Are there disadvantages in asymmetric bridges ?

wuzzo · #1 10-08-2013, 02:24 AM

I'm considering an asymmetric bridge for my custom jumbo. To my eye it compliments the lines of the guitar and makes it a thing of enhanced beauty- but will it have a negative effect upon the vibration of the sound-board ?
More succinctly, does the shape of an acoustic guitar bridge impact upon tone ?

ukejon · #2 10-08-2013, 05:26 AM

Great question. I also wonder to what degree the symmetrical shaping of the bridge plate either enhances or nullifies the asymmetric bridge effect. Would a bridge that tapers to emphasize the trebles need to have a bridge plate that does the same? Is that even possible or a bad construction idea?

wuzzo · #3 10-08-2013, 11:18 AM

You know, I hadn't thought about the bridge plate. Yes, you've made it a very interesting question.

Rodger Knox · #4 10-08-2013, 02:58 PM

I suspect that the shape of the bridge and bridgeplate has very little effect on tone, as long as the weight and height of the strings off the soundboard are similiar.

I'm not sure what "tapers to emphisize the trebles" means, and I doubt alternative and/or asymmetric shape could have a significant effect, positive or negative. When it come to the bridge/bridgeplate, it's all about the weight. Minor changes in shape that also change the weight will be more noticable, but it's the weight that's making the difference.

jeff crisp · #5 10-08-2013, 06:05 PM

Quote:

Originally Posted by wuzzo

I'm considering an asymmetric bridge for my custom jumbo. To my eye it compliments the lines of the guitar and makes it a thing of enhanced beauty- but will it have a negative effect upon the vibration of the sound-board ?
More succinctly, does the shape of an acoustic guitar bridge impact upon tone ?

If a bridge is looked at as a brace (which I have often seen quoted) then (from that alone) I would guess that different shapes will affect the tone just as tapered verses scalloped does. Whether it's a negative effect or not might come down to the sound you like. But I don't know, I'm just speculating. I would guess though that some of the bridge shapes like Sobels are more to stop stresses than anything else.

wuzzo · #6 10-09-2013, 02:03 AM

Would a bridge of similar asymmetry to the F-holes in an archtop raise any concerns with luthiers ?

wuzzo · #7 10-09-2013, 02:18 AM

Quote:

Originally Posted by Rodger Knox

I suspect that the shape of the bridge and bridgeplate has very little effect on tone, as long as the weight and height of the strings off the soundboard are similiar.

Thanks for that. I know next to nothing about the construction of good guitars. I tend to think of my guitar's top in terms of a quality hand-drum skin and when I see good hand-drummers ' shape ' the skin with one hand to alter the tone I wonder if the guitar bridge has a similar effect. Of course, a drum skin has no support underneath so it's probably an irrelevant comparison. However, I'd rather ask these questions- dumb as they may seem to some- than worry in silence.

arie · #8 10-09-2013, 09:39 AM

Quote:

Originally Posted by wuzzo

I'm considering an asymmetric bridge for my custom jumbo. To my eye it compliments the lines of the guitar and makes it a thing of enhanced beauty- but will it have a negative effect upon the vibration of the sound-board ?
More succinctly, does the shape of an acoustic guitar bridge impact upon tone ?

-asymmetrical bridge. more glue surface on one side, more mass to one side.
-tonal implications of off center mass.
-kasha, brondel, elkayam, etc...

what does your builder say?

charles Tauber · #9 10-09-2013, 09:58 AM

Quote:

Originally Posted by wuzzo

More succinctly, does the shape of an acoustic guitar bridge impact upon tone ?

Good question. Unfortunately, I don't think there is a "hard" answer, just lots of anecdotal opinions.

In the 1960's, Kasha theorized that the bridge of classical guitars should be "impedance matched". The "treble" side of the bridge should be thick and narrow providing stiffness, but little mass and better match the shorter wavelengths of higher frequency sounds. (For a rectangular cross section, stiffness is proportional to the cube of the height.) The bass side should be wide and thin, providing mass with little stiffness, and better match the longer wavelengths of lower frequency sounds. The bridge was split in the middle to allow torsion (i.e. each half to "do its own thing"). The bridge was one component in an overall design, including braces that did not run continuously under the bridge. Schneider took-up the cause and made numerous instruments of that design. Schneider was later hired by Gibson to design/consult on the Mark series of steel string guitars, which incorporated the "impedance matched" bridge. The Mark series was not successful from most standpoints.

