These are actually jbls high end pro audio subs.. used in stadiuma theatres and jbl is top of the line tech in pro sound.. interestingly these things are basically indestructible on a Burp. The motor topology protects it from overexcursion even on 2 crowns strapped.. over 10k watts. Even long term they have great heat dissipation due to the unique motor topology but down low 800 to 1k will get most of the performance out of.them.. still a very conservative rms spec on these.. very low distortion motor though and very controlled inductance... These will play 100hz+ with authority and still go low.. rarity these days in car audio