ESI Aktiv 10S

-first it is very not flat, 30Hz cutoff specs is very kind, maybe at-20dB then? And even with the lowest cutoff dial? Basically just a potatoidal frequency response.
-add to that that specs are wrong: the 100Hz cutoff for satellite is wrong, this is actually 50Hz and the switch is reversed also. I swapped between 3 different units I think (hanks Thomann) before doing the measuremtns by myself... And obviously no news from the manufacturer since I presented them the final results showing their device was not to specs...
-so both combined it doesn't make it very useful by itself, plan separate equalization for the sub and for your satellites if you want to do something clean...
But I still kept it because in the price range it has nice options (phase, footswitch...), and once separate equalization is achieved the entire setup sounds nice. Just beware of what you are buying.

Ok, so there were some issues with mine.
It broke down the next day it arrived and i ended up repairing and improving it.

Initially it would sound kinda hollow, I tried to adjust it as best as possible with my 5" monitors and left it at that. But the next day, i left everything powered on and went to the store to buy something. When i came back there would be power but no sound.
I opened it up and for some reason it had some resistors blown. After more investigation, nearly all the opamps were fried too. It turns out that a rectifier transistor was faulty and it gave 22v instead of 15v.

So i decided to replace them and change all caps with Nichicon high grade audio caps.
All i can say now is wow! It is a beast! It is loud, it sounds deep and full and you can clearly hear and feel frequencies as low as 30hz but most of all it completes the low end on my 5" monitors perfectly and i couldn't be happier.

The crossover knob (50Hz-180Hz) is just for the subwoofer crossover and does not affect the connected the satellite speakers, like the satellite crossover switch (100Hz or OFF).

By using the satellite crossover switch the connected speakers can run full range (OFF) or with 100 Hz high pass (100Hz) with 24 dB/octave.

The settings of the subwoofer crossover are related to the low end of the ESI uniK 08+ speakers.

The 12 clock position of the potentiometer for the sub crossover is around 115Hz.

By setting the satellite crossover to 100Hz you have can set the subwoofer crossover knob to 11 clock around 100Hz.

The whole thing is of course dependent on the room conditions and should be tried out, but it is best to measure it correctly.

Hope this helps !

I'll start by addressing the main thing I was worried about before ordering: Does this subwoofer actually do 30hz as the specs promise? The answer is yes, thankfully.

Setting the crossover to 50hz and adjusting the phase, the sub integrates very nicely with my Kali LP6 monitors. I listened to it and measured it in two different rooms: In my bedroom/home-studio it extends to 33hz before rolling off, whereas in my living room it's flat to 27hz! Not bad for a budget sub. I also took some close up measurements of the woofer & port, and the combined response is -3dB at 30hz. This may not be the most accurate measurement method, but it's a good sign nonetheless.

The fully adjustable phase is very useful and in my opinion more subwoofers should provide this instead of a simple 0-180 switch, and the standby mode works really well and has never interrupted me when working at low volumes. It's also optional to enable in the first place so +1 for that.

There's some significantly pricier studio subs out there that have more or less the same features and bass extension, so this is a really good offering at this price and I can easily recommend it.