Jameel
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Bridge size and material: how does it affect sound?
Some ouds have small bridges, some larger. Some are wider (parallel with the strings) and some are longer (across the face) than others. I'd like to
hear your opinions on the effects of different bridge sizes. Is a certain size/shape more efficent in getting the soundboard moving? How about bridge
material. Classical guitars (more similar to ouds than steel string) use ebony or rosewood, or other dense materials, whereas ouds typically use
lighter, less dense woods. Lets explore this...
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billkilpatrick
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one variation that's always interested me is the additional insertion of a sliver of bone or hard white plastic into the bridge, like those found on a
guitar.
both the classical guitars i own have them; all three of my charangos have them; one mandolin i own does and the other doesn't and both my ouds do not
have them.
do you know why they are omitted from the oud bridge? do they enhance the sound of an instrument in anyway?
in both cases, the bridges on my ouds are very business like, utilitarian looking - no arabesques or anything fancy about them at all. given the
rococo excesses displayed on some (mainly arab) ouds, i find this remarkable.
- bill
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AGAPANTHOS
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Any question reffered to the bridge of the oud constitutes a crucial topic.Unfortunatelly there is no scientific evidence and research concerning the
technical treatment of this matter.We approach it from a totally empirical point of view. In the meanwhile there is an important collective know -how
and practice which is guiding all of us engaged in the construction of the instrument.In other words this matter needs to be examined through an
applied scientific approach and research in order to testify empirical approaches, used since now and to trace certain guidlines
My opinion on this matter is based on two very essential characteristics.
a) the material of the strings and
b) the low energy of the strings ( due to their material and relative short string length) , transmitted to a relatively large body with a
considerable air volume enclosed in it.
In any case the wood of the bridge has to become from a quater sawn plank of a stiff, dense and heavy tropical hardwood (not only ebony or rosewood)
for reasons concerned mostly with mechanical stability (strength-stress).
The shape, the mass and the weight of the bridge are the most crucial parameters to be handled by the craftsman.
None of the above mentioned parameters could be handled according to one certain standard because all are a function of a whole system of other
parameters and technical aspects, for example the shape of the bridge is a function of the bracing system and the arching of the top of a given
instrument, the mass of the bridge is a function of the mechanical strength of the given top, e.t.c. e.t.c.
The only standard we can a priori accept is that the lighter is the better for the (any) bridge.
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Jonathan
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On the one hand, you would think that you would not want anything too heavy, so that the face can resonate more freely.
On the other hand, it would seem that the denser wood might be able to transmit the vibrations of the string to the face a bit better.
Absolutely no help, I know.
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Brian Prunka
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One thing I've wondered about is the height of the bridge and the resulting torque on the face.
I think that the issue of having a strip of bone may result from having a fretted instrument. In order for the frets to be in tune, the distance from
the nut to the bridge has to be fixed more exactly. It seems also to make the sound more brilliant.
bill, you mention that one of your mandolins has a strip of bone . . . where is it? doesn't the mandolin have a floating bridge?
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billkilpatrick
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| Quote: | Originally posted by Brian Prunka
bill, you mention that one of your mandolins has a strip of bone . . . where is it? doesn't the mandolin have a floating bridge?
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yes, a 100-something year-old bowl back - set into the bridge of which is this sliver of bone. frets could be the answer but precise vibrating string
lenght would be important in all string instruments.
the effect of torque is an interesting observation but in all cases - height, width, density, composition ... who knows what all else - there
wouldn't seem to me to be tremendous room for variation: with a bridge too high the strings will sound like mush; too low and they'll buzz; a bridge
too wide will smother resonances from the sound board, etc., etc..
might have a look through the "cantigas de santa maria" illustrations - lots of oudy looking lutes - to see if the bridges there are more or less
consistent.
- bill
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zeryab
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the strip of bone is called a saddle.
and the main purpose of it is to adjust the string action(hight of the strings).
becouse age and string poll usually warp the sound board outward and that couses the strings to lift high above the fingerboard,
so with the saddle all you have to do is remove it and sand it on a flat surface to lower the strings or shim it ( add a strip of wood underneath the
saddle) to highten the action, witch is something
you can't do with a sadlleless bridge.
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billkilpatrick
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"saddle" ... ah yes ... i forgot what it was called.
thank you - that makes perfect sense.
would it be correct to say the saddle itself - irrespective of the height it's supporting the strings - doesn't effect the sound of the instrument?
- bill
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zeryab
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To a degree, the material of the saddle can contribute, but not determine the brightness of the strings. for example a lot of musicians prefer to use
bone nuts and saddle for there bright effect on the strings and because they are also strong and would last a long time .other good materials include:
horn, ivory ,graphite to name a few. plastic on the other hand is the least desirable material to use because of it softness and dampening of the tone
that the strings produce.
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billkilpatrick
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there's an image of an interesting bridge - with mustache - from "alfonso X book of games" located here:
http://games.rengeekcentral.com/prblms/F18R.html
- bill
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kasos
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Thanks for the interesting thread.
