In Reply to: Re: The most important question may be... posted by mauimusicman on February 24, 2007 at 01:06:32:
>>Because of the way first-order crossovers change the phase (the time delay) as they crossover, the result is a CONSTANT time delay at ALL frequencies between the two drivers.<<I'll answer this, but I'm going to be very measured because--though what I said makes sense to me, others who are clearly knowledgeable have disagreed with me in this thread. I am not a speaker builder or an engineer. I'm trained as a physicist and I think in terms of first principles--which when naively applied sometimes are too simple to apply to real-world problems. Furthermore, I've been out of research for more than a decade and earned my PhD more nearly 15 years ago--so I'm rusty. So until I can get to the point where I understand--and either agree with or can refute--their points of view I'm not going to write much more on this subject.
My understanding--which might be wrong--is that there is a constant, 90 degree PHASE DIFFERENCE between the drivers in a first-order crossover configuration. But 90 degrees of phase is equal to 1/4 of a wavelength--NOT a fixed time difference (because the speed of sound is frequency/wavelength independent the time it takes for sound to travel a quarter of a wavelength depends on HOW LONG that wavelength is). So, for example, 1/4 or a wavelength at 1 kHz is not the same distance as 1/4 wavelength at 1.1 kHz. If you offset the drivers so that they they emit a 1kHz signal so that it reaches the ear at precisely the same time, then, it seems to me, a 1.1 khz signal will have a small time offset relative to perfect time alignment.
As for my ponit #3, it's so obvious to me that if you don't understand I must have it wrong, and I'm not being facetious. I simply mean that if (say) a 100Hz signal reaches the loudspeaker from the amplifier intact, 1/4 wavelength--90 degrees of phase--is, what, two and a half feet, roughly?
So there you go. Hopefully I haven't humiliated myself too much.
Cheers,
Jim
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Follow Ups
- Re: The most important question may be... - Jim Austin 05:59:56 02/24/07 (3)
- Re: The most important question may be... - mauimusicman 02:05:45 02/25/07 (1)
- Good description - dlr 06:53:20 02/25/07 (0)
- If more people could talk to each other like these two do.. - Craiger56 09:26:54 02/24/07 (0)