At the heart of some of these discussions is the fact that the piano industry — particularly the high end of the business — is very conservative, in large part because consumers are spending a lot of money to buy something they know little about and thus are easily scared away from anything that departs from the "old-fashioned" way of doing things. In addition, the purchase of a high-end piano is often the expression of a conservative part of one's nature — the desire to invest in something enduring and traditional, not cheap or trendy.
Because the design and construction practices used in making the best pianos have evolved over a long period of time, a certain wisdom is embodied in them that should not be too quickly tossed aside. But it must also be remembered that most of these practices are a century old and evolved under certain technological and economic constraints, some of which no longer exist. In other words, there may be better ways of doing things now that are not being pursued for reasons that have no basis in logic. The low end of the piano market is less constrained by this conservatism, but is still influenced by it.
One of the choices you may need to make among consumer-grade pianos is that between a solid spruce soundboard and a laminated soundboard. First, it must be said about this and any other tone-related technical issue that if the piano sounds good, you needn't question why — just enjoy it! However, since the technical issue may be raised by the salesperson (usually in the context of steering you toward or away from a piano with a laminated soundboard), you may want to know more.
Traditionally, the soundboards in all pianos have been made in the form of a solid sheet of vertical-grain (quartersawn) spruce. This solid spruce soundboard, as it is called, is made by gluing many narrow planks of spruce together, edge to edge. The soundboards of all performance-grade and many upper-level and mid-range consumer-grade pianos are still made this way. The soundboard is bent into a slightly convex shape, called crown, to better resist the downward pressure of the strings and to enhance the tone. Over many years' time, the wood gradually dries and shrinks, causing the crown to flatten or disappear and cracks to form. Although sometimes the problem is primarily cosmetic, if severe enough it can and often does affect the instrument's tone. Usually it takes decades for this to happen, but in very dry indoor climates, problems of this sort can occur even within the warranty period.
It was in large part to lessen warranty costs from prematurely cracking soundboards that, in the 1960s, several manufacturers developed laminated soundboards. These soundboards were essentially sheets of plywood. The sandwich of wood and glue prevented the soundboard from cracking or losing crown. The problems with these soundboards were three-fold: First, the pianos into which they were installed were usually the cheapest, and deficient in a variety of ways unrelated to the soundboard. Second, engineers failed to take into account in its design that a plywood soundboard would have different vibrating characteristics from a solid one. Third, although sometimes spruce was used in the plywood, often cheap, inappropriate woods such as basswood or lauan were used, disguised by an outer veneer of spruce. As a result of these three factors, these pianos usually sounded poor, giving the term "laminated soundboard" a bad name. Laminated soundboards of the plywood type are still used by a few manufacturers.
Over the past couple of decades better laminated soundboards have been developed, and the pianos into which they've been installed are more advanced, too. The principal new type, known as a "veneer-laminated" or "surface-tension" soundboard, consists of a core of solid spruce (essentially a solid spruce soundboard) covered on both sides by a very thin veneer of spruce. This type of soundboard vibrates much more like a solid one than a plywood one, but still retains the benefit of protection against cracking and loss of crown. Pianos with these soundboards usually sound reasonably good, and occasionally very good. Although solid spruce soundboards may still have a tonal advantage, the laminated feature can be an advantage in durability, particularly in challenging climates, and may contribute to better tuning stability through the annual cycle of seasonal climate changes.
Despite the improvement, you'll generally find these new laminated soundboards only in entry-level or lower mid-range pianos. But the reason for this has less to do with their quality than with marketing: Laminated soundboards are a feature still used by manufacturers to differentiate a lower-cost instrument from a higher-cost one for marketing purposes, even when the laminated one might arguably be better. If you're shopping in the entry-level price range and a piano with a laminated soundboard meets your musical and other expectations, there's no reason not to purchase it.
The piano's cast-iron plate is the gold or bronze-colored metal framework across which the strings are strung. For well over 100 years, plates have been made using the wet-sand method of casting, which works something like this: Wooden molds are made in the image of the front and back of the plate. Each mold is pressed into a tray of moist sand, thus transferring the shape of the plate to the sand. The moisture enables the sand particles to stick together to retain the impression. The two trays of sand representing the front and back of the plate are clamped together, and molten iron of a carefully controlled chemical composition is poured into the cavity created between the two impressions. When the iron cools, the trays are unclamped and removed, revealing a cast-iron plate identical in shape and appearance to the wooden molds. Although factory engineers have largely perfected this method over the years, the plates produced in this manner are quite rough, requiring a lot of sanding and finishing work, and vary slightly in dimension from plate to plate, which is less than ideal for highly automated factories that depend on uniformity.
In the 1960s, to manufacture plates that were more uniform, and faster and less costly to make and finish, Yamaha developed the Vacuum Shield Mold Process, or V-Pro. In this method, fine dry sand is used, and a thin plastic film and vacuum pressure keep the sand in place to retain the mold shape. This process produces plates that are not only more uniform, but also show decorative detail much more clearly while requiring less finishing work.
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.
Grand 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.