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| Author: | Bailey [ Tue Oct 05, 2010 9:55 am ] |
| Post subject: | unbalanced lattice classical |
What would one do to attempt to balance a lattice braced classical???? This is a completed guitar and the lows boom and sustain like crazy and the trebles seem weak in comparison and a little lack in sustain. Hard to play this guitar with tonal balance. I've heard tell SOMEWHERE that adding a weight to a certain area of the top near the bridge can even tonal discrepancy out SOME. Is this a myth???? I placed different sized formed balls of "UHU HOLD IT" removable plastic adhesive to the bridge and top areas near the bridge and seem to get some small tonal changes that are helpful. If I do find a good weight and location combo on a exterior test....what would I use as a permanent attachment to the interior as a possible cure........or is this only a dream I had once..... Any ideas? K Bailey |
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| Author: | Alexandru Marian [ Tue Oct 05, 2010 10:28 am ] |
| Post subject: | Re: unbalanced lattice classical |
Sounds to me like the top might be too thin. Can you give us some specs: top thickness, density, LB width, and lattice specs too? |
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| Author: | wbergman [ Tue Oct 05, 2010 12:07 pm ] |
| Post subject: | Re: unbalanced lattice classical |
What finish did you use? |
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| Author: | Mike Collins [ Tue Oct 05, 2010 1:06 pm ] |
| Post subject: | Re: unbalanced lattice classical |
What Alex posted! We need specs. to help you ! Mike |
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| Author: | Alan Carruth [ Tue Oct 05, 2010 1:12 pm ] |
| Post subject: | Re: unbalanced lattice classical |
Lattice tops tend to use the lattice itself for stiffness, and the top itself is only a membrane that moves air. Iirc, Smallman tops run around .6-.8mm thick (.02"-.03"), so there's not much stiffness in the actual plate. Generally the lattice tapers to nothing at the edges, so the only stiffness there is the plate, and this makes the width of the clear space at the edge critical. "... the lows boom and sustain like crazy and the trebles seem weak in comparison and a little lack in sustain." It's hard to say without having the instrument in the shop to test out, but it does sound to me as though the clear space at the edge is a tad wide. This would make the top move like a 'long throw' speaker, with the center acting like a piston and most of the flex at the edges. This is a pretty efficient way to move air, which accounts for the 'boom' and long sustain, but if the edge is too loose the resonant pitch wil be low, and the trebles weak. 'Tuning' the completed top on a lattice brace guitar is always a problem. If you use CF there is not much you can do in the way of trimming the brace heights to effect local stiffness, so you're left with changing the mass. Since you can't really remove much of that either, the only mechanism you're left with is adding weight. This goes against the whole objective of a lattice top, which is to get the stiffness you need with the least possible amount of weight, so it's of limited utility: once you've got the weight up to that of a 'normal' top, the advantage is gone. Smallman does use poster adhesive to fine tune his tops, but that assumes they're 'close' to begin with. If they are not, he just routs them off and starts over. My understanding is that, at one point in his carrer, he was discarding about 1/3 of the tops he made. Maybe he's gotten better at it by now. Anyway, any diagnosis I can make here is just guesswork in the absence of data. |
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| Author: | Howard Klepper [ Tue Oct 05, 2010 1:25 pm ] |
| Post subject: | Re: unbalanced lattice classical |
There's not much you can do short of retopping. This illustrates why a few conventional guitars ought to be built before one experiments. |
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| Author: | Bailey [ Tue Oct 05, 2010 1:39 pm ] |
| Post subject: | Re: unbalanced lattice classical |
Top is PO Cedar thinned to .076. and not tapered thinner at the edges Lattice runs very close to edge near bottom and about 1/4 from sides. |
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| Author: | John A [ Tue Oct 05, 2010 2:05 pm ] |
| Post subject: | Re: unbalanced lattice classical |
What about the thickness of your back ? |
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| Author: | senunkan [ Tue Oct 05, 2010 2:08 pm ] |
| Post subject: | Re: unbalanced lattice classical |
A good resource to ask will be David Schramm I think; he builds in the Smallman style. http://www.schrammguitars.com/wu.html From the video you can see that CF tows are glued to the rims edges probably to stiffen it. According to David Schramm in his various posts, he actually strung up the guitar and tunes the lattice before closing the back. |
