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  #76  
Old 01-02-2018, 07:16 AM
hat hat is offline
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Originally Posted by Alan Carruth View Post
Louie Atienza wrote:
"I believe the reason the saddle is as far forward is because that's what allows the strings to "apply" the most "torque" on the bridge for the given string height off the top."

Ummm....

I think you could say that the further the back edge of the bridge is from the centroid of rotation the lower the maximum stress is on the back edge of the glue line holding the bridge to the top. The centroid is not at the saddle location, so far as I can tell, but some way behind it, depending on the break angle. The actual torque of the bridge is a function of the string height above the top and the total tension, assuming the strings are attached to the bridge and not to some sort of tailpiece. At least, that's what my measurements said.

Torque on the top is mostly detrimental so far as I can tell. It does allow the tension change and longitudinal wave signals in the string to drive the top, but these hardly add any power (none that I could measure) and only change the timbre a bit.

I'll note that Flamenco guitars can be quite loud, even though they generally have the string much lower to the top than Classical guitars. In fact, I'd say that having the strings lower is what allows them to be so loud. The top can be built more lightly, since it doesn't have to resist as much torque load, and that makes it easier to move. This shows that torque doesn't produce sound, but can actually hurt sound production.

At any rate, if the goal is the reduce the peeling stress at the back edge of the bridge why can't you just make the bridge wider? It worked for Martin. If you're making it narrow to keep the weight down, why not use a lower density wood? With lower stress along the front of the slot from moving it back and/or slanting it you don't need the strength of rosewood or ebony to keep it from splitting out or peeling up.
so, a lot of your comments leads me to the thought that using a tailpiece would produce quite a bit of improvement in tone and sound, if what you say is correct in that torque is detrimental. This reminds me of the old Gibson 12 strings that used a tailpiece - most were quite good sounding, until string tension caused them to implode.
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  #77  
Old 01-02-2018, 07:22 AM
LouieAtienza LouieAtienza is offline
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Quote:
Originally Posted by Alan Carruth View Post
Louie Atienza wrote:
"I believe the reason the saddle is as far forward is because that's what allows the strings to "apply" the most "torque" on the bridge for the given string height off the top."

Ummm....

I think you could say that the further the back edge of the bridge is from the centroid of rotation the lower the maximum stress is on the back edge of the glue line holding the bridge to the top. The centroid is not at the saddle location, so far as I can tell, but some way behind it, depending on the break angle. The actual torque of the bridge is a function of the string height above the top and the total tension, assuming the strings are attached to the bridge and not to some sort of tailpiece. At least, that's what my measurements said.

Torque on the top is mostly detrimental so far as I can tell. It does allow the tension change and longitudinal wave signals in the string to drive the top, but these hardly add any power (none that I could measure) and only change the timbre a bit.

I'll note that Flamenco guitars can be quite loud, even though they generally have the string much lower to the top than Classical guitars. In fact, I'd say that having the strings lower is what allows them to be so loud. The top can be built more lightly, since it doesn't have to resist as much torque load, and that makes it easier to move. This shows that torque doesn't produce sound, but can actually hurt sound production.

At any rate, if the goal is the reduce the peeling stress at the back edge of the bridge why can't you just make the bridge wider? It worked for Martin. If you're making it narrow to keep the weight down, why not use a lower density wood? With lower stress along the front of the slot from moving it back and/or slanting it you don't need the strength of rosewood or ebony to keep it from splitting out or peeling up.
Well, I'm thinking in terms of torque relative to having the same saddle further back from the front edge, keeping the string height the same. Granted it's not a large difference.

But, using the example of the Flamenco guitar, the strings are at a negative angle relative to the top, in my view getting the "lever arm" of the point at the front edge of the bridge to the saddle top closer to 90 degrees, where the lever arm is most efficient.

I believe the Flamenco is more lightly constructed, it almost has to be by the nature of the music. They do seem to sound "louder", but they have a very quick attack, and aside from body resonance, quicker decay. They're almost a bit yappy and bright. If one were to put steel strings on such a guitar it would likely sound like crap, before it imploded... I don't necessarily believe that uber-lightweight is the end-all, be-all as far as "tone" or "voice" of the guitar. I think there is some "ratio" of the "weight" of the components, to the torque produced by the strings, that we fall into, whether we are aware of it or not.

