The Heretics Guide to Alternative Lutherie Woods

[johnallg]

I agree, interesting. I thought maybe a half tone so as not to set up an uncontrolled resonance.

[jingle_jangle]

Seems to make sense...it would be counterproductive to have standing waves interfere or cancel each other out before leaving the sound hole or vibrating the top surface from within. Tuning in unison would make this more probable, it seems.

I must add that I'm still learning the finer points of this art, and it is intriguing and a bit nuts.

[wayang]

And, of course, so are you...

[johnallg]

Learning the finer points - that's no doubt a never-ending journey, Paul.

[elysrand]

It seems to me that all this must be further complicated by the fact that a guitar's sound output is composed of so many different frequencies, and it is inevitable that - no matter how you build the vibrating resonating structure of the guitar, there will always be some phase reinforcement and phase cancellation at all times for some frequencies, and the opposite for others, all at the same time.

[jingle_jangle]

And in this sense, it's a black art, much like speaker design...but there has been a good deal of progress made over the years re: rough ground rules. It is interesting to see that both fields have their theorists and folks who are pushing the envelope to build an empirical knowledge base.

[elysrand]

We could build the perfect speaker enclosures and drivers if they only had to reproduce one note each. Imagine if we could do that, and drive them much like the large pipes on an organ with perfect parametric filters and dedicated single-freq optimal amps in each enclosure. Eighty-eight cabinets lined up, alongside one another and in a stack to form a matrix array of cabinets from large to small...

OK, for my next engineering geek tilt at a windmill.....

[jingle_jangle]

Like this?

It is a gag, Elys...don't go all literal on me, now!!!

88 notes...like a piano keyboard? Why not just put a piano in the space??? What about overtones and extensions? Second and third-order harmonics?

Now you can bowl me over with factoids...

[elysrand]

I don't bowl.

But regardless, there is no problem here. The physics of the space between 4000 Hz and 20kHz is relatively independent of enclosure anyway, so all that is handled by a single set of horn and planar radiators in a cloud of piezos or even better, a plasma columnar emitter. It is all those pesky long-wavelength sections of the Fourier series that are difficult.

Since all the energy for a particular passband goes into one driver, it does not matter if a note is the fundamental at 400 Hz or a harmonic at 800Hz. the speaker for 800 Hz (plus or minus X Hz) handles both a fundamental at 800 Hz and a harmonic falling at 800 Hz of a 400 Hz note. Like a 1/3 octave spectrum analyzer, each driver handles a narrow part of the spectrum. It is like bi-amping, except that we now have 100-amping. The entire audio spectrum is covered. It just gives us the ability to create the acoustically-perfect enclosure and driver for each of those narrow bands of frequencies. With proper attention to filter roll-offs to prevent band-edge ringing and compromises in phase-delay, and proper phasing of the relative distance to the emitter zero-phase plane of each driver enclosure's aperture, I see no further problem (except that it would all be horrendously expensive. But what is money when it comes to achievement of near-perfection?

OK, again let me heft up and ready my lance, and go tilting.... got a windmill you want taken down?

[jingle_jangle]

I understand the part about "money"...

[elysrand]

I understand the part about "money"...

Oh Paul, you are so needlessly self-effacing! We all know you are truly brilliant and combine a shrewd intellect with stupendous artistic and design ability. You understand all of what I said, except you are far ahead of me and have probably already tried a half-dozen designs of this and now have a full-size working prototype almost into production by now. C'mon, admit it and put all this bellderolia behind you!

[jingle_jangle]

Still looking for a discount on those acoustics, eh, Elys? Er, "bellderolia"? Time to get out the dictionary...

I did build two sets of speakers my senior year of HS. One set were box-type bookshelf speakers in ordinary AC plywood, with single 6X9s and a cardboard tube ducted port. They were about 10" X 10" X 16", I recall. From plans in Mechanix Illustrated, I think. I painted them black. They're in my studio in Brasil now. Good ripping late night crank 'em up we gotta work late speakers, and still functioning 41 years after construction...

The other set WERE my design; parabolic sections in both plan and elevation, wider in the middle that at top or bottom, 40" high by about 15" square in the center section. The aim was to cut standing waves for a nicer response. I made them out of plywood bulkheads and upson board outer skin (it bent nicely), using only hand tools. I covered them in maroon Tolex and the grille cloth was charcoal gray saran; Fender stuff. 2 X 12" Allied Radio instrument speakers in each. They were my band's PA speakers. I have no idea what happened to them!

[henry5]

I understand the part about "money"...

I think that's one of the funniest things I've ever read.....