Official Luthiers Forum!

Ken, gorgeous bridge, rosette and pickguard, looking at those pics really made me think of the creativity involved through every step of the build, this guitar is very inspiring and am looking forward to do just that on my next few builds. Thanks for sharing!

Mattia, i'm with Hesh saying how this thread is more and more fascinating and lookin' fw to see the results you're gonna have with your tests!

I'm gonna have to buy me a scale!

Cool thread!

[QUOTE=Serge Poirier] Ken, gorgeous bridge, rosette and pickguard,
looking at those pics really made me think of the creativity involved through
every step of the build, this guitar is very inspiring and am looking forward
to do just that on my next few builds. Thanks for sharing![/QUOTE]


Thanks Serge! One of my biggest influences is James Krenov, the furniture
maker. I wuold encourage you to check out a couple of his books from the
library, very inspiring.

Thanks Hesch.

[QUOTE=Mattia Valente] Hesh: good questions, and ditto.

Update: I've decided on an EIR bridge for this guitar, sticking with the
design, and going thinner. I found a very, very, very dark piece of EIR in my
small pile of EIR-blanks-that-are-big-enough, almost black/purple with a
few slightly lighter streaks, that'll blend in with the overall look nicely. A
touch of oil might darken it to quasi-black. [/QUOTE]

That will turn out nice , I think.

Thanks Ken, i'll be checking that out for sure, this guy must have a lot of background and tips in his books!

Serge

John Mayes asked:
"could you elaborate (in as simple terms as
possible for the ones among us who don't do babblespeak..namely ME) as
to why you say this [that break angle should not effect tone]."

Acoustically the main 'job' of the bridge is to tell the string how long it is. Ideally, for this, the bridge should be massive and rigid, so that it doesn't move at all. The problem with that is that the guitar wouldn't make any sound. So, as so often happens on the guitar, there's a compromise involved, where you reduce the stiffness and mass of the bridge and top enough to get some sound, while keeping them high enough to make the string behave itself.

So, to the extent that the bridge is working properly the only part of the string that matters is that between the nut and the top of the saddle. So long as you have enough downbearing force on the saddle top to keep the string from hopping off when you pluck it hard, it should work alright, and any more angle won't make any difference, so far as I can tell. The amount of break you need is a little hard to specify exactly, but it seems to me that 15 degrees or so should do it most of the time. I'll note that that's the most common break angle at the nut, and most people don't use anything much different, or make sweeping claims about the benefits of different angles, at least on guitars. You _know_ when you don't have enough break angle.

It's really hard to talk about this without bringing up the concept of mechanical impedance, and that's a can of worms if ever there was one. What this is all about is really the mismatch of impedance between the string and the top of the saddle. It's just possible that a sharp break angle could effect this, although it's hard to see how, and I'd be willing to bet that it would mostly change things in the very high frequency range. That's important, but also hard to measure.

The big problem, as I say, is that on most guitars it's hard to change _only_ the break angle, Usually you change it as a consequence of changing the saddle height, and that introduces it's own differrences into the tone equation. When I finish my current time-wasting 'science project' on string vibration I'm going to try looking at break angle as an independant variable. It might be a while; I've got some orders to catch up on, and then I'll have to make a pretty tricky new bridge for the 'corker'. Don't hold your breath.

Somebody with a good grasp of basic engineering principles ought to be able to answer this: let's say you put the bridge pins right up close to the saddle (or, if it's a pinless bridge, achieved the same effect by other means) so that the break angle is sharper while the saddle height is the same... what happens?

I understand what Al is saying, and that this change is unlikely to make any difference in the mechanical impedance issue. What I'm wondering about is mechanical advantage, and how that may affect transfer of string energy into the bridge and into the top.

Does it increase the down pressure on the saddle? Seems like it would, but I'm not so sure. Nor am I sure what effect that would have on how string vibrations are transfered into the top. If that little length of string between the saddle and the pin is pulling down harder on the saddle, it must be also pulling up harder on its other end, where it's anchored into the bridge/bridge plate. Is that really possible? It makes me think of the Lorax lifting himself up by the seat of his pants and flying away... If that is possible, though, have we then increased the torque on the bridge? Or is that effect cancelled out by the fact that the point of down-pull and the point of up-pull are now closer together, thereby reducing leverage?

Of course, the proof is ultimately in the pudding (man, I love guitar pudding!). Like Al, I question whether changes in sound appearing to result from changes in break angle are actually resulting from some other factor(s) that is(are) being changed along with the break angle.

_________________
Todd Rose
Ithaca, NY

https://www.dreamingrosesecobnb.com/todds-art-music

https://www.facebook.com/ToddRoseGuitars/

[QUOTE=Todd Rose] If that little length of string between the saddle and the pin is pulling down harder on the saddle, it must be also pulling up harder on its other end, where it's anchored into the bridge/bridge plate.   [/QUOTE]

I understand that we haven't increased the force of the pull, but we've changed the direction of the force, so that there is (or so it would seem) more downward pull and more upward pull.

