Dynaudio 9S

Got the 9s since I already have the LYD-7s from Dynaudio - they say the 9s was created especially for the LYD series of speakers so it was an easy choice for me.
And a good one, too! The sub is tight, punchy and rather detailed as most sealed designs are.
Build quality is good and just what you'd expect from a sub at this price point. Don't be fooled by the 9.5" woofer, it plays well in small rooms(up to medium ones) I did prepare a bit before getting it: some bass traps in the front corners and installed REW plus measurement mic. After unpacking I spent a bit of time with the placement and measurements to get it the sweet spot and phase and time aligned with the main speakers, it was a bit of work, but you do it once every now and again, so it's fine.

It's weird to review a sub by itself as it's supposed to part of a bigger system. Now that I've integrated it properly with my lyd7s I think it's better to talk about the system as a whole now that the 9s was added:
The bass goes lower(no surprise there). Soundstage is now deeper(taller to be precise) more natural. Low mids are now cleaner/less muddy. Mids and low mids have better transient response, are less compressed, more detailed. Everything is just better across the freq range. The lower bass extension is only half the story, the other half is the speakers being released from bass duties and really shining on the rest of the range.
The difference is not subtle, either. I really feel that I made an upgrade.
Now, you may want to take all of this with a grain of salt, as speakers with high crossover frequencies like the LYD7s, Neumann KH 120 II or Barefoots which are all at around 4khz, do benefit way more from unloading the bass duties to a subwoofer then most speakers, that usually have the crossover at about 1.7 to 2.2khz.(but the later also benefit, don't be worried)
Conclusion: The sub is good, just what I expected, it's the only sealed solution in that price range which makes it a no brainer even if you don't have the matching speakers or high crossover ones.
I highly recommend!
Cheers!

Well i paired this sub with BM5 MKIII , it feels that lacks power and doesn't merge good with my BM5s.
I moved it all around the room, tried different adjustments on crossover and gain but did not help. Maybe this is not the best pair for BM5 MKIII with my room accoustics, the BM5 MKIII sounds way much better standalone on full range than 9S + BM5 with HPF on 80Hz or 60Hz.
Another mention is that the first 9S that i received , out of the box, it had a rattling noise coming from the voice coil if the volume was above 50%, but it was easily replaced by Thomann - good and reliable services from them.

I bought the Dynaudio 9s subwoofer for critical nearfield listening at home.
I'm using it with Genelec G4 speakers. The main advantage over home subwoofers is that it has an HPF filter on XLR, which largely helps resolve room acoustic issues at low frequencies.
Problems arise from how the room reacts to the bass produced by the speakers. The subwoofer allows for resolving irregularities through optimal room positioning, adjustment, and by cutting the bass and sub-bass from the main speakers. Freed from the associated bass and boom produced in the room, the speakers can perform great; the sound becomes wider, more precise, more focused, more detailed – in short, holographic. The subwoofer, in turn, delivers noticeably more neutral, deep, and cleaner bass.
This is generally speaking, but the Dynaudio 9S exhibits unique qualities. Being a sealed enclosure, the bass is fast, firm, and nuanced. Its 9.5" size and 300W power ensure great dynamics and extension.
I tested several models with different operating principles: bass reflex, passive radiator, but none managed to be as convincing as the Dynaudio 9s.
Once positioned and optimally tuned, the system enters another class; it's closer to realism. It's the biggest upgrade imaginable that can be made to a stereo system.