I'd like to clean up a few points here before the end of the year. ;-)
Yes, I was wrong to call Dunlavy designs D'Appolito arrays. I do know John Dunlavy liked symmetrical driver arrays because they simulated a point source speaker when matching mid and woofer pairs equal distance (respectively) from the tweeter. I believe all of John's designs had first order crossovers to maintain time and phase coherency. Whatever D'Appolito uses or did use, it apparently was not first order.
Rrog called me out saying SC IV measurements were at 10 feet, not 3 meters. Well, I was referring to the Princess which had factory measured responses made at 3.5 meters, thus my suggestion for 10-11 feet listening distances. And as I think we agree, each room will be different so there is NO specific formula. Trial and error is necessary unless you are extremely lucky.
The third point is my agreement with Rrog in not understanding how adding a subwoofer will help the midrange when the main speakers and amp(s) are not being rolled off. My introduction to good subwoofers came from a dealer who demoed a sub set up by playing s solo violin recording! When the approximately lowest two octaves (20-80 Hz) are removed from the signal going to the main amp and speakers, their job becomes easier and improvements in upper bass and midrange can be realized, in addition to potential extended bass response. Now I cannot say that Jonathan did not hear improvements extending into the midrange (I was not there), but I will suggest he will hear a greater improvement if he reconfigures his system to roll off his SC IVAs and main amp within the range of 50-100 Hz. The best point must be determined in his system.
Lastly, Dunlavy utilized stepped baffle designs, in addition to wool felt, in his Duntech speakers. As I recall the DAL speakers have a flat front baffle but still utilize the wool felt and crossovers to assist the time and phase alignments. Yes John was among the relatively small group of truly great speaker designers.
Yes, I was wrong to call Dunlavy designs D'Appolito arrays. I do know John Dunlavy liked symmetrical driver arrays because they simulated a point source speaker when matching mid and woofer pairs equal distance (respectively) from the tweeter. I believe all of John's designs had first order crossovers to maintain time and phase coherency. Whatever D'Appolito uses or did use, it apparently was not first order.
Rrog called me out saying SC IV measurements were at 10 feet, not 3 meters. Well, I was referring to the Princess which had factory measured responses made at 3.5 meters, thus my suggestion for 10-11 feet listening distances. And as I think we agree, each room will be different so there is NO specific formula. Trial and error is necessary unless you are extremely lucky.
The third point is my agreement with Rrog in not understanding how adding a subwoofer will help the midrange when the main speakers and amp(s) are not being rolled off. My introduction to good subwoofers came from a dealer who demoed a sub set up by playing s solo violin recording! When the approximately lowest two octaves (20-80 Hz) are removed from the signal going to the main amp and speakers, their job becomes easier and improvements in upper bass and midrange can be realized, in addition to potential extended bass response. Now I cannot say that Jonathan did not hear improvements extending into the midrange (I was not there), but I will suggest he will hear a greater improvement if he reconfigures his system to roll off his SC IVAs and main amp within the range of 50-100 Hz. The best point must be determined in his system.
Lastly, Dunlavy utilized stepped baffle designs, in addition to wool felt, in his Duntech speakers. As I recall the DAL speakers have a flat front baffle but still utilize the wool felt and crossovers to assist the time and phase alignments. Yes John was among the relatively small group of truly great speaker designers.