As one could make the bridge wider, that does reduce the "torque" effect of the strings on the top, but then you could only go so far until the guitar feels like a Tele strung up with 12s (and I did play that way for a long time!) I had experimented with a maple bridge once, but thought it sounded awful and shrill and lacking of "meat" to the notes compared with a rosewood bridge. Maybe a harder wood of the same weight could have helped?

My particular bridges area little wider, and they actually flare out toward the wings, and are slightly canted, tapered toward the back, and they're longer than most since I have a wider X-brace angle. I also build my bracing I feel stiffer than many at the front of the bridge; since there is a pushing of the top "down" at the front edge as well as a pulling "up" at the rear, reducing one I feel reduces the overall rotation of the saddle. I also use a bridge plate with a wider footprint to mitigate localized bending at the area just behind the bridge.
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  #78  
Old 01-02-2018, 01:32 PM
Alan Carruth Alan Carruth is offline
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LouieAteinza wrote:
"Well, I'm thinking in terms of torque relative to having the same saddle further back from the front edge, keeping the string height the same. Granted it's not a large difference."

That's my point: where the saddle is on the bridge makes no difference in the torque on the top. It probably makes a difference in the peeling stress at the back edge of the bridge, but that depends somewhat on the design. Old Gibsons, with the reverse belly bridge, show as much top distortion as other old guitars that are similarly built, but the bridges tend to come up more, in my experience. The torque on the top is the same, but the bridge load is different.

hat wrote:
"So, a lot of your comments leads me to the thought that using a tailpiece would produce quite a bit of improvement in tone and sound, if what you say is correct in that torque is detrimental."

The things you do to eliminate bridge torque lead to other structural issues, and addressing those can be just as bad. Standard guitar designs have evolved to sound good and hold up well under the string loads they carry. The trick is to make them strong enough without adding unnecessary weight.
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  #79  
Old 01-03-2018, 08:30 PM
LouieAtienza LouieAtienza is offline
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Quote:
Originally Posted by Alan Carruth
That's my point: where the saddle is on the bridge makes no difference in the torque on the top. It probably makes a difference in the peeling stress at the back edge of the bridge, but that depends somewhat on the design. Old Gibsons, with the reverse belly bridge, show as much top distortion as other old guitars that are similarly built, but the bridges tend to come up more, in my experience. The torque on the top is the same, but the bridge load is different.
If we look at the simplified "triangle" diagrams and add the force vector representing the strings, it would be obvious that the "lever arm" represented by the front leg of the triangle would lean back from the "pivot point" which would typically reduce the torque, but also lengthens it which would increase torque. So without sitting down and calculating it, I'm not sure which has the larger rate of change in terms of effect on torque, but the torque would likely be different. The "centroid" would change, but that may also change as a function of the localized stiffness fore and aft of the bridge. I've observed the bellying, or deformation, on Gibsons, and maybe there are similarities but not the same. They definitely don't sound the same, or even similar other than they're both acoustic guitars, that's for sure. All I'm going to say is that the bridge has to be really looked at as a system, incorporating the soundboard, bracing, bridge plate, and their relationships to one another, not just looking only at the bridge unit itself.

Quote:
Originally Posted by hat
so, a lot of your comments leads me to the thought that using a tailpiece would produce quite a bit of improvement in tone and sound, if what you say is correct in that torque is detrimental. This reminds me of the old Gibson 12 strings that used a tailpiece - most were quite good sounding, until string tension caused them to implode
It is the torque on the top from the string's "pull" on the bridge that gives us the sound of the modern x-braced steel string flat-top guitar. It may be detrimental to the structure if the structure is not properly designed; but it is also detrimental to build a top such that the strings cannot effect any kind of movement on the top as well. You see this at the guitar store - guitars with tops that are flatter than (insert mid-west state), and don't sound too good. And the strings feel stiffer than bridge cables.

