Interesting - so just to see if I understand this - for instance, the ELAC Debut 6.2 speakers have their high impedance mark about 2kHz and have a minimum impedance of 5 ohms. So should they fare better or worse in terms of frequency curve normalcy with an Aiyima A07 amp? Better because they would present the highest demand in the mid-range band and NOT in higher frequencies?
Here is the simplest model of the amplifier output filter (figure from
source.) It is a LC low pass filter with a nominal cutoff frequency of 1/sqrt(L*C) in rad/s.
As an example I use L = 20 μH and C = 0.5 μF, which gives a cutoff frequency of 316 228 rad/s = 50.3 kHz. These are the frequency response plots with 2, 4, 8, 16, 32 Ω speaker impedance. You can see that the speaker load impedance, if it is purely resistive, affects only the Q of the filter. The higher the impedance, the higher the Q. Therefore, a resistive speaker impedance only affects the top end of the frequency range, and has negligible effects at < 5 kHz.
However, the speaker impedance can be inductive or capacitive in addition to being resistive. Below are plots again with 2, 4, 8, 16, 32 Ω but with an additional -45° and +45° phase angles. You can see that the speaker impedance phase can also have significant effects on the resulting frequency response.