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Importance of phase and timing optimization when incorporating sub woofers ?

For incorporating a pair of sub woofers into a music system, how important is it to be able to optimize phase ( continuous adjustments and not just 0 or 180) and timing ( optimizing delay ) ? Reading on this subject, some say to get the best seamless integration, the two above factors are essential. REL is frequently mentioned as the most musical/fast/detailed sub woofers for music, however they only allow of 0 or 180 deg phase and no other room correction, as compared to Velodyne DD’s or JL Audio’s. I could utilize something like the JL Audio CR-1 crossover, but adding an additional piece of equipment into the audio chain wouldn’t be my first choice. On the other hand, the added benefit, might make the addition of a well made crossover a net plus ??? Regardless I plan on having my room/system measured to assist with incorporating what ever two subs I go with.
Thoughts from experienced users?
jim94025
mike_in_nc
1,147 posts
 
Adjusting phase will smooth the FR around the crossover frequency. The effect is noticeable by ear and it is measurable. (It is best done with a measurement mic.) Without such adjustments, one may have large dips in the FR due to cancellations.

As Eric said, adjusting delay and phase are essentially the same thing.

snbeall
63 posts
 

I used to think and understand phase as delay in a sense but have come to understand that delay is not quite exactly the same thing as adjusting phase. Yes, by adjusting phase you will "match up" two overlapping sources in the crossover region. However, you may be as much as a full wavelength or more BEHIND in timing. So the impulse response and initial attack will be blurred.

That said, I don't understand why many of these EQ and sub management systems that allow you to adjust from your seat remotely do not have a continuously adjustable phase option to adjust from there as well. Nor do the auto EQ room correction devices seem to adjust phase automatically...

nekoaudio's avatar
nekoaudio
489 posts
 
Adjusting delay precisely (which will match phase) makes a big difference in my experience. Adjusting only phase isn't equivalent: your subwoofer could be 100 feet away and you can match phase while playing a sine wave but it will be easy to tell the difference in timing.
snbeall
63 posts
 
it seems that subs are generally delayed by positioning distance differences. Add even more delay if they have any servo processing/EQ being done. Seems that there should be the option to delay the mains to adjust phase precisely - rather than subs in some instrances. Do any room correction systems do so utilizing impulse responses and delay mains or subs as needed to match phase?
erik_squires
16,057 posts
 
+1 nekoaudio

@snbeall - In an ideal world, you are right. I mean, DSP itself adds processing time, so even if you originally had subs at the same distance acoustically as your mains, just putting a processor in the bass path introduces 1-2 mSecs of delay (i’m guessing).

In practice though, I find that matching the phase and slopes correctly using the sub alone can be really really good sounding. This keeps your mains "pure" and your sub disappears.
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