Also, while we don't want to burden the guitar with unnecessary weight, at the same time I think it's ridiculous to remove weight just for the sake of it. I've played featherweight guitars that sounded amazing, and played featherweight guitars that were, well, meh. There has to be balance and proportion in everything, and what you giveth in one area you have to taketh away in another and vise versa because there's no "free lunch". At the same time we love the sound of these guitars as much for what we don't hear as much as what we do, just as much as the space between the notes make music as much if not more than the notes between.
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  #80  
Old 01-03-2018, 10:03 PM
Alan Carruth Alan Carruth is offline
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LouieAtienza wrote:
"It is the torque on the top from the string's "pull" on the bridge that gives us the sound of the modern x-braced steel string flat-top guitar. "

Why do you say that?
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  #81  
Old 01-03-2018, 10:54 PM
LouieAtienza LouieAtienza is offline
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Quote:
Originally Posted by Alan Carruth View Post
LouieAtienza wrote:
"It is the torque on the top from the string's "pull" on the bridge that gives us the sound of the modern x-braced steel string flat-top guitar. "

Why do you say that?
Well, what other form of bridge/bracings gives that prototypical flat-top (Martin) sound?
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  #82  
Old 01-04-2018, 08:23 AM
printer2 printer2 is offline
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Quote:
Originally Posted by LouieAtienza View Post
Well, what other form of bridge/bracings gives that prototypical flat-top (Martin) sound?
Ladder braced guitars do not sound like Martins and the difference is not the bridge but the bracing. Maybe I am missing what you are saying.
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  #83  
Old 01-04-2018, 08:47 AM
LouieAtienza LouieAtienza is offline
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Originally Posted by printer2 View Post
Ladder braced guitars do not sound like Martins and the difference is not the bridge but the bracing. Maybe I am missing what you are saying.
It's the whole system... not just the bridge, which there seems to be a fixation on. Gibsons are x-braced, and have similar tone bars; even they don't sound like Martin. A Somogyi is x-braced, and many of them have similar tone bars, yet they sound anything but similar other than they're steel-string guitars.

While the strings do cause a "translation" of the bridge, it is the bridge that pulls the back part of the top into some form of bulge or deformation, and it is said back part of the bridge that is resisting said pull of the bridge. But in my opinion, doing anything to the bridge, without consideration of the other parts of the top, is curing the symptoms, not the causations.
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  #84  
Old 01-04-2018, 12:28 PM
Alan Carruth Alan Carruth is offline
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Louie:
You are certainly correct in saying that you have to consider the whole system in talking about both the sound of the instrument and the stress on the parts. That's not what I'm asking.

What I have been trying to do is isolate the torque force, the stress on the top, from the strain, the way the top deforms. Altering the braces, or any of a number of other details, will change the strain for a given stress, and also change the sound, of course. Taking a Martin with 'straight' braces and scalloping them changes both the way the top distorts and the tone. Different people might have varying opinions as to whether the change was an 'improvement', and worth the structural risk. It is also quite possible to make guitars with different bracing that will show the same strain under the given stress. On that line, I've built a close 'tonal copy' of an older Martin in which the top bracing was actually not very similar to the original. It was not 'identical' in sound, of course: having tried to make copies that sound alike I'm wondering if that's even possible, but it was 'close enough' for a very picky customer. I remember working on the repair of a nice Classical guitar some years ago that amazed us by being ladder braced. It sounded like many of the better fan-braced tops I've run into. So there's no direct 'pipeline' from any particular bracing scheme and tone except in a very general sense, with lots of exceptions.

What I was trying to address was your initial remark: "It is the torque on the top from the string's "pull" on the bridge that gives us the sound of the modern x-braced steel string flat-top guitar." This seems to imply that it is a torquewise vibration of the bridge under varying string tension that produces most of the sound. Maybe that's not what you meant to say, but it's a common model that I believe is incorrect, and I wanted to address that, if that, indeed, was what you were trying to say.
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  #85  
Old 01-04-2018, 01:03 PM
LouieAtienza LouieAtienza is offline
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Quote:
Originally Posted by Alan Carruth View Post
Louie:
You are certainly correct in saying that you have to consider the whole system in talking about both the sound of the instrument and the stress on the parts. That's not what I'm asking.

