| Subject: | Re: [RESOGUIT-L] Choices in the GOLDEN AGE of Reso. | | Date: | Wednesday, November 2, 2005 19:08:30 (-0800) | | From: | Richard DeNeve <richard_d13132 @.....com>
|
This phenomenon is why I think of the reso body as a
bass reflex speaker cabinet. The large air movement
of the speaker - the cone - caused by its greater
movement from the bass notes is "reflected" from the
body and out the ports. That is, the large surface
area of the cone moving in slightly pushes a pushes a
jet of air out of the ports, or sound holes.
What little I have been able to find to read on the
subject says that port diameter and length of ducts
(tubes hanging below the sound holes that some folks
have tried in the past) define a volume of air that
has a certain weight (OK, mass, for you scientists!).
This mass could be varied by changing the tube length.
The port can be located in relation to the speaker
more or less ideally - for a single note. It should
be very loud. But if you were to change the
frequency, port location, and/or air mass, you would
lose loudness.
Of course, we are changing frequency all the time.
The best one can hope for is to find a "best
compromise" for a range of frequencies (e.g. the bass
string notes on most resos) and adjust sound hole size
and location, total guitar body volume, and internal
body distances (via body shape and baffles) to change
the relative loudness of various notes in the target
range and thus "color" the sound to your liking. Most
folks would want pretty good bass sound reflection
(reflexion) over a range of frequencies, with no
strong "spikes" or wolf notes at any.
I have heard it said that, with a dreadnaught sized
flattop guitar, the optimal sound hole size is about
3-1/2 inches for sound projection. The player can't
hear as well, but the people in front hear more
loudness at most notes. Bobby Wolfe in North Carolina
and Gary Chansler (Dewey Slide Well) have experimented
with sound hole shape, size(s), and location.
As you noted, Jim, close off the sound holes and see
what happens. In fact, I use the Saga screens in my
sound holes, as they have less space closed off by the
screen mesh. And Paul Beard sells screenless rings to
make them completely open. Whatever gives your ears
that "best" sound.
Dick DeNeve
--- Jim Warren <dobro@adelphia.net> wrote:
> Take something fairly solid and cover the
> screenholes, then play,
> you will be surprised at the results. Even something
> like a paper envelope
> will make most of the low end disappear, especially
> if you have
> removed the screen hole covers. Try it ! Jim
> Warren
>
> ----- Original Message -----
> From: <kbrown@mail.utexas.edu>
> To: <resoguit-l@elistas.com>
> Sent: Wednesday, November 02, 2005 5:48 PM
> Subject: Re: [RESOGUIT-L] Choices in the GOLDEN AGE
> of Reso.
>
>
> > Quoting mshannon@gis.net:
> >
> > "I've been wondering lately what contribution
> the soundholes make at all.
> > ..wouldn't the soundhole be almost an
> afterthought?"
>
>
>
>
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