The 24s, like a lot of smaller acoustic suspension speakers of the era, have a relatively low sensitivity (86dB or thereabouts), combined with woofers that reach their mechanical limits a bit early. When pushed hard, they tend to bottom out. But they weren't designed to be played at concert levels...and they can still fill a smaller room without issue. Yiou might find that they run out of steam, so to speak, in a larger room.
That said, I really like them (at least as well as the more expensive 17s and 20s...which have the same sized woofer).
One other thing about them....they were sold both as part of the KLH 24 component system, and stand-alone. The system version has RCA speaker terminals, whereas the stand-alone version takes standard bare wire.