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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
audiokinesis
2,737 posts
 
At low frequencies, speakers + room = a "minimum phase" system. In English, this means that the frequency response tracks the time-domain response. 

So if you have an in-room bass peak in the subwoofer region, you will also have modal ringing at that frequency - the energy will there will take longer to decay into inaudibility. (It is the frequency response peak that we actually hear; the ear as very poor time-domain resolution at low frequencies but arguably has heightened resolution in the loudness domain.) The good news is that when you fix one (by EQ or bass trapping or some other technique), you simultaneously have fixed the other.

Therefore, in my opinion, the phase adjustments on a subwoofer amp (and/or timing adjustments within a bass management system) are tools to be used with the focus on getting the frequency response smooth. Smooth bass = "fast" bass. In other words, don’t sacrifice frequency response in pursuit of what you think would be better phase response. In the bass region when the frequency response is right, the time-domain response (which includes the phase response) is also right. 

Duke
erik_squires
16,056 posts
 
No it could not possibly matter less.  


Man who constantly argues against science completely misunderstands the problem, writes nonsense in long form.
dpac996's avatar
dpac996
698 posts
 
JL Audio has a lengthy white paper on this subject; interesting read. Check out their website for another viewpoint, and one where the author does not insult the audience.
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...

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