Why not acoustic suspension?

As I implied previously, though, a good closed box has superior fidelity to a goo ported box. Ported boxes(including passive radiators) are boom boxes compared to closed boxes assuming proper design.
 

That’s a misleading statement IME, especially regarding passive radiators. Some of the most articulate and defined bass I have heard came from ported, MLTLs, or passive radiator designs. I will say the average ported box does sound boomy relative to the average sealed box design, but like most things in audio, there are notable exceptions. It ultimately comes down to the competency of the design. 
 
 

I've had 9 or 10 pairs of speakers over the years. In the last 2 decades speakers lived in my space limited home office system where desktop/nearfield placement is mandatory. I found out the hard way that the 3 sealed/acoustic suspension designs simply sound better and interact less with the room than the 3 ported speakers. It's not even a close contest.

My current speakers are the vintage sealed KEF 103.2s, which are wonderful 2-ways (soft dome tweeter + 8" woofer). Two more recent sealed speakers that also worked beautifully here were the ATC SCM12 Pros (Their smallest studio monitor, a passive design) and the Aerial Acoustics 5Bs. 

I have a vintage pair of Boston Acoustics A40 2-ways (also sealed) in the living room. They sound great in a location that would cause real trouble with any ported speaker.

All in all, I'm a big fan of sealed/acoustic suspension designs. At least to my ears, the bass sounds more forceful, controlled and tuneful than any ported design's does, and I've had some good examples of those, too.

Magico speakers are closed box. I'm not sure if they are acoustic suspension although I think they claim it. But I suspect they are not.

Sonically, you can tune any closed box to a given transfer function, closed box or acoustic suspension. The advantage of acoustic suspension is smaller boxes but at the price of lower efficiency. What may have been especially important about acoustic suspension is the smaller box because stereo and acoustic suspension came about the same time. And the smaller boxes made two speakers more acceptable.

One problem that was basically ignored when acoustic suspension first came out was efficiency. The tube amps of the day were underpowered(the super popular Dynaco Stereo 70 was rated at 35 watts optimistically and 50/60 watts was a big deal) for acoustic suspension so they were never heard at their best. When we finally got good, high power amps it was too late and bass reflex had taken over.

As to bass response. The knee point(-3 dB) is usually lower for bass reflex than closed box. So for most music bass reflex sounds bassier. However reflex rolls off faster and deep down closed box, while reduced in bass, takes over. Plus and I think most important a great closed box is more accurate in bass quality(less bass overhang) than a great bass reflex speaker. The problem seems to be that most listeners like the bassier sound of extra overhang perhaps because we're used to it since reflex rules.

It is for posts like this that I keep coming back to Audiogon! Great discussion, learned several things about the two sets of vintage acoustic speakers I own, KLH Model 17 with up-graded tweeters, and a mixed pair of AR-2’s (one = 3-way AR-2ax; one = 2-way AR-2a). The 3-way sounds much better to me. The plan is to convert the AR-2a to an AR-2ax, but that will mean replacing the baffle in the AR-2a. 

I’ve used this acoustic suspension/sealed speaker- Opera Seconda off and on for 15 years.

Currently use ESL’s.

Convincing/impactful bass at all volume levels. 2 REL subs used for full immersion. A poor mans Sonus Faber-Italian, beautiful veneer/leather. I use tube power.