MBL omnidirectional speakers. How do they sound ?

I think they're a very good loudspeaker.  I also think they're not a good value.   There are other loudspeakers I like as well if not better, for less money.

In this league, I'd encourage you to audition the big Avalon loudspeakers.  You can get some of the older, Eidolon models for $12,000 or less on the used market.

What's an even better value is for you to build a Linkwitz LX521 or Orion system.  Both will stand up against the MBL or Avalon systems without breaking a sweat.  You can build either, with amplification, for $6000 or less.  They're extreme hi-end the common man can afford.  But if you feel you just have to drop $20,000, go right ahead.

Here are some comments I made in another thread a six weeks ago. I've expanded for this topic.

I most recently heard the Corona line integrated amp, CD/DAC, and their entry level speakers (approx $30k for the three pieces) and it was very lovely. Fairly close to much more expensive systems in their line up. That was compared to the Noble line amps & dac with the 101E MkII. Source was a computer playing files vs. the Corona CD player. Bass was better with the 101E MkIIs ($70k for speakers alone) but really both systems just sing. I've also heard the Extreme system several times and other systems with their mid-line speakers. So I know what they sound like. For reference, my system consists of a McIntosh integrated, Martin Logan Vantage ESLs, Shunyata Research, & Oppo 105.

I have heard one of the midline floorstanding Mbl speakers with other manufacturers amps & source. I didn't feel it was as good as the all Mbl systems I'd heard on that day or in other dealers or at the Show Newport. I think there is a special synergy with an all-Mbl system. After all, I'm sure that they are voiced with amps/sources in each respective line.

It has been over three decades since I've had a system that was totally built by one manufacturer. Mbl has definitely inspired me to think about that again. Really, it is my dream system. But at $30k it is a BIG stretch, really out of reach if I'm honest with myself.

I have used MBL 101 E speakers the last five years, and love them !
They are power hungry, hard to set up and ruthless at finding the flaws in your system. But when everything is right they just bring you to the recording venue. Good live recordings are just spooky with these speakers. I have used them in relative small rooms with success, you need a little over 1 meter of room behind them and a lot of absorbers on the side walls. They do work best with the big 9011 MBL amps, the mid bass is hard to energize with lesser amps.
I used big Krell FPB 750 amps and did not realize how much better the mid bass could get, until i got a 9011 in the system. There is a synergy between these amps and the power hungry speakers.  I currently use only one amp set up for stereo. My listening levels rarely exceed 85 dB, and can not recommend levels under 75dB.