the great bracing debate

[dmoss74]

i know this is a touchy subject, and hard to specifically quantity, but here goes anyway:

i have a recording king om guitar (sitka/hog). i love the sound, but he bass does lack a bit. so if i am understand it, by shaving some of the bracing, it would enhance the bass response of the guitar? i'm not saying i want to do it, but is that the desired effect people get by doing that? i understand that by doing so, you would be compromising the structure of the top itself too.

basically, i am guessing that every maker braces specifically for the sound they desire, thus a (same model and specs) martin sounds like a martin, a taylor sounds like a taylor etc. and if by subtracting some of the bracing you add bass response, do you therefor lose some mids?

also, the top of my RK has a fairly rough underside. does that have a significant effect on tone?

[marioed]

Hello,
I'll take a stab at answering your questions. Shaving, or more likely scalloping, the braces may improve the bass response and if done correctly it will have minimal effect on the mids and trebles. The problem is 1) knowing where to remove material and 2) knowing how much material to remove. If too much material is removed in the wrong place it can make the bass 'muddy' and hurt the mid and treble response as well as seriously compromising the structure. There are guitar tech's like Bryan Kimsey, who specialize in revoicing tops and are very good at what they do. To me it is not a DYI project I'd do on an expensive guitar.

As to bracing and signature sound, the bracing along with other factors such as the thickness of the top, back and sides work together to produce the sound. Bracing can vary in terms of the pattern the braces are laid out on as well as the thickness, height and shape of the braces. There are a lot of different bracing patterns like ladder bracing, x-bracing, double x-bracing and lattice bracing that are used. Factors such as the angle of the x-brace; location and number of the tonebars and fingerbars; how the braces are profiled; whether they are left at height, scalloped or tapered; whether the top is a uniform or tapered thickness; the thickness and shape of the bridge; and the thickness and bracing of the back will all contribute to a signature sound. I'm sure there are other factors I've left out as well that contribute to a guitars voice.

With all these variables it's easy to see why copying a signature sound such as a pre-war Martin D28 is difficult. As to your last question about the roughness or smoothness of the underside of your top. I'm sure that it has some effect but I'd guess it is minimal. I like to sand the undersides of my tops to about 320 grit so they are pretty smooth.
Regards,
Ed

[gitnoob]

I've been considering doing the same for my cheapie Silver Creek. I like the tone, but I'd like to see if I could improve it.

Here's a post from somebody who's already done it:
http://www.acousticguitarforum.com/f...4&postcount=50

FWIW, the braces on the Silver Creek (similar to your RK) are already scalloped, but they're quite thick. In the post above, he deepens the scallops, but I was thinking of trying to take some material off the sides are reshape the braces width-wise rather than depth-wise. In theory, this would reduce mass more than it would reduce strength.

[martinedwards]

Originally Posted by gitnoob

I like the tone, but I'd like to see if I could improve it.

you might. on the other hand you could destroy it. you take the risk......

I was thinking of trying to take some material off the sides are reshape the braces width-wise rather than depth-wise. In theory, this would reduce mass more than it would reduce strength.

your theory is correct.

reduced mass will increase the tops ability to transmit bass.

reduced STRENGTH will increase the tops chance of failing completely.

[dmoss74]

Originally Posted by marioed

Regards,
Ed

thanks for all the info, ed.

[barrangatan]

I hope I'm not going off topic here. I have been reading about shaving braces, and the one question that usually comes to mind is: How do you actually go about the process? Will the top need to be removed first? If not, how does one get enough room and clearance to make sure that the shaving is done correctly?

Thanks in advance.

[martinedwards]

you reach in through the soundhole.

growing an extra wrist is a great help........

personally, I wouldn't bother

[Kitchen Guitars]

Use a mini belt sander.

[gitnoob]

Originally Posted by barrangatan

I hope I'm not going off topic here. I have been reading about shaving braces, and the one question that usually comes to mind is: How do you actually go about the process? Will the top need to be removed first? If not, how does one get enough room and clearance to make sure that the shaving is done correctly?

That's one reason I haven't done it. Reaching in and removing material isn't that hard, but seeing what you're doing is. I suppose you could drop a webcam in the soundhole while you shave.

As far as tools, I have a mini-spokeshave and thumb-planer standing by.

With sandpaper, you can get a good feel for what you're doing, but sanding doesn't remove material very fast.

[Christian Reno]

Originally Posted by gitnoob

....With sandpaper, you can get a good feel for what you're doing, but sanding doesn't remove material very fast.

This is a good thing IMO. I have sanded the centers of the braces a little at a time and popped the strings ends and pegs back in every few minutes to see if I can tell if I am making things better or worse.

[SteveS]

If you want a guitar with good bass response, buy a guitar with good bass response.

[gitnoob]

Originally Posted by SteveS

If you want a guitar with good bass response, buy a guitar with good bass response.

I'm interested in how the bracing affects the voice.

I took a look at your site, and I see you have a mechanical engineering background. I'd be interested in hearing about your approach to bracing and voicing.

Are you using any engineering principles? I-beams, for example. Do you just tap tune, or do you have some more rigorous metrics?

[SteveS]

For great bass response I build light tops and brace and carve/tap tone to allow max movement of the entire plate. It is the whole top, not just the braces, but the brace design scheme, the overall weight of the top, and the stiffness of the system.
Engineering principles? Sure - Stiffness, beam moment of inertia, end treatments, deflection under load, etc.

[SteveS]

Originally Posted by dmoss74

......also, the top of my RK has a fairly rough underside. does that have a significant effect on tone?

Significant? It depends on how rough and how good your hearing is. You could sand that surface smooth and then you'd know.

For sound control in rooms, do you want a smooth or a rough surface? Do rough surfaces tend to dampen sound or reflect sound?

FYI - I now sand the inside of my guitars with 200 grit and put on a coat of shellac. I think smooth is important - and it looks better too!

[gitnoob]

In the case of the guitars being discussed here (Recording King and Silver Creek), we're talking about very inexpensive instruments with all-solid-wood construction. Sure, we could pay (a lot more) for somebody else to build and voice guitars for us, but where's the fun in that?

In the OP's case, he's looking for improved bass response. In my case, I'm happy with both the bass and volume, but I'm interested in making the guitar less "harsh" sounding.

I've sampled a couple of tap tones, noted the fundamental, looked at the FFT, and compared it to a similar OM that sounds less harsh.

It's not obvious to me what to target in terms of either tap tones or where to remove material. I'm willing to destroy my instrument in the pursuit of an education, but I'd prefer to improve it.