At 01:27 06-09-18, Andrew Bernard wrote:

>A harpsichord cavity is not a loudspeaker, or a guitar, and functions
>differently to them. You don't need a port. Most often instruments are open
>at the belly rail anyway, with a very large air gap. Even instruments that
>may have a sealed cavity, again, you don't need one.

Thinking about this some more:

There is a large cavity in a harpsichord -- below the soundboard, and 
one is tempted to assume that it must have SOME effect on the sound. 
The arguments against this are that the walla are only parallel in 
the vertical dimension, which precludes the standing waves of 
resonances in the horizontal plane. The parallel walls formed by the 
base and the soundboard are about 7" apart, which at the normal speed 
of sound is a half wavelength at about 3.2 kHz, and moreover, these 
boundaries are not a fixed distance apart, since the soundboard is 
vibrating. Add to this the effect pointed out above of the large port 
at the belly rail and it is clear without doing too much calculation 
that any such resonance would be very broad. As far as a rose is 
concerned, its area would be a small fraction of the belly rail port.

There are parallel and stiff vertical walls in a rectangular 
muselar/virginal. I have no experience of such instruments, but I 
wonder if this is not resposible for the strong formants and 
different character of their sound.

A totally sealed and rigid cavity will, of course have modes of 
resonance, but these would be irrelevant if the walls are too stiff 
to allow significant acoustic interaction with the rest of the instrument.

Perhaps those here who make Flemish-style instruments and who attach 
the base at a late stage in the construction process can tell us 
whether doing so effects a significant change in the sound of the instrument.

On one occasion, in a new house, I did notice that the fundamental of 
low C of my instrument (62 Hz) was louder than it had been when in 
other buildings. I attributed this to the distance from soundboard to 
ceiling in the room and the consequent support of a standing wave.

David

::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
Note:  opinions  expressed on HPSCHD-L are those of the  individual con-
tributors and not necessarily  those of the list owners  nor of the Uni-
versity of Iowa.  For a brief  summary of list  commands, send mail to
[log in to unmask]  saying  HELP .
::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::