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


Cube Audio (Poland) designs single drivers and single driver speakers. 

Principals are Grzegorz Rulka and Marek Kostrzyński.

Link to the Cube Audio Nenuphar (with F10 Neo driver) speaker page: 

https://www.cubeaudio.eu/cube-audio-nenuphar

Link to 6Moons review by Srajan Ebaen (August 2018):

https://6moons.com/audioreview_articles/cubeaudio2/

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Parameters (from Cube Audio):

Power: 40 W

Efficiency: 92 dB

Frequency response: 30Hz - 18kHz ( 6db)*

Dimensions: 30 x 50 x 105 cm

Weight: 40 Kg


* Frequency response may vary and depends on room size and accompanying electronic equipment.
david_ten
I'm reporting on impact of adding a jantzen-audio-100-ohm-10-watt-audio-grade-superes-resistor--255-944 to each of the positive speaker terms on the Vinnie Rossi L2iSE.  This lowered the damping factor driving the Nenuphars from 800 to 80 and was suggested by Mr. Rossi as an experiment.

Immediate impression was the overall sound just got cleaner and more relaxed.  After extended listening it was obvious those impressions came from a clearer/cleaner mid range and mid bass.  The lower bass also sounded slightly better, not deeper, but as if the deepest notes weren't hitting a dead end.  The other clear benefit was how much better the L2iSE sounded at low volumes.  Everything remained in balance at a lower spls (before the mid bass on down sounded weak). Of course I was unaware the sound could have been improved in any of these ways--except in the loss of bass playing at lower volumes (and I'm talking pretty low here, with the L2iSE volume setting at 14 or 15 instead of the 24-27 where I normally listen).

It looks a little weird to have these green resistors the size of lady finger firecrackers back there and to think of this huge sound coming through their little wires wrapped around the WBT speaker terminals and the banana plugs.  But there you have it, my newly hot rodded L2iSE swinging even freer than before.  

What if I added another resister on each side and brought the damping factor down to 8  (which is what my SIT-1s batted at)?  We'll see what Vinnie says about that.

(BTW I am far from qualified to be recommending that you try adding these resistors to your own amp or integrated.  My gear's designer was kind enough to entertain this experiment, guiding me to make sure that nothing was shorted when I connected the resistors.  If you're considering such a mod, I would first run it by your amp's manufacturer/designer.)
For future readers: In case the above link expires, please note that the link text is somewhat misleading. It is for a 1ohm 10w Jantzen Audio Superes resistor.

And @stephendunn, congrats on the outcome. And good information. I didn't know that a 1 ohm resistor in series with a driver had this effect. Apparently I need to learn more about damping factor calculation and meaning...
Want to correct an error in the type of resistor mentioned above.  I copied and pasted the Parts Connexion listing for the part which is actually a 1 ohm resister not a 100 ohm resistor as the listing states.  Which interestingly enough brings the damping factor to 8.
Stephen,
Congratulations!
It’s interesting that this simple step reduces the DF by a factor of 10 and improves what was already a very high level of sound quality. This was an excellent suggestion from the knowledgeable Vinnie Rossi. It certainly does stimulate the curiosity of what happens if DF is reduced to 8. Fun stuff.

Cal,
Since an amplifier’s DF and output impedance have an inverse relationship I wonder if this output impedance is ’effectively’ increased with use of the resistors or is the nominal speaker impedance as seen by the amplifier decreased?
Charles
Speaking of DF, a couple of weeks ago I was cruising the intranets reading about damping factors and came across an article by a couple of guys who put together PA systems (which explains why they talk about speaker cable lengths of 50 and 100 feet).

At any rate, they noted that the DF decreases with longer speaker cables so I may try 8' versus 16' speaker runs. They provided some numbers:

50'    12AWG   8ohm   DF= 49.1
50'    12           4                  24.5
50'    12           2                  12.3
100'  12           8                  24.9
100'  12           4                  12.2
100'  14           4                    7.9
100'  16           4                    4.9