They are not as efficient as you might think in a horn. Say, like a lot of Klipsch.
A lot of the JBL's seem to dig a good current speaker. In fact, I tried a McIntosh amp with them, and preferred an older Harman Kardon that delivered a crap ton of current to them.
They do a lot right, excellent snare and kick drum sound (the 3900's that I owned). But, I felt they didn't move as much air down low as I like. I like bass, and prefer to not have to use my subwoofer for 2 channel listening.
Good speaker. I think at retail it's overpriced for the quality of the cabinet and finish, but used or on a good discount it's a fun speaker.