These speakers handle a lot of power (300 W rms) and have high frequency extension up to around 5 kHz. They ought to make good guitar speakers as well. Also, properly baffled (EBS - extended bass shelf) would do well as bass guitar speakers. They were originally used in very pricey 4 way studio monitors as woofer/midbass with an 18 inch Fostex Laoratory Series woofer, horn and tweeter.
T-S Parameters:
fs - 35 Hz
VAS - 153 Liters (5.403 cu ft.)
Qts - 0.21
Qms - 5.2
Qes - 0.22
mms - 55.6
For more T-S details :http://petoindominique.fr/php/mysql_listehp3.php?marque=FOSTEX
These are excellent speakers, a screamin' deal at the listed price. Were I not planning to travel there is no way in hell I would let them go. The price isn't going any lower.