Proabably a silly question, but is the electrical phase across a loudspeaker equal to the acoustic phase produced?
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Electrical phase only matters to your amplifier, and it doesn't matter much to well-designed ones.
Acoustic phase is a function of frequency response. Frequency response is only affected by impedance if your amplifier has appreciable output impedance (tube amps) or if your wires have high resistance. Less expensive class D and T amps can also have appreciable frequency response changes based on load impedance - could be why many think they sound "Tubey" 😉.
Either I've completely miss-understood, or we're talking about two different thigs... I thought when you have an electronic phase shift across a frequency range, for instance a capacitor on it's own in series with a tweeter... as the frequency decreases the electrical phase will shift 90 degrees, therefore everything hitting the tweeter at those frequencies would be 90 deg out, and there would be an easy-to-plot shift as impedance varies.
My question was really if you measure the electrical phase across a raw driver with a freq. sweep, surely the phase shift should be noticeable in the acoustic output of the driver? i.e. the phase at a specific frequency would match both electronically and acoustically, when passing an AC current over a loudspeaker driver at a specified frequency....
My question was really if you measure the electrical phase across a raw driver with a freq. sweep, surely the phase shift should be noticeable in the acoustic output of the driver? i.e. the phase at a specific frequency would match both electronically and acoustically, when passing an AC current over a loudspeaker driver at a specified frequency....
Are you talking about the angle of the impedance, or the angle of the signal? Two quite different concepts. You need to say which you mean.
Assuming you mean the angle of the signal, then it is almost meaningless to compare the angle of the electrical signal with the angle of the electrical signal. However, what you can do is note that changing one by X degrees means that the other eventually changes by X degrees too. I say 'eventually' because every speaker is a filter with some energy storage mechanisms so output changes don't instantaneously follow input changes.
Assuming you mean the angle of the signal, then it is almost meaningless to compare the angle of the electrical signal with the angle of the electrical signal. However, what you can do is note that changing one by X degrees means that the other eventually changes by X degrees too. I say 'eventually' because every speaker is a filter with some energy storage mechanisms so output changes don't instantaneously follow input changes.
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Not a silly question at all. The formulas for calculating component values of crossover filters assume that electrical and acoustical phase are identical. If not, then in the crossover region summation isn't according to plan.
As DF96 says, the driver is a complex (resistive and reactive) load at any frequency except the resonant frequency, so output will never exactly follow input.
The equations for crossover filters work, so there must usually be a fair amount of correspondence. By the equations "working", I mean that measured frequency response through the crossover region ends up being close to flat.
Regards,
cT
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