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Tonebar positions and angles
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Author:  J De Rocher [ Tue Oct 31, 2017 4:00 pm ]
Post subject:  Tonebar positions and angles
On steel string guitars with two tonebars, is there any rhyme or reason to different positions and angles used by different builders? Can anything be predicted about their affect on the sound of the guitar based on their placement all other things being equal (yea, I know). I know some think that the term tonebar is a misnomer, but it seems like their placement could affect how tight or loose the top is south of the bridge and the x-brace arms or affect the difference in flexibility of the top between the bass and treble sides.

Of the four examples below, the one on the upper left seems pretty common with the bars parallel to each other and relatively close together. Other layouts have the tonebars splayed at the x-brace end, splayed at the rim end, or some have them angled more directly toward the tail end of the top. I'm sure there are other variants too.

Attachment:
Tonebar positions.jpg
Author:  edstrummer [ Tue Oct 31, 2017 4:56 pm ]
Post subject:  Re: Tonebar positions and angles
J De Rocher wrote:
On steel string guitars with two tonebars, is there any rhyme or reason to different positions and angles used by different builders? Can anything be predicted about their affect on the sound of the guitar based on their placement all other things being equal (yea, I know). I know some think that the term tonebar is a misnomer, but it seems like their placement could affect how tight or loose the top is south of the bridge and the x-brace arms or affect the difference in flexibility of the top between the bass and treble sides.

Of the four examples below, the one on the upper left seems pretty common with the bars parallel to each other and relatively close together. Other layouts have the tonebars splayed at the x-brace end, splayed at the rim end, or some have them angled more directly toward the tail end of the top. I'm sure there are other variants too.

Attachment:
Tonebar positions.jpg
I am trying a different position for lower tone bar on one top after reading about Larsen Bros. in a GAL mag article. Second top is more traditional . Both are OO size.Image

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Author:  meddlingfool [ Tue Oct 31, 2017 5:24 pm ]
Post subject:  Re: Tonebar positions and angles
All things being equal, yes, they will indeed have subtl effects on the timbre of the instrument (not as much as top and brace thickness by any stretch, but we're saying all things being equal, right?)

No matter what bracing pattern you use, the top will nearly always want to vibrate in the same modes.

Think about how the bridge moves the top to make sound, then think of how those subtle bracing changes might be able to affect how the bridge moves...
Author:  Clay S. [ Tue Oct 31, 2017 6:21 pm ]
Post subject:  Re: Tonebar positions and angles
Depending on the stiffness of the top I will angle the tone bars more or less. I think of them as structural the same as the X brace. I use them to help the top stay "flat" across the lower bout. I don't mind a little "pull up" but I think when the top has a round belly it hurts the way it vibrates as well as contributes to peeling bridges. The Musser brace (a.k.a. P.M.T.E.) is an add on for when the tone bars don't provide enough stiffness across the top.
To provide more stiffness set them closer to what a ladder brace would be and don't scallop too much.
I think one reason braces are angled is to reduce the stress created by cross grain gluing which ladder bracing creates.
Author:  SnowManSnow [ Tue Oct 31, 2017 6:25 pm ]
Post subject:  Re: Tonebar positions and angles
So here’s my disclaimer... I’m soooooo new I don’t know which side is really up... but I know from some online courses the bridge moves top to back and thus moves the top.
To me tone bars just SEEM to be in the way of that movement. They are in direct opposition it seems.
But then again.... this is my over thinking. Sometimes tradition is tradition for a reason.


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Author:  bftobin [ Tue Oct 31, 2017 8:02 pm ]
Post subject:  Re: Tonebar positions and angles
There are some who believe they can adjust the treble or bass response of a guitar by placement and angle of these
two braces. Same idea of a 'treble bar' in classical guitar bracing patterns.
Author:  Rocky Road [ Tue Oct 31, 2017 9:28 pm ]
Post subject:  Re: Tonebar positions and angles
Ervin Somoygi goes into depth in his books describing the different modes of top movement, and also, of his philosophies on bracing. Pricey book set, but a valuable look into the techniques of a master builder.


