experimental bridge designs

[Brian Evans]

I've been reading a lot about mandolin's lately and found this today; http://www.murphymethod.com/index.cfm?e ... ntentId=87 which I found quite fascinating to browse through.

It's a quite involved blog on researching bridge designs for archtop mandolins, in particular F type, so I thought there might be some relevance to archtop guitar. I further researched violin and other violin family bridges, and the whole idea of sculpting the bridge to influence the travel of the vibration path seems well accepted, with most people using a design pioneered by Stradivarius, I think. So it seemed to me that this should have fairly direct relevance to archtop guitar, and wondered why it hasn't shown up on many instruments? I've just found a couple of instances of non-adjustable bridges. Everyone seems to use some variation on the two wheel adjustable bridge, or a ramp adjustable bridge, neither of which pay much attention to the way the vibration travels through the bridge. Benedetto devotes a paragraph to this but admits that the research hasn't been done. He says the one-piece violin style bridge is acoustically superior but almost never uses one on the guitars I've seen.

Any thoughts on this?

Brian

[Michael Lewis]

Well, those guys say some things that at first sound logical and good, but if you do your own experiments you may find other results and conclusions. Some people have suggested the Gibson style adjustable bridge is a poor design because it has so many design flaws (metal adjuster posts and wheels, saddle not supported directly under the strings, heavy, etc.). But in practice it works very well.

A violin style bridge works very well for a violin.

[Alan Carruth]

Standard archtop bridges mostly affect the sound due to their mass. I have seen wheel adjustable ones where the top was so small that it could flex and alter the tone, but that's exceptional. Certainly a well made wedge type bridge should act pretty much as a solid mass.

Violin bridges have various resonant modes, and act as filter elements between the string and the box. You can actually tune them, and partially make up for problems with the way the box works. There's no reason you couldn't do the same with an archtop. I suspect that what you'd end up doing is reducing the high end sound, so it might not be as wonderful as alll that. It's time consuming to tune a bridge, too: you have to keep taking the bridge out and putting it back in. One thing that helps a lot with this is a bridge jack to lift the strings off the bridge without having to slack them off. You could do this with a regular wheel or wedge adjusting bridge if the adjuster is powerful enough. Just stick it in behind or in front of the one you're tuning and jack the strings up.

Of course, the bridge on the violin also works differently from the one on an archtop, mostly because of the sound post. Violin bridges are set up to convert the side to side motion of the bowed string into a vertical force on the top at the bass bar. The post 'nails' the treble foot of the bridge down, and it then rotates around that fixed point, acting as a bellcrank.

[Beate Ritzert]

In this forum, there is already an older thread on this, isn't it?