Issue 10

Q's and A's

Answers to questions sent in by the readers:

Q. I've heard that good wood for instrument-making is becoming increasingly hard to get. What is your opinion about this? What is being done?

A. Really beautiful, quality tonewood is indeed becoming scarce. Some instrument-making companies have been stockpiling for decades, and this makes it harder for the small hand-maker like myself to find and purchase suitable wood. These instrument-making companies, mainly in Asia, often use wood of a quality far surpassing the quality of their finished instruments. Inadequate drying, inappropriate adhesives and poor finishing dooms many of these instruments to a short, trouble-prone life. Instrument makers also compete with veneer mills for the most beautiful wood. Enterprising bass makers are reacting by seeking out and using alternative woods to the typical flamed maple and spruce; walnut, poplar, willow, cherry, pine, redwood, and cedar are all being used with good results. Ebony remains the wood of choice for fingerboards and other pieces of trim, but the quality is slipping because of hoarding and lack of current supply. There is a rumor circulating that it will soon be embargoed, just as Brazilian Rosewood has been since the 1970s. Makers are looking into alternative woods to ebony for fingerboards, and some are proving suitable. Man-made composites are also meeting with some success. One thing I find odd is that no one seems to be doing anything substantial to ensure the future supply of fine tonewoods. I would hope that at some point tonewood "plantations" might be developed to supply future luthiers.

Q. I had a cedar soundpost installed in my bass, and I like the result. Do you think there is a reason it sounds better?

A. The soundpost is a region of the bass that is fraught with mystery and misinformation. In order of importance, are; Position, Fit, Tension and Material (mass). In my opinion a soundpost is little more than a stiffener or piston. It creates an area of the top table where little vibration occurs (an anti-node), and it also spreads the string energy to the back of the bass. When positioned in the "right" place, with the "right" tension and fit, a bass will respond and sound great. When a spruce soundpost is changed out for a cedar post of slightly lower mass, most of the change in sound is probably due to a slight change in position, fit or tension. I do believe that the change in mass may have a small effect on a bass' sound and response. However, my many experiments using soundposts of different densities to change a bass' tone have been disappointing and inconclusive.

Q. How much camber, or scoop, should I have in my fingerboard?

A. That depends on how you play, and on what type of strings you play. Generally, I like to see about 1.5mm on the G side and about 2mm on the E side with the bass under string tension. ( A five-stringed bass with a low B string needs about 2.5mm or so under the B string.) A bassist who plays aggressive pizzicato will likely need more. A player with hand problems or arthritis who plays lightly can get away with less. I've read that classical players need more camber than pizzicato players, but I have not found that to be true. Gut strings require a bit more fingerboard scoop, as well as a slightly higher nut. Luthiers disagree on where the lowest point of a fingerboard should be; somewhere between the fifth and the octave seems to work best.

Q. Does my bass need a winter and summer soundpost?

A. Do you live in a very changeable climate? Do you have a flat-backed bass? Does your bass tend to swell and shrink a lot with seasonal changes? Sorry to answer a question with more questions, but if you answered "yes" to any of them, you probably do need both a winter and summer soundpost. Basses are quite wide, and as wood contracts and expands mainly across its width, changes in environment can cause a lot of tension in a bass. In the winter, or dry time of year (especially with indoor heating) a bass' soundpost can become dangerously tight. This tightness can result in top table bulging or cracking. In the summer, or more humid time of year, the post may become quite loose. An overly loose post can cause some sagging of the top table, and in some circumstances the soundpost can fall over. Either situation is not optimal for playability and sound. Flat-backed basses are more prone to the affects of climate, as the braces in the back contract and expand in the opposite way as the back wood, flexing the back and creating more change in the distance between top and back plates; hence the need for multiple soundposts. I like to fit the soundpost for a round-backed bass in the spring or fall, and in many cases it will work out okay year-round, especially if the owner is careful about keeping the relative humidity from becoming dangerously low during the winter.

Q. What is purfling, and what is it's purpose?

A. Purfling is the thin inlayed stripe around the perimeter of a string instrument's top and back plates. It is found in most, but not all basses. Purfling is usually made of three thin strips of wood veneer or fiber, generally in a black-white-black configuration. It is installed in a groove which the maker cuts into the plates, and is usually installed about 7-10mm from the outside edge. Some luthiers make their own purfling, while others use commercially available material. The purpose of purfling is two-fold: 1) It looks nice, and shows off the luthier's skill, and; 2) It can help to prevent damage to the plates by resisting cracks spreading from the edges inward.

Well, that's all for now. I'll be answering more of your questions in future issues, so if you have one, please send it to Happy thumping and sawing!



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