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Speaker Asylum General speaker questions for audio and home theater. |
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Speaker Asylum General speaker questions for audio and home theater. |
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In Reply to: The most important question may be... posted by Jim Austin on February 23, 2007 at 04:44:02:
I'm sorry, but it's hard not to respond to this. All of this is absurd:"1. You have to use first-order crossovers because they have a phase shift that doesn't depend on frequency. And first-order crossovers have a low slope"
Low slope, yes. The first sentence has no bearing on real drivers, but in addition there are crossovers, both passive and active and not DSP, that are transient-perfect.
The electrical transfer function of the crossover is immaterial except as it relates to how it's transfer function couples with the transfer function of the driver itself to yield the acoustic crossover from the system. Any system that uses a true first order electrical XO will in no way result in a first order acoustic output from the driver.
First order acoustic crossovers (BW1) from real drivers (2nd order bandpass devices) are minimum-phase with a group delay that is fully dependent on frequency. The only crossovers using real drivers that are not are DSP generated linear-phase types. The crossover sections of non-DSP BW1 crossovers maintain a constant relative phase relationship of 90 degrees at all points (phase quadrature), but there is a phase rotation in the summed response due to the bandpass nature of the drivers.
"2. Time-alignment is achieved by offsetting the drivers by an amount equal to the phase shift. BUT THIS CAN ONLY BE ACHIEVED AT A SINGLE FREQUENCY."
This is just absurd. Time alignment has nothing to do with any single frequency. It has to with the location of the absolute acoustic center and is relative to all frequencies.
"3. It can also only be achieved at wavelengths (eg, frequencies) where the required offset is of roughly the same dimention as the loudspeaker: 3 inches, yes. 10 feet, no."
Totally absurd.
dlr
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Follow Ups
- Re: The most important question may be... - dlr 18:01:13 02/23/07 (4)
- Re: The most important question may be... - Jim Austin 18:34:16 02/23/07 (3)
- And that means absolutely nothing (NT) - dlr 18:58:53 02/23/07 (2)
- To you. (NT) - Jim Austin 19:02:38 02/23/07 (1)
- No, with the physics - dlr 20:16:36 02/23/07 (0)
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