Right, I thought it was perhaps something of an acoustical one-way diode effect, but your explanation about notching filters (completely outside the guitar) shows that this is probably not the case.
One question then, does the cut out of the rose play any particular role? In other words, can one freely choose the rose pattern whatever the lute, or could this have a negative effect. I understand that Warwick Frei copies often have either a Warwick Frei rose, or a Charles Mouton lute painting rose. Would such a choice have any effect whatsoever on the sound of the copy, and would that effect be distinctly audible? I rather guess that it would not be audible, but my guesses are often wild. Regards Anthony Le 19 sept. 07 à 14:35, Ray Brohinsky a écrit : > Try 3. First one went to Anthony, only. Second one (for which I am > abased) didn't have a word of my reply in it. <hangs head> > > The lutehole is a port-tuning device for miked acoustic guitars. > > Guitars generally have a resonance which matches neatly with the pitch > of the A string. If you mike the guitar (in almost any way you can > think of) and put that sound into the same hall with the guitar, > feedback from the hall's speakers to the body of the guitar excites > the resonance, peaking notes in the area of the open A string, the A > string vibrates (or a fifth-fretted E string or harmonically-related > notes) and feedback ensues. I wouldn't characterize it as screaming, > myself, it's more of a bull-moose-in-heat effect, which goes on and on > until it has either eaten up all the energy available and becomes a > steady tone, or is damped, one way or another. > > The lutehole changes the hole's port resonance. This may also mitigate > the airmass resonance behind that port. In engineering terms, it > increases the impedance between the body resonance and the air, and > luteholes are probably intended to be a physical filter centered at > A=110. The same effect can be gotten by notching the sound board for > the guitar's channel/s at 110Hz and balancing the depth of the notch > (in my church, it takes about -12dB!). Either way, the feedback is a > byproduct of the sound system, the speakers and their placement, the > hall's shape and absorptive character (which changes with the number > and placement of bodies, preferrably warm ones), the guitar's body > size, enclosed air mass and hole size. > > As for changing the characteristic of the guitar to improve it's > outdoor use without amplification? I wouldn't give it much chance. As > a notch filter, it is removing A string intensity. Without the sound > system and/or hall to resonate and increase the effect, the guitar > does a fair job as it stands, but arbitrarily notching 110Hz (with > unspecified other acoustic affects which a good sound guy can adjust > for, if there's amplification) for unplugged performances is probably > a Bad Thing(tm). > > ray > > > > To get on or off this list see list information at > http://www.cs.dartmouth.edu/~wbc/lute-admin/index.html
