Thin bridge on my guitar. will anyone take a look?

noodlenot

Hi all! Here´s a (thumbnail´d) picture of the bridge on my selmer replica:



Also, here´s a link to the manufacturer: http://www.apc-instruments.com/indexen.html (it´s the 802 model) - there are more images there, in case you´re interested.

As you can see, it´s a thin bridge (0.295 inches wide). As i´ve never found a bridge like this anywhere else (the bridges i´ve see on the selmer replicas out there are much wider and look "sturdier"), i was wondering if someone around here could tell me if they have seen bridges like mine and how could a thinner bridge affect the sound of the guitar (having a smaller object to transmit the vibrations to the soundboard).

Thanks in advance,
Miguel.

Jeff Moore

If the trick is to get as much of the strings energy through the bridge for getting the top to vibrate, then have the lightest bridge is likely the way to go. I think the lighter the better because it seems to be commonly thought to be right and intuitively makes sense to me. There may be some downside, but I can scarcely tell the difference between the light bridges I make and the heavier ones that come with the guitars except that they might be a little louder with the light bridge.

I don't know where you'd buy a bridge like that except for the maker. Bergeijk also makes very thin bridges - he's in Belgium?
I make lots of bridges but I use the standard width, though I carve em down to get them as light as possible. Mine aren't particularly pretty or finished off. I do it for getting both intonation and of course the height where I want it. I don't want to do it for others cuz I need the guitar to do it well, and I don't want to sand and polish. Once I stain em to match, you can't see the poor finish unless your pretty close.

I doubt there's any problem with your bridge being thin and light. Bergeijk does them this way for the reason I gave. Most luthiers hollow out the bridge to achieve some weight loss. I've never seen a GJ guitar with a solid un-lightened bridge.

The problems I see with most bridges is that they are not intoned (the guitar doesn't play in tune up and down the neck), and a few new bridges are not mated very well to the top (the feet don't sit flat on the surface of the guitar). This can have a profound effect on the sound that anybody would hear when compared to a well fitted bridge. Keep in mind that the foot of the bridge only needs to mate where the truss is inside the guitar. Bridge makers will often relieve the very ends of the bridge which is not over the supporting structure inside. In other words it isn't necessary that ever bit of the foot is in contact just that most of the foot is in contact and particularly that portion over the strut - brace - or what ever you call that little support peice under the top and under the bridge.
It doesn't have to be perfect but real close. If you see daylight between a significant part of the bridge foot and guitar top, it needs help, unless you like the extra twang and drop in volume.

If your guitar sounds good, your bridge is probably fine. Most luthiers are pretty good about fitting the bridge but its easy to see daylight if you check.

