Absolutely correct. Woofer placement behind the mains require compensation for sound arrival alignment at the listener position. The use of a phase control can effectively align phase response but the fact remains that the sub will always be delayed by at least a half cycle from the leading impulse signal from the mains. The only way to align the impulse signal is use dsp and retard the time arrival of the mains. These are uncontested facts. Barry Ober from JL Audio and others have discussed this ad nauseum. However David is correct that "at the end of the day (uh, how about the beginning of the day also?), it's only about good sound and not measurements". Barry would agree and feels that even without dsp, you can get very satisfactory sound with a good phase alignment control for the woofer. If this is done well, the slight offset in the impulse wave between sub and mains will not sonically detrimental to most listeners. Here once again, perfect can be the enemy of good. Many, if not most, audiophiles who use subwoofers do not use dsp and find their sound to be sonically pleasing with judicious set-up of their subs.
All the best on your speaker selection although I have to admit your choice has surprised me from our past conversations,
I could not agree with you more that perfect is the enemy of good and even excellent.
I have had a lot of experience with 4 piece systems like the IRS and Genesis back in the day. I don't really know how much they were playing with the bass wave forms but when set up properly at HP or at Lyric or at some of my clients they were really great sounding systems. They were in my opinion very difficult to get right or almost right.
I am not a fan of sub woofers used in audio unless they have been designed with the speaker and this can be great but usually EXPENSIVE . I think asking a consumer to be a speaker engineer is asking a lot. I have seen and tried numerous brands with different speakers and always feel at the end it was better without.
There are various reasons for that. One they by insertion into the listening space cause problems just being there. Second the sonic signatures of the different speaker systems don't play nice together. When done passively always create a bump in the bass . Fourth they can adversely effect imaging and phase as you mentioned. If done with an electronic crossover this is probably the best
way however this is a very expensive and complex process. I understand why people try it since the position of a speaker for low frequency coupling and balance is not always the right place for sound stage and midrange and hi frequency balance.
The cost of goods plus gear IMHO is usually much more than finding a better speaker system and for many this exercise is more science fiction than actually improving the sound of the system.
My choice in music is not pipe organ nor electronic and having a natural midrange and great soundstage with layering is far more to my taste.
Hope all is well and enjoy the music