Audio is ferried via a single 3.5mm mini-jack, and the rotary volume control is integrated into the top of one of the speakers.
JBL's claims that the Duet III provides an "extraordinarily powerful, yet smooth and accurate sound" are a little overblown, however. Acoustic music fares well, with a wide, reasonably deep soundstage and an impressively crisp performance.
Up the ante with more dynamic material, though, and its limitations are clear. Crank up the volume and the built-in 30W digital amplifier begins to struggle, with the music taking on a coarse, muddy quality.
Meanwhile, the modest bass output robs music of scale and leaves dance music sounding lightweight. At this price, we'd expect them to do much more than just look good.