What if an acoustic guitar did not need top bracing?

[Mr Fingers]

didn't you write this:

"the current wood bridge glued to the top with bridge plate below and various top bracing for strength and stability has been around for a long time without much improvement."

That's the statement that offended me because thousands of good luthiers experimenting with alternative approaches to generating tone and managing force have produced alternative designs. If you're only talking about manufacturers, you're not looking at where innovation happens. It also would have helped had you defined "improvement." One reason Martin keeps cranking out D28s is because they sound like D28s. It would be interesting to know what tonal outcomes you may be seeking, since as many of the posts describe, the tone/volume effects of various bridge/stringing systems are recognized.

[Jabberwocky]

A guitar top with no bracing is basically a banjo. So, it is going to sound like a banjo.

[dekutree64]

There are two zero-force designs I know of. One uses 3 horizontal bars so the strings go down and then back up to create the break angle. The second uses horizontal break angles filed into the saddle, 3 angling toward the left and 3 toward the right so they cancel out. The reason you don't see anyone experimenting with them is because they're both patented.

As for whether it would actually sound better or not, it's hard to say without building a lot of experiments. You lose the tension change signal that you get with strings attached at the bridge, so the basic tone will probably be closer to a standard tailpiece bridge. But with total freedom to manipulate stiffness, mass, and downforce, it would take a long time to learn how to optimize it. I suspect you could at least make it significantly louder than a traditional soundboard. That would be particularly beneficial for acoustic bass guitars. Classical players also like loud guitars, for un-amped performing. But as far as richness of tone, fan bracing for classcals and X bracing for steel strings both seem to perform very well as-is.

[drguitar001]

Originally Posted by dekutree64

There are two zero-force designs I know of. One uses 3 horizontal bars so the strings go down and then back up to create the break angle. The second uses horizontal break angles filed into the saddle, 3 angling toward the left and 3 toward the right so they cancel out. The reason you don't see anyone experimenting with them is because they're both patented.

As for whether it would actually sound better or not, it's hard to say without building a lot of experiments. You lose the tension change signal that you get with strings attached at the bridge, so the basic tone will probably be closer to a standard tailpiece bridge. But with total freedom to manipulate stiffness, mass, and downforce, it would take a long time to learn how to optimize it. I suspect you could at least make it significantly louder than a traditional soundboard. That would be particularly beneficial for acoustic bass guitars. Classical players also like loud guitars, for un-amped performing. But as far as richness of tone, fan bracing for classcals and X bracing for steel strings both seem to perform very well as-is.

I'd be interested in seeing what you are describing in the bridges you described above; one of those may be similar in design to what I have on paper and in mind. I looked for a similar design to mine but have so far been unsuccessful. I realize that few thoughts are ever original so it is likely that someone has already built something similar if not exactly the same.

I also agree that traditional bracing for various guitars has worked very well and have provided the tone guitarists enjoy. I really am not trying to reinvent a bridge or a guitar, I am trying to solve a concern I had about gluing a bridge on a flat top mandolin and thought how this answer might work on a flat top guitar.

[drguitar001]

Originally Posted by Mr Fingers

didn't you write this:

"the current wood bridge glued to the top with bridge plate below and various top bracing for strength and stability has been around for a long time without much improvement."

That's the statement that offended me because thousands of good luthiers experimenting with alternative approaches to generating tone and managing force have produced alternative designs. If you're only talking about manufacturers, you're not looking at where innovation happens. It also would have helped had you defined "improvement." One reason Martin keeps cranking out D28s is because they sound like D28s. It would be interesting to know what tonal outcomes you may be seeking, since as many of the posts describe, the tone/volume effects of various bridge/stringing systems are recognized.

