The A370PEQ Delay/Phase control lets you adjust the time delay at the crossover frequency for the sub. That is what the 0mS to 18mS range means on the control means.
HAL, I appreciate your effort, however, I don't think you understood well what my concern was (not sure if it is valid).
If the subwoofer is placed behind the main speakers, the sound coming from it would be delayed compared to the main speakers. By using the knob which delays the signal from 0ms to 16ms I will be able to put the sound in phase, but I will delay it even more.
My understanding is the mains and sub will end up being in phase, but the sound from the sub will be delayed by a cycle, two cycles, not sure.
That's why I posted the question whether this time difference is the sound arriving to the listener position between the mains and subwoofer will be noticeable or not (even though sounds of both sources are "in phase").
I hope this makes more sense now. I will repeat, I am not claiming anything just trying to comperhand whether it is worth trying to integrate my mains with the subs or not.
Thanks!!!