I have had some experience with FR designs, and many have a lot to offer. Most however have a shout in the midrange at about 1K that I cannot listen to! Round and round I went to find a driver that satisfied my preferences. The Mark Audio came very close with the 10P model, but I wanted more bass. This driver was used in a small back loaded horn design. I want to build another in the future but with the 12P driver instead, and in a larger cabinet.
Audio Nirvana drivers (the classic series, w/o whizzer cones and alnico magnets) have a good overall sound including bass, but are slightly recessed in the upper midrange.
I have also tried an interesting design by Deware audio that uses a unique open baffle design with a Hemholtz resonator for the lower cabinet. Truly, the choice of drivers matter here. The FRX2 drivers sold by Decware are great sounding, BUT just know that they are voiced for tube application. Their prices may stop you in your tracks at 600 ea. too. These drivers are quite unique themselves by using a special transformer to deal with the shout issue, and to tame some of the phase response anomalies of this driver.
Audio Nirvana drivers (the classic series, w/o whizzer cones and alnico magnets) have a good overall sound including bass, but are slightly recessed in the upper midrange.
I have also tried an interesting design by Deware audio that uses a unique open baffle design with a Hemholtz resonator for the lower cabinet. Truly, the choice of drivers matter here. The FRX2 drivers sold by Decware are great sounding, BUT just know that they are voiced for tube application. Their prices may stop you in your tracks at 600 ea. too. These drivers are quite unique themselves by using a special transformer to deal with the shout issue, and to tame some of the phase response anomalies of this driver.