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Good on you Joe! You are doing the right thing if it makes sense to you. Small changes are the key if you feel you are on the right track...

I was never one to believe that there is a bass and a treble side to the guitar. The strings at the bridge are separated by about 2 inches and I'm sure when I hit the low E-string that it still vibrates the top on the right or lap side of the lower bout. So I find it interesting about the unsymmetrical scalloped bracing. I'm sure that technique does something to the tone but I just have a hard time believing that there is distinct sides of the guitar with regards to frequency. I'd love it if some one had some data they can point out to me to correct me if I'm mistaken. I've not ever tested the hypothesis myself but am just overly skeptical about it.

Having said that I've always tap tuned my tops as well, and again, I don't think it has any real meaning hahahah. I've only built just north of 60 guitars and I keep tap tuning them and waiting for some magical understanding of what I'm supposed to be getting. Listening to what Dana was doing though does sound a lot like what I look for. More for just an over all musicality rather than certain notes. But I love to have an unbraced top, sounds like a dead thud, then brace it to a high and tight ping and then carve out the bracing till it starts to sing.

I always do that but I cannot claim to have any control what so ever in doing so. Perhaps after 200 guitars I will who knows, I just keep trying anyway.

Having the bracing asymmetrical does not imply that one side or the other is treble or bass, it just potentially adds more complexity to the nodal patterns. I agree with you that sound radiation at any given freguency is from the entire top. I have heard anecdotal story (meaning I can't refer to the thread I read it in) of someone accidentally building a classical with a slanted treble bar the opposite way (reading the plan as an X-Ray rather than looking from inside, or vice-versa) and in the end hearing no difference from one with the bar oriented correctly. I would pretty much expect that. Probably same as if you put the slanted Martin tone bars on the opposite way.

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Jim Kirby
kirby@udel.edu

did notice a couple of things in the video clip. he seems to go for a large variety of different tap tones across the top whereas i go for one tone evenly dispersed across the entire top. different methods, different guitars. the asymetrical scalloped bracing is interesting. i go for tapered bracing on my stuff but i'm influenced a bit by james goodall. like i said different strategies. he is very successful at what he does while i'm pretty much a fringe builder of no consequence at all. i also put the back on last giving me opportunity for final tuning when the top is glued up and bound.

my only criticism is that in the video he seems a little bit of a messy worker imo. quick, hacking moves with the chisel, dragging the plane across the top when thinning braces, etc.. and chips under the top while working on it. but i suspect we're seeing the experience of chopping out a zillion tops at work here.

nice video though, thanks for sharing

Yup, also glue the back on last. A few drips of glue don't bother me much, and the ability to hear taps on a glued top are valuable to me...

"my only criticism is that in the video he seems a little bit of a messy worker imo. quick, hacking moves with the chisel, dragging the plane across the top when thinning braces, etc.. and chips under the top while working on it. but i suspect we're seeing the experience of chopping out a zillion tops at work here."

He did say that someone comes along behind him to tidy things up with sandpaper (I wonder how much that changes things). He also said he sets the top aside and does final voicing after preliminarily voicing several tops. Many of the older great sounding guitars had glue slathered around on the inside. I think the "make the guitar as finished on the inside as the outside" is a relatively new aesthetic and makes little difference in the sound or structural integrity.

how much indeed. sanding out chip dents and plane tracks from a top removes wood and changes tone.

I want to add that I was surprised Dana didn't really feel for the flex across the x-braces but more in the area around the finger braces. I've always been mostly interested in the flex across the x-braces as they are the primary structural braces.
I'd be interested in what approach everyone else takes when you feel for the flex of a top?

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We are all in the gutter but some of us are looking at guitars.

I use the terms bass side and treble side in a similar way to left and right. Just means "the side that that the low E string is attached to", which depends on whether the guitar is left or right handed. Granted, you don't really have to change the bracing for left or right handed, but saddle compensation, cutaway, armrest bevel, fan frets, all get changed. Plus left and right are ambiguous if you're talking about a free plate... which side are you looking at it from?

That said, the main benefits of asymmetrical bracing in my mind are that it partially eliminates the phase cancelling of the cross dipole mode, and causes it to pump air through the soundhole. If one side goes up when the other side goes down, perfectly symmetrically, then there's no net change in air volume, so no pumping. Violins do this to the extreme. The soundpost pretty much prevents the treble foot of the bridge from moving up and down, so all the side to side motion from the bow causes it to pivot, pumping the bass foot up and down on the soundboard.

The disadvantage for guitars is that the looser side still needs to be stiff enough not to deform excessively, so any asymmetry is created by adding more stiffness than is absolutely necessary. Not good for small guitars, where you're fighting to get the resonant frequencies as low as possible.


Same here, learned from the Somogyi book. At the free plate stage, I'm tapping around listening for "tight" spots, which usually correspond to an overly tall brace on the other side. But really I'm mostly feeling the stiffness with my hands, flexing in all different directions. I usually keep my thumbs on braces though, so as not to stress the glue joints.

Then get to the open backed box stage and carve more by sound, mainly adjusting the perimeter stiffness. Much more meaningful tap tones than the free plate. I've mostly been building in thin top style so far, so I don't do any thinning of the soundboard itself.

Next year, I want to try some thick top building. Maybe a pair of 0 or 00 guitars, one using something close to the standard X bracing pattern, and one minimalist style... very thick, low density redwood or cedar top, with only the upper transverse brace, a light X, and bridge plate. And of course a lot of thinning of the plate around the perimeter. Quite interesting to me that thick and thin top builders seem to agree on about how thick the perimeter should be, so the main difference is whether the central stiffness comes more from the plate or bracing.

I love this thread, I love this forum.

I really don't flex much after the braces are on, do it all by tapping. Wouldn't get much out of flexing across laminated X braces. There really isn't a lot of flex.
Then there is ladder bracing. Never have seen any asymmetry in ladders and I don't flex them after bracing is on. For me, the flexing is used in determining acceptable top thickness.

another avenue to think about is what robert bouchet was doing with his classicals. i read that he basically made all of his tops more or less the same thickness, then braced to work with the characteristics of the individual top to produce his tone. at least that's one way of dealing with that pesky variable and it would allow one to use top wood of greater variations.

I would bet there are many that have done exactly that and wouldn't admit it.



Another viable way of doing it. Makes me wonder if he "tampered" with the instruments after the boxes were together though. Reaching into a finished box to shave bracing is not my idea of a good time. Sanding or scraping the top in areas is...
A lot can be done by tapping if you have THAT tone in your head and standardize your tapping. I have used the "T" handle end of the same wooden handled reamer for years to tap, and also derive knowledge by scraping a fingernail across the grain of a braced top. Lots of ways to do this stuff, the important part is to always do it the same way. I have always used the soundhole to hang the top on a thumb as Terry recommended too.