I realize that in the boutique guitar world, there have been many changes to the instrument, but in the manufactured guitar world (where 99.99% of all guitars made come from) there has been little change. Please do not be offended, as no offense was meant. I was thinking about how easy it might be to incorporate a simple change to manufactured guitars that might allow them to be louder, more stable, lighter braced, and fuller toned. Boutique guitar makers have their own ideas on what makes a guitar "better" and I was not trying to diminish their work nor was I including their often brilliant ideas in the mundane world of GC acoustics.

So please accept my apology for not carefully including every thought or idea of every different guitar ever built either currently or in the past. I was making a broad statement just like saying that "guitars still use strings". You and I both know that this is not the case in every "guitar" built or conceived.

So again, please accept my apology for angering you.

[DenverSteve]

Originally Posted by Jabberwocky

Nik Forster has a nice solution:

Not to seem, or trying to be, argumentative but that is an archtop/electric guitar not a flat top steel string acoustic. Completely different build needs although it may be excellent.

[Alan Carruth]

You've got a 45 degree break angle ('way more than you need, BTW) without any down force: the strings must be breaking sideways. That's what they do on pianos. There are two or three pins in line at the top of the bridge, and the string threads through them. They do use some minimal down force, if memory serves, but with the tons of tension on a piano and the (relatively) thin soundboard it can't be much. You might well be able to patent the idea on guitars, but I'd say that's 'prior art'.

The experiments I've done show that torque wise motion of the bridge caused by the twice-per-cycle tension change of the strings does not produce appreciable power. Raising the strings higher off the top can alter the timbre of the instrument somewhat, as there is more leverage for the torque to move the top, but it's an inefficient way to produce sound, and the torque force is much lower than the transverse force of the string.

As has been pointed out, arch top guitars do sound different than flat tops, but it's not due to the different way the strings drive the top, simply because there's not that much difference. Arch tops with tailpieces don't feel the tension change force in the top, but, as I've said, that's not the main force on the bridge top. Keep in mind, too, that the tension change happens twice per cycle. If flat tops were driven primarily by the tension change, and arch tops by the transverse force, then flat tops would sound an octave higher than arch tops with the same strings. Do they? Arch tops sound different because they're built different. The arched plates work somewhat differently, and F holes 'hear' the air in the box differently.

Oh yes, and biscuit bridge resos also use a tail piece to take the tension, and couple the strings to the bridge tightly without appreciable down force. That's the direction you're going with a braceless top. It's a great sound in it's way, but not everybody's cup 'o tea.

I know the guitar as we have it is not 'perfect'. However, the more I learn about how they work the more I think the traditional designs are pretty close to optimized. It's not going to be easy to improve on them in any major way. I wish you luck, though.

[printer2]

Originally Posted by Jabberwocky

A guitar top with no bracing is basically a banjo. So, it is going to sound like a banjo.

No not necessarily. The banjo has effectively a zero mass top, even getting rid of the braces would not get close to it. The braces on a guitar might only be about 20% of the total mass, not a lot to loose.

Originally Posted by drguitar001

...I was thinking about how easy it might be to incorporate a simple change to manufactured guitars that might allow them to be louder, more stable, lighter braced, and fuller toned....

Doubt there will be much interest in a better (theoretically) mousetrap. People are generally happy enough with what is being sold today. A lighter braced guitar would be an easier damaged guitar.


Ah, about time Alan stopped by.

[drguitar001]

Originally Posted by Alan Carruth

You've got a 45 degree break angle ('way more than you need, BTW) without any down force: the strings must be breaking sideways. That's what they do on pianos. There are two or three pins in line at the top of the bridge, and the string threads through them. They do use some minimal down force, if memory serves, but with the tons of tension on a piano and the (relatively) thin soundboard it can't be much. You might well be able to patent the idea on guitars, but I'd say that's 'prior art'.

The experiments I've done show that torque wise motion of the bridge caused by the twice-per-cycle tension change of the strings does not produce appreciable power. Raising the strings higher off the top can alter the timbre of the instrument somewhat, as there is more leverage for the torque to move the top, but it's an inefficient way to produce sound, and the torque force is much lower than the transverse force of the string.

