I have found measurements on SLS 10!
That looks good! I have to say that. Especially in relation to the price/ costs of the SLS 10.
First the conclusions, I translated via Google Translate so it may contain some errors because I am not so good at German:
"The frequency response:
Due to the relatively high voice coil inductance, the sound pressure in the near field begins to drop slightly from 150 Hz. This can also be seen in the course of the angle-weighted sound pressure. This is irrelevant for a subwoofer, for a woofer in a 3-way system it partially compensates for the baffle step.
On axis, the frequency response of all 4 chassis runs at a distance of 20 cm from 240 to 1800 Hz in a corridor of only +/- 0.9 dB width - there is nothing to complain about! The membrane resonance at 2.5 kHz is only a maximum of 5 dB louder than the middle level in 3 of 4 drivers. Bundling sets in from 900 Hz, which increases only gently up to 1.2 kHz and only rises more sharply above that (although the increase is still very even).
Delayed ringing only occurs at the membrane resonance of 2.5 kHz.
All 4 drivers behave almost identically up to 1.8 kHz (the maximum deviation at a distance of 20 cm between 10 and 1800 Hz is only +0.63/-0.66 dB) - that's extremely good!
The distortion factor:
The "harmonic" distortion factor K2 runs linearly over almost the entire range of use and is - as usual - strongly dependent on the excitation level. In contrast, the higher distortion components up to an average sound pressure level of 95 dB hardly increase with the excitation level, only at 100 dB does a greater level influence become apparent.
At an average sound pressure level of 85 / 90 / 95 / 100 dB, K2 is on average 0.40 / 0.72 / 1.31 / 2.45% in the frequency range from 40 to 500 Hz. A mean value of 0.16 / 0.17 / 0.23 / 0.36% applies to K3 in this area.
The membrane resonance is below the range of maximum ear sensitivity and therefore the K3 distortion maximum does not coincide with the range of maximum sensitivity for K3 (see distortion factor - how much is too much?).
According to the article mentioned above, K2 would be inaudible in the level range under consideration. However, the K3 peak at 800 Hz would be well above the threshold of perception at all levels considered, but K3 remains inaudible up to 500 Hz. The K5 peak at 500 Hz is also audible at all levels considered up to 95 dB - although it is only approx. 0.13% at maximum.
Level linearity: The level linearity was determined for an excitation voltage of 2 to 20 volts, which corresponds to an average sound pressure level of 84 to 104 dB at a distance of 1 m! Between 50 and 2000 Hz, even at 20 volts (= +20 dB), only sporadically more than 0.5 dB dynamics fall by the wayside, between 200 and 600 Hz there are hardly any signs of dynamic compression even at 20 volts excitation level."
HiFi-Selbstbau - Das Online-Magazin
www.hifi-selbstbau.de
An Peerless combo maybe?
SLS 10 plus:
The THD measurements at voltage level 2.83 Volt were carried out with High Pass Filter "on" (2nd order Butterworth type, 80 Hz cutoff, HPF2-80) The THD measurements at voltage level 4 - 11.2 Volt were carried out with High Pass Filter "on" (2nd order Butterworth type, 150 Hz cutoff, HPF2-150)...
hificompass.com
Hm, I'm going to think about that. Crossover around or a little below 500 Hz maybe.