It's surprising how little discussed the bridge is, considering its (literally) pivotal importance in transmitting sound from the string to body of
the instrument. By analogy, the bridge has much in common with a microphone - if the mike's not working, or is only transmitting part of the
signal, it doesn't matter how good your speakers and the rest of your system are....
On several of my instrument purchases (not at all restricted to ouds, and including bowed as well as plucked instruments from various regions of the
world), the floating bridge was lost at the time of purchase. I've had to make my own replacements, often without much to go on in terms of
models, which has led to quite a bit of experimentation on my part. I can't speak from any advanced scientific perspective, but I've learned the
hard way about some of the things that work, and some of the things that are less successful....
Almost anything can be made to function as a bridge. OK, I'm exagerating a little, but hear me out. I was a 'hit' with my son Brandon (7 years
old) when I tried using one of his plastic Lego blocks as a bridge on my (bowed) Thai coconut rebab. In many respects, it actually worked quite
well. It fulfilled many of the most basic functional needs - it was light, it reduced unecessary dissipation of vibration on the way to the
soundboard by being hollow, and it was long enough to activate several parts of the soundboard at once. This particular plastic piece was itself
bridge shaped, so it concentrated the sound vibrations through two 'posts' at each end and thus didn't unduly dampen the soundboard. And, to boot,
the connecting round ridges at the top kept the rebab's two strings from slipping into each other....
One of the earlier posts on this thread suggested that plastic was not an appropriate material because it might dampen sound. Well, yes and no....
Really, it's a case of which end of the tonal spectrum you're dampening or enhancing the transmission of, as the case may be. The lego bridge worked
relatively well (to my ear) in the case of the rebab because this particular sort of plastic seemed to muffle highs, and efficiently transmit low
sounds - not altogether a bad thing when assessing the merits of a bridge on an instrument sometimes prone to shrillness. On the other hand, if you
wanted to emphasize the brightness of the sound, plastic might not be your best choice - something hard like bone would probably do this better.
I've also made functional bridges out of pencils, popsicle sticks, and just about every sort of 'found' wood you can imagine. Some of the same
considerations apply to bridge wood as to other woods used in instrument construction - on the whole, the older and the drier it is, the better it
seems to communicate vibration. I read somewhere that this has to do with the cellulose cells getting hollowed out over time, and this makes
intuitive sense to me...... Of course, older and drier wood is not as stable, from a mechanical point of view. I've had quite a number of lovely
bridges (from a sound perspective) simply collapse under the pressure of the strings. In my experience, bridge making is one of those 'art of the
possible' situations - you keep making the bridge thinner, and file away excess material until you can't take any more away without compromising it
from a structural perspective.
Although the basic principles I've described above apply to pretty much any stringed instrument, there's room for endless variation when you look at
the needs of a particular instrument. The bridge is under a different set of stresses depending on whether the string is being bowed or being
plucked. And, especially when looking at the tremendous diversity found in the construction of instruments in different parts of the world, you
also find different needs depending on the thickness and composition of the soundboard, what bracing is used, and whether there is a soundpost, among
other considerations.
For example, the rebab I referred to earlier has a thin wood soundboard, relatively little in the way of bracing, and no sound post. There's only
two rather thin strings, and, relative to a guitar, not a lot of string pressure. Because of the lack of bracing or sound post, the challenge in
this case is to spread the vibration across as much of the soundboard as possible. A wide spread between sound posts works best. But a thick post
(at least at the area of contact with the soundboard) tends to work better than a thin one, because a relativel wide area of contact seems to help
make up for the absence of transmission through bracing....
On the other hand, I've got hide topped instruments with somewhat different needs. My Serbian Gusle has a thick parchment on it as a soundboard - no
bracing or soundpost here, obviously.... For this instrument, a wide separation between posts is best, for the same reasons as for the rebab, but
instead of posts with a wide contact surface, a narrow point works best (this seems to be because a wide contact point apparently reacts poorly
against the slight unevennesses in the hide to produce a range of differentials - in plain English, unpleasant squawking sounds). On the other
hand, the hide topped erhu has a snakeshin hide, which is thinner and more even - making a wider contact area feasible.
I've not yet been so bold as to experiment with my oud or lavta bridge (fixed bridges remain a bit of a forbidden zone for me), but have got good
results (to my ear anyway) from thinning out the floating bridge on my saz, using the same principles I've gained from experience with the other
instruments.
And, just in case you were wondering, I did ultimately replace the lego piece on the rebab with a wooden bridge.....I suppose tradition still counts
for something.....
Take care, Mark
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Elie Riachi
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Interesting topic Jameel.
There shouldn't be much difference if any from the classical guitar as far as the characteristics of the material used to make the bridge. It seems
to me that there should be a difference in the grain orientation between floating and fixed (floating being flat grain, and fixed being straight).
The bridge should not absorb the vibrational energy and should be light. So the type of would should have the highest strength per mass ratio. It
seems to me that building a stringed instrument is a lot like building the body of an aircraft, as light and strong as possible.
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