Subwoofer inverted impulse response - Page 2 - Home Theater Forum and Systems - HomeTheaterShack.com

Old 07-01-09, 02:42 PM
Elite Shackster
brucek

Join Date: Apr 2006
Posts: 7,514
Re: Subwoofer inverted impulse response

Quote:
in the processor it really is just altering delays
But how is the phase control any different, other than it is in the analog domain?

Does the phase control (as a low Q, all pass filter) not offer linear phase response over its range and result in the same effect as the time delay?

brucek
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Old 07-01-09, 05:11 PM Thread Starter
Shackster
vidger1

Join Date: Apr 2008
Location: zimbabwe
Posts: 10
Re: Subwoofer inverted impulse response

I have another question, when looking at the graph posted by Brucek I noticed that the shape correspond (roughly) to my sub graph, but in the time domain, my sub peak is at + 5ms where Brucek's one is located at exactly 0ms. What hypothesis can we infer out of these observations?
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Old 07-02-09, 03:24 AM
REW Author

John

Join Date: Apr 2006
Location: UK
Posts: 6,308
Re: Subwoofer inverted impulse response

Quote:
brucek wrote: View Post
But how is the phase control any different, other than it is in the analog domain?

Does the phase control (as a low Q, all pass filter) not offer linear phase response over its range and result in the same effect as the time delay?
No. The typical normal/invert sub "phase" control is simply a switchable inversion. For variable controls it is an all pass that is reasonably linear through the middle of its operating range but not at the ends.
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Old 07-02-09, 03:28 AM
REW Author

John

Join Date: Apr 2006
Location: UK
Posts: 6,308
Re: Subwoofer inverted impulse response

Quote:
vidger wrote: View Post
I have another question, when looking at the graph posted by Brucek I noticed that the shape correspond (roughly) to my sub graph, but in the time domain, my sub peak is at + 5ms where Brucek's one is located at exactly 0ms. What hypothesis can we infer out of these observations?
That the measurements were made with 2 different versions of REW, one which used the IR peak as the time=0 reference point and the other which used the first point before the peak where the response exceeds 10% of peak level. The location of the t=0 reference doesn't make any difference to the IR or the frequency response, deciding where to place it is not important until phase or group delay are being analysed (which REW currently doesn't offer).
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Old 07-02-09, 04:45 AM Thread Starter
Shackster
vidger1

Join Date: Apr 2008
Location: zimbabwe
Posts: 10
Re you working

Thank you John,

So, if I want to align (temporally) my sub with my mains, by capturing the sub impulse and afterwards my mains impulse, I cannot use REW to draw any conclusions from potential delay between the impulse peaks of the mains and the sub?

Is it a feature you are currently working on for REW?

Regards
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Old 07-02-09, 08:48 AM
REW Author

John

Join Date: Apr 2006
Location: UK
Posts: 6,308
Re: Re you working

Quote:
vidger wrote: View Post
So, if I want to align (temporally) my sub with my mains, by capturing the sub impulse and afterwards my mains impulse, I cannot use REW to draw any conclusions from potential delay between the impulse peaks of the mains and the sub?
Correct

Quote:
vidger wrote: View Post
Is it a feature you are currently working on for REW?
Yes, V5 allows a left channel loopback to be used as a timing reference.
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Old 07-02-09, 11:08 AM Thread Starter
Shackster
vidger1

Join Date: Apr 2008
Location: zimbabwe
Posts: 10
Re: Subwoofer inverted impulse response

Well... REW V5 sounds fantastic!!!

If you're looking for beta testers, you know were to find me
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