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| Author: | Eric Reid [ Wed Oct 06, 2010 12:39 pm ] |
| Post subject: | Re: unbalanced lattice classical |
One interesting article can be found by searching the web for: Fine tuning of guitar sounds R. Bader |
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| Author: | JohnAbercrombie [ Wed Oct 06, 2010 1:39 pm ] |
| Post subject: | Re: unbalanced lattice classical |
Eric Reid wrote: One interesting article can be found by searching the web for: Fine tuning of guitar sounds R. Bader Thanks for that, Eric. Interesting article. A couple of comments: 1- The paper deals with the results from a computer model of a guitar, not measurements of an actual instrument. If you compare the resonance spectrum of the model in Bader's paper vs an actual spectrum from a real guitar top, there are differences. Of course in 'real life' it's more difficult to isolate the resonances from the different parts of the guitar. 2- As I read it, one of Bader's conclusions is notable: Increasing top thickness decreases 'brightness'- which I think most folks would interpret as decreasing the high frequency response ie emphasizing bass. I've found the opposite to be true when voicing an actual classical guitar and running response spectra as I thinned the top and shaved braces, but I was looking at the response of the whole guitar. Cheers John |
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| Author: | Markus Schmid [ Wed Oct 06, 2010 2:27 pm ] |
| Post subject: | Re: unbalanced lattice classical |
Bailey wrote: [...] I've heard tell SOMEWHERE that adding a weight to a certain area of the top near the bridge can even tonal discrepancy out SOME. [...] I don't know where you heard or read it, but I read that in AL #89, spring 2007, p.45. Jim Norris did that before closing the box. He strug up the guitar which was placed in the mold without having yet put the back on it and experimented with adding small weights of ebony on the lattice nodes until he was satisfied with the result, then he epoxied them into place and closed the box.I am not an expert on guitar sound engineering, so this is just my subjective opinion (or coffee ground reading, if you want): I doubt that this metod of fine tuning will cure your problem completely (if anything at all). After having read Al Carruths comment: if I were in your situation, before routing off the top I'd probably experiment by glueing a 1" - 1.5" wide rim of thin cedar or spruce on the top (from outside), just to see what happens when stiffening the border of the top, to learn something. |
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| Author: | Elman Concepcion [ Wed Oct 06, 2010 3:02 pm ] |
| Post subject: | Re: unbalanced lattice classical |
How about adding a treble bar? To make the pattern asymmetrical and reduce the vibrating area on the treble side as well as add mass most likely in the place it needs it most. You can experiment by putting a small treble bar on the outside and stick it with double tape (not the strong type) and see what you get. If you do add a treble bar and it does not improve the trebles You loose nothing as it won't hurt anything IMO. |
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| Author: | JohnAbercrombie [ Wed Oct 06, 2010 4:48 pm ] |
| Post subject: | Re: unbalanced lattice classical |
Markus Schmid wrote: After having read Al Carruths comment: if I were in your situation, before routing off the top I'd probably experiment by glueing a 1" - 1.5" wide rim of thin cedar or spruce on the top (from outside), just to see what happens when stiffening the border of the top, to learn something. I've read that Smallman pours epoxy into the space at the edge of the soundboard to reduce the top area when fine-tuning the guitar....so that would be the same sort of 'fix'. Cheers John |
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| Author: | patmguitars [ Wed Oct 06, 2010 6:21 pm ] |
| Post subject: | Re: unbalanced lattice classical |
Bailey I see from the picture that you used kerfed lining and a standard Spruce harmonic bar below the soundhole. This is pretty different from most lattice builders who "isolate" the lower bout by either building a massive frame around it (Smallmann) or use solid lining and a thick Maple harmonic bar (Byers). The idea is to try to "contain" the vibrations in that specific area and in the case of Smallmann, to provide a solid frame for added stability and rigidity. I don't know if that is part of the answer or not, but since most succesfull lattice builders use that system, I would tend to believe that it is something quite important. The lattice bracing (as any other building feature) is part of a system, and transposing only one element of it into an otherwise "standard" guitar will probably not yield the expected results (been there, done that...). My 2 cents. Pat |
