I bought this for my studio, as my monitors were lacking low end for when I mix down.
I qualified at the British academy of new music in 2009 as a sound engineer, and also produced music on this course alongside, and was wary due to the low price.
When it turned up, I was pleasantly surprised. The sound quality is fine for something in this price range, even a couple of hundred above for replicating frequencies in this range.
I saw few posts mentioning the crossover being "just a low pass filter"- this IS a type of crossover, so does exactly what it is meant to.
Somehow, it has actually reduced the noise my monitors produce when powered on as well, it used to be a loud click, now it is quiet.
This is indeed a very powerful, and loud, subwoofer if you want it to be that, or you can set it at an ideal reference level.
I have put two stickers on the rear volume dial, one for reference, and one for my own "party mode" which is louder, but still not even halfway up in a fairly large room.
There is a huge amount of excursion on this subwoofer, another thing that surprised me in this price range. It has never soft bottomed on me.
The only reason I didn't give 5 stars for features is the lack of a foot switch.
If you wish to add a sub to your studio, or are using some cheaper monitors and also want a sub to just listen to music, I couldn't recommend anything more than this product.