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Author:  J De Rocher [ Tue Oct 31, 2017 10:02 pm ]
Post subject:  Re: Tonebar positions and angles
Ed - Did the GAL article say what effect that different lower tone bar position would be expected to have?
Author:  jfmckenna [ Tue Oct 31, 2017 11:01 pm ]
Post subject:  Re: Tonebar positions and angles
I've been taking guesses and wild stabs at this for 25 years :D

Mostly at least based on traditional designs and tweaks from experience but yes it makes a difference. I have no problem calling them 'tone bars' per se though all the braces will affect the tone. It helps to have had built about ten classical guitars too and of course to understand the 3 primary modes. The fan braces of a classical guitar for example stiffen up the long dipole mode and emphasize the cross dipole with the lower transverse brace essentially stopping the whole thing such that the whole of the 3 modes is contained below that in the lower bout, more or less. The X-brace seems to almost create three tops! One below the X and below the bridge to the tail block and then two areas where the finger braces are. It just helps me to visualize it in this way when considering bracing even if I'm wrong ;)
Author:  Trevor Gore [ Wed Nov 01, 2017 6:05 am ]
Post subject:  Re: Tonebar positions and angles
J De Rocher wrote:
On steel string guitars with two tonebars, is there any rhyme or reason to different positions and angles used by different builders? Can anything be predicted about their affect on the sound of the guitar based on their placement...
meddlingfool wrote:
...No matter what bracing pattern you use, the top will nearly always want to vibrate in the same modes....

Ed's right in that plates (guitar tops) are naturally wont to vibrate in specific symmetrical modes and to make them do differently (asymmetric modes, for example) is fairly difficult, in that it takes quite a lot of bracing to force a difference, with the risk of "locking up" the top whilst attempting to do that. Changing the center frequency, amplitude and damping of a mode is quite straight forward (just shave a brace or change its position slightly) and differences can be heard, mostly fairly subtle.

However, there is one difference between Gibson and Martin that is worth discussing, pertaining to what I call "real" J45s and "real" Dreadnoughts. Because there have been so many variants of both models' bracing over the years, probably most examples of both makers don't fall into what I call the "real" category which, to me at least, defines their iconic sounds.

Let's start with the variant I've called a "real" Dreadnought. The bracing is laid out like Jay's top right photo, but scalloped like the bottom left photo. Typically, that scheme results in symmetric mode shapes, with monopoles, a cross dipole and a long dipole, though the dipoles can be somewhat suppressed in amplitude.

On the other hand, a "real" J45 has closely coupled lower face braces (Jay's tone bars) which are tapered rather than scalloped and typically look something like this:

Attachment:
DSCF6509.jpg


What the close-coupled, unscalloped braces do is force a node to produce a diagonal dipole mode in place of the normally symmetric dipole modes. It looks like this:

Attachment:
DSCF9395.jpg


This produces a third major peak in the guitar's frequency response curve at ~350Hz (the resonant frequency of the diagonal mode), higher in frequency than the main top monopole (which is typically ~170Hz) as below, and goes a long way towards explaining the difference in sound between "real" J45s and "real" Dreadnoughts, because "real" Dreadnoughts do not have that major radiating mode in the lower-mid frequency range.

Attachment:
J45 FRC.jpg


If you scallop the lower face braces, you get back to Dreadnought-style symmetrical modes of vibration.

Both in the classical guitar world and the steel string world, specific guitar types have their own patterns of modal vibrations and getting the modes you want tuned to the right frequencies is what "voicing" (aka modal tuning) is all about, as I discussed recently in this OLF thread.
Author:  truckjohn [ Wed Nov 01, 2017 9:34 am ]
Post subject:  Re: Tonebar positions and angles
Thanks Trevor.

I was just about to go dig up the post where you explained it the last time. ;)

It's interesting when shaving the braces on a braced top that is done "J-45" style... Aiming for some of that classic Gibson "thunk" - but not so much that it sounds dead.... At first - the top "taps" with a very short decay and perhaps a not too musical sound (to me).... And then you shave the tone bars a bit - the musical sound starts to appear and they get just a bit longer decay.. (That's when I stop on my J-45 pattern.. I still want some thunk).

If you keep going a bit more - you find the top taps sounding more and more musical with a longer and longer decay... The guitars lose the classic "thunk" and push towards more overtones and longer sustain....

What I have found is that many people (except fingerstyle instrumentalists) talk about liking a lot of overtones in theory - but they often don't in real life... What they seem to like in real life is a strong fundamental and a faster decay for singing/accompaniment sort of duty... Some thunk but not too much. ;)
Author:  meddlingfool [ Wed Nov 01, 2017 1:02 pm ]
Post subject:  Re: Tonebar positions and angles
That reminds me...

I have had a top all braced up like the top photo since a few weeks after the books came out. Then I got busy and it's just been sitting on a rack. Might be time to finish the job...
Author:  Haans [ Wed Nov 01, 2017 4:10 pm ]
Post subject:  Re: Tonebar positions and angles
Maybe that's why fingerpickers (differentiating from "fingerstylists") play Larsons if they can find one.

Image

Image

Note the widely splayed, laminated X, straight bracing with straight tapers instead of scallops and the square and straight tone bars. Differing from Larsons, my backs used laminated bracing, scalloped along with the usual high arch. Had I not quit, I probably would have done a straight taper on the back braces next. Backs were very "live".

