The V-Pro method is used by a number of large Asian manufacturers, where it fits in well with their rapid, highly automated production. All smaller manufacturers, including those of the highest quality, use the traditional wet-sand method. From this it might be assumed that the wet-sand plates are superior in quality, and companies that use this method often make a point of mentioning it in their advertising. However, the reason for the difference is more likely to be one of economics than of quality--the capital costs for starting up a V-Pro plate foundry are very high, and there is not enough advantage to most piano makers to undertake this. For some large Chinese manufacturers that still use the wet-sand method, the low cost of labor to finish the rough plates outweighs the cost of building a new plate foundry. For smaller, high-end makers that might in theory employ the services of an independent V-Pro plate foundry, there is little advantage because these companies finish their plates to very high standards anyway, and the labor saved by starting with plates a little less rough is not significant. In addition, due to the aura of superiority surrounding wet-sand plates, the switch by a high-end maker to V-Pro plates might engender negative publicity that would hurt sales.

There is some talk that plates made by the wet-sand method may be less likely to steal energy from the strings, or that V-Pro plates may add some unwanted metallic sound to the piano tone, but the truth is more complicated. According to the experts I consulted, when plates are made by the wet-sand method, the moisture in the sand, when contacted by the molten iron, produces a large amount of steam. To counter the invasive effects of the steam, the plates, to retain their strength, must be made thicker than would otherwise be the case. The V-Pro method, using dry sand--and thus producing no steam--allows plates to be made thinner if desired, as might be the case with an inexpensive piano. Rather than remain inert, as it's supposed to, a plate with less mass will have a greater tendency to ring in sympathy with the vibrating strings, thus causing a loss of tonal energy and creating a metallic distortion to the tone. However, if a plate is made just as massive by the V-Pro method as it would have been by the wet-sand method, these negative effects do not occur, and the V-Pro plate works just as well as the wet-sand one. Therefore, any differences between the two types of plates are more likely to be related to the price and quality of the pianos in which they're used than with the casting method per se.

The Piano BookGrand Piano Rims

The wooden rim of a grand piano serves two functions: structural and acoustical. Structurally, it's the foundation to which the cast-iron plate is bolted, and as such it assists the plate in supporting the tremendous tension exerted by the taut strings. The acoustical function is less well understood. The soundboard is glued along its perimeter to a shelf formed by the inner rim of the piano case. The vibrational energy in the soundboard thus contacts the rim, and is either reflected back into the soundboard or is siphoned off into the rim, depending on the density of the wood used in the rim's construction, and on the stiffness and total mass of the rim. Dense woods and a stiff, massive rim will reflect sound energy to a greater degree, causing the sound to sustain longer, whereas softer woods and a thinner, more flexible rim will tend to absorb more energy, causing the sound to disappear sooner. This is why most of the best grand pianos have very thick rims made of dense woods such as maple and beech. (Bösendorfer, a high-end piano, has a relatively soft, spruce rim and so may seem an exception to this rule. But spruce transmits sound well, so the tonal energy is not so much lost as spread throughout the structure, which then becomes an extension of the soundboard.) Less expensive grands may use softer woods like lauan (sometimes known as Philippine mahogany, though lighter and more flexible than true mahogany), or alternating layers of harder and softer woods.

Two things are important to note here. First, the hardness or density of the wood in the rim has nothing to do with the rim's ability to fulfill its function of structural support. A rim made with a less-dense wood like lauan won't "fall apart" or cause the piano to go out of tune faster; the issue is strictly one of how the rim affects the tone. Second, the words hardwood and softwood are botanical terms that have little to do with how hard or soft the woods actually are. So when a piano ad touts a "hardwood rim," or a rim made from "select hardwoods," chances are that the woods involved are not very hard at all; if they were, the ad would likely name the actual species of wood instead of hiding behind such general and potentially deceptive terms.  ¤

 

FALL 2009 -- page 88

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