I wouldn't casually reply to an old thread, except mr roper recently added something to it, which seems justified since it's very specialized experiencial info he added. I didn't notice the original post date before I started writing, so I put quite a bit of thought into this reply, and here it is:
Some great advice so far, /\mr roper's sounds like valuable experience.
Check this out:
Sustain is related directly to two things:
1.The amount of energy (vibration) transferred from the strings to the body.
Less transfer = more sustain, as well as less volume/resonation/projection from the body.
More transfer = less sustain, more volume/resonation/projection.
2. The stiffness of construction.
Something stiff rings like a bell whereas something soft can be used to absorb sound. But you want the right amount for the instrument to be playable. You can't play most bells by hand, they're too hard. So drumskins are softer.
And the How:
For #1:
How can you reduce energy transfer and convert it into sustain? (it'd be easy to pad it, but that just eats sound, there'd be no gain in sustain)
-By adding mass (weight) to the body surface, so it vibrates less easily, and/or by adding mass to the interface between the strings and the body, i.e. bridge and/or saddle. Mass creates resistance by being hard to move. It's inertia. Even heavier strings vibrate longer, but they're harder to pluck and sound deeper.
The challenge with increasing banjo sustain, is that it's designed to favor volume and projection over sustain, so the body is a thin skin.
This is why people are advising you replace the bridge with a heavier one, and/or even weighting it. This will deepen the tone, so be prepared for that.
The indian tabla drum uses a similar concept to achieve it's deep tone. The black spot on the drum is tree sap and iron powder.
The problem is that you haven't made the skin any less flexible, so once enough energy/momentum is imparted to the weight to "get it going" (like a bicycle or car) the skin vibrates easily, creating a very deep tone.
This is why people are suggesting a very tight skin, possibly even a plastic one. It's stiffer. It actually resists vibrating, without weighing more, so the tone isn't deeper. It should actually raise the tone, so you could feasibly also add weight to the bridge. Great combination.
I don't like plastic skins (I'm a djembe drummer) so I can't advise that, but I suggest a thicker skin, and looking into which ones are stiffer, and if there's any treatment you can apply to stiffen it.
Replacing the material that the walls of the drum are made out of with something heavier would also help sustain, though again, it will lower the tone. The tone ring might work on this principle, it's mass that you have to get vibrating, so once you do it rings like a bell. A bit like a fly wheel in a car which keeps spinning once you put enough energy into it. Metal rings, but heavier/stiffer walls would have a wood-y sound.
Basically think of your instrument as vibrating so easily, that it's able to convert all the plucking energy into sound right away.
There's none left to "sustain" it. But if the instrument is heavier, and stiff, it takes longer for the string to send it's vibrations into the heavier object. I think the reason it's hard to grasp, is we feel like "but if it doesn't vibrate easily, won't that mean it makes less sound?"
Well, you're asking for sustain. If you want the same volume for longer, but at the same plucking strength, you need a bigger instrument.
So it's a tradeoff. If you want more sustain, it will be quieter. (assuming there's no gains to be made in simply making sure the connections are optimally tight, which there very likely could be, as mr roper found out)
I'm curious how this turns out.
. ). Anything that minimizes the area that the head contacts the rim could help with sustain, and IMHO using metal, particularly bronze or brass, at the contact point between head and pot will not only brighten the tone, but may help with sustain.
