Soundhole size and effect on body resonance

[Dave Bagwill]

This is a strange fellow, you should know that going in: but is he on to something or is this nonsense? Please listen to the end, it's only a few minutes long.

http://youtu.be/-f9Tu-ca-P4

[TonyinNYC]

That guy is bananas!! Might be something to it though.

[Dave Bagwill]

Obviously I need to invent one of those thingies he uses, except make it an adjustable diaphragm so if you change tuning by a half step or if you go with an open tuning, you can simply enlarge or shrink the soundhole to achieve the correct resonance. Right? :-)

[TonyinNYC]

Oh yeah. Totally.

[Rick Aliwalas]

Mass produced plastic version:
http://www.planetwaves.com/PWOport.Page

-rick

[Dave Bagwill]

If I made one out of BRW (of which I have none) and got Tommy Emmanuel to endorse it (which he wouldn't), I could make a killing selling them (which I won't). :-)

Though if I had one here right now as per the advertisement, I'd try it for fun..

[Tim Benware]

There is something to it. What he is saying is very similar to tuning a ducted port loud speaker. However he is a little less scientific in that he's trying to change the opening to match the tuning, one could also change the tuning to match the opening. Both of which result in note canceling and/or frequency phasing (in or out). It's really trying to get everything vibrating in phase to reduce note canceling effects. There's more to getting it correct because you need to take into consideration the total volume of the box and thickness of the port (sound hole) and match them up. There is a formula for this. If done right it can really increase volume by making the energy transfer more efficient. If you've ever seen a ducted port loudspeaker you know there is the speaker cone and a hole with a tube (the ducted port) into the enclosure that serves to get the speaker vibrations in phase.