LOL, Twl, the "pulsating Nissan"; what a beautifully accurate image! The Primal Thump (or Thud) is a killer product, indeed!
Among the best thud machines IMO, are industrial washing machines and factory bottling lines: they keep a steady rythm AND offer bonus sound effects, well into the KHz region!
To link onto Sean's post and yours above, and deepen my confusion...
To reiterate the obvious, in striving for correct phase across a speaker's spectrum,we are limited by having to:
a) coordinate drivers between themselves (in the case of multiple drivers) AND the enclosure,
b) coordinate vs. a specific listening position,
c) coordinate vs. a given room's/chamber's/space's acoustics.
An electronic c/over may help tame some of the room/chamber related inefficiencies and allows for better use of power, as Sean notes. But, do we have correct phasing within the whole spectrum of each (or THE) driver? Or is it too much to ask that the driver reproducing (fortuitous example) 150-3KHz provide correct "musical timing" at both ends and @ 1,5KHz?
Because if it doesn't or even "sort of" does, no amount of speaker positioning or engineering seems likely to completely correct the phasing. I mean, what can one do? Slow down the 1,2-1,8kHz fundamentals so that their 600/900Hz harmonics can catch up? Or speed up the cello sound so it can catch up with the violin?
I'm coming to realise that a lot of engineering is necessary to trick my ears into believing in the reproduced sound of the symphony orch. that emanates from my pulsating multidriver boxes, and it's NOT only a matter of dynamics...
Case in point: the Genesis V (dipole/bipole) I'm now using combine a 4th order quagmire of capacitors (c/over as per Twl) for the mid-highs, with an electronic crossover controlling the built-in sub (as per Sean). One of the controls on the electronic c/over is "phase", expressed in degrees, 0-180. This *does* mean phase & not polarity.
So I can correct for time-related problems in the sub's 20-110Hz area (the c/over point is my choice). So far so good. However, even if we assume that the phasing is correct from 85Hz down(my present c/off for the sub), the harmonics reproduced, par exemple, by the woofers are NOT necessarily always in phase with the fundamentals coming from the mid-high section. So, where's my timing? (I might as well dispense with the expensive Mr B. Walter altogether :))
Furthermore, when we use many drivers (and the enclosure, of course), the speaker becomes a system. So, as Sean suggests, we'll have to tune/engineer the c/over accordingly in order to accomodate the combination of drivers... Probably in relation to the slowest transducer in the system -- it being rather difficult to speed up a driver unit to reproduce its core frequencies in phase with the rest. Then, we will have some overlap between drivers. Assuming the room has no reflections that excite certain points in our reproduction system (as per Murphy's law, the weak, c/over points of course), we're in business.
...A nightmare. I apologise for the long, confusing diatribe; the only excuse I can proffer is, I'm not an engineer!
I'm off, as many others in quest of the sound that will defitively seduce the omnipotent ear, to purchase the next $20-200k speaker.
Cheers!
