KNOWLEDGE
Guitar Anatomy - Soundholes
If you have been seeing a lot of interesting
modern guitars with a lot of unusual soundholes, you may be wondering what they are all about. Your guitar probably has one big hole in the middle of the guitar. Although most guitars have always had, and still do have, one centred soundhole, that orthodoxy is changing. As with most unconventional ideas, there is much misinformation and conjecture about the purpose and effect of multiple soundholes. I shifted the soundhole to the upper bout initially in the eighties to increase the uninterrupted area of my guitars’ and basses’ tops. Later, after studying the research of Helmholtz, I experimented with dividing the hole into two, unevenly sized, smaller holes. To understand the double soundhole it is useful to first understand the function of the
Harry Fleishman
soundhole of a conventional guitar. The term soundhole has led most people to believe that most of the sound of a guitar comes from the hole in the top. In fact, if one covers the hole only the low register is strongly affected. This is because the soundhole is actually a low frequency port, not so different from the bass port on a bass reflex speaker cabinet. Each aspect of the design of a guitar contributes to its tone. However the cavity resonance is based on a simple mathematical formula and can be set independently of the “voice” of the guitar, though it will, of course, have some effect on the voice. We can either use the following formulae to calculate the Helmoltz resonance of the guitar’s body, or we can make educated guesses based on similarly sized existing guitars. The Helmholtz resonance is the natural lowest range of the cavity, in this case the guitar body.