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Stuffing Cavities To Reduce Maple Shrillness

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I've got an all-maple strat which has the "swimming pool" rout in the body. It's got Kent Armstrong dual rail humbuckers in bridge and neck, and single coil in the middle. The guitar always seemed extremely shrill and trebly, especially with the bridge pickup in use. I wired it for master volume and tone, with a separate push/pull to split the humbucker coils. I swapped the tone cap for a .047uf which has helped control the treble, but I think there's more to it....

I've read lots of people say that the reduction in wood because of the swimming pool rout affects tone adversely, but maybe there's another way to look at it - I suspect that the lack of wood under the scratchplate creates a tone chamber that resonates like any accoustic chamber would, but not in a musical way. There was a high, tinny reverb that could be heard before plugging in which I guess found its way into the amplified sound.

So, I placed half inch thick foam in the cavities under the scratchplate, and couldn't believe the difference - the guitar sounds much more focussed and controllable, highs are sweet without being shrill and I'm not fighting with the tone controls on the guitar or amp any more. I wish I'd done this years ago.

Quite an interesting experiment, as I was just contemplating this very idea last night since I've been starting some Maple bodied builds lately, interesting how answers come when you need them.

Seriously, I was just last night pondering putting something in the hollow cavities of The Phoenix and thinking over the possibilities of how it might possibly soften the tone, and wham, I read this post today...funny...

What do you all think of this?

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Those LA Jazz/studio guys of the seventies used to stuff their 335's with cotton wool to resist feedback I do recall.

I've alwasy considered most strats to be like semi acoustics...large amounts of hollowing under the scratchplate and in the trem cavit. The large scratchplate effectively a thin plastic top. This probably does contribute to the sound.

However, as the scratchplate/top vibrates...so too do the pickups attached to it on a strat. The result could be microphonic feedback, or transient high frequency edge from the pickups vibrating, made worse by single coils of course.

So, it is not surprising that these non-musical transient vibrations are damped down by such a strategy.

I don't think however that it is anything to do with it being made of maple although a very bright sounding guitar might make the symptom worse.

In some heavily chambered guitars I suppose they might benefit from it. Of course, ironically, people often intend the chambering to "improve tone" by adding back these high end acoustic transients. Of course there are other reasons to chamber things like weight.

I've always had in the back of my mind a very light construction technique that uses foam sandwich techniques...or even squirting liquid expanding foam into a guitar to support a thin flexible back and front.

Part of the attraction to the "tone-flow" thing (small connected cavities) or some of warmoths and other bodies with lots of small chambers or internal slots is that you get the weight loss without these excessive vibrations.


So...on a strat with a very thin top with pickups attached to that I can see how you might get some improvement...but I don't think the maple side of things makes a big difference unless the guitars are very resonant.

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I had a strat copy like that - a lot of the tinny reverb he descibes could be the springs from the trem. On the build I made with a strat-style trem, the springs seemed to vibrate whenever I hit a certain note - (I think it was A#, but I can't remember now) I put plastic tubing inside the springs to keep them from vibrating so much, but took it out, because I kind of missed the weird sounds I could coax out of that guitar with a whole lot of gain going on. The strat copy I had (swimming pool route) that made a lot of noises like that, I thought about that, maybe the scratch plate was vibrating. I ended up replacing the springs holding the pickups in place with compression tubing and it made a lot of difference. I think a little foam under the pickups could do it too, I don't see the need to go filling the whole cavity.

If those kent armstrong pickups, the double rails are the ones I'm thinking of, they're just kind of shrill pickups too. At least, the ones I tried once where. But I think a lot of what he describes are the things that give strats their character, the weird little noises you get from the trem cavity and such.

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  • 3 weeks later...


I have a best I can describe jazzmaster copy body and neck. I am building the pickguard, bridge, and tailpiece for it. (I dont have these parts)

Anyhow, this has a swimming pool route and some extra removed. it has a huge opening in it.

I have been debating on what to do with this guitar to take advantage of this.

I was thinking clear pickguard with a hole like and acoustic in it. throw a piezo bridge on it.

then I was thinking dual humbuckers and a piezo bridge.

Maybe I can get some subtle 355 sounds mixed with some archtop like piezo tones?

or maybe it will sound like crap and I will spray right stuff expandable foam in it.

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Perhaps a little off-topic, but I do recall a trick of popping cotton wool balls into toms so they bounce on the bottom skins adding a little brushy pffhdm and shorter decay. Anyway.

I think it's debatable, but probably a can of worms to do so. In my opinion, small cavities in solidbody instruments create smallish resonances/attenuations. Great for weight loss, probably not so for frequency interference? Joshua probably experienced that in the negative with the component resonance. I should really complete my semi-hollow 8-string to experiment and experience this myself. That is completely hollow with 1cm of material on the sides and blocks to hold hardware. Worst of both worlds? :-D

I don't buy the reverb thing on the basis that the cavities are so small that there is little opportunity for a natural mix of frequencies. The small nature of instruments in my mind would create very specific resonances and attenuations like comb filter. Perhaps some people (Brian May's Red Special, perhaps?) hit an unintentional sweet spot accidentally? Then again on the flipside, it could be argued that body shapes or whatever do the same thing. The Strat that sounded great in D.

Sorry I didn't try and solve some great mystery here, but I think these "tone" cavities are just as relevant as the bits that remain and despite adding a character for sure, they'll be difficult to predict and engineer. And your next bit of wood will be different too Drak. Suck it and see. If you look at it from an acoustic dampening point of view, you might as well fill those weight reducing cavities with lead to reduce the high frequency mush!! :D

Hold yer breath when you burn 'er!

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Massive maple bodies reduce highs, not increase them. Mass interacts with a system to the degree that lack of stiffness allows. The less stiffness, the more highs are rolled off by the existing mass. The guitars that I've played that have cavities do sound different. They sound to me like the primary effect on the tone is through mass reduction, and little or none through acoustic resonance of the cavities themselves. In other words, they sound lively and bright with even neck response and long sustain, like all light weight guitars.

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