Active xover question about delay

[georgehifi]

Can anyone tell me, how many milliseconds of delay is equal to revervsing the phase on a driver?

Cheers George

[morpheus82]

it depends of frequency you want to reverse, it is half of the period of the wave you have to reverse, for example for 1KHz is 0,5ms.

[georgehifi]

Better explain what I'm trying to do, I have an electrostatic panel that goes down to 160hz passively crossed, then a 12ins bass that goes up to 160hz active 4th order.
The problem is that the esl panel is 4ins in front of the bass voice coil, now if I had the esl actively crossed over all i would have to do is delay the esl (acording to the Rane AC22 active xover manual) 1.75ms and than they should be aligned.
But I only have the Rane (when I get it) on the bass, now I can delay the bass but that's going the wrong way, so what I thought is reversing the phase of the esl that should then be (electricaly) behind the bass driver then I can delay the bass with the delay control till it lines up with the esl. But I need to know by reversing the phase of the esl how many milliseconds that is equal to?

Cheers George

[djk]

This is kind of a 'why bother' type of thing. 4" at 160hz is trivial, the whole wavelength is about 84". When you are that close just adjust the level and be done with it. Long published an article years ago in the AES suggesting just that.

[georgehifi]

Originally posted by djk
This is kind of a 'why bother' type of thing. 4" at 160hz is trivial, the whole wavelength is about 84". When you are that close just adjust the level and be done with it. Long published an article years ago in the AES suggesting just that.

Sheeeet, I was hoping that a little couple of millisecond tweak would give me audio bass nirvana.


Cheers George

[AndrewT]

Hi,
what if you have 4m behind @ 120Hz crossover,
Just to expand the theory could be helpful.
Would reversing the phase of one allow the delay to be inserted in the "wrong" half?

[georgehifi]

Originally posted by AndrewT
Hi,
what if you have 4m behind @ 120Hz crossover,
Just to expand the theory could be helpful.
Would reversing the phase of one allow the delay to be inserted in the "wrong" half?

Andrew your screwing with my head, what do you mean?
Is this aimed at my ignorance or are you saying it does matter to get things phase perfect.
Below is the Rane bass xover delay chart

Cheers George

[phase_accurate]

The largest group-delay is introduced by the lowpass part of the crossover itself. In the case of 160 hz @ fourth order this is around 3 ms which is more than one yard.
If you want to time-align then you'd have to concentrate on this rather than the 4" you mentioned.

BTW:Time alignment can't be achieved by driver reversing, only phase alignment can be done that way.

Regards

Charles

[AndrewT]

Hi George,
I was expanding on your question to cover the region of much larger distance offsets.

But I think Charles has answered the question, if I understand him correctly.

He says you can correct a phase error by reversing the phase.
He has not said you can move the delay from the upper frequency speaker to the low frequency speaker by reversing the phase.
I was attracted to your idea of transferring the delay from the upper frequency speakers to the bass speaker to help preserve the signal quality going to the main frequency range.

I can see from your Rane extract that I would need about 80 on the adjustable scale, just a bit beyond MAX I fear.

An analogue delay for 5.6m of physical offset might well be impossible and if applied to the mid and treble may well interfere with the sound quality.

[georgehifi]

Looks as though my experiment won't happen now the price of the Rane AC22 has gone too high for me to gamble with it.

Cheers George