Below: a reprint of the article*, mentioned by MC, (01-06-2022 8:36 PM) written by Roger Sanders, who has since gained a certain amount of respect as a speaker designer.
When I had my shoppe in Winter Park, FL (circa 1980): a customer wanted a pair of subs, to accompany his Acoustat Model III system.
They worked so well, when loaded with the 10" drivers Speakerlab used in their Nestorovic bass system, crossed with a Dahlquist DQ-LP1 and driven by a Halfer DH-500; I built another pair for myself (and: bought a pair of Model IIIs).
Then, built a few others, which I combined with passive crossovers, JVC ribbon tweeters, Audax dome midranges and very smooth, 10" Peerless woofers. Everything but the 10" woofers and their 5 Ways, were contained in moveable housings (for time-alignment and directivity), which sat atop the TL cabinets.
They sold as fast as I could build them.
I’m still using my original pair, crossed/aligned with a TacT 2.2X, into a Hafler 9505 and: now sporting a pair of SEAS Extreme (not from Taiwan) L26ROYs.
Their performance (measured and auditory): excellent, with a tube-driven pair of small, Emerald Physics speakers, crossed at 80Hz (10th order).
Still have the old Nestorovic 10s, in a closet. (sentimental value, or: backup?)
Whether just for the valuable insights/info, or: to build one’s own pair:
More, from Roger Sanders and Speaker Builder/Audio Amateur, here:
http://sanderssoundsystems.com/audio-related-articles
Happy listening!