Hi Teddy!
I love a good "Sub Story"
Long time Multi Sub user here, and have for Years, been under the Tutelage of one of the best. His ideas/suggestions have always trumped any Audio nonsense I may have conjured up.
Maybe you could share with us some specifics. Which Mains are you using? Ported? Sealed?
What about your Room? Dimensions?
What types of placement limitations do you have in that space? (We all have them)
In terms of Phase Alignment, this is usually quite easily measured with sftwr such as Room EQ Wizard. I'm typically looking for a "notch" in the FR that may suggest a Sub Polarity issue which is easily corrected.
The Blauert/Laws studies of the 1970s give us some insights as to the Audibilty of these time-alignment matters. Sadly, I don't have a link readily available, but you have Google as well as I.
*Edit: Polarity, and Phase are not truly the same thing in this discussion. Blauert/Laws looked at the audibility of Group Delay. It seems that threshold was rather high (3.2ms at 500hz)
Were we to to extrapolate that to the frequencies a Sub is dealing with, we would be in the 30ms range. That's 30ft!! Unless you live in a Church, your Room probably wouldn't allow for such error. Us folks in smaller rooms have far bigger Fish to Fry!
Else...it gets involved, but not anything outside your ability to resolve.
Let's get you hooked up!!
Curt
Vintage 2018 ADI-2 DAC. "Classic AKM4490 Edition"
Cables: Red, and White Ones.
Speakers: Yes