Official Luthiers Forum!

Over the last few days I have been studying tone bars and their effects on moving them.

Most times on the guitars I build they are relatively in the same place on the x-brace leg. I have noticed that some builders and designers place them so close to the "X" that you actually have to cut the bridge plate in order to get them in there. Some tone bars actually are so long that their ends have to be tapered to nothing in order to miss the kerfed lining when attaching the top while others are not so long.

I am having a hard time putting together all of the information I have found and this is where I am getting thrown:

Are the tone bars there for creating varying tones (highs, midrange, bass) ? Or, are their main purpose to provide extra support (bracing) to keep the top from developing a belly?

If they are there mainly for tone qualities, how is tone affected by moving them closer to the "X" and how is it affected by shortening them?

Am I jumping in over my head by even wondering about this? I think you all can see where I am headed...

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Reguards,

Ken H

They say pictures are worth a thousand words, so here is a visual on what I am talking about:

In the first two pictures, notice that the tone bars are attached to the X-brace leg very close to the intersection of the "X" and are so long that they had to be tapered to nothing in order to miss the kerfed bracing when the top was attached:

 

Now this next picture is one of my tops that is fresh out of the clamps and hasnt been cleaned up, shaped or sanded yet, but you can see that the tone bar is much further from the "X" intersection and will miss the bridge plate by a good way.

I realize that these are all different styles of guitars, but I am wondering what effect, if any, moving the tone bars closer to the bridge plate would have?

_________________
Reguards,

Ken H

PM sent.

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"An adventure is only an inconvenience rightly considered. An inconvenience is an adventure wrongly considered." G. K. Chesterton.

[QUOTE=SteveS] PM sent.[/QUOTE]

Some secret message regarding tone bars?

If so, then why even publicize the fact that there's a PM being sent!

<Sigh> (in my best Mario impersonation)...and I thought this was supposed to be a place for sharing!

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JJ
Napa, CA
http://www.DonohueGuitars.com

I too, am very interested in this topic. It must be a volatile subject. If any of you have opinions I'm sure many of us would like to hear them. Our bark is much worse than our bite, so take the plunge and take a position.

Cheers,
Dean

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Dean

Me too!  Me too! (jumps up and down waving hand)  I wanna know the answer too.  C'mon Steve, spill the beans.  Curious minds want to know.

When you are tapping the top and listening to the tone produced you find a spot to hold the top while tapping. There are definitely "sweet" spots to hold at to produce the best tone. Seems to me, if your braces and tonebars passed through those spots, it might be a good thing. Of course, it will pass through some non-nodal points, too, but it might be worth checking out.

Ron

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OLD MAN formerly (and formally) known as:

Ron Wisdom

Somewhere in the middle of Arkansas......

[QUOTE=Hesh1956] Ken some builders run a brace from one X leg to the other right at the back of the bridge plate. If I recall correctly I think that Lowden does this.[/QUOTE]

So do I, and I believe Mario does as well.




Colin

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

I add my vote of curiosity.

It is really hard to say what effect moving the tone bars closer will have without knowing what is going on with the rest of the top. The whole structure is a system. The effect of changing one component will vary depending on the effect all of the other components are having.

If the top plate itself was somewhat flexible across the grain compared to the stiffness along the grain, you might be better off with the tone bars closer to the bridge. That will do more to enhance the cross grain stiffness in the areas where it is needed the most. It will also do less to enhance the effect of the long grain stiffness by moving the braces closer to the long dipole node line which runs across the top right behind the bridge.

If the top is really stiff across the grain it might be better to move them down a bit so that they influence the long dipole more and the cross grain stiffness less.

Changing the angle based on the stiffness ratio of the top also works well. Point them in the direction that needs more stiffness.

On my tops, I try to get a sense of the stiffness ratio of the top and then change EVERYTHING a little bit. Top thickness and graduation, bracing position, bracing angles, bracing dimensions...... to try to get the whole top to have a certain "balance", and  to behave in a way that has proven to work well for me in the past.

Mark

If you havent figured it out yet, I am not the kind of guy that does things in the same old way just because it has been done that way for 100 years. I am also not afraid to have a failure as I believe that innovations are born out of attempts and failures.

