By B.J. Fine
It will sometimes happen that the soundboard will get
out of control and strings will start to buzz or slap against it or against the 4' bridge.
There are several possible solutions to this problem. Each has its own unique advantages
and disadvantages and its own special applicability.
There are, broadly, three categories of solution:
- pushing up under a sunken bridge (the happiness bar)
- pulling down on some member fixed to the underside of the
soundboard (either the 4' HPR or the cutoff bar)
- heating the soundboard and thereby reducing the warp.
In passing, it should also be mentioned that reducing
the downbearing of the strings on the bridges will indeed reduce the downward pressure,
but this is more in the nature of a long-term hedge than an actual and expedient solution.
Happiness bars have been in use for many years now
(since the days of the Hubbard & Dowd workshop, in fact) and some makers use them
routinely in a preventative manner without untoward effect. If they make any difference in
the sound, it is negligible and, as a rule, it is impossible to spot the presence of one
by sound alone. They do not change the sound of individual notes and cannot be found by
listening for dull notes. They come as close to being the ideal practical solution as
would seem possible. They do have theoretical drawbacks, though. They do apply pressure
directly to the sounding part of the soundboard and thus must change, even if only
slightly, the frequencies of the modes of vibration of the soundboard. This is enough to
turn off some owners.
This leads us to the second method, the pull down. There
are two varieties: a rigid restraint and a sprung pulldown. The rigid restraint is a
classical solution. Some old instruments (but by no means all) have seemingly original
spacer blocks and nails that fix the 4' HPR rigidly to one of the upper frames, typically
in the middle of the string band. This allows the soundboard to stay flat in the middle
and helps alleviate some of the chance of strings slapping or buzzing. It should also tend
to keep the regulation more stable. But again, it was not a universal practice by any
means. If it is theoretically more inviting to have a 4' HPR that can float, then the
modern solution would be to epoxy and pin a custom made brass plate to either the 4' HPR
or the cutoff bar and then arrange a moderately week screen door type spring between the
plate (to which somehow a hook had been attached) and the bottom of the instrument. The
spring should be extended no more than 1 1/4 times its closed length but should be
extended more than slightly to avoid buzzing of the coils against each other. This is a
difficult device to attach. However, its advantage is that the spring is fixed to a
relatively dead part of the soundboard. The major drawback, of course, is that it is
nearly an absolute certainty that any tension joint in or on wood will fail at some point
in the future, perhaps in ten years, perhaps in a hundred. One would hope that the
soundboard would be trained into shape by that time, however.
The third method is simply to heat the soundboard
thereby driving out excess moisture that is a major part of the cause of the most severe
soundboard warp. The simplest and easiest is also the most temporary. Lay a heating pad of
the sort bought at a drugstore on the strings over the offending part of the soundboard
and close the lid overnight. (Be sure to turn it on.) In the morning the soundboard will
most likely have corrected its more major warps and be playable. However, it will
immediately begin to revert to its former unruly state unless there is a fortuitous
weather change so that the chances are that by the evening the strings will be buzzing
again. More likely to be of help during extended periods of hot humid weather is some
device that can warm the instrument from within. A fifteen watt light bulb would do the
trick, but some people are understandably offended by a harpsichord that glows in the
dark. Piano supply houses sell devices that achieve the same ends. One we are aware of is
called Damp-Chaser and is available from Tuner's Supply Company of Boston. There are
probably other sorts available for voltages other than the American standard of 120 volts.
Here there are two distinct disadvantages. First, the
installation of one of these devices is time consuming and messy, involving at least one
hole in the bottom or lower belly rail. Some method must likewise be devised for attaching
the power cord so that it will be either removable or retractable. The second drawback is
somewhat more serious for instruments that must move often. Humidity is the most important
atmospheric variable affecting the state of the soundboard as well as the instrument's
tuning and regulation. Therefore, it is imperative, if the tuning and regulation of the
instrument is not to become an utter nuisance, that the heating element be left on day and
night, week after week, during hot humid spells. If it is left off for a couple of
hours,the instrument will no longer be held at an artificially low moisture content and
will immediately start to absorb water. The result of this, of course, is that the
instrument immediately starts to go out of tune, out of regulation and the soundboard's
hills and valleys will become more pronounced once again. Ideally, even on stage, the
heater should be plugged in. What is most important is to try to keep the instrument's
soundboard at some sort of stable moisture content and if this has been achieved by means
of an electric heating system then the harpsichord, for all intents and purposes, will
have to become addicted to electricity for the duration of the bad weather.
Of all the solutions, however, this is the only one that
does not involved restraining the soundboard in some way. Rather, it attacks the problem
directly at its roots by managing the atmosphere around the soundboard and therein lies
its value. It does maintain an artificially low moisture content in the soundboard, but
not one to which the soundboard would be otherwise unaccustomed. One must, of course,
remember to turn the device off at the end of the siege of hot humid weather.
It would be entirely possible to use all three methods,
but one is usually sufficient. The best approach is always to restore the soundboard to as
flat a state as possible. Some indications for specific methods might be:
- if the 8' bridge is depressed, use a happiness bar
- if the 4' HPR is too far up, tie it down
- if the ribbed area area is up, use heat.
Remember, though, the idea is to make the soundboard
flat again, the rough places plain.