i was at the ces in chicago in 1976 and Saul Marantz gave me a demonstration of some tube gear with stacked modified dahlquist dq-10s with dual subs in a hotel suite. he had blankets hanging over mirrors and no other tweaks i can remember. but the sound and demo was incredible. great memory.i worked at a dahlquist dealer and never did sell a stacked pair but sold many pair of them with mcintosh electronics and thorens turntables. the good old days. ha. but i think todays gear is much better with the new technology and materials. about 5 years ,in the early 80s, later infinity brought out a huge pair of speakers with rows of ribbon like tweeters and poly drivers that were more expensive than almost everything else and they were very nice. i don,t remember the model number.