10/2/2020: The Spatial M3's continue to improve. No sub needed, in fact adding subs with these speakers really impairs the sound no matter the setting as low as 35 Hz, it throws the balance of the speaker off, Clayton also mentioned this that this could happen because you're adding back to the room what the OB speakers were designed to avoid. The Woofers on the M3's are just to fast and open. They actually made the speakers sound bright. Go figure. Another thing about these speakers, they tell you in a minute on any changes you make in your system down to the power cord powering the amplifier.
If I had to say one thing that took some time to adjust to is how open and boxless these speakers are, the music is just there in space with details, speed, and realism. I have them locked into my room now, but I am sure I try them a bit further apart to see if they can be further improved. But now I just want to sit back and enjoy them. All recordings sound fresh, with new insights, I would not call this speaker analytical, it an open window to the recording. Bass is strong but clean, a stand-up bass sounds natural, not slow or booming like a sealed bass tends to reproduce, sounds like a real stand up bass, light and agile at times, then a growl yet while remaining open sounding like life.
Vocals are another strong point, you hear all the nuances and the power of the vocal range. Highs are very open, in fact on a Dead Can Dance recording I heard the faintest ring of bells towards the end of one track, I've never heard them before. My journey with these speakers has been an education, how far they have come and improved and how I learned about them and setup, but also to follow Clayton advise, give them the much-needed time to break-in and you will be rewarded. Played some Telarc Classical recordings that I know quite well and the M3's nailed them with ease, no stress, no strain, no distortion, music just flowed I just felt like sitting back and enjoying the performance.
As far as I know, these still may not fully be delivering what they are capable of. I've not put the hours on them as many as stated they need. I am also now firm on these speakers sound better without the spikes in the front of the speaker in my room, not even close now. Improvements: More Dynamics, Presence, Better highs, and mid-bass and bottom end all now night and day better. Jim Smith wrote an article on spiking speakers and he found about the same as I have in my 35 years in this hobby, most of the time they do more harm than good. A kettle drum in back of the hall on a recording came to life without the spikes, sounded like the real deal, deeper, clearer and more dynamic. https://www.psaudio.com/article/spiking-your-speakers-whats-the-point/
Along with my Quads ESL 63 speakers that were fully rebuilt from the power supply up, these are some of the best speakers I've heard/owned in 30 years in this hobby. Pictures of my room along with room treatments which I am sure really help me get the sound that I am enjoying, your room is always a big part of the final sound you hear. I can now fully and easily hear even a change of one power cord anywhere in the system, heard them before but not to such an extent. Tells you how transparent these speakers are without being bright. My question now is if I might add a tube preamp in the mix to go along with my McIntosh amp. PrimaLuna EVO 400 comes to mind.