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| Author: | David LaPlante [ Wed Oct 06, 2010 6:25 pm ] |
| Post subject: | Re: unbalanced lattice classical |
I would also like to know the back thickness as well as the side thickness. |
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| Author: | Bailey [ Wed Oct 06, 2010 6:30 pm ] |
| Post subject: | Re: unbalanced lattice classical |
Thanks for all the info. everyone. I'm going to continue to play around with weights applied to certain areas and see what I can determine. I think this can be remedied without removing and replacing the top. Action is also quite low and requires a fine touch and even though high tension Savarez corums do seem to help with the uppers volume...they also add to the lower boom. I would also rather play with med. tension strings and keep string tension for the lattice top down a bit. LB width 14...waist 9 side and BR backs are .080-.085. Kent |
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| Author: | David LaPlante [ Wed Oct 06, 2010 6:45 pm ] |
| Post subject: | Re: unbalanced lattice classical |
Sides are fine but the back at only 2.1 mm or so (.085") is contributing I think to the overwhelming bass. With a very thin top such as you have made I would want it to be around 2.5 mm (.100"). |
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| Author: | WaddyThomson [ Wed Oct 06, 2010 7:35 pm ] |
| Post subject: | Re: unbalanced lattice classical |
Actually, Smallman guitars have a very thick, laminated back that is not active at all, other than acting as a reflector. The backs are very stiff. |
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| Author: | Bailey [ Fri Oct 08, 2010 9:43 am ] |
| Post subject: | Re: unbalanced lattice classical |
I got a deal on the BR and it came to me at .100.....so by the time I cleaned it up....that's what I had left. When to tap the back....it does BOOM BIG. Could be my problem. KB |
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| Author: | David LaPlante [ Fri Oct 08, 2010 11:05 am ] |
| Post subject: | Re: unbalanced lattice classical |
Try attaching some additional mass to the back alone (inside or outside) and see if that moves the response closer to where you want it. |
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| Author: | CWLiu [ Fri Oct 08, 2010 2:24 pm ] |
| Post subject: | Re: unbalanced lattice classical |
I think your top is too stiff and the treble is so weak that you can't hear its sustain. In other words, it decays rather slowly but is not very audiable. And the boomy bass was mostly contributed by the back. Loosen the top or stiffen the back alone won't solve both(treble/bass) problems. |
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| Author: | Alexandru Marian [ Fri Oct 08, 2010 3:04 pm ] |
| Post subject: | Re: unbalanced lattice classical |
I'm not so sure the top is too thin with all that bracing in there....Also if the width is really only 14, that is small = stiff. I wouldn't even think about trying a lattice in anything smaller than 14.6 As for the back, it depends on the rest. I tend to make a meatier back too, however my best guitar to date has a thin back of IRW, regular density. Upper bout is 2.2mm and lower bout goes down to just 2 towards the edges. |
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| Author: | WaddyThomson [ Fri Oct 08, 2010 3:09 pm ] |
| Post subject: | Re: unbalanced lattice classical |
In truth, if it's a Smallman type of lattice, they vibrating area is much smaller than the lower bout anyway. It's an oval shape that clears the wings of the lower bout by about an inch and at least that at the tail. It's glued to that Plywood frame, and controlled. I understand that Smallman adjusts his tonality by adjusting the size of the oval area. These guitars have a very small diaphragm for vibrating. Also, Smallman has these little carbon fiber stitches around the outside of the vibrating area to give it strength at the edges. It's a whole horse of a different color from a regular guitar, and you have to think of it differently. |
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| Author: | Alexandru Marian [ Fri Oct 08, 2010 3:11 pm ] |
| Post subject: | Re: unbalanced lattice classical |
And to add to the confusion, my own experience with (traiditional) under/over built guitars: underbuilt: nice big warm bass, however clarity and crispness of the trebles suffering. overbuilt: strong clear crystalline trebles, but overall tending towards a nasal tone. Bass very tight and clear but lacking depth and warmth. |
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