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In Reply to: Not necessarily posted by dlr on February 23, 2007 at 15:30:30:
"Designs are made on a desired axis. The targets can be met on that axis, or very closely. But all designs fall apart to one degree or another off-axis."This is exactly what I meant. Alignment can be achieved on certain axis, which may be the basis for a designer to claim that the speaker is aligned. But to be honest, a designer should spell out the condition for alignment. And that would be something like this:
"To take advantage of our phase-aligned design, a listener should place his/her head in a certain position with regard to speakers and avoid head movement during listening. The protractor for the correct speaker-head positioning can be found in the user manual."
What is surprising to me is that even a coaxial driver, like Insignia, is not perfectly aligned, as one might expect.
Follow Ups:
I was surprised at just how much offset there is in the acoustic center of the coaxials. It appears that even in the much more expensive TAD drivers such as their 5" (or thereabouts) version, the mid and tweeter are not aligned in time. In fact, the shallower the coax, the more delta in the impulse. This does not prevent good phase tracking of the crossover since a small amount of delay control is possible even passively, but these won't ever work ideally in a time-aligned system. They can't. The impulse response makes it clearly evident.I don't think that it's necessarily bad to advertise correctly the attributes of a system as designed since most systems are used with the driver axis not far from straight ahead. Even at 15 degrees I suspect that most systems are acceptably close to the design axis.
It's a bit over the top to suggest head positioning and such, but some systems did exhibit a need for "head-lock". That was somewhat the case with my Apogee ribbons. It shows the benefits of auditioning before purchase. If you can't or won't do that, then it's just buyer beware. People know that systems sound different off to the side.
dlr--There is indeed a difference in acoustic centers with coaxial drivers.Ed Long and Doug Stax made phase corrected crossovers for the famous Altec 604 coaxial driver; Long's was used in the Urei monitors and Sax's Mastering Lab crossover was used in the Big Reds.
Jeff Markwart designed such crossovers for the Altec 604 and 605 drivers, his web site is very informative even for those not interested in Altecs.
Looks like an interesting site. Thanks for the link.
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