Official Luthiers Forum!

I am new to this forum, and I wish I had found it a long time ago. There is some good information here. That being said I have a question. I have been building electric guitars for a couple of years now and am contemplating acoustic. I actually have a lot of questions about acoustics, but I figured I would start with the bracing. The way I understand a guitar is that it is just a hemholts(sp?) resonator, so if the top can vibrate more, then you get more sound. The problem being that the string tension would warp the top since by itself it is not strong enough. So, hence the bracing. The problem with the bracing is that it makes the top stiffer, and does not allow it to vibrate as much. (Please correct me if I am worng on any of this). So, I guess my question is why do people brace the way they do? and does the bracing serve any other purpose other than structual? I have a very differnt idea of how to brace a guitar, and I don't really have the experience to know if it would work, or exactly all the the bracing does.

thanks
John

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John Thiessen
http://www.iszacguitars.com

Hey John,

Welcome to the OLF, you are going to like it here, if you like acoustics that is!! I am a new builder as well, on my first still but have a LOT of research on building, should have stopped reading and started building a few years ago, but Oh Well. What you are stating above is prety close to true, although you can have a top that is not stiff enough and you will loose a bunch of tone, think of the skin of drum head, too loose and the sound is soft and muddy. So there is a fine balance you are trying to reach between "near destruction and awesome sound". Al Carruth has said it many times that are very few new ideas in guitar making, and he is probably right, but there are some here who have tried innovative bracing patterns with succuss, Grant Gotz comes to mind. I am using the Larrivvee/Laskin/Manzer bracing style that some others like Tony Karol use, but the majority use the Martin style, tried and true, hard to argue with success. But one of the attractions of building your own guitar is the ability to experiment. A knowledgable person would advise to build in a traditional style, to hone your skills and so that you have a guitar with which you can measure against others, then, once you have been able to get the sound you were looking for and are confident in your abilities, make some changes. But don't make too many at once as you will not be abale to tell which change gave you the result you were hoping for or which one just didn't work. But hey! My first is all original, I have drawn it up my self and modelled my bracing from photographs and just asked lots of questions here.

Good luck and ask away...some of the experts will be by shortly to give you some GOOD advice!

Shane

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Canada

I'm new to this too (about six years now but until recently classical guitars), so I have the same questions as you. There are people here who have made a life of guitars and are very willing to share.

For what it's worth (about $.02) here are some observations I've made.

Leaving the top free to vibrate is not the deal. If it was builders would have gone to tail pieces long ago and removed the stress from the top, but they didn't.

The braces serve as support for the string force but they also serve to stiffen the top. An unstiffened top would be lacking in sound production from what I can tell.

Again, this is just my opionion but, the idea is to allow the top to vibrate within certain frequencies.

That means you have to find a bracing scheme that works with your box and amplifies the frequences you want. (everybody's idea of what sounds right is different.

The best place to start is a standard plan that has produced a guitar you like.

The guys that know should be along soon.

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Joe Beaver
Maker of Sawdust

Welcome to the OLF John.

I would echo these gentlemen's statements. A lot of guitars have been built by a lot of companies/individuals and most stay close to the tried and true with small variations. There's probably more than just a few reasons.

That said, there is no reason you can't build anything you want any way you want. I would be in favor of building at least one in a "conventional" manner. In building acoustics there is a ton of stuff to learn just in the processes.

If you do it this way or jump right into testing your own designs is up to you. If you have questions about you own bracing patterns then make up a drawing and post it here. You'll get more opinions than you want, but you'll also get a lot of food for thought. In the end if you build it and it doesn't work you can always take off the top and replace it with another.

Good luck and keep us posted on your progress.

The idea I was thinking was not a new bracing pattern really, but a different way to brace the top.    Basically, instead of scaloping or doing the p******c thing, doing the inverse of that. The brace would attach to the top near the sides and in the middle for a x type pattern, and be cut away inbetween. hopefully the picture works. I think this would allow the top to vibrate more while still keeping it strong and stiff. Maybe I am over enginerring it though. what do you think

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John Thiessen
http://www.iszacguitars.com

I think that I have seen pictures of this type of bracing. You may want to search the archives.

Al

It's true John, there are examples of people that have used these 'bridge' type braces. You could search the MIMF forum archives as well...If it comes to me who has done this I will let you know.

Shane

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Canada

Welcome to the OLF and good luck on your adventure!

Mike

I didn't figure I could have been the first one to think this up. I am curious if it works though. Also, how it would change the sound of the guitar.    I appreciate everyones quick response. this forum is great!