Bob Holo

The amount and nature of the contact of the bridge has to do with the designer's choice of how to handle the mechanical impedance transition between the bridge and the top. Essentially it's a question of how much of the string energy you want to put into the top and the nature of the movement & acceleration/deceleration you want the soundboard to experience. Thin long bridge feet in general tend to put more energy in initially,though that's not always the case and is somewhat dependent on the nature/placement of the pliage/bombe & the bridge tonebars. More initial energy is good for volume but sacrifices sustain & etc. It all depends on what you want to do with the energy. The energy either vibrates the soundboard, travels along the bridge and shoots down other strings causing more complex harmonics to occur, or turns into heat as a result of the vibration, or is lost in dampening as a result of material properties or the characteristics of the joints. (...well I guess that also turns into heat, but unlike the heat created by string vibration it's not an inevitable product of the string movement... it's just more of a pure "loss" of energy due to poor design and/or poor workmanship) Mass and strength (modulus) of a bridge is also important as Jeff said, but just in terms of "why thin?" it's just the designer's choice of where he wants to "spend" his "energy budget" If the guitar sounds good, then the designer did his job well. Something else that is important... the relationship between the height and the length of the bridge relative to the frequency spectrum of the instrument. We tend to think of bridges as moving up and down, but if you slow-motion photograph them it's more like "all hell is breaking loose" earthquake style. They go up & down... back & forth (rotate)... they even demonstrate some torsional movement to the extent that the bridge design allows it. Envision the bridge as though you attached a handle to the center of a thin sheet of metal. The sound you get would depend on how you shook the handle. Straight up & down would give you one sound, back and forth would give you another, random shaking yet another... the design of the bridge influences how it is capable of moving and the design of the bridge/soundboard interface influences how that movement charges the soundboard. So the design of the bridge and the way it contacts the top is the designer's solution to the problem of the mechanical impedance transition between the bridge and the soundboard given the variables of weight/mass/strength/tuning/dimensions of the soundboard and bridge. Your solution depends on the rest of the system and your desired outcome. There was a Scandinavian university who did some interesting research on this several years back... their name starts with a "K" I believe... their papers are buried somewhere on a bookshelf in the shop. It's interesting stuff though - yet another area where the violin world is so far ahead of the rest of the stringed instrument world when it comes to actual hard research. I probably have five times more research on violin acoustics than guitar acoustics and the quality of it is generally stellar. While there are still some myths and faith-based controversies in the violin world (most having to do with varnish and ground-coats) in general, the hard cold light of science has been shown on most aspects of violin acoustics to the betterment of the art form. By the way, that's not a slam on faith - it is simply intended to say that faith is much better tool for describing complex subjective human experiences and science is a much better tool for describing complex objective acoustic machines such as violins/guitars... It's getting better all the time, but the guitar world still seems to have a few people who "feel" strongly about very objective design decisions and they insert what amounts to alchemy into a design decision without controlling the actual variables that influence the outcome. I hope the guitar design world eventually matures as the violin design community has. To the extent that I can eventually contribute to that - so much the better. Uggh. Now I remember why I stopped posting so much... just can't seem to write a short answer to a simple question. Back to the shop... quite a unique and amazing instrument out there and I just came in to rest my neck which has been craned over it all morning.

Craig Bumgarner

Bob,

As always, learn so much from your posts, thanks for weighing in. Would you care to comment on how adding a saddle to a Selmer style bridge fits in the equation? I made a saddled bridge last spring so I could try various piezo pickups. It seems to be fairly good acoustically, but not as good as the all wood one. The saddle is not tightly captive and in light of your earthquake, all hell breaking loose description, I wonder if some of the energy is being lost in the fit of the saddle to the bridge. I've seen saddles on the Selmer style guitars of no less a builder than Jean Pierre Favino, so, though not common, they must not be all bad when done right.

Craig

noodlenot

wow, thanks so much for the replies, guys! i really didn´t expect so much detailed info. it´s really appreciated and i´ll take some time digesting it all.

Bob (if i can call you that), could by any chance the scandinavian university be Kungliga Tekniska Hogskola (http://www.kth.se/) ? i have some papers regarding violin and guitar acoustics from them that i´m going through at the moment.

once more, thanks everybody.

Miguel.

asd123321

A study I read said the bridge doesn't actually go up and down in relation to the top but moves in the direction of the strings. The one side of the bridge would be trying to move down then the other. It would seem then a narrow bridge wouldn't affect it so much and it would
have a weaker sound. How does it sound?

Heretic

Bob:

Golly,that's some explanation!
On the the Gitane instruments, the makers use a large contact area on the ends of the bridges as opposed to Selmer's/ Dupont's design of raised ends - like flying wings.
What effect does saving off the ends have on tone and volume? I've done this on my own instruments, together with carving our the insides of their ebony bridges, and achieved much better sound. But I did this as an act of faith thinking that Selmer and Dupont were smarter than me, and by doing so, I'd benefit - which I did. But, I don't know why, besides lightening the mass.
Any ideas?

djangology

Personally, I would think about buying a stock DuPont Bigtone bridge and install it onto that guitar. And I mean "think about it" because I've never seen one of the guitars your playing and so there may be some reasons (such as neck angle) that you might not want to alter the bridge that came with the guitar. If its a well made guitar, truly in the style of a Selmer, then I would think that there should be no reason you cant swap a normal DuPont bridge onto it.

Bob Holo

Yes, that's the University.

