I believe the more accurate description would be 'conga' drum.
I happen to have a pair of these I bought new in early '71. They actually sound pretty nice, but the bass doesn't go very deep. At the time they were very 'avant-garde' style, more of a design statement. Most of the major Japan brands had a round or octagonal omni-directional speaker, based on classical styling, intended as tables. This was Sony's take on the trend, as evident in the 'entasis' description.
http://en.wikipedia.org/wiki/Entasis
Below is the data sheet that came with them, along with a tiny flannel cloth like you'd get with a camera or binoculars. :headscrat