Does the type of wood used in the bridge impact the tone/sound?

[Hoyt]

The question to me is, does the particular wood, shape, mass, etc., make it sound better than another bridge?

[Goodallboy]

Originally Posted by Hoyt

The question to me is, does the particular wood, shape, mass, etc., make it sound better than another bridge?

Some say yes, some say no.

Some disagree with both of those opinions.

[Alan Carruth]

Define 'better'.

[Br1ck]

I own a Custom D 35. It was ordered with a rosewood bridge and fingerboard, wood binding, and a koa wedge. It makes sense to me that the bridge would have the most effect on tone. The guitar is one of very few D 35s I've ever liked. Brian Kimsey said it was the best D 35 he'd played. He tends to like punchy guitars. Someone paid significant money to get the rosewood "downgrade." Who knows if the guitar could be duplicated. It might just be the people who made it had a good day. Maybe the original owner was disappointed.

[mercy]

Wood type on the bridge makes a difference if the two are exactly the same size and shape.

[Scotso]

The answer is definitely maybe, might, and could.

[Brent Hahn]

What would it sound like if the saddle was in direct contact with the top, with no bridge material in between?

[John Arnold]

I have played guitars where the bone saddle was sitting right on the spruce top, and they tend to sound harsh. Acoustic guitar bridge design is such that the sound travels from the densest, hardest material with the smallest surface area (steel strings) to the softest, least dense material with the largest surface area (softwood top). The intermediate steps (bone saddle and hardwood bridge) are progressive in hardness.
Most of the difference in sound between bridge woods can be attributed to the weight. Heavier woods tend to accentuate bass and sustain, while lighter woods accentuate trebles and quick response.
Unlike most Martin guitars, classicals traditionally have ebony fingerboards and rosewood bridges. The lower tension of nylon strings will favor a lighter bridge.

[silvereagle48]

Originally Posted by Alan Carruth

The mass of the bridge certainly affects the sound, and so can the stiffness. Other than that it's hard to say. It would make some sense, for example, that the damping of the bridge might do something, but it's a very difficult thing to test out. The other major caveat, of course, is the deceptively simple phrase: "all else equal". Two bridges made to the same specs of different woods will likely have different mass, and stiffness too, so you have two (or more) variables in play. That's one of the things that keeps this all 'interesting'.

excellent answer

[Alan Carruth]

John Arnold wrote:
"... classicals traditionally have ebony fingerboards and rosewood bridges. The lower tension of nylon strings will favor a lighter bridge."

It's not simply, or even primarily, the lower tension, IMO.

The initial wave form of a plucked string, and thus the balance of overtones it produces, is solely dependent of where you pluck it. If you pluck it, say, 1/7 of the way up from the bridge, the relative power of the overtones will diminish as you go up, with no energy at all in the 7th partial, and relative peak heights will be the same no matter what material the string is made of. This mix changes over time.

If the string is on a 'rigid' mounting most of the change will be due to the nature of the string material, and, in particular, the damping. Steel has relatively low damping: if you tap on a steel bar or plate it will produce a more or less defined pitch, and can continue vibrating for quite some time. Nylon has much higher damping; tapping on a similar piece of nylon will give a 'thud' with a less discernible pitch that dies out fast. The energy of vibration is dissipated much more quickly in the nylon. In most cases damping tends to 'lose' a certain amount of energy per cycle of vibration. It's not really 'lost' of course; it's mostly turned into heat, but it takes a lot of energy to warm things up noticeably.

One common way to express a measure of damping is the 'quality factor' or 'Q value'. There are a couple of ways to find it, but at root it's a measure of the proportion of energy that is dissipated in each cycle of vibration. A Q value of 100 means that 1% of the energy that was there at the beginning is 'lost' for each cycle. This works like compound interest, so that you don't get to half the energy in 50 cycles in this case; it takes more like 72. Note that this is not tied to a frequency: the higher partials, with more cycles per second, die out in a proportionally shorter time.

Internal 'losses' are not the only thing that gives nylon strings higher damping. Nylon is a lot less dense than steel, so the strings need to be fatter to produce a given tension at a fixed length and pitch. As they vibrate the fatter strings have to move more air. This doesn't produce sound: it's more like trying to run in knee deep water, sucking energy out of the string with no useful result. According to one standard source, this 'viscous' damping dissipates energy about as fast as the 'internal' damping of the string material does for nylon strings. Steel strings have much lower losses from both causes.

Thus, if you mount a steel string and a nylon string on a heavy, rigid beam, and pluck them both in the same place with the same force, the initial wave forms will be alike, and they should sound the same. If you look at the same two strings a couple of seconds later the steel string will still have plenty of energy in the higher frequencies, but the nylon string will have almost none above 3-4 kHz.

IMO this difference in itself pretty much defines the different problems you face in making steel and nylon string guitars. With steel strings the problem is to get enough low end to balance off all the highs. With nylon strings the problem is to make as much sound as you can with the small amount of high frequency energy the strings give you.

All of this results in a bunch of changes in the designs. One of them is the use of a much lighter bridge and top on the nylon string guitar, which favors high frequencies and allows for reasonable output with a minimum of input energy. The lighter top dictates lower tension to avoid damage. In the extreme case of Flamenco guitars, which are more lightly built than classicals, the strings are also lower to the top to reduce bridge torque. Other differences, such as the top brace layouts can also be related to this, although the connections and reasons may not be as clear.

There are reasons behind the traditions, but sometimes they're not obvious.