My eyes aren't sharp enough to tell if they're 10's or 12's, but those are woofers from Peerless's SLS line. Which brings up my question: how loud are they at full excursion. (Not signal, but basket noise, etc.) I know the SLS8 is pretty quiet, but it's also moving less air.
As for midwoofer, I love the B&C 8NDL51, but if you want something else the old Peerless HDS205 was pretty darn good so the new Exclusive ones should be, too.
Those appear to be 4 12" drivers. I have considered folding the cabinet (H) as such to reduce the overall size, but have not done so. How does this affect your resonant peak? Was it harder to measure/supress? I assume with this sort of setup, you are active, possibly DCX?
I would suggest the W22 . There are less expensive options that are easier to work with (XO wise) of course. The B&C looks like a very nice unit, with the bonus of higher efficiency, probably closer to your other units. I can't imagine you're set up is passive though. Some of the newly released Seas and Peerless 22 cm midbasses look very good also.
I did the same Z- or M-frame construction, albeit with only two 10" drivers per side. The resonant peak was at almost the same frequency as the identical drivers had in my Ripoles (sort of W-frame) of the same depth. But the resonant peak was "squeezed" some way (flatter and wider).
Note: while you get no impulse compensation in a H-frame (and full compensation in a W-frame), half of the impulse is compensated in a Z-frame with 90° angle between driver planes.
I would not mount neighbouring drivers in the reverse-basket-configuration anymore, that Linkwitz recommends for a H-frame. It´s just my gut feeling, but I attribute a certain double peaking I have with that configuration to the highly asymmetrical position of the drivers.
I agree with you Rudolf. Thats probably the biggest reason why I have hesitated to go that route. I use to wonder why SL did not try to say, offset the midbass on the main panel, i.e., add some asymmetry, but the more I experiment, the more I realize that he does just about everything for a very specific reason (suprise, suprise ). The asymmetry will give you what appears to be smoother response (depending where you measure from - and with my limited measurement capability/knowledge), but in reality, you simply have a less clearly formed single peak that can be notched and instead have multiple smaller ones that are harder to see in the measurements because they are spread out and diffused. I guess the question then becomes - do you find this objectionable - soundwise? My short answer would be yes. But this is DIY after all, different budgets, room requirements, SAF's,etc. So to each their own.