One interesting aspect of external crossovers, is that so many aspects in the cabinet are devoted to vibration management. Gluing the parts to the board impinges on thermal stability, but if left unglued, they rattle and buzz and introduce microphonics. Out of the box, that aspect is not a problem. Also, a major limit to directionality of coils is their position in the driver magnetic fields. That goes away too. And the heat thing is big; the enclosure keeps getting hotter, whereas the EXO self-cools. And two-sided boards become practical for isolation of resistors from caps. You get the picture.
SDL - I love the basement idea. But also, these EXOs will be in presentable cabinets of their own. I can’t help it, I was born that way.
Tomic - I have reverted to point to point on masonite - no printed circuits. When rebuilding Beetle’s 2.4s (late / Chinese, on PCBs) we noted coils with up to (perhaps) 20% variation from spec. Those changes were required to re-balance considering the capacitive coupling to the PCB traces. I prefer to keep the coupled capacitance separate from the inductance. I am also at greater liberty to manage the layout to avoid parallel leads and/or bring them to contact and twist to virtually eliminate self-capacitance.
I am loving the audition material selection. By randomizing it via the next album alphabetically, I have reduced the tendency to design for only the best audiophile material. I learn as much from ordinary or substandard cuts as I do from great cuts. However, anyone is welcome to send the Chesky catalog or other great stuff.
Eric - you are most welcome to share your turbulent / laminar flow ideas if you wish, either here or via PM. I have a setup that works, but might be significantly improved. I cover the baffle with F11 pure wool felt at 1/8 or 1/4", covered with the finest Ultrasuede Fine fabric. The drivers and bezels are covered with a stretchy version of USF. The US surface fibers are so fine as to be moved by the pressure - shear waves. The effect is lovely. I am now working with an aerospace engineer with a technology patent for surface flow dynamics management for spacecraft re-entry.
No end to the fun.