What I have been trying to do is isolate the torque force, the stress on the top, from the strain, the way the top deforms. Altering the braces, or any of a number of other details, will change the strain for a given stress, and also change the sound, of course. Taking a Martin with 'straight' braces and scalloping them changes both the way the top distorts and the tone. Different people might have varying opinions as to whether the change was an 'improvement', and worth the structural risk. It is also quite possible to make guitars with different bracing that will show the same strain under the given stress. On that line, I've built a close 'tonal copy' of an older Martin in which the top bracing was actually not very similar to the original. It was not 'identical' in sound, of course: having tried to make copies that sound alike I'm wondering if that's even possible, but it was 'close enough' for a very picky customer. I remember working on the repair of a nice Classical guitar some years ago that amazed us by being ladder braced. It sounded like many of the better fan-braced tops I've run into. So there's no direct 'pipeline' from any particular bracing scheme and tone except in a very general sense, with lots of exceptions.

What I was trying to address was your initial remark: "It is the torque on the top from the string's "pull" on the bridge that gives us the sound of the modern x-braced steel string flat-top guitar." This seems to imply that it is a torquewise vibration of the bridge under varying string tension that produces most of the sound. Maybe that's not what you meant to say, but it's a common model that I believe is incorrect, and I wanted to address that, if that, indeed, was what you were trying to say.
Alan, I didn't mean to cause confusion. While I agree that different systems can produce results that are very close, I personally wouldn't pursue a different method unless I achieved a different result. Otherwise I'm just reinventing the wheel. Again.

If I'm not mistaken, ladder bracing has been around since gut-string lutes, so I don't necessarily find it odd to see in a "modern" instrument. It just may well be a viable option depending on the repertoire of the player. But to say one guitar sounds just as good as another or better does not mean that they sound or play the same.

As to the quote in question - the speed of my thoughts are far greater than the 120wpm or so that I can type. Especially at 11pm! But it is that whole system - bridge, x-brace, bridge plate, finger braces, pins, saddle, body depth,,, and all their dimensions - that creates the sounds we are familiar with. Surely, there is probably a lot of latitude within those parameters
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  #86  
Old 01-04-2018, 07:17 PM
Alan Carruth Alan Carruth is offline
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LouieAtienza wrote:
"But it is that whole system - bridge, x-brace, bridge plate, finger braces, pins, saddle, body depth,,, and all their dimensions - that creates the sounds we are familiar with. Surely, there is probably a lot of latitude within those parameters "

I guess what I'm trying to get at is that I don't see bridge torque per se as a major factor is sound in most cases. It the experiments I did people could hear a difference when I nearly doubled the string height off the top (from 11mm to 18mm), but the actual difference in the measured sound was not large. I really question whether most people would hear a change of a mm or two. Also, what changed was the timbre, not the overall power or sustain. Given the magnitude of the effects you can get by swapping out bridge pins to change the mass of the bridge, or taking a few judicious shavings off a brace, I put torque pretty far down on the list.

Of course, reducing the torque allows you to lighten up on bracing, and that can give a big change in sound, but it's the bracing, not the torque, that makes the difference.

By the way, I'm not really trying to pick on you! I just got confused by some of what you wrote, and was trying to clarify it. I guess my posts get confusing sometimes too....
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  #87  
Old 01-12-2018, 10:57 PM
printer2 printer2 is offline
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Thought of this topic when I came across this video. Thought some might want to take a listen.

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  #88  
Old 01-13-2018, 09:42 AM
Otterhound Otterhound is offline
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Originally Posted by printer2 View Post
Thought of this topic when I came across this video. Thought some might want to take a listen.

Poking the bear ?
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  #89  
Old 01-13-2018, 10:07 AM
printer2 printer2 is offline
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Poking the bear ?
I thought about that. Then I thought most everyone would appreciate how much the difference in sound there is, given that otherwise the guitars are made the same. Even with Youtube being what it is I do hear the archtop or floating bridge sound on the one compared to the other.
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  #90  
Old 01-13-2018, 10:19 AM
Otterhound Otterhound is offline
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Originally Posted by printer2 View Post
I thought about that. Then I thought most everyone would appreciate how much the difference in sound there is, given that otherwise the guitars are made the same. Even with Youtube being what it is I do hear the archtop or floating bridge sound on the one compared to the other.
I heard an immediate difference in brightness and decay/sustain .
Wonder what would happen if he were to run the strings through the bridge at the same location and anchor them underneath the top or even use a second set of holes to run the strings through the bridge and top and then back up through again to tie them off in that manner . Or maybe ........
This could get interesting should one want to toy with the idea/possibilities .
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