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Most hammered dulcimer makers offer both laminated and solid wood instruments. (In the photo, the dulcimer on the left has a laminated birch soundboard and the one on the right has a solid sapele soundboard.) We say “laminated wood” because the word plywood is so often associated with the crude, splintery stuff that packing crates are made out of. Essentially it's the same concept, but musical instruments are made out of very high-grade plywood, which looks and sounds quite nice and is very durable.
One of the main reasons for using plywood is that it comes to us in ready-made sheet form. It is much quicker to cut a dulcimer soundboard out of a sheet of plywood than it is to start with a 2-inch thick hardwood board and mill it to the desired size and thickness. Because of this, plywood instruments are usually less expensive than their solid wood counterparts, although this does not mean they are lower quality.
A significant benefit of plywood is its exceptional stability. With changes in the surrounding humidity, solid wood will swell or shrink in the direction perpendicular to the grain lines. This is constantly happening in very little bits and is usually unnoticeable, but occasionally you’ll find that more extreme changes in humidity will throw a dulcimer’s tuning out of whack. And if the air gets too dry (below 40% relative humidity is risky), it’s possible for the wood to shrink so much that it cracks.
Because plywood consists of multiple layers of wood with different grain directions, it is relatively impervious to humidity changes. Our solid-wood dulcimers are known for their tuning stability, but the plywood ones are even more stable and there is less to worry about in the way of potential cracking. If you live aboard a boat, a laminated instrument is a good choice!
The sound difference between the two types of material is much harder to qualify. It’s important to note that the design and construction of an instrument will have a much bigger impact on the tone than the choice of material, but there is a subtle difference between a dulcimer with a solid wood soundboard and back and the exact same instrument with a plywood soundboard and back.
The most useful way we have found of describing the difference is that you simply get more of everything with solid wood. Plywood instruments can have a very beautiful and satisfying sound, but solid wood tends to produce a slightly richer and more complex tone, with more clarity and resonance. We’ve observed that solid wood also matures with age, causing the sound to develop and open up over the life of the instrument. Plywood instruments do open up the more they are played, but not to the same extent. (There are players who prefer the cleaner and less complex tone of plywood over the richness of solid wood!)
Depending on the quality of your computer speakers, you might be able to get a sense of the sound by going to our dulcimer video page and playing the Overture (plywood) and D45 (solid sapele wood) recordings one after the other. The difference is there, but it’s pretty subtle. Solid wood is still considered to be the top of the line, but plywood instruments are definitely not “just for students.”