_________________
Todd Rose
Ithaca, NY

https://www.dreamingrosesecobnb.com/todds-art-music

https://www.facebook.com/ToddRoseGuitars/

[QUOTE=Todd Rose] let's say you put the bridge pins right up close to the saddle (or, if it's a pinless bridge, achieved the same effect by other means) so that the break angle is sharper while the saddle height is the same... what happens?   [/QUOTE]

The string will break. The windings will separate at the sharp break angle and buzz. Just a couple of possibilities.

let's say you put the bridge pins right up close to the saddle

Like this? <g>

Okay, my point wasn't really about having the pins right up close to the saddle, it was about changing the geometry of the bridge, however that is accomplished, such the saddle height is the same relative to the top of the guitar, but the string break angle is sharper.

So, my questions remain about what the mechanical effect of this would be and what the resultant difference in sound might be...

_________________
Todd Rose
Ithaca, NY

https://www.dreamingrosesecobnb.com/todds-art-music

https://www.facebook.com/ToddRoseGuitars/

Todd,
As Alan and other Analytical types can tell you, you are correct in your
thinking. In the violin world the break angle is an important issue and one
that must be delt with in a practical way. Especially the bass violin which is
not really standardized. Often a good bass violin luthier will raise the saddle
in order to lessen the downward force on the bridge. In old instruments
there can be a remarkable difference in sound by getting the right force on
the bridge. It is not just the force but another thing is the ballance between
the two angles. If one is sharper the imballance will cause the
bridge to either fall back or front over time as the strings vibrate. If the
angles are equal the bridge stays upright. But in a guitar the saddle is in a
slot so this is moot. KenMcKay38762.3470023148

Oh boy, Ken, in this context I'm not sure but what mentioning the violin or archtop guitar constitutes a 'red herring'. The geometry and forces are so much different that it's more of a distraction than a help, IMO. Yes, changing the break angle on a fiddle of any size, or an archtop, will definetly alter the tone. Usually on archtop guitars more downbearing=worse tone once you get past about the 10-12 degrees you need to keep the strings from hopping off the bridge. Violins are a whole 'nother game, owing to the soundpost and the way the strings are driven. Let's not go there.

On flat tops and classicals there's a torque on the bridge owing to the fact that the strings are up off the plane of the top. The bridge is trying to twist around a line that is parallel to the saddle, with the back edge moving up and the front edge down. The more I think about it, the more I beleive that the break angle and pin location simply effects the location of that line within the bridge. The magnitude of the torque force itself is set (I think) by the string tension and the saddle height off the top, but where exactly the maximum force is on the bridge might vary. Maybe...

Hmmm....

As a matter of fact, I thought about this some more and realized that a sharper break angle (pins closer to saddle or whatever - once again, I'm not talking about increasing the saddle height, but changing the geometry in other ways) would exert more of a forward force on the saddle, toward the nut, not more downward force. It seems like this would increase the overall torque on the bridge as well... In any case, on a guitar, unlike a violin, we have to account for the fact that the strings are anchored in the bridge itself, so there's a pulling force on the bridge, the angle of which is altered by the break angle of the strings over the saddle. The distance between the saddle and the anchoring point of the string would seem to mean a difference in leverage (apart from the leverage effect of different saddle height) as well as a difference in angle, so how the torque is affected is more complicated math than I'm capable of.

It would seem that, if more downward force on the saddle is a good thing for sound, that perhaps more important than the break angle is tilting the saddle back so that its angle of tilt roughly bisects the break angle. Maybe a sharp break angle and a fairly radically back-tilted saddle would be the ideal... I'm still not sure if that would actually increase the downward pressure on the saddle, nor whether that would make any difference in the sound.

String breakage is another consideration, but Mario seems to avoid this problem... presumably by carefully shaping a gentle curve into the saddle, is that right, Mario?

Note: this post was written before seeing Al's latest post, which gives me more to think about...
Todd Rose38762.6680555556

_________________
Todd Rose
Ithaca, NY

https://www.dreamingrosesecobnb.com/todds-art-music

https://www.facebook.com/ToddRoseGuitars/

Well, the bridge is glued to the top, which is glued to the bridge plate... I'd consider it a single laminated structure (unless it begins to delaminate!), not really separate parts. That which pulls up on the bridge plate is pulling up on the bridge (or vice versa in the case of a pinless bridge), as well as the top. The location of that pulling force is determined by the design of the bridge - where the bridge pins are.

I suspect that Al is right, that the "magnitude of the torque force itself is set by the string tension and the saddle height off the top" and cannot be changed by altering only the break angle or pin location, just as the Lorax cannot lift himself up by the seat of his pants.

But, it would seem that manipulating the break angle and saddle tilt does change the amount of force pushing the saddle down into its slot, or forward into the front wall of its slot, and that that could have an effect on sound, n'est pas?

_________________
Todd Rose
Ithaca, NY

https://www.dreamingrosesecobnb.com/todds-art-music

https://www.facebook.com/ToddRoseGuitars/

Pardon my intrusion. I know it`s a different animal, but the break angle on my Hamilton piano is only 4 degrees...

_________________
Give me 50 cents worth of regular.
Check my oil too, if you don`t mind,,,