These are Klipsch Synergy III B-2. The manufacturer only rates them down to 62 Hz, nevertheless, the amount of bass that they deliver for their size is amazing. I ran some test tones on them, and I can hear plenty of audible bass down to about 42 Hz, which given their size (H:12.5” x W:7” x D:8”) and only a 5.25" woofer is really impressive. For proper home theater experience, you'd need a subwoofer though, but for music listening, not necessarily.
Overall sound stage and detail is pretty good, too. Generally Klipsch speakers are considered "bright", meaning they overemphasize high frequencies, which has to do with their high frequency driver design, so it's best to pair them up with a less bright amp/receiver to balance things out. I'm powering them up with Denon AVR-2801 at the moment.
Anyway, if anyone is looking for small speakers with good low-end extension, I can definitely recommend these. But they're better off being placed on stands rather than tucked in on a shelf or against a wall - they have a rear-firing bass-reflex port, so you need to leave some space in the back to avoid running into bass issues.
FYI, I compared them to Infinity Primus 160, which are somewhat larger, have a 6.5" woofer, and are rated down to 49 Hz, but in my room, their bass response wasn't nearly as good as the Klipsch. Below 50 Hz, there was basically no clearly audible bass to speak of.