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John Thiessen
http://www.iszacguitars.com

[QUOTE=Mustang_jt] The idea I was thinking was not a new bracing pattern really, but a different way to brace the top.    Basically, instead of scaloping or doing the p******c thing, doing the inverse of that. The brace would attach to the top near the sides and in the middle for a x type pattern, and be cut away inbetween. hopefully the picture works. I think this would allow the top to vibrate more while still keeping it strong and stiff. Maybe I am over enginerring it though. what do you think

[/QUOTE]

Torres back in the 1860s used this style of bracing on his open harmonic bars, and some great builders, see Joshua French's site, use open bars now, on both classical and SS. I see no reason why they shouldn't be used more frequently.

The correspondents above are quite right in that most people just copy the Martin bracing pattern, because most people don't build enough guitars to develop their own pattern, so it makes sense to follow a tried and tested route. This is particularly true of those part time builders who sell their guitars because their choices are, to a large extent, driven by the market which is used to Martin bracing.

A number of the more adventurous builders have broken away however, have a look at Howard Klepper's site (you can't get much more adventurous or inspirational) he has developed his own bracing pattern. There are other examples out there, Jimmy Caldwell come to mind. Have a hunt round the OLF member sites.

That said until the principles and effects of bracing are fully understood or at least lightly grasped, a close variation on the Martin pattern is a good place to start.

Colin

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

[QUOTE=Joe Beaver]

The braces serve as support for the string force but they also serve to
stiffen the top. An unstiffened top would be lacking in sound production
from what I can tell.

Again, this is just my opionion but, the idea is to allow the top to vibrate
within certain frequencies.

. [/QUOTE]

I agree with this....I always aim to build "light and stiff".

One of the constant battles a luthier faces is finding a happy sweet point
where the top is adequately braced to withstand the forces exerted by the
strings but not so heavily braced that vibration is suppressed to the point
where the sound of the instrument suffers.

Cheers Martin

Another thing that Torres did was build a guitar with no braces. When I visited the Brune workshop last year we discussed this quite a bit. According to what Mr. Brune said the braces on a classical guitar are not braces but sound distributors. To prove this he built a guitar with no braces and took it to a GAL convention. The response was overwhelming. A friend of mine in Brazil just did an experience with building a guitar with back and sides made of cardboard. According to him the instrument sounds great!   

    The guitar had be proved many times that the top is the sound generator. Torres built one out of paper mache.
     The top must have balance and in that the bracing is part if the scheme. Also gut strings have different loads and therefore braced differently than steel strings.
   Personally I don't think it is east to equate a number for all guitars as there are different styles and ears so we build to make that guitar suit a particular need.
   If the top is too weak , aside from the obvious problems the headroom or the amount of distortion is more prevalent. The 3 most common styles of bracing are parabolic , scalloped and standard.
   We as builders want to take the energy of the strings and use as much of it as possible for tone a volume. Have fun searching.

john hall

John, since you have engineering training, you should download a copy of
Howard Wright's doctoral thesis. I think you can find a link to it on MIMF.
Also look around at the site of the University of New South Wales
department for musical physics.

A guitar body differs in some important ways from a Helmholz resonator,
BTW, one being that a helmholz resonator is supposed to be perfectly rigid.

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Howard Klepper
http://www.klepperguitars.com

When all else fails, clean the shop.

The bracing, IMO, is mostly there for structural reasons: to add stiffness without adding much weight. It also has a 'small' effect on the tone. However, since the difference between the best guitar you ever heard and the worst one is also 'small' in an objective sense, it pays to use the 'best' bracing setup and spend some time fine tuning it. The 'best' bracing pattern is what I'm going to use on my next guitar....

All of the conventional 'braceless' tops I've ever seen have folded up. I've heard of Brune's guitar: I've also been told that it has large and relatively thick maple tap plates, iirc. So it's not exactly 'unbraced'. Leaving out the bracing can make a sweet sounding instrument, but it's not a way of reducing weight, and thus tends to make a soft sounding one.

It's possible to make 'braceless' tops using 'sandwich' construction, but that's cheating, too. In effect, the whole top becomes the brace.

Wright's thesis will help you get a handle on what's going on. Another good free source is 'Acoustics for Violin and Guiitar Makers' by Eric Jansson. You can download it as .pdf files from:
http://www.speech.kth.se/music/acviguit4/
You'll need to get part1.pdf through part9.pdf. It's a big download, but well worth it.

Thanks everyone, you have been most helpful. I don't know when I will get around to testing this, but when I do I will let you all know. I am also going to look up those links everyone sent.

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John Thiessen
http://www.iszacguitars.com

Hi John, welcome to the OLF and good luck with your new passion!

Serge

If you interested in bridge style braces you may want to check out the Kasha/Schneider design braces. They are pretty sweet.

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Joe Beaver
Maker of Sawdust