In this day and age with our Planet in such distress, I make it part of my mission as a harp builder, to only use wood from sustainably harvested sources.
This is mainly hardwoods native to North America, Cherry, Black Walnut, Rock Maple, and Oregon Myrtle wood. I do use Hawaiian Koa wood, when I can get a supply, though it has gotten very scarce. Koa is now a protected tree, and is being planted and grown with the future in mind, but for the present is hard and expensive to obtain.
There are other tropical woods that are being grown and harvested in a sustainable way, which I will use from time to time. Please inquire about these woods such as Mahogany.
Spruce for my Sound boards
I build all my harp sound boards from forty year air-dried Engelman Spruce tone wood.
I buy it from a family that has been cutting Spruce for Violins, Viola, and Cello tops, for three generations in the high elevation Oregon Cascades. One old growth Engelmann Spruce tree can supply the material for hundreds of harp sound boards, as well as many Violin, Viola and Cello tops. I use the very wide Cello-Top wedges that are about two feet in width. This way I sometimes end up with just two or three joints in my sound boards, on my largest harp models. This wood is the perfect tone wood, with very close grain lines, dark distinctive winter growth lines, and summer growth lines that are not too wide.
Why is using this high quality tone wood good for your new harp`s sound ?
This is because when you play your harp, the plucking and strumming of the strings produces sound vibrations that move in various ways through and out of your harp. Some of that sound is translated into air movement that actually compresses and pumps air in and out of your harp`s sound box. This aspect is affected by the air volume inside the harp sound box, and the size and placement of the harp`s sound holes, as well as the shape and smoothness of the inside surfaces of that sound box.
The best acoustic stringed instruments of any kind are those made with the highest quality solid spruce soundboards. The finest violins, cellos, guitars, Grand Pianos, etc. are all built with spruce soundboards. So it would be a compromise to entertain the thought of using anything but quarter-sawn old-growth spruce for the soundboard of a fine harp.
But other vibration/ sound waves are sent directly through the harp`s sound board, and are amplified and projected outward by the sound board. As those vibrations pass through the sound board, they will follow the path of least resistance, which is the dark hard winter growth lines in this solid Spruce. The softer Summer growth lines also carry the sound, but they transmit the vibrations at a slower rate. This combination of hard and soft growth/ grain lines helps to give a solid Tone Wood it`s natural warmth and complexity of sound. Musical vibrations (sound waves) are also passed through the wood along the grain lines. The heavy winter growth rings give a quick response and a bright edge to the sound. The softer summer growth rings add a more mellow quality sound which, when combined with the brightness of the hard grain lines, yields the unmistakable richness of tone color that musicians look for in any instrument of value.
A sound board with a hardwood veneer over the top tends to flatten the dynamics of this complexity of sound color, flattening it at both the higher and lower ends of the sound waves. The fact that this Tone Wood is also twenty year air-dried, also aids the richness of the sound, because as the Spruce dries, over many years, the cells become more naturally open and their structure changes to enhance the sound. This process is apparently disrupted by kiln drying the Tone Wood, but when allowed to naturally occur it will continue to improve in sound forever. this is one of the factors in the Old Master Italian Violins, that their tone wood tops,( Spruce), have been drying naturally for over 300 years ! This is why vintage guitars and old-world violins are such prized possessions.
Part of the secret of the tone of my custom harps, is the use of this superior and well aged sound board wood.
The process of making a high quality spruce board involves selecting fine grain spruce, re-sawing it to slightly over 1/4” thickness, and edge-gluing it together in short boards to achieve the size of soundboard needed for the harp. Once glued, the board is tapered from about 1/4” thickness at the bottom (bass end) to 1/8” thickness at the top (treble end). Ideally, this tapering is not “flat” but rounded (slightly convex) to maintain a full body in the mid-section. Likewise, the board is also tapered from the mid-line out to the edges, by reducing the thickness about 20 percent along the sides. This tapering gives the board more flexibility to vibrate freely.
After gluing up, I store my spruce soundboards in a “dry box” to make sure the wood has the lowest moisture content (under 7 percent moisture) it will ever have. Installing the board when it is at its driest state helps ensure against further shrinkage from climate changes. It does not hurt the board to expand with humidity, but further shrinkage can cause cracks along the grain lines or glue seams.
A quality spruce soundboard can be “tuned” before it is ever installed. This is accomplished by the “tap test”, a long tradition of listening to the sound of the board when tapping it with one’s knuckle. The low pitched tone emitted can be adjusted up or down by further thinning the board in various places, as a wooden xylophone key would be tuned.
Serious builders do not use plywood for soundboards. It is cheap material and does not generate the high quality sound desired by good musicians. You cannot taper it without sanding through the thin veneers. Consider how plywood is made: The log is soaked and boiled and peeled at high speed. The peelings (veneers) are then dried quickly before being glued together under high pressure and heat again. The end of all this ripping and tearing at the cell walls of the plant results in a material that, under a microscope, barely resembles wood any more.
Plywood is made with each layer having the grain lines running at 90 degrees to the adjacent layers. Sound waves do not travel well through these criss-crossing grain lines. Plywood also has a film of glue between each layer, and that further inhibits the sound waves from flowing naturally and smoothly through the material. And finally, the glue essentially “freezes” the wood into a static condition so it will never mellow and mature over time to yield a better sound.
Furthermore, the glue in plywood is likely to break down over time, both from repeated seasonal humidity cycles, as well as from all the vibrations generated from playing the instrument. These factors will cause de-lamination, buzzing inside the layers, and eventual failure of the plywood.
A properly prepared spruce soundboard, on the other hand, is a great deal stronger than plywood, and it will last much longer. Although it takes a great deal more time and craftsmanship to make a solid soundboard, it is well worth the effort. Do it right, and you will get a harp that sounds wonderful!
Thank you for coming to visit my Harp Pages, please let me know how I can bring your Dream Harp to Life !
Follow your Bliss, and live your Life in Joy!
Glenn J. Hill