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发表于 2009-2-17 19:31:27
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你这厮...我都给你
Obviously, Don’s the bigtime expert on this issue, but I think there are some basic ideas that I can contribute and we can talk about as a community until the FAQ is done.
One thing that is important is that different species of wood have different average densities.
The second very important issue is whether the wood has uniform grain, or bilayer grain and pronounced growth rings.
Woods like maple and alder have very even density throughout any single piece, and different pieces from different trees tend to be relatively uniform. The grain in these species is even, with fine dark growth ring lines.
Other woods, such as swamp ash and mahogany, have a bilayer grain with wider, more uneven growth rings and large dark areas. The dark parts of the growth rings are much denser, heavier, and stiffer than the light parts. Depending on how much light and dark meat you get in an individual sample, there can be wide variation in weight and tonal qualities.
The strength of the woods with pronounced bilayer grain tends to vary more or less linearly with their weight. The shorter the summer, the tighter the grain, the more dark layers, the stronger and heavier the wood.
Only northern spruce is suitable for acoustic guitars because the short summer produces many strong dark layers close together.
As I understand it, the stiffer and denser the wood, the better vibrations, especially high frequencies, are transmitted.
However, there is a limited amount of energy in a vibrating string. It needs to cause the guitar to vibrate and bounce that energy back with different overtones to give it “tone.”
An infinitely dense and hard guitar body would transmit frequencies well, but would absorb all the energy of the string before it gave anything back. An example of this would be a solid maple on maple guitar, especially a large one, like a a set neck. The closest example of this I can think of would be George Lynch’s tiger charvel, which is solid maple with a maple neck, weighing in at 12 or 14 lbs. His tone with that guitar has an outrageous popping attack, and not much in the way of sweet sustain. Overbuilt acoustics can sometimes have a little bit of this banjo-y sound, but the large amount of glue on most examples tends to roll off the high end.
Extremely light guitars are usually going to be summer-y swamp ash. Swamp ash tends to sound scooped from the interplay of the two densities of the wood, with the dark layers transmitting highs well, and the pillowy white layers providing the thump. Lighter swamp ash will tend to start damping those highs. However, as the guitar gets lighter, you get a more blooming sustain, as the string vibration has no problem setting the whole guitar on fire, you get a lot more of those overtones bouncing back. An extreme example would be the sound of a very light spruce archtop electric — almost uncontrollable feedback. This would be a practically useless guitar for George Lynch, but if you wanted a rolled-off attack with a blooming sustain — presto. A very light ash strat will have a touch of this.
Mahogany has a tighter envelope than ash, in terms of the difference between a very dense piece vs. very light. Also, the difference between the light and dark parts is less, giving it bigger mids.
Alder, there’s very little difference throughout, or between pieces. It transmits all frequencies well, and has that pronounced upper midrange bite.
Maple has very little difference at all, and is so dense and stiff that only small amounts are used on any one guitar to keep it from being overbuilt.
The basic way to sweeten up a heavy piece of wood is to hollow it out. Air vibrates very easily, giving you midrange bloom. A soundhole boosts the lows. You get something like that bilayer quality of a medium piece of swamp ash or northern spruce between the very stiff dark wood, and substitute a chamber for the absent light wood.
Also a chambered piece of heavy wood won’t be neck heavy, and is also sturdier than if it were made of light wood, which would easily become damaged.
It’s not a mistake that most nice guitars are about the same weight, hollow or not. If you come across one that’s an aberration, listen carefully. It’s a matter of balance — most builders and players agree on about where the balance is. You might prefer to agree with George Lynch or Tal Farlow than with the main stream.
Lastly, one factor that’s not realy a consideration at Grosh, but which can dramatically increase the weight of a guitar and affect tone is the amount of glues and fillers. The more pieces of wood, the more glue, the more weight. However, glue is not stiff — it damps basically all frequencies and sounds bad. If there’s a heavy guitar with no attack, it’s main body material may be bondo.
I’m sure many people will have lots to say on this subject. This is only the very beginning of an answer, with almost no treatment of what the actual balance of sound should be, but hopefully it can be some holdover for Don’s FAQ and allow further discussion on the boards in the meantime. |
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发表于 2009-2-12 10:40:49
