Why not horns?

"Anyway, thats neither here nor there. Probably not the best choice of words to indicate that the idea of time coherency by design is exceedingly rare. To the best of my knowledge, only Vandersteen and Thiel on a consistent basis anymore."

Also OHM Walsh.

Even single driver speakers are not perfectly time and phase coherent. But close enough** to trick us into thinking they are.

** Subject to debate.

Cdc - I'm not well schooled in the matters you brought up just now but my sense is that you are demonstrating that an Aveo gets decidedly better mpg. than a Corvette. Of course, you are right but the parameters qualify the argument.

I recall you mentioning earlier that you listen at 65 db. Probably the areas where you find your single driver to excel are dependent on keeping the SPLs down. My average listening level is more like 85 db (still not very loud) and I suspect your single driver might keep up at that level in a small enough room. Mr.decibel would not get much of a bang from that approach, however, because he says he listens at upwards of 100 db., though I can't imagine how.

So, while specifications are very useful, even essential, they are dependent on circumstances and conditions that don't always appear on the stat sheet.

I'm pretty tempted by the logic and testimonials I read about with single drivers but I can't see them as a realistic replacement for my horns.

Cool! Thanks Mapman.
Ima check that out.

Prez, I hear what you are saying but I think the manufacturers are using terminology to confuse the layman in an attempt to carve out a unique slot in the marketplace. In other words, marketing BS. A change in arrival time is a change in phase no matter how it is done. They are synonymous. If you read Thiels papers they admit as much.

Either the different frequencies arrive at the ear with the same timing relationship they had when they were put on the recording or they do not. If not it could be that the drivers aren't aligned, That a digital or electronic delay was employed, or there is a phase shift through some reactive device like a crossover.

If they want to distinguish phase shifts caused by crossovers as phase coherency since they are frequency dependent and those caused by driver alignment as time coherency since they are not frequency dependent I'm on board with that, but time alignment and time coherency are the same thing.

By eliminating all reactive components after my amps (no crossover what so ever) and implementing the crossovers digitally before the amps I should only have phase shifts caused by the reactance in the drivers and hopefully the bulk of that is outside the band of frequencies they will be fed.. Each band can also be digitally shifted in time so they should be close to being time and phase coherent to use Thiel's terminology. The purists cringe when you talk about digital processing but so far so good.

One point of clarification, Even first order filters cause phase shift as you approach the cutoff frequency. Thiel claims that they have achieved equal but opposite shifts from the drivers above and below the cutoff so they cancel.

The phase shift is kept low by using very gradual (6 dB/octave) roll-off slopes which produce a phase lag of 45° for the low frequency driver and a phase lead of 45° for the high frequency driver at the crossover point. Because the phase shift of each driver is much less than 90° and is equal and opposite, their outputs combine to produce a system output with no phase shift and perfect transient response.

I'm still trying to wrap my head around that one. If one driver produces a sound shifted in time so it occurs slightly earlier than those in the passband and another produces the same sound slightly later how can that add up to no time change?

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