mandolin bridges

**keymandoguy** · May-12-2004, 3:08pm

I just read an article that said the less a bridge weighed the more volume you would have ? I was thinking of installing a Sullivan Bridge on my mando, so if I drilles some tiny small holes in the bottom to make it lighter waould this increase volume even more than from rosewood to ebony ?or would it weaken the bridge too much ? opinions please thank you.

**sunburst** · May-12-2004, 3:52pm

It takes a lot of wieght difference to notice much more loudness. I doubt if you can drill away enough wood to get a noticeable improvement without compromising the structure of the bridge.
Here is an article by Frank Ford. It might be the one you read, but if not, he states that it took a lot of weight loss to make much difference.

**Dave Cohen** · May-12-2004, 4:06pm

Drilling holes in a Gibson-type bridge foot will not decrease the mass a great deal, but it will weaken the bridge foot. In those bridges the adjusting posts and wheels are big contributers to the total mass. They are made of steel, w/ a density of around 7 - 8 grams/cc. The gibson adjustable mandolin bridges weigh in at around 14 to 17 grams. The Weber "Brekke" bridges weigh in at around 13 grams.

Frank Ford has an article on his frets.com website in which he describes building a one-piece maple bridge which he drilled out for a total mass of around 3 grams. He claimed a large increase in volume, but not necessarily a "better" sound. Red Henry has similar descriptions on his site. He has settled on around 6 grams as optimal. He also sells those bridges. which are one-piece, non-adjustable. He similarly makes grand claims for his bridges. I make adjustable bridges in various materials. The maple ones weigh around 5 grams; the ebony ones weigh around 8 to 9 grams. Imo, lighter is better, but I don't make grand claims. Why not? Well, at low frequencies, the top and bridge function as one. At higher frequencies, the bridge makes some of its own contributions. So we need to consider the total mass of top plate plus bridge. In an f-hole type mandolin, a very light top will have a mass of around 100 grams. That is for an A-model; f-models will be heavier. A heavy top, such as some of the heavier pieces of Adirondack spruce, will weigh in at as much as 160 grams. So for one of those, you can see that decreasing the bridge mass from 14 grams to, say, 6 grams is a kinda small perturbation. The audible differences will not be large, though they may certainly be noticeable.

So what can you do? None of the bridges are very expensive, compared to a mandolin. You can easily try a few at not too much expense, until you find something that floats your boat and fills your heart.

**Michael Lewis** · May-12-2004, 11:44pm

It has been my experience that a given bridge can produce different results on diferent mandolins. #An example: at the request fo a customer #I put a Brekke bridge on a teens Gibson A model. #He was so happy with it that he had me put one on his F model, but it sounded poorly so we put the original bridge back on. #Same bridge, different results. #

Considering the ways the parts of a standard adjustable bridge can work can drive you crazy. #One thing I have found is that the saddle needs to be fairly stiff. #By thinning a saddle to get a lower action I have occasionally gone too far and it ends up too flexible resulting in a mushy sound and a loss of volume. #The mass (weight) of the bridge alone isn't the main determining factor of the results, but where the mass/stiffness is proportioned in the bridge. #Combine this with the physical structure of the sound board and the strings, and the ways they interact, and things can get pretty busy. #A small change in any one of the variable elements can make (or not) a big difference. #There are nearly infinite possible variations to try, but what is needed is a "good" combination for a specific instrumant.

**french guy** · May-13-2004, 1:30am

One my latest mando ,(C model) I've made a one piece (non adjustable) ebony bridge , weight 9 grams , but the main difficulty is to adjust this bridge to the top in tension under the strings pressure because of the top deflection .
(I remember , my top wieght is 125 grams and the back 135.)
In other words , I think the foot of a gibson adjustable model is more able to follow the top deflection than a one piece model ( more stiff ) .

**Joe F** · May-13-2004, 6:34am

I recently replaced the top portion of the bridge on my Kentucky A-model with one made from graphite. #The increase in volume was noticeable immediately, as well as a brighter overall tone (My strings at the time were about 4 months old, and they sounded like a couple months had been shaved off their life). #I attribute this to the lower mass and higher stiffness of the graphite, compared to old wood bridge.

I posted a picture of the new bridge previously in this thread.

**Dave Cohen** · May-13-2004, 7:01am

Joe F, the only problem with that is that graphite composite is fairly dense, around 2 g/cc, iirc. So you won't lose any mass by switching from ebony to graphite. Now, graphite is much higher modulus, but I don't know what, if any, the audible effect of that is yet.

**Michael Lewis** · May-13-2004, 11:47pm

If you tap same sized pieces of graphite/epoxy and various woods used for bridges(ebony, Bz. rosewood, maple, etc.) you will hear that the graphite rings more efficiently and at a higher frequency (clear, bright, sustaining). Bz. rosewood is the next closest in livelyness but rings at a lower frequency (pretty clear, sweeter than carbon, brighter than ebony or maple). Both ebony and maple don't ring very well, I think they have more of a damping effect on the energy passed through them. That being said, think about the fact that of these materials, ebony usually sounds best on a Loar or similar mandolin. The traditional receipe needs some damping, not the most efficient material. To me, that seems like there are a whole bunch of opportunities to develope a new tonal character that Gibson hasn't yet.

**frets1** · May-15-2004, 10:02pm

I have a fosselized walrus ivory bridge on my Sam Bush Gibson. I don't know exactly how much it weighs but, it has to weigh more than the ebony. The volume is noticably louder and the tone and sustain are much improved. I'm no expert but, I do know when something sounds good and my bridge sounds GOOOOOOD!