I made a few Kasha models, none of which I thought were successful, and have played other Kasha models, none of which struck me as improvements over conventional designs - most, in my opinion, weren't as good as the best of more conventional designs.

Klein borrowed the "impedance matched" bridge design, incorporating it into his guitar designs. His instruments have been well-recieved by such notables as Joni Mitchell.

Thus, there are examples of very good instruments with asymmetric bridges and examples of not-so-good instruments with asymmetric bridges. I'm not able to conclude much from that about the isolated effect of asymmetric bridge design.

Bruce Sexauer · #10 10-09-2013, 10:36 AM

In a symmetrical guitar an asymmetrical bridge throws in variables which are hard to quantify, potentially distorting an otherwise orderly system. If only it were that simple! On the other hand, in an asymmetrical guitar, a symmetrical bridge might have the same type of effect, conversely. Most acoustic guitars are already asymmetrical under the skin, but the way the string tension is transferred into the top to generate sound might be best viewed from the standpoint of the membrane rather than the structure, this is my approach. Kasha seemed to approach the guitar as structure, being preoccupied with bracing as he was . . . IMO. I am a membrane guy and find great utility in the asymmetric bridge in my asymmetric work, no so much otherwise.

charles Tauber · #11 10-09-2013, 12:38 PM

Quote:

Originally Posted by Bruce Sexauer

Kasha seemed to approach the guitar as structure, being preoccupied with bracing as he was . . . IMO. I am a membrane guy ...

Thanks for that, Bruce.

That puts simple words to a dichotomy I encountered long ago and could never quite put in the right perspective - until now. In the 1980's, during the peak of my interest in Kasha's work, I attended a masterclass with Jose Romanillos. Richard Schneider was also at the event, though not attending the masterclass. Although he didn't speak of it that way, what Romanillos taught was the top-as-membrane. What Kasha/Schneider were about, to the best of knowledge and experience, was structure.

wuzzo · #12 10-09-2013, 02:58 PM

Well, ' structure ' or ' membrane ' in the ascendant it seems to me- from your conversations- that an asymmetric bridge isn't known to affect tone one way or the other. Certainly, my luthiers- Avalon Guitars- are offering me the option and I think I'll take it on the basis of your opinions expressed here. Sometimes you have to trust your own instincts and the asymmetric design seems so ' in tune' with the guitar's lines that I'm inclined to think that it might actually be beneficial to the instrument's performance. It was my idea, mind- they're not trying to sell me something.
Thanks for entertaining my enquiry.

wuzzo · #13 10-09-2013, 03:00 PM

Quote:

Originally Posted by arie

what does your builder say?

He says my guitar is going to be ' drool-worthy '

AcousticMoose · #14 10-09-2013, 08:12 PM

Asymmetric is the way to go. You may have heard some say asymmetric braced guitars feel fuller. That could technically be true. The braces reflect sound waves. Matching sound waves will cancel one another out. In theory, sound waves inside your guitar would be more likely to cancel one another if the guitar's bracing is perfectly symmetric. What are the odds of getting that kind of accuracy in a build? That's a question that hasn't been addressed.

Bruce Sexauer · #15 10-09-2013, 10:43 PM

Quote:

Originally Posted by wuzzo

Well, ' structure ' or ' membrane ' in the ascendant it seems to me- from your conversations- that an asymmetric bridge isn't known to affect tone one way or the other. Certainly, my luthiers- Avalon Guitars- are offering me the option and I think I'll take it on the basis of your opinions expressed here. Sometimes you have to trust your own instincts and the asymmetric design seems so ' in tune' with the guitar's lines that I'm inclined to think that it might actually be beneficial to the instrument's performance. It was my idea, mind- they're not trying to sell me something.
Thanks for entertaining my enquiry.

Ok; if you have a plan then it is an experiment, and then maybe you will learn something. But if you are just doing it "cuz", then you are doing nothing but rocking the boat. Not that it actually matters.

I saw Schneider demo Kashas ideas in Schneiders work at one of the Healdsburg Festivals in a workshop, and mostly everyone politely kept their mouths shut. Brilliant thinking and dedicated workmanship simply isn't enough.