Anybody ever try a red spruce bridge?

[joehendrick]

I have to make a bridge for an F octive I'm building. I have never bothered with bridge building. I usually get a Cumberland for the mandos and mandolas I've done. Steve doesn't do octaves.

If the goal in bridge building is the most support with the least amount of mass to transfer the sound from strings to body, I was wondering if building the bridge out of red spruce and the saddle out of ebony or maple would create some magic. Seems like the spruce is pretty tough and could support the stress without collapse with the right design. Yes it would still be adjustable either as a bridge with a slot that would allow for different height saddles or the traditional threaded posts. It also seems that since the top and tone bars are red spruce it might help sound transfer. What do you veterans think of this theory?

Joe Hendrick
Scenectady, NY

[Pete Jenner]

Soft wood doesn't work for a bridge. Lengthy explanations will no doubt follow.

[Jim Adwell]

I agree with Pete Jenner, but I don't have time right now to frame a coherent reply. No doubt someone will soon, though.

[MikeEdgerton]

Red Henry did some work with different hard woods. I don't know of anyone that has researched soft woods.

http://www.murphymethod.com/index.cf...t&contentId=92

I would think you might have a problem with the slots getting deeper faster.

[Dan of SC]

I'm a rookie, but I still have 2 cents. I don't think threaded posts would work because spruce is too soft to hold them firmly. An ebony or bone saddle might. It also occurs to me that a spruce bridge, being softer and less dense might actually absorb and dissipate some of the vibration of the strings.?

[sunburst]

I've never tried a softwood bridge, but I can't think of any reason why it wouldn't work, as long as there is a hard material for the strings to bear upon, and any adjustment mechanism is up to the challenge (if the bridge is to be adjustable).
On the other hand, I don't see any reason why a softwood bridge would be of any advantage compared to a more "traditional" bridge material.
The biggest factor in how a bridge sounds is the mass of the bridge, followed in some order by stiffness, size, and perhaps internal damping of the material (and maybe other things...). While softwoods (like spruce) are generally less dense than the hardwoods normally used for bridges, design can be used to lower the mass of a bridge, and there will be some optimal mass for the bridge for the sound we, as individuals, want to hear. It is probably not true that lighter is better beyond that optimal mass, so therein lies the reason that I see no advantage to using spruce and having to deal with the potential problems of adjustability (if desired) and durability. We can surely achieve our optimal mass using stronger, more durable, less problematic materials.

[mrmando]

If you have a hardwood saddle set into a softwood base, won't the string pressure push the saddle downward over time, deeper into the base?

[Tavy]

I'm pretty sure it would work, however:

* Spruce is pretty compressible: I can imagine it getting squashed over time.
* It would fray at the edges where the end-grain is exposed.
* You can probably make an ebony one that's just as light by carefully removing material here and there.

But.... in the time taken to post this you could probably have made one... wouldn't take long to carve one to shape from spruce and try it and see? Of course you would need to make an ebony as well just so you know what "conventional" sounds like

[bingoccc]

FWIW - The Janka rating for Red Spruce is only 490. Ebony, depending on the species, runs well over 2,000, even over 3,000.

[Jim Adwell]

A spruce bridge with the same mass as an ebony bridge would be huge in comparison, and since spruce is really soft compared to ebony it's probably pointless.

On the other hand I've never tried a spruce bridge. Hmmm.

[mandobassman]

If you have a hardwood saddle set into a softwood base, won't the string pressure push the saddle downward over time, deeper into the base?

I wouldn't think so. If that were true, the bridge feet would do the same thing to the mandolin top plate.

[hank]

Mike's pointing you in the right direction over at Red's Maple bridge site. Give him a call, a very nice guy that knows solid bridges. He and others have experimented with base footprint, relief holes and slots in a similar fashion as violin bridges. I would suggest Rosewood or Maple if you don't want ebony. Rosewood can be very hard and almost free of internal damping.

[darylcrisp]

if you really want to investigate the redspruce as bridge material, maybe laminate a thin wall hardwood on both sides to help as sidewall support-kinda like an ebony or maple sandwich. might be interesting and fun.

d

[tom.gibson]

I think the OP's question is a good one, and it's crossed my mind too. Whether such a bridge was laminated vertically like Daryl suggests, or capped with ebony, or had an adjustable ebony saddle, I'm sure it could work. If capped with ebony it would probably be similar in weight to a classical or bandolim bridge. Try it and report back!

It all raises some questions for me. A number of times people I've read people saying there is an optimal weight for the bridge, below which the sound becomes harsh or excessively trebly. On the other hand I seem to remember our experts (was it Dave Cohen?) saying we should treat the bridge as essentially part of the top. Now we want the top light for efficiency, but perhaps not too light if efficiency is bought at the cost of tone. So why is it not a question of an optimal weight for the entire top+bridge? Why should the weight of the bridge in isolation be an issue?

[sunburst]

...why is it not a question of an optimal weight for the entire top+bridge? Why should the weight of the bridge in isolation be an issue?

It is a question of the mass of the entire top, but the top is more structural than the bridge. In other words, the top can be made only so light before it's structure begins to suffer. The top must support the bridge, and the bridge need only be strong enough to stand up under string pressure.
Also, there is the consideration of the localized mass of the bridge. If, for example, we have two mandolins with a bridge/top system of the same mass, but one has a very light top and a heavy bridge while the other has a very heavy top and a light bridge, the former has more mass localized under the strings. That will result in different modal frequencies, and it would also most likely result in quite a bit of difference in stiffness of the top.
Generally speaking, the top is what it is by the time we start to ponder bridges, and for a top of a given mass and stiffness, the bridge mass that is just right for the sound we want to hear has the optimal mass for that top (and hopefully the rest of the instrument too).

Bottom line: any time we change something it can effect many other things in complicated ways.

[tom.gibson]

An excellent answer as always.

Of course, even if the weight of a spruce bridge was the same as an 'optimal weight' ebony bridge, the difference in material properties (damping etc) would make it worth a try...

[Ivan Kelsall]

Myself & another few Cafe members have been having a discussion re. how a 'standard' style mandolin bridge,made in Maple would sound. The Maple,already being less dense than Ebony, would automatically be lighter,but would it confer any benefit over Ebony ?.
I read about Red Henry's work on one-piece, lightweight bridges,but they were exactly that - one-piece,non-adjustable. Has anybody ever made a standard design Maple bridge to see (hear) what the differences might be ?,
Ivan

[pops1]

Rolfe makes maple bridge with an ebony saddle for most all the Phoenix mandolins.

[Dave Cohen]

I made a couple of all-maple two piece adjustable bridges (adjustable in the usual way, with the two threaded posts and adjusting nuts, all metal parts from aluminum). Other than the fact that they weighed about 5-6 grams, as opposed to the 9-10 grams for my ebony adjustable bridges, I didn't observe any difference. I did accelerance spectra on all of the bridges, found essentially no bridge motion below 5 kHz in any mandolin bridges. That included two Henry-style one piece bridges from Red himself. several conventionally adjustable bridges in different materials (ebony, EI rosewood, cocobolo, maple), and some three-piece sliding wedge bridges a'la Jimmy D'Aquisto. Compared to bowed-instrument bridges, mandolin bridges are all very short, very stiff, and very massive. Violin bridges do show some bending motion, referred to as the "bridge hill". But even in violins, that motion is up around 2.5 kHz. You can intuit from looking at a mandolin bridge that any "bridge hill" would occur at a much higher frequency than is the case for violin bridges.