As has been pointed out, arch top guitars do sound different than flat tops, but it's not due to the different way the strings drive the top, simply because there's not that much difference. Arch tops with tailpieces don't feel the tension change force in the top, but, as I've said, that's not the main force on the bridge top. Keep in mind, too, that the tension change happens twice per cycle. If flat tops were driven primarily by the tension change, and arch tops by the transverse force, then flat tops would sound an octave higher than arch tops with the same strings. Do they? Arch tops sound different because they're built different. The arched plates work somewhat differently, and F holes 'hear' the air in the box differently.

Oh yes, and biscuit bridge resos also use a tail piece to take the tension, and couple the strings to the bridge tightly without appreciable down force. That's the direction you're going with a braceless top. It's a great sound in it's way, but not everybody's cup 'o tea.

I know the guitar as we have it is not 'perfect'. However, the more I learn about how they work the more I think the traditional designs are pretty close to optimized. It's not going to be easy to improve on them in any major way. I wish you luck, though.

Thank you Alan, I was hoping for a response from someone as knowledgeable about guitar construction as yourself. I have read that you have done a lot of testing in the area of string energy transfer to the top of the guitar (the physics of what goes on and such). Is it your understanding that the top of a flat top guitar NEEDS not only the cycles per second vibrational energy of the string to properly drive the top but also the alternating torquing more pull/less pull of the string on the top to produce the kind of energized volume that a good flat top can produce? In otherwords, does just the vibrational mass of the string drive the top enough to produce good volume if the torque of the string pulling on the top disappears?

BTW, the design I am working on has the ability to allow for a change (adjustments) in the break angle behind the saddle of each string individually (possibly allow the user to "tune" each string response for best balance?). As you might guess, this is a work in progress and already has gone through 6 different upgrades in just the last few days.

This is getting exciting.

[Jabberwocky]

Originally Posted by printer2

No not necessarily. The banjo has effectively a zero mass top, even getting rid of the braces would not get close to it. The braces on a guitar might only be about 20% of the total mass, not a lot to loose.


...Ah, about time Alan stopped by.

It is not about the mass. It is about the rigidity.

[Jabberwocky]

Originally Posted by PastorSteve

Not to seem, or trying to be, argumentative but that is an archtop/electric guitar not a flat top steel string acoustic. Completely different build needs although it may be excellent.

It is the concept that is shown. A matter of rejigging it for acoustic steel-string, no? No different to how the steel-steel itself is an adaptation of the gut-string guitar.

[drguitar001]

Originally Posted by Jabberwocky

It is the concept that is shown. A matter of rejigging it for acoustic steel-string, no? No different to how the steel-steel itself is an adaptation of the gut-string guitar.

My guess is that you could adapt something like that design to a flat top guitar, but as cool as it is, it is nothing like what I am talking about. I may have found a way to use my design as a retrofit on standard acoustic guitar pin bridges. Stay tuned...

[Russ C]

Thanks Alan, that bit about the torque or tension energy should have been obvious but I hadn't thought of it - a higher saddle will add more 2nd harmonic, no extra fundamental.
Maybe not noticeable though.

[ukejon]

Originally Posted by Jabberwocky

A guitar top with no bracing is basically a banjo. So, it is going to sound like a banjo.

My Rainsong has no bracing and doesn't sound like a banjo at all!

[printer2]

Originally Posted by drguitar001

...Is it your understanding that the top of a flat top guitar NEEDS not only the cycles per second vibrational energy of the string to properly drive the top but also the alternating torquing more pull/less pull of the string on the top to produce the kind of energized volume that a good flat top can produce? In otherwords, does just the vibrational mass of the string drive the top enough to produce good volume if the torque of the string pulling on the top disappears?

I think Alan said,

...the twice-per-cycle tension change of the strings does not produce appreciable power...