Image

Never speculated much on why, I just can't be as bold as some out there and say that "this brace makes it sound this way". Instruments are way to complicated to be doing that. I made very small and single changes, the old way of building by feel. Never built in batches either. There were never any short cuts to the way I learned to build, no spread sheets, no nodes or modes or pixie dust. No "instant gratification" .
Much was learned from many years of mandolin building, and some of that knowledge was applied to building guitars. Granted, this is the hard way to go about building, but you learn through the fingertips of your hands.
I did prefer the rich, clean, clear tone with a tendency to be less muddy than the usual X braced fare. It's a fat, solid sound...

Here's a white oak and a BRW GC-6, red spruce tops...

https://www.youtube.com/watch?v=R1AetWKkSHE

https://www.youtube.com/watch?v=AUom7ZcMzFw
Author:  jfmckenna [ Wed Nov 01, 2017 6:20 pm ]
Post subject:  Re: Tonebar positions and angles
Haans wrote:
Maybe that's why fingerpickers (differentiating from "fingerstylists") play Larsons if they can find one.


Haans, do you mean they use plastic or metal finger picks? That those tops look like they need to be driven hard. But I don't know, never played one. Is that laminated carbon fiber and wood?
Author:  Haans [ Thu Nov 02, 2017 7:59 am ]
Post subject:  Re: Tonebar positions and angles
From everything I gather, "fingerstylists" play with what Jorma called pyrotechnics. They play up and down the fingerboard while doing "pops, rythmic taps, various pings" and such. Fingerpickers just play tunes around chords, finding melody notes within the chord while playing a syncopated bass. It's sorta like playing both hands on a piano with your right hand. Partials are played up the neck, but are associated with the chords. A thumping bass such as Big Bill Broonzy is a variation.
No, the guitars don't have to be driven hard. Hull plays hard. I had to raise the action on several guitars before he could play them. He is a fingerpicker. Picks are an option, but I don't care for the sound much.
No, that is BRW and red spruce. The tops don't need to be driven any different than any other guitar.
Author:  jfmckenna [ Thu Nov 02, 2017 9:01 am ]
Post subject:  Re: Tonebar positions and angles
Ha! I like that, Pyrotechnics LOL! Kind of reminds me of what Frank Zappa used to say his boy Steve Via played - Stunt guitar! Of course he loved Vai too.

I just went on a reading spree on Larson guitars, very interesting to say the least. It almost looks like they incorporate the X-Brace and ladder bracing together and get something real unique out of it.
Author:  Jonny [ Thu Nov 02, 2017 8:13 pm ]
Post subject:  Re: Tonebar positions and angles
edstrummer wrote:
J De Rocher wrote:
On steel string guitars with two tonebars, is there any rhyme or reason to different positions and angles used by different builders? Can anything be predicted about their affect on the sound of the guitar based on their placement all other things being equal (yea, I know). I know some think that the term tonebar is a misnomer, but it seems like their placement could affect how tight or loose the top is south of the bridge and the x-brace arms or affect the difference in flexibility of the top between the bass and treble sides.

Of the four examples below, the one on the upper left seems pretty common with the bars parallel to each other and relatively close together. Other layouts have the tonebars splayed at the x-brace end, splayed at the rim end, or some have them angled more directly toward the tail end of the top. I'm sure there are other variants too.

Attachment:
Tonebar positions.jpg
I am trying a different position for lower tone bar on one top after reading about Larsen Bros. in a GAL mag article. Second top is more traditional . Both are OO size.Image

Sent from my SM-T230NU using Tapatalk


I would love to see and hear the end results
Nice work!
Author:  jfmckenna [ Thu Nov 02, 2017 10:01 pm ]
Post subject:  Re: Tonebar positions and angles
I would love to hear something braced like that too.
Author:  edstrummer [ Fri Nov 03, 2017 7:34 am ]
Post subject:  Re: Tonebar positions and angles
J De Rocher wrote:
Ed - Did the GAL article say what effect that different lower tone bar position would be expected to have?

Not specifically. The Larsen guitars had several unusual features such as laminated braces with rosewood centers, finger braces that didn’t touch the X brace, and the tonebar placement particular to their instruments. He mentions how much he liked how the originals sounded as the reason he decided to copy their design.


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Author:  Haans [ Fri Nov 03, 2017 7:51 am ]
Post subject:  Re: Tonebar positions and angles
jfmckenna wrote:
It almost looks like they incorporate the X-Brace and ladder bracing together and get something real unique out of it.


Don't know that Larsons ever did a combination of X and Ladder bracing, jf, but I used a combo X/ladder on several instruments, mostly the large "Prairie State" type jumbos. It worked well. Here's an early version.

Image
Author:  jfmckenna [ Fri Nov 03, 2017 8:04 am ]
Post subject:  Re: Tonebar positions and angles
Very cool Hans thanks for sharing.
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