X brace vs. tone bars ?

[Bernie Daniel]

I don't think any conclusions can be drawn or ideas supported by one example from one factory.

Surely, the sole function of braces and so called 'tone' bars is to increase stiffness. If that's the case then a slightly thicker top should produce the same result. It would be interesting to see how a thicker top with no bracing affects Q also.

Peter the truth be I really don't have any experimental data to tell me what the role of tone bars or x-braces (i.e., just structural, just for tone, or both).

Nor have I even built a mandolin so everything I say is my opinion -- which is not worth too much.

When you say "Surely, the sole function of braces and so called 'tone' bars is to increase stiffness." I have no data to either refute or support that view (and I assume it is your opinion also?)

But if you read post #9 in this string it is obvious that Dave Cohen does have knowledge, and he has built mandolins, and he has also actually done experiments using different bracing on the same mandolin top. Now I submit that you can't get more relevant information to the question at hand than that.

One mandolin or not it is still real data and I don't see any other actual experiments refuting Dave's work.

Bottomline, I'm a scientist and I go with the data that's all.

[Bernie Daniel]

I don't know, but the Sunis and the Shi'ites have been at war over this very issue for hundreds of years. So it must be important.

Too bad they did not ask me -- I could have given them a SWAG!

[sunburst]

Braces are intended to (and do) add stiffness. The thing is, "tone bars", being roughly parallel and in line with the grain of the top add almost all of their stiffness in the fore and aft direction. Wood (especially softwoods like spruce) is considerably stiffer in that direction already, so tone bars add to the difference in stiffness lengthwise and crosswise the grain. X-braces cross more wood fibers of the top (because their arms are diagonal), so they can add stiffness in both directions. With that in mind, however, it is up to the luthier how stiff he/she leaves the braces after carving, and generally the top itself is by far the stiffer part of the system (as opposed to the braces contributing most of the stiffness), so contribution from the braces is secondary to the top itself. In other words, the stiffness added by the braces, whatever configuration, has only so much significance in the total stiffness of the top, and the stiffness of the top has only so much influence on the sound of the mandolin, so... how much difference in sound should we expect from bracing systems? To me, it seems that we can't expect very much difference attributable to brace configuration alone.
Also, as I often do, I look for consensus of opinion in situations like this. When there is debate and little consensus, that says to me that any difference is small if it exists at all, because an obvious difference would result in more consensus of opinion. (Sort of back door science...)

[Pete Jenner]

But if you read post #9 in this string it is obvious that Dave Cohen does have knowledge, and he has built mandolins, and he has also actually done experiments using different bracing on the same mandolin top. Now I submit that you can't get more relevant information to the question at hand than that.

One mandolin or not it is still real data and I don't see any other actual experiments refuting Dave's work.

Yes Bernie, I have seen and played Dave's mandolin with the removable plate/plates (can't remember if the top and back were removable or not.) and discussed some of these topics with him and John at Dave's place in Virginia.

[Mike Bunting]

Jesse McReynolds played a mandolin with no tone bars, but I can't remember the builder.

[Bernie Daniel]

Jesse McReynolds played a mandolin with no tone bars, but I can't remember the builder.

He also played a fiddle with a 20-penny nail for a sound post....although that might be OT.

[pfox14]

A master luthier once made the point to me that the least number of braces you can get away with, the better. Braces are needed for structural strength to prevent the top from caving in or distorting, but in theory a top with no braces would vibrate the most and probably sound the best. I've always just copied what has been time-tested to be the right number, size, and shaped braces for a given design.

[Dave Cohen]

On the other hand, the top plates of Greg Smallman's classical guitars owe all of their structure and vibratory properties to the CF/balsa lattice bracing. The relatively thin (ca 0.5 mm) top plates are really just membranes for pushing air. Do they 'vibrate less' for being predominantly bracing? Apparently not. They are generally acknowledged to be louder than conventional classical guitars. Meaning they push more air, and to do that, the plates' motions have to have greater amplitudes.

So what does it mean when someone says something 'vibrates more'? Faster/ That would mean higher frquency. Sometimes better, sometimes worse, but not ncessarily 'better'. Does it mean that more of the plate vibrates? If so, that is false. All of the normal modes of motion of plates are global, i.e., they occupy the entire area of the plate. That leaves greater amplitude.

A plate with no braces will not necessarily vibrate with greater amplitude. As Sunburst already pointed out, braces allow a given stiffness with less mass. Remove braces altogether, and you have to make a heavier plate to get the same overall stiffness. The UK physicist Bernard Richardson has shown that a plate with lower effective mass will vibrate with greater amplitude for a given driving force, in turn moving more air. And a plate with lower actual mass will have lower effective mass.

http://www.Cohenmando.com

[Pete Jenner]

Remove braces altogether, and you have to make a heavier plate to get the same overall stiffness.

Yes I thunk that too
I am going to build a mandolin with no braces in the same batch (to be commenced in the next few weeks) as two other braced mandolins and a mandola. All I can hope is that it makes acceptable mandolin noises and has good volume. I will report back.

[Perry Babasin]

"The Loar" 700 and "The Loar" 400 have no tone-bars...