Per Hallgren -> RE: soundportparty in my patio (Jul. 15 2009 20:30:27)
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I don't have a long experience of soundports but I have used them a couple of times on my own guitars and the port is something that I always keep in my toolbox for use in finetuning a guitar nowadays. It has improved some troublemakers for me where the guitars happened to be tuned too close to G resulting in a bad g note and sound. The effect of a port, as measured with a frequency analyzing computer program, is 1. raising the "Helmholtz resonance" somewhat (depending on port area), 2. opening up for the second air resonance so it can correspond with the air outside the box (presuming the port is near the neck end of the box) and 3. working as a second air vent for the box. Anders, I'm not saying that you're hearing is wrong and that your peghead did not get lower in tuning, but I believe that that lowering of the tuning was caused by a different relation between the neck resonance and the Helmholtz resonance. The Helmholtz ALWAYS get higher with a soundport. The moral of this is that some guitars may improve, others will not. It depends on the starting point. Tom, I agree in most of what you say. I guess it is the air vent function of the port that "inhibits the guitar from gaining a certain homogenized dimensional build up to its voice". In my experience (which isn't that big) some guitars gain by losing some of that "build up". The instrument gets more relaxed so to say. And some guitars will not gain of losing that "build up". As you say, it all depends on the guitar, and once again, some guitars will improve, others will not, so my statement about soundports is that they should be used careful and with respect. Don't add ports to all your guitars at home folks!
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