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

@rwpollock Obviously it's *best* to just let the speaker designer make all the decisions for you, but there are a lot of subwoofer options out there that have all the basic features of the BASiS subs.  The full range driver is indeed "rocket science-ish", but looking at the subs makes me think there are plenty of other more cost effective solutions that might work just fine. 

The pandemic has hit almost all of us, so I'm also on long delay, but I'm still thinking about building the sealed box diy version of their monitors and pairing with my existing subs (the 2 x 12" bass units of Coincident PREs) and subwoofer amplifiers (Dayton audio SA1000 monoblocks). Won't look as pretty and may not sound quite as good, but it should be close at the worst.

It is generally recognized that overdamping the Nenuphars is not a good idea. At 6moons Srajan wrote in his review of the First Watt SIT-3 about driving the Nenuphars:
"...you won't be surprised to learn that the SIT-1 and SIT-3 were the perfect antidotes; better than the F5 and F7, very much better than the Pass Labs XA-30.8, radically superior to 200-watt class A/B specimens of the 1Mhz ultra-bandwidth persuasion."

As an example of the last, the Soulution 501 has a damping factor of 10,000 (which would correspond to an output impedance of 0.0001 ohms). The Mola Mola, a class D amp, has an output impedance of 0.003 while the Bryston 4B clocks in at 0.016 ohms. Still too low to be of interest.

Moving on to a couple of tube amps, the Audio Research VT80 has an output impedance of 0.12 while the Aesthetic Atlas is 0.25. With OTL amps, the LTA Z10 impedance is 1.2 ohms and their Ultralinear is at 1.6 ohms.

Looking at the solid state amps that Sjaran ranked we see a consistent pattern:
SIT-1  4 ohms
SIT-3  0.26 ohms
F-5  0.025 ohms
F-7  0.01 ohms
Pass XA 30.8  0.007 ohms

Here are the output impedances of the First Watt stable:
F-1  80 ohms
F-2  15 ohms
SIT-1  4 ohms
SIT-2  4 ohms
J-2  0.4 ohms
SIT-3  0.26 ohms
F-4  0.2 ohms
F-3  0.12 ohms
F-6  0.06 ohms
M-2  0.05 ohms
F-5  0.025 ohms
F-7  0.01 ohms

Which leads to the exit question: Has anyone listened to the F-1 or F-2 with the Nenuphars?

Robert

Yes, it is high.
Here is a link from FirstWatt on the F1:
www.firstwatt.com/f1.html
"It has both balanced and single-ended inputs. The input impedance is nominally 80 Kohm, and the output impedance is 80 ohms."

And from the F1 manual:
www.firstwatt.com/pdf/prod_f1_man.pdf
"Input Impedance, unbalanced  50 Kohms, 8 ohm load

Output impedance  80 ohms"

In his 2004 review of the F-1, Dick Olsher wrote:

"Current drive offers a major alternative to the speaker-amplifier interface. A transconductance amplifier is operated as a current source with a high source impedance relative to that of the speaker. The output impedance must also be linear and frequency independent. An ideal current source would possess an output impedance so large as to be considered infinite relative to that of the speaker. The F1's 80-ohm impedance is certainly adequate in this regard."

Just to complicate things, I was reading back through the thread and came across toetapaudio's comment from a year ago (6/20/19):

"We are getting great results driving the Cubes with Mola Mola Makua/Kaluga’s and look forward to trying Bakoon amplification soon with the Cubes."

The Kaluga's output impedance is listed as <0.003 ohm with a damping factor >4000.
www.mola-mola.nl/kaluga.php
Go figure.