Re: poly vs. nitro clear coat - age

"RichL" <rpleavitt@xxxxxxxxx> wrote:

The Repair Guy wrote:
Dave Van <daveYOUR...@xxxxxxxxxxxxxxx> wrote:
The Repair Guy wrote:
Jim <a...@xxxxxxxxxxxxxxxxx> wrote:

A true test would have to use the SAME
guitar (finish, test, strip, finish, test), played
by a freakin' robot (to make sure all notes
are hit the same way).

Easier way: ignore wood, use artificial body.
If you're only testing for differences in finish,
the body material shouldn't matter as long as
it's uniform (well... uniform compared to wood,
anyway).

But the argument is about the impact that finish
has on the wood.

My mistake. I thought it was about the effect
finish has on a guitar's sound. Maybe I mixed
up threads...

If there is any effect of the finish on tone at all,
it would matter whether the finish is on wood
or something else.

You could use any (reasonable) material and
change finishes, if the point of the experiment
was to look at properties of different finishes.

From the point of view of physics, what matters
is the difference between the elastic properties
of the two materials. (This will bore most folks,
but I'll continue anyway....) With no finish at all,
the wood surface is "free" to vibrate any way
it wants to. In physics, it's called a free-surface
boundary condition. Now, if you had a finish
material with elastic properties and sound
speed identical to wood, there would be no
practical difference, i.e., a sound wave wouldn't
even "see" the finish as a different material,
and again the surface would be free to vibrate,
as in the just-wood case. It's analagous to a
perfect impedance match in electronics.

Okay. But you'd have that same boundary
condition between styrofoam, say, and lacquer,
wouldn't you?

Any difference in tone therefore results from
different elastic properties. The sound wave
sees the difference and partially reflects from
the boundary between the wood and the finish.
The other part of the sound wave travels to the
finish surface and reflects back. The two
reflected waves can interfere (in principle)
and change the sound.

I've been thinking very little of a solid body
electric's body wood directly affects sound.
Seems to me the important part is the neck,
center of body, bridge. You could rout tone
chambers out near the edges of the body,
but I doubt they'd have nearly the effect they
would in the center (say, between pickups).

The other effect the finish has is, in essence,
changing the boundary condition at the
surface, because the finish material can be
either stiffer or more compliant than the wood.
The thinner the finish, the less all this matters,
however. In reality, such effects are very
small, especially for an electric, unless the
finish is "gooped" on.
If the thickness of the finish is large enough for
all this to matter significantly, then the
conclusion is that if you change the wood to
a different material, the results will change.
With the finishes on good solid-body guitars,
however, this is not the case; it's just too darn
thin to matter in the first place.

Ah... as I remember saying - finish matters
very little, and finish thickness matters more
than finish material. I feel vindicated now :-)

Y'all can wake up now, I'm done.

I appreciated it.
"Y'all"? What kind of physicist says "y'all"?

The Repair Guy
repairguy1993 dot netfirms dot com
.

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    ... has on the wood. ... If there is any effect of the finish on tone at all, it would matter ... properties of the two materials. ... The sound wave sees the difference and partially reflects ...
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  • Re: poly vs. nitro clear coat - age
    ... has on the wood. ... properties of the two materials. ... The sound wave sees the difference and partially reflects ... boundary condition at the surface, because the finish material can be ...
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