As for the other questions: Well, it's all about energy transmission... so a lot of these issues go straight back to that. So, here' goes... Sound waves get attenuated when they encounter a mechanical impedance differential which is just a fancy way of saying that they hit something that vibrates in a different way. In other words, the nature or amount of the resistance to the sound changes... Why is that? Well, a number of reasons, but for now just consider that a frequency which is good at propagating through one type of material is usually bad at propagating through a material that is substantially different. Consider that a bird whistle may carry for miles through air because it is focused and has a high pitch... and a whale's call may carry for miles through water because it is powerful and low-pitched... But you couldn't hear the birds call from even one inch under the water and you couldn't hear the whale's call from even one inch above the water. Why is that? You don't want to know. Mechanical wave propagation does not make good cocktail party conversation. Just know that different types/frequencies of energy travels through different materials in different ways and most energy is lost or filtered when the medium or substrate through which a (sound) wave is traveling changes.

So, why tell you about bird calls and whale song to answer a question about bridge feet? Simply this: to help you visualize in a grand way, what happens in much smaller ways when sound travels between materials that are only slightly different... spruce vs. rosewood... silver vs. ebony... galalith vs. brass... piezo element vs. rosewood bridge. All those transitions attenuate the sound and these attenuations are frequency dependent. In other words, they're filters.

So let's apply it:

What happens when you put a piezo element on a bridge instead of cementing it into the bridge? Well, you have constructed an acoustic filter of some type. Does it sound good? Depends on whether it passes the frequencies you want and attenuates ones you don't want...

What happens when you change the size of the bridge feet? Depends on whether you like what your changes did to the mechanical "circuit" represented by the bridge and its contact with the top.

So, basically all of these things are essentially filters. The "why they work or don't work" is a bit more complicated, but the outcome is something to be judged by you, the player. If you like the sound of the thin bridge or inset piezo... then rock on, man. Just don't do anything to the guitar that's permanent so you can go back to your original setup easily. There is a special level in hell for people who mod nice guitars and a special level in heaven for people who are good instrument custodians and/or who restore them to their original state.

Oh, and yes, the up & down motion of a bridge is really more of a seesaw motion than a pure pistonic up-n-down.

noodlenot

Bob Holo wrote:

Mechanical wave propagation does not make good cocktail party conversation.

you´ve never been to my cocktail parties, right? well, thanks again for the fine dissertation, Bob, it helped to glue some scattered info i had hanging around. it´s greatly appreciated.

as for changing the bridge, i was not thinking of doing such a thing (at least not for now), as i would have to change the moustaches and study the neck angle properly, and i´m afraid i would end up damaging more than improving my guitar - even if it´s not a proper selmer replica. i just wanted to know if there are more people having thinner bridges and grasp the consensus around that kind of bridge and it´s properties.

as for how it sounds, i wouldn´t be a proper judge of that, since this is the only selmer style guitar i´ve heard so far (i´ve not played much steel stringed guitars either) and my technique is still very immature. i could post some sound samples if anyone is interested, though.

once again, thanks for all the input.

Miguel.

Jeff Moore

I wasn't suggesting you mod anything, but for those are seeing lots of daylight under their bridge they should look at Josh's thread: the first one under "Guitars, Strings etc...."
I've seen new guitars cheap and not with one edge of the foot doing all the work. Don't be afraid to get your guitar working properly, but do work very slowly and check everything often as you go. My limited experience with professional guitar techs has been very positive, but I've only used guys who've been at it a long time.
An ill fitting bridge sounds pretty bad.

If you want to see how many thin bridges are out there, a good sample of the best guitars "out there" are on the store section of the site. I can't recall seeing a thin bridge. Even so, I wouldn't be concerned. Nearly all of the bridges adhere very closely to the art deco fashion of Maccaferri's brilliant design. Few luthiers depart from the tradition. I hope that Bob's wide discussion of bridge design helps with the idea that thin is fine if the luthier makes it work.

I guessed you were concerned about the sound. I suspect that anyone new to the sound (several years or more!) has to wonder about the thing they just bought.
The Maccaferri sound was new to me eight years ago. I now prefer these guitars but the old standards of guitar sound still make them sound a bit foreign, and also hard to judge. There so much variability in these that it stays interesting, and hard to find a sonic foothold.
After years of exclusively playing these and maybe three years of playing really good ones, my own evaluation of what is good is still in motion. Among others I have a Dupont VR. It's awesome and seems most useful for all that I do without giving up anything from its GJ credentials, but ya never know.