Interesting, but how did it sound to you?
If you mean "stacked"; They sounded fantastic!! But that was back in the mid 70's.
System was:
Rabco ST7 TT with straightline tracking
Denon 103 cartridge
Citation 17 Preamp
Dahlquist electronic XO
Pair Bridged Citation 16 amps (for L&R DQ10 Mains)
Citation 16 stereo amp (for Stereo Dahlquist subs)
Stacked and mirror imaged DQ10's for L&R Mains
Stereo Dahlquist Subs.
I hope I remembered that correctly.