Both version I and II Duettas have a extended lip to the case front as above, the version I has a large rear board extension with feet. Duetta II's had metal support legs which screwed to the speaker similar to the Calipers.

The Duetta II was more fine tuning than a new speaker, According to Alvin Gold, writing inStereophile (Vol 10 no. 2), Leo Spiegel said that one of the purposes of the Mk II revisions was to make the Duettas more sonically compatible with compact disc. The II is, therefore, softer and less detailed which was not necessarily to everyones preference.

The top part of the M/T ribbon was canted back about 5 degrees to improve vertical dispersion and the crossover became a compound circuit, starting at 6 db/octave increasing to 12 db/octave once well clear of the cross-over region. This approach, of course, was used on several models to come, including the Diva.

There were at least two different Duetta II. The early ones (I had this one) had an efficiency 4 db lower than the later (106 db vs. 110 with 100 watt amp). The later one also had considerably extended high end response. The early one was IMO too limited on the top end. Martin Colloms, writing in Stereophile (Vol. 10 no. 1) complained about this point. Other writers using the later version found no such problem, eg George Graves, Stereophile Vol. 11 no. 5.

Both types of Duettas can be converted to Signatures with new drivers and crossovers.