Binders
They're the coolest binders I've seen. They have a single, oversized knob which tightens a plastic plate with copper contacts. Spades are best, but bananas will work. They're probably the same one they use on the Tone.
Sean Casey from Zu wrote me an e-mail in response to my inquiry about these earlier today:
"The Tones, are a really cool loudspeaker. They are a simple sealed box but we are doing some cool stuff with it. The main driver is a very similar to that in the Druid, same cone, suspension, basket, magnet; we changed the motor a bit and left the phase plug out, to allow it to work a bit better with the enclosure. Super tweeter is mounted on the outside of the fixed grill. Fixing the grill allowed us to also reduce baffle resonance nodes quite a bit and also intigrate upper end presence region diffraction and resulting comb distortions. The sound is very close to the Druid, just doesn't play as low. Still gets down their pretty deep though, deep enough to be satisfying. Very response, just like the Druid."
These guys are freakin' speaker geniouses. But, 101 db will expose system noise and reduce the usable volume range of your pre/amp. 5 watts is plenty of power, you could use more but quality is much more important than quantity with these.