Great 16 ohm Full Range loudspeakers

Does seem Dukes speaker impedance would be OTL friendly.

Second the Altec Valencia 846A, the 16 ohm version, although the 846B (8 ohm version) is also very good. If money is not a consideration, then my first recommendation is the Shindo Latour's. Best overall speaker I have ever heard.

The Audiokinesis Dream Makers are 16 ohm and the Jazz Module 12 ohm. Both are OTL friendly. The MA-1 amps could easily power either speaker.

The MA-1 is very comfortable with 8 ohm speakers and a good number of 4 ohm speakers.

In fact its smaller brother works fine with 8 ohm speakers too.

Impedance peaks can be dealt with by Zobel networks if the designer of the speaker was expecting the peak to reduce the output from the amplifier.

Zu Soul superply, 16ohm, 101db efficiency. I haven't heard them but I have other 12ohm Zu speakers which I like.