Impluse Response show subwoofers much further than they are ?

ric982

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Hi,
Feel free to tell me whether this is the wrong place for this type of question but,,

I have a 9.2.4 setup with equidistant satellites at 4.9 ft. I've measured all the speakers separately from he listening position with bass management on.
I have a reference loop set up on a separate channel. I'm working on time alignment.

The impulse responses of the 7 satellites I've measured are all clustered around 4.35 ms (4.9 ft) +/- 1" as shown below. (One of the satellites has reversed polarity).

The subs are on the floor but not to much further behind the satellites, so I would expect there distance from the listening position to be on the order of 6.5 ft ,and would expect them to measure at about 1+ msec behind the satellites. But they are showing up about 6 and 7 msec later as shown in the second picture with one satellite and both subs. The subs don't have a phase setting or a polarity setting (neither do the satellites).
There's no treatment on the rear wall so might be getting a bet of a bound off of that.

Any idea why the delays on the subs seem so far off? It's perhaps 2x the distance from the listening position than they should be?

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ric982

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This is the R channel (Satellite, XO, 2 Sub) room response in case that helps any.
The lowest room mode is 34 Hz (15 ft 5") and that 120 dip is probably 3rd harmonic of that.
Subs driven through LFE with 150 Hz LPF in the impulse response measurement.


1701480618536.png
 

sm52

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The impulse peak from the subwoofer should be 2-3 times further than the impulse peak from the other speakers. This is caused by the properties of the large subwoofer driver.
 

ric982

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Well I'm not quite sure what happened above vs here. But here's the R with the 2 subs. Scaling is different for sure, but the subs look like there at 7 and 8 ms (not 10 and 11) vs 4 ms for the R. 2x as you say.
Thanks for the rersponse. I'm a bit new at this.

1701609338183.png
 

sm52

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In your case, the difference between R and Sub is about 2. If you take a larger Sub, the difference will be about 3, but definitely more than 2. For some reason the graphs in post 1 are different from post 4.
 
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