On a positive note
Previous tests with 4R//2.2uF load and 4R7//(2.2uF+1.6uH+0.3ohm) loads have shown that Ncore does not like and does not work well with high capacitive load, even if there is a small inductance and small resistance added to the capacitor. It was the so called "worst case" test and I understand than not many users here will connect the Ncore to Martin Logan Montis or to Sound Lab A-1. Still, it does not mean we should stick with tests with load resistors only.
For the purpose to simulate "usual" 2-way passive speaker, I have the dummy load with this impedance:
The test setup looks like this
The test frequencies chosen for THD+N vs. level
63Hz: 13.74ohm/-51°
500Hz: 13.52ohm/+44°
2310Hz: 7.105ohm/-9.2°
10kHz: 10.35ohm/-43°
This is quite "light" load
1. Noise
Noise (with NC252MP connected to Topping D10s) is very good 72.91 uV(A)
2. THD+N vs. output voltage
At 63Hz, we can see the nonlinearity of the big 18mH inductor that simulates woofer resonance, above 10V. Real speaker behaviour is similar.
3. THD+N vs. frequency at 9.5V output voltage and 2 measuring BW
Below 60Hz, the influence of 18mH inductor nonlinearity. Real speaker behaviour is similar.
4. Conclusion
With resistive load or with complex load of most usual speakers with dynamic drivers, the Ncore behaves very well.