Innovations like the McPherson guitars and Ovations and double tops and lattice braced guitars were born from ideas that people tried that were not afraid of thinking "out of the box" (no pun intended). I am asking this because I dont want to waste time and materials if someone else has already tried any of this. Even if it was a failure and discarded, what did it do when the braces were changed from the traditional Martin style??

Inquiring minds want to know

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Reguards,

Ken H

[QUOTE=Colin S] [QUOTE=Hesh1956] Ken some builders run a brace from one X leg to the other right at the back of the bridge plate. If I recall correctly I think that Lowden does this.[/QUOTE]

So do I, and I believe Mario does as well.




Colin[/QUOTE]

Colin...at the risk of being presumptuous I'll describe what I know abuot this brace. I've been using this "tone enhancer" as well ever since Mario described it several years ago. Here's how he uses it as I remember:

With each top he makes a brace that fits snugly behind the BP that also touches each leg of the X-Brace. He does not glue it in place but rather sets it aside until the entire guitar has been finished. During the initial set-up period, he sometimes glues it in place to enhance the tone. I don't know what % of the time he uses the tone enhancer. In my case, I have used it in 5 of seven guitars. It really can make a dramatic difference.

Thanks again to Mario for sharing this information! Perhaps if I screwed up the description we can induce him to post again!!! <BG>

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JJ
Napa, CA
http://www.DonohueGuitars.com

[QUOTE=JJ Donohue] [QUOTE=SteveS] PM sent.[/QUOTE]

Some secret message regarding tone bars?

If so, then why even publicize the fact that there's a PM being sent!

<Sigh> (in my best Mario impersonation)...and I thought this was supposed to be a place for sharing! [/QUOTE]

I'm working on double secret tonebars.

What gives you the right to stand in judgement of me and how I decide to share? You have no idea what the PM was about. It could be a purely personal message.

Sometimes people don't log in to know if they have a PM.

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"An adventure is only an inconvenience rightly considered. An inconvenience is an adventure wrongly considered." G. K. Chesterton.

Somewhat related question.  Is it better to have more and thinner tone bars or fewer and fatter ones?  My uke plan calls for three tone bars, but I have seen layouts that use five.

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A higher purpose for wood.
Rich Smith
Issaquah, WA

[QUOTE=Ricardo] Somewhat related question. Is it better to have more and thinner tone bars or fewer and fatter ones? My uke plan calls for three tone bars, but I have seen layouts that use five.
[/QUOTE] I don't know how to answer that question specifically for ukes, but for me with guitars, my goal is to adequately support the top with the lightest weight possible.

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"An adventure is only an inconvenience rightly considered. An inconvenience is an adventure wrongly considered." G. K. Chesterton.

Are tone bars meant to be structural?

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A higher purpose for wood.
Rich Smith
Issaquah, WA

[QUOTE=Ricardo] Are tone bars meant to be structural?
[/QUOTE]
I would guess yes to that. Whether of not they where meant to be, they certainly are.
While being structural, I think the name gives us a strong clue that they are very important to the tone also, which they are.
If you made a guitar without the tone bars, I think you'd be very disappointed in the tone. If you made the top thick enough, it would be able to stand up structurally, so they aren't entirely necessary as structure.

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"An adventure is only an inconvenience rightly considered. An inconvenience is an adventure wrongly considered." G. K. Chesterton.

I like to flare my tone bars. I set them into the X brace close together. The
upper tone bar goes straight towards the end of the opposite X brace and
the lower tone bar flares out into the belly of the guitar. To clarify, my
tonebars are not parallel. - Justin

[QUOTE=jmanter]I like to flare my tone bars. I set them into the X brace close together. The
upper tone bar goes straight towards the end of the opposite X brace and
the lower tone bar flares out into the belly of the guitar. To clarify, my
tonebars are not parallel. - Justin

[/QUOTE]

What difference in tone do you think that makes Justin? That is exactly the kind of thing I have been wondering about.... moving the tone bars to different locations and/or making them long or short..

