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Hey Guys,

I’m trying parabolic bracing for the first time and need help deciding if I’ve trimmed enough, too much, or the right amount from my lower x. This is my third guitar, so I haven’t developed an ear for tap tones or the feel for the right amount of flex in a braced top yet. Here are the specs:

Redwood top
Parlor size with a 13 inch lower bout
Bracing width ? inch with a 5/8 inch height at the x tapering to 7/16 at the bridge plate, and then ending at about 3/32 at about an inch away from the side. The 3/32 inch thickness runs about an inch to the side and is tucked into the lining.
Tone bar is 3/8 high at the mid point.


Any suggestions appreciated. Please check out the pics and let me know what you think.

BruceH

Brian,

Looking good.

As many here know, I'm a great advocate of parabolic bracing. I like the attack, it produces a very explosive sound which responds very quickly. It's especially good for the more modern complex fingerstyles, tapped harmonics etc. I use a variation of it now almost exclusively for both front bracing and on X-braced backs. I often vary it by having the tone bars lightly scalloped which I find gives a slightly richer tone, and helps control the mids on cedar topped guitars.

I don't use an end scallop but, carry the parabola right to the end of the brace, and to the centre of the X-brace. Make sure the braces are parabolic in cross section as well. I like to add a parabolic bar behind the bridge patch as well (an idea, like many others, stolen from Mario!)

Most of the tuning of the top is done by judicious thinning of the plate towards its extremities in the lower bout.

I love parabolic bracing, my Civil Engineer son tells me it makes much more sense than scalloping in weight reduction and, structurally, from an engineering standpoint is more efficient. I just like the sound it produces!

Colin

_________________
I don't believe in anything, I simply make use of a set of reasonable working hypotheses.

That looks good to me too. I do something very similar to that. In my version the ends of the parabola flatten out a bit sooner and feather out to nothing. I do not tuck the brace under the lining. (Got that from Charles Fox)

Thanks for the feedback, guys. I’ve trimmed the braces and fit the top into the sides this morning, and after your feedback, thought that the bracing could use a little more shaving. I trimmed back the x-bracing to make it flatten about ? inch sooner and then brought down the tone bar about a 1/16th of an inch. The top rings much better now, and I noticed one other interesting observation: When I put it on the sides and tested the deflection, I noticed that the top moved at the perimeter of the lower bout and not much at the bridge. Sort of like a speaker cone ... hmmmm.

Colin – I also tried Mario’s brace behind the bridge on my first guitar. It worked great and tamed a harsh-sounding top. I’m sort of trying to emulate the concept by putting a slightly bellied section on the aft portion of my bridge plate. Time will tell if it works.

BruceH

[QUOTE=John Kinnaird] I do not tuck the brace under the lining. (Got that from Charles Fox)[/QUOTE]

John, What do you feel the advantage to this is? And do you not worry about the braces popping off?

TIA,

Roy

I like to free up the perimeter. I am not afraid of the brace poping off, it never has and I do believe that if it is feathered out that it just won't. Fox says something similar.

John

John, thanks for the reply. There's so many ways and so many opinions that sometimes it seems the more I learn the more in the dark I am. But tidbits like this really help out.

I have no experience with parabolic bracing so ... what can one expect the tone difference to be compared to a standard scalloped braced top? I would guess that it might be higher pitched and percussive. I would also guess that it would withstand a heavy attack quite well.

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tim...
http://www.mcknightguitars.com

Tim,

Parabolic X and tones, and fingers produces a very explosive sound but can have less sustain in the lower mids, making a guitar that responds very quickly and clearly for the more complex modern fingerstyle playing. Plenty of string control for slack tunings such as DADGad. The tone is very rich, and modern techniques such as tapped harmonics love it. Good in both European and cedar could work well in sitka for very hard players. Don’t forget the braces should be parabolic in cross section as well.

I also use a hybrid system with parabolic X brace and lightly scalloped tone bars. Produces a controlled feel like the full parabolic system but with a slightly richer tone. Good with very light string gauges (10's or 11's which I always use). I feel that it helps to control the mids in cedar tops whilst still producing a big open sound. My personal favourite system of the moment.

A parabolic treble side X on large bodied guitars, can add definition and control the bases for hard players.

I also use parabolic X on the backs.

Just my opinion.

Colin

_________________
I don't believe in anything, I simply make use of a set of reasonable working hypotheses.