18 lbs is very light for a tower. Are they built out of ply?
here ere the specs
Break in time: 100 - 150 hours
Placement from rear wall: 6" - 3' / 152 - 914 mm
Placement distance apart: 2' - 12' / 610 - 3 658 mm
Mass Loading: 10 - 20 lb / 4.5 - 9 kg in each cabinet
Frequency Response: 40 Hz - 20 kHz ± 3 dB (with proper room positioning)
Impedance: 4 ohms
Sensitivity: 87 dB
Recommended Power: 20 - 80 W
Crossover frequency: 2.4 kHz, 2nd order Linkwitz-Riley (optimized)
Woofer: 4.5" / 114 mm sandwich cone double magnet”
Tweeter: 1 impregnated textile dome 0.75" / 19 mm (low resonance freq.)
Max SPL's: In average size listening room (12' x 20' / 4 m x 6 m)
103 dB peak (12' x 15' / 3 658 x 4 572 mm) from pair at 7' / 2 m
Dimensions (w x h x d): 5.1 x 33.5 x 7.1" / 130 x 850 x 180 mm
I'm not sure the bolded line is their weight or not. To me mass laoding infers add additional weight to the cabinet but I'm not sure. I do know that they have a "lock and mitre" joints (if that makes sense) and their fit and finish are 2nd to none.