Questions about top and saddle, please

[rodmbds]

Hi everybody! I really appreciate you taking the time to read my thread.

I have a Brazilian guitar, brand name Rozini. It's a hybrid which originally can take steel strings but I use it strung with nylons - it's similar to the Martin New Yorker, I guess (???).

Anyway, I've sent them a message about using nylon strings and they kindly answered me saying it's fine, that the only difference from their nylon model would be the metal tuning machines and a "reinforcement" on the top.

Messing around with a flashlight I've noticed, on the inside, near the soundhole, two pieces of wood attached to the top. They are glued and don't seem to be connected to the bracing.

Having said that, I've always noticed that the guitar sounds "boomy" and "bassy" with nylon strings; when I had it with steel, this was great because it countered the treble steels, but with nylons it just seems muddy.

My questions:

1) do you think those two pieces of wood are the so called reinforcement that the manufacturer mentioned? The top is spruce, solid, according to manufacturer.

2) could they be any reason why the guitar sounds bassy?

Here's a thought, hope you guys don't laugh at me!

3) have you experienced using two different materials for the saddle? I mean, I was thinking about having the bass strings over plastic (to tame the boom) and the trebles over bone (brighter?). Is it "doable"???

Thanks a lot in advanced guys, any comment will be appreciated.

[Alan Carruth]

There's a simple reason that nylon strings don't sound as 'treble' as steel; they have a lot less high frequency energy. It's simply the nature of the strings.

As a material nylon has much higher 'damping' than steel. That is, if you tap on a plate of nylon it goes 'thud', while steel tends to ring for a while. The nylon actually dissipates the energy of vibration faster than steel. This effect is more pronounced as you go higher in frequency.

Also, because nylon is much less dense than steel nylon strings need to be thicker to carry similar tension at a given pitch. The thicker strings have to move more air as they vibrate: it's sort of like trying to run in knee deep water. This also tends to cut down on high frequencies fast.

You can use something like a UST to actually see the force the string puts on the top of the bridge saddle as it vibrates. If you set one up on a stiff and heavy beam you can look at the string itself without the vibrations of the body changing things. If you pluck a steel string and a nylon string on such a rig you'll see that the initial wave form will be exactly the same for both. They will have the same amount of energy in each overtone to begin with, assuming the plucks are the same strength and in the same place. Within a second or so the nylon string will have very little energy above about 3000-4000 Hz, while the steel string will still be going strong out to at least 8000.

This is why steel string guitars tend to be made differently from nylon string ones, aside from the generally higher tension of steel. On a steel string instrument you have to get enough bass to balance out all of the high end. With nylon strings you have to get the most out of the small amount of high frequency the strings are giving you. Many of the differences in design and construction follow from that. Its also why it is often less than satisfactory to swap string types on a given guitar.

[Truckjohn]

Yes. What Al says.

Heres the thing...
Steel string guitars are often designed around bringing up enough bass to balance out the abundant treble.

Nylon string guitars are built around accentuating the treble available to complement the abundant bass....

By their nature - steel strings have about double the string tension vs nylon. And so the bracing and bridge has to be designed for this.

And so.... You either end up with a guitar that can only handle super light steel strings or a quiet thumpy nylon string.

[Bax Burgess]

The isolated pieces of wood may be for reinforcement around the soundhole. For saddle material try corian. What I use is from Luthiers Mercantile International. I don't know about corian, other than their stock. Corian, compared to plastic, tusq, bone, or micarta, will clarify and add volume to treble and bass, which can be distastefully harsh or absolute perfection - depends on the guitar.