Mahughes, no, that is as opposed to the Druid.
Afc, the ZU speakers are all fairly high efficiency. So they encourage the user to use lower-powered amplifiers if they can. An excellent example of this is the Definition, which is 6 ohms. A lot of people want to put a smaller amp on that, because they really don't need the power.
Now with OTLs, you have a phenomena of economy of scale- the bigger the OTL, the more efficient it becomes with low impedance speakers. That is why are larger amps like the MA-1, MA2 and MA-3 can fly in the face of conventional OTL mythology as they can be quite comfortable with 4 ohm speakers.
But smaller OTLs, because of this economy of scale, don't make good power into lower impedances. Normally the ZU speakers are 12 ohms, and almost any OTL made can drive that easily. But 6 ohms... now if you want to use a 30-watt OTL, with that impedance it will play, but it won't sound right.
There was/is a 30-ohm version of the Definition, that plays beautifully with smaller OTLs. And now there are newer ZU speakers that have a switch so you can set that impedance high if you want to, allowing for a lower powered OTL and the speaker to strut their stuff.
