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In Reply to: RE: Might need to take some measurements? posted by morricab on September 07, 2014 at 13:00:18
Despite the fact that the Alexia has one driver inverting, the ear perceives all drivers as being "time-coherent" when heard from several feet away at the recommended listening position. That is my interpretation of Atkinson's words.
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Not time-coherent. I don't agree with your interpretation of JA's words. You have to think about group delay as well as phase. The order of the crossover affects both phase shift and group delay. That is why a 4th order LR crossover can be in phase but not really time coherent because the phase rotation delays the wave propagation. The Alexia even inverts polarity.
"This graph reveals that, as in the Alexandria XLF, the tweeter is connected in positive acoustic polarity, the midrange driver in negative polarity. However, with the tweeter module set up by Peter McGrath, the graph also shows that the negative-going decay of the tweeter's step smoothly blends with the negative-going start of the midrange unit's step, confirming the excellent frequency-domain integration of their outputs seen in fig.4. "
JA doesn't mention time coherence at all. He talks about frequency domain integration.
Check out square waves from the Thiel CS5
http://www.stereophile.com/content/thiel-cs5-loudspeaker-measurements-0
Not as good as the Quad 63 but not bad all the same.
.., "... the output from all the speakers drive units ARRIVE at the ear" and "the brain's temporal fusion window", etc.., would seem to be related to TIME domain behavior. That's the conclusion I was able to draw after reading the quotation in the post above.Thanks for your helpful input.
Edits: 09/09/14 09/09/14
The measurements clearly show that this speaker is like the vast majority of speakers reviewed. NOT TIME or PHASE coherent.
The reviewers words are trying to imply with separate facts a different fact that actually is not a fact.
Not saying the speaker in question is bad or the review is invalid, but it does not qualify as a type of topology that your original post was targeted against.
Well, you seem to be pretty sure about all of the above so I guess I'm willing to let the subject go for now.I would try emailing John Atkinson to ask him if he'd care to chime in but because his responses are so often met with hostility around here, I doubt that he'd feel like responding one more time.
BTW, my original post was not "targeted against" anything or anyone in particular. I'm taking a poll, that's all...
Edits: 09/09/14
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