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.