Cube Audio Nenuphar Single Driver Speaker (10 inch) TQWT Enclosure

From JA at Stereophile.

"McIntosh specifies the MC462 as being able to deliver 450Wpc (26.5dBW) into a load matched to the nominal output Autoformer tap. With clipping defined as being when the THD+noise reaches 1%, fig.6 indicates that the MC462 exceeded its specification even with both channels driven, its 8 ohm output clipping at 516Wpc into 8 ohms (27.1dBW). The trace in this graph stops at 1%, as that is when the amplifier’s protection was triggered. Into 4 ohms (fig.7), the McIntosh’s 8 ohm output clipped at 720Wpc (25.6dBW). It’s fair to note that I don’t hold the wall voltage constant for this test; with both channels clipping into 4 ohms, the wall voltage had dropped from 121 to 115.4V. The MC462’s 2 ohm output delivered 190Wpc (22.8dBW) with both channels driven into 8 ohms at 1% THD+N, 298Wpc with both channels driven into 4 ohms (21.7dBW, fig.8), and 536W (21.3dBW) with one channel driven into 2 ohms"

This type of amplifier (On paper) is truly the opposite of the kind of amplifier the Cube Audio designs of the Nenuphar had in mind to drive this speaker. Single driver crossoverless with intentionally easy impedance load and highly damped driven design.

It will be very interesting to see how this pairing works out. You just never know until you listen. Best of luck @kragon. 
Charles

@tomic601  @charles1dad  Thanks!  The credit goes to and is well deserved by everyone!!!

@khargon  I've been (mostly) hands-off through the build process. I'll share the design elements / approach later. 

The incoming amps will output around 3 watts... which is by design...the focus being on maximizing sound quality over power output. To illustrate the point, my current amps were designed to maximize output from the 2A3s and deliver ~ 4 to 4.5 watts.

@david_ten Thanks for the bit of info.. excited to hear your thoughts.. I used to own purposed built 300B amp for headphone listening, these builds really do bring out the best from our speakers.  Please share some photos of the amp when you get the chance.

@charles1dad From Stereophile I also see this:

The output impedance was lowest from the 8 ohm Autoformer tap, at 0.09 ohm at 20Hz and 1kHz, rising to 0.13 ohm at 20kHz. The 4 ohm tap’s output impedance was almost twice that of the 8 ohm tap—not what I was expecting—while the 2 ohm tap’s was 0.14 ohm at low and middle frequencies, rising to 0.185 ohm at the top of the audioband.

So from the 4 ohm taps, the output impedance is double (almost) of the 8 ohm taps, going to 0.18 to 0.26.. giving the damping factor of <50 (similar to the SIT-3) going into 8 ohm loads.. so yeah, crossing my fingers and toes that it’ll work out.

McIntosh has always been recommended with Zu and works beautifully. Won’t be surprised to work ok here.