Rontec, your post appeared while I was composing my last post. As I understand things, the changing phase of a second order filter is in opposite directions for high and low frequency sections, and is 90 degrees out of phase at the crossover frequency in each section. Changing the physical placement of the drivers relative to one another will not correct this. If the drivers were connected in the same polarity (i.e. both moved the same direction with the signal) the there would be a net 180 degree out of phase condition at the crossover frequency... perfect cancellation if the acoustic centers were aligned. Connecting the drivers in opposite polarity provides constant power response from the system through the crossover region. Unfortunately this results in a situation where, with transients, one driver sucks while the other blows... so to speak.
If we were dealing with periodic (i.e. perfectly symmetric and repeating) waveforms like sine waves, then physical placement could correct any errors. With the highly asymmetric, transient waveforms of real recorded signals, the drivers must be in the same relative polarity and aligned correctly to stand a chance of reconstructing them properly.
Opinion is only as valid as its verifiable supporting evidence.
Thank you, mah. This article will require considerable study, but looks to be worth the effort. I sure like the term "transient perfect" and the various square wave responses look a lot like what I have heard, i.e. clean vs. scrambled. If I understand the author correctly, the "2nd Order Transient Perfect" crossover connects the drivers in the same polarity with aligned acoustic centers and fills the response hole at crossover by overlapping the responses somewhat. Nice!
"Perfect" replication of a broadband point-source acoustic impulse by any two non-coincident tranducers is simply not possible. There are just varying degrees of a reasonable facsimile. A percussion impulse originates from a single pinpoint location.
Two bullets on converging paths won't become one when they collide.
"[I]We're going all the way, till the wheels fall off and burn[/I]!"
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[I]"Time wounds all heels"[/I]
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WOW!
A lot of interesting thoughts here. Since I have the ability to change polarity as well as distance of the 2 drivers in my set up, I think I will just experiment and choose that which sounds best to my ears. Theory, papers and opinions are great but in the end isn't what sounds best to the listener what we are all trying to achieve?
After I complete my project I will post my conclusions.
Thanks,
MM
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