Spatial Audio Labs

I ran a set of X5's for a year or so and really liked them.

I have since found a set of AZ Crescendo MK2's and have them in the system now.

The Spatials are a very good sounding speaker and actually sound better everywhere in the room and at low listening levels.

The MK2's sound better in the sweet spot but not by much. I did run a pair of SVS 3000's with the X5's and also with the MK2's.

I have a pair of X5's. They are the most revealing speaker I have ever owned, which is a bit surprising given how relaxed they are. Any upstream changes are clearly evident. The tweeter is probably the most natural sounding in my experience. Properly setup there is a fairly narrow sweet spot, enough for two people. The tweeter's vertical dispersion is somewhat limited - you will notice as you sit down in the sweet spot how things come into focus. I am currently trying to get a more layered depth to the image. I am waiting for an Aesthetix Romulus to arrive, replacing my PS Audio Directstream Sr. I did audition a Pass XA25, which did indeed provide the depth I was looking for, but there were other issues with it, so back to my Rowland 535. Like any dipole they need to be out in the room a considerable distance, mine are ~4 ft from the front wall. All in all, they are really satisfying speakers.

The most difficult part of a loudspeaker to manufacture is the enclosure. The reason big ESLs are relatively inexpensive is that they do not have one. It is much easier to make a simple plate so Spatial can make a very competitive loudspeaker and probably make more money doing it. I myself have made several open baffle speakers for friends pairing them with sealed subwoofers which brings us to the problem, bass. There is no sub bass. As the wavelengths get longer they simply cancel out. Above that bass performance depends entirely on the room and how sound bounces around. In the right room these speaker can sound very bass heavy. Distance from the wall is also important. Having measured X3's I can tell you there is no way anyone will get remotely flat bass response out of them even with room control. But bass can be very difficult to evaluate. people can "hear" the note even with the fundamental missing. 
Our brains fill in the blanks. 
The best way to use these speakers is with subwoofers crossing up a bit higher at 100 Hz at least. This will dramatically clean up your midrange and give you controllable bass as low as you care to go. This is not much different than any dipole loudspeaker as they all have the same failing. 

The X5s make me happy.  

Over the past 40 years I have gone from electrostatics and ribbon speakers, including Beveridge 2SW2, Sanders, and Magnepan (1.6 and 3.6), to open baffle speakers designed by Clayton. Prior to the X5s I had the original Emerald Physics CS2.3s and then the Spatial M1 Turbo S model, which is the predecessor to the M3 Sapphire. With the X5s I feel like I have arrived. To the point of not even being curious about other speakers.

As a point of reference, I exclusively stream Tidal and Qobuz, alternating between a Lyngdorf TDAI-3400 for casual listening, and an MSB Analog DAC -> Whammerdyne DGA-1 (4.2 watt 2A3 SET) amp for real music listening sessions.

I agree with markmuse in that the X5s are an uncanny combination of revealing and relaxed. An open window to whatever is upstream, to my ears. And impressively robust yet tight bass, even only 2' out from the front wall. Perhaps I am sacrificing a bit of soundstage depth by not having them out farther, but they sound so friggin beautiful and uncolored I don't care.

This is why I mentioned their ultimate upgrade which I heard before and after.
stock it has a decent inductor , and clarity Csa capacitors which are better then average . These is only 2 capacitors and 1 inductor 
the VH audio Odam capacitors are the top upgrade caps , and matched to within .05% per pair , and awg 16  Jantzen 
Copper foil wax inductor , truly raises the  bar  in detail, image density and sound
staging for only about $600 in parts  and will still fit in the stock Xover space.