Originally Posted by rcohen
When using different model subs or the same subs with different filter settings, differences with frequency dependent phase can cause additional cancellation problems. I was running into this until I noticed that I didn't have the subs set consistently. In some cases, different models can be configured to have matching phase properties. That REW simulator won't account for this.
It is indeed very important for low bass phase consistency. If someone has to mix different types of subs, check out if there is a way to make them as phase consistent as possible towards the bottom end. Most ported subs have 6th order roll-off (4th order from ported configuration itself and second order or 3rd order from rumble filter) while most sealed sub has 4 order roll-off. However, our sealed sub without the rumble filter turn on is more like between 2nd order and 3rd order. The rumble filter in our sealed sub adds a 3rd order. So to mix our ported sub with our sealed sub, we need to turn on rumble filter on the sealed sub and uses the lowest phase delay ported subs of ours which is FV15 or FV15HP in one port mode.
Also, if the subs are significantly different distances from you, I found that independently time aligning them was really important.
Either of these could ruin the sound. Always good to measure.
On the other hand, this distance difference affects the mid bass rather than the low bass. To enable distance adjustment, one can use line-in (instead of lfe in). You need to set the sub distance in AVR to be the furthest sub. Then for each of the remaining subs , we need to use the delay adjustment knob on the plate amp to make its sound arrive later. So set its delay knob equals the distance difference(in ft) divided by 1.1. That is the amount of delay we need in milli-second.
So the above two adjustments are completely orthogonal. Don't try to use distance adjustment to fix the phase difference resulted from bass roll-off of different order. It simply won't work.
In short, if one pays attention to both of the above, he will have the low bass and mid bass covered for phase consistency (and then intrapolate to in between) .