I know the theory and that many people swear by these types of crossovers. To me it seems like a great idea but I am a little skeptical that if in the real world "acoustically complementary" is realistic between 2 radically different drivers located at a set distance from each other that may or may not be ideal. In your experience can you actually measure the pre-ringing or lack thereof reliably "in room"?
I think you are spot on, questioning the reality of achieving acoustically complementary response....and most particularly between subwoofers and main speakers.
Subs and mains must be co-located to have any hope of producing acoustically complementary response, to anywhere other than a chosen listening spot.
Which for me, raises a very ironic point regarding the issue of potential pre-ring audibility. We hear about the issue all the time when it comes to crossovers, but why is it never discussed with multi-sub bass management?
Any program like Dirac or whatever, that uses
any mixed phase filtering, has made phase corrections that do not have naturally balancing offsets, as they do in acoustically complementary crossovers.
Ever hear about anybody taking about pre-ring potential with their multi-sub bass management? I haven't. If optimization programs are using more than IIR to manage multi-sub, they sure as heck have potential.
I think of the sub to main crossover as just another crossover, like those in the main speaker. And like drivers in the main speaker that are co-located in a fixed manner for fixed acoustical results, I think it's optimal to have the sub or better said,
the sub drivers, co-located in fixed manner.
Imo/ime, maintaining acoustically complementary crossovers between all driver sections is fundamental to excellent speaker design, whether crossovers are minimum phase or linear phase. And that ain't gonna happen when subs are located away from mains !
Anyway, yes, I think I can measure pre-ring potential accurately.
I think the correct way is as anechoically as possible , not "in-room" if that means at listening position. It's just another speaker measurement, that falls into the same camp as spinoramas, imo/ime.
The measurement is simply the set of on and off-axis impulse responses, particularly Step response. As it shows dips below zero prior to impulse peak, with potentially audible pre-ring.
I've found thru a lot of polar measurements of my DIY synergy horns, that it's kinda not worth paying attention to, as not much changes compared to good reference axis Step response.
I think that's because, even when fully acoustically complementary summation is breaking down as evidenced by variances in polars, the regions of frequency response that are capable of pre-ring are pretty small...well, at least for me,.... because I use steep crossovers.
Steep complementary lin phase crossovers minimize the potential lobing range between drivers, because the critical summation span is dramatically narrowed (vs low order crossovers). (I'm sure you are well aware of this...typing for group at large)
Here's the electrical crossovers I use with a 4-way syn horn that sits directly of top of a sub.
Xovers are at 100, 300, 750, and 3400Hz. All are 96 dB/oct LR.
Note how narrow the summation regions between drivers are. Take the low to mid crossover at 300Hz, it's probably only 40Hz wide within the range that matters, where both drivers are contributing relative equally (within 3dB of each other)
Those narrow regions are the
only regions capable of potential pre-ring, because all other frequency regions are single driver section only.
Tone bursts confirm this, as there is zero envelope warpage in non summed frequency ranges..
The Step response is of the summed electrical sections...complementary works huh!
Hope I made sense...
I can't believe more folks haven't jumped into lin-phase crossovers, I guess not due to pre-ring scare.
And how many folks have jumped into mixed-phase sub optimization with no pre-ring concern at all.
A bit ironic imo