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Instructions for Warped Soundboards



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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:

  1. pushing up under a sunken bridge (the happiness bar)
  2. pulling down on some member fixed to the underside of the soundboard (either the 4' HPR or the cutoff bar)
  3. 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:

  1. if the 8' bridge is depressed, use a happiness bar
  2. if the 4' HPR is too far up, tie it down
  3. if the ribbed area area is up, use heat.

Remember, though, the idea is to make the soundboard flat again, the rough places plain.

 

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