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Reguards,

Ken H

First, what Mark said. It's a system, and all has to work together; changing one thing usually calls for changes somewhere else. Thus, _every_ system of tone bar placement works for somebody, and doesn't work for somebody else. There is no magic anything.

I heasitate to put this in, because it's very tempting to take it as a simple overarching truth, and hence to misconstrue. Still: I tell my students that the point on the top at the centerline at the upper edge is all structural, and has nothing to do with tone. The point on the centerline at the bottom edge is all about tone, and has nothing much to do with structure. The ratio of structural to acoustic importance varies depending on how close you are to those two points. The tone bars, being behind the bridge, have much more effect on tone than they do on structural strength, and the further down those bars you go, the less they are 'structral' bars and the more they are 'tone controls'. PLEASE don't let me hear in some future discussion that 'Al said that you could make the top tissue thin at the tailblock because it has no structural role'. This all has to be taken within reason, and follow 'accepted practice', even if at some distance.

Several years ago now I made a 'matched pair' of guitars, with the only difference being the tone bar placement. One had more or less 'standard' tone bars (or, at least, my version of it) and the other had a double-X brace. I took them to the ASIA meeting that year, and had a lot of other makers play them, without telling them what the difference was. There was a small, but definite (about 2:1), preference for the double-X top, even though, as one builder said when told: "But that doesn't WORK!". And that builder prefered the double-X!. Sure, one test, even when well-controlled, doesn't mean a lot, but it does suggest that 'alternative' tone bar placements can be made to do the job.

I was working on the theory that the 'free' plate mode shapes partly determine the assembled tone, and used the double-X to facilitate getting the shapes I want. Other people have different notions, and follow different paths to realize what they consider to be the 'desireable' end. But it comes back to seeing the top, and the guitar, as a system, and figuring out the role of the different parts in relation to that.   

[QUOTE=Alan Carruth]
I was working on the theory that the 'free' plate mode shapes partly determine the assembled tone, and used the double-X to facilitate getting the shapes I want. Other people have different notions, and follow different paths to realize what they consider to be the 'desireable' end. But it comes back to seeing the top, and the guitar, as a system, and figuring out the role of the different parts in relation to that.   [/QUOTE]

Alan,

are you suggesting that it is not necessarily the tone bars *or* their placement or length but rather the area of the top that is left "open" or "free" that makes the tonal differences?

hummm.. this changes my train of thought all together..

_________________
Reguards,

Ken H

Ken, I can't say one way or the other if it has any real or "perceived" effect on
the tone. In my mind, they provide better support for the top if they fan
away from each other as they move away from the X. If you look at the OM
picture I'm using as an avatar you can see it, although it was a subtle flare
on that particular guitar. On larger guitars I would use more flare because
I'm trying to cover more surface area. This being said, it's something I do
because I like it and that is how I was trained to do it, the science behind it
might not be sufficient enough to support the theory. - Justin

I'm not Al but....

I don't think that it what Al said at all. I think what he said was that most builders believe that the double X brace doesn't work because when Gibson did it it was a failure. Yet, when Al did it, it worked great. The difference is that as a component of the Gibson "system" it was the wrong thing. However, it fit into Al's system really well.

There is no "one thing" that "makes the tonal difference". What makes the tonal difference is having all the components work together in a way that produces the desired result. It is all about creating a system that has a certain "balance". And even the "correct" balance will depend on many factors including the tone you want the guitar to produce, the attack of the player, the style of music... etc.

I know that probably doesn't help much as you wonder where best  to put the tone bars. I wonder every time I glue them down as well !!  I arrive at a "best guess" by trying to put their placement and the effect I think it might have, into the context of the rest of the instrument's structure and the tonal character I want from the guitar.

Mark

Ken, Many moons ago, about year 2000, I queried Charlie Hoffman regularly. I took his lead in making my bracing off a proven pattern. At that time he used the same bracing scheme on all his similar size guitars.

I think there is some simple wisdom in doing that, so I adopted that policy myself. I think smaller bracing is in order on one of my instruments, the L-00, but otherwise it's identical on my dred or GA, etc.

Too many variables. Do it some way that works for you and the results should be repeatable.

Many good ideas in this thread though.

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http://www.dickeyguitars.com