Cat+Fight.jpg
 
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