Why not more popular?

A couple of years ago, I got my first set of open baffle speakers. I've owned a few pairs of Magneplanars and many box speakers over the years, but my current speakers are the first true open-baffle speakers I've owned. 

I am absolutely smitten with the sound. Musical, dynamic, powerful, and an amazing deep, open, airy sound stage, with none of the weird boxy resonances or port huffing that I've heard from so many box speakers. 

What I don't understand is why there are so few speaker companies making open baffle speakers, and why are they not more popular among audiophiles?
I've owned many good speakers from the DQ10 days, and yes they could do bass if you had a big enough amp, say the Threshold 400A they could sake the room, to Dynaudio Confidence speakers, ProAc, and Quad ESL's. I decided to try the Spatial Audio M3 Sapphires which are OB speakers. Like all new speakers, one had to allow them to burn in and learn how to set them up properly. Reading many of the anti-OB speaker comments and their sound, is nowhere what I am hearing in my system. Clayton woofers are designed for OB speakers period, in the past box woofers have been used and they suffer bass roll-off. The tweeter in the M3's was selected to work with the woofers and the open baffle and covers a large range from the midrange to the highs up to 40Khz. Once burned in the bottom end is so good, with detail, speed, and texture, that one does not need a subwoofer, in fact, I tried them and they ruined the coherence of this fine speaker. They are nowhere near boring, they make music sound alive, open, and tonally right. They produce what you feed them, you change a power cord or interconnect or speaker cable you will hear the change big time, meaning coloration is very low as well as distortion. They rock out, they play Jazz, they do baroque, large play symphonies, the piano is dead-on right, brass and horns also. They are also just enjoyable to listen to and as my wife says that sounds live. After being with my rebuilt Quads 63's by Kent at Electrostatic solutions, and enjoying them for almost 9 years, I wanted a change, I heard many speakers at my dealer and none for the money could match my Quads and they were 12-20K. Thus my research and finding Clayton Shaw speakers and after speaking with Clayton decided to take the plunge. Clayton is honest and upfront, I wanted the X5's but he suggested the M3's as the best speaker for my room and distance from the speakers. He was dead right, the wrong speaker for a given room is a waste of money because they just won't work. While no speaker is perfect, and you can always wish for if it only had this or that, but overall the M3's is one of the better sounding speakers I've heard or owned, and they are a real value vs. sound quality. After Quads, it is very hard to listen to a box speaker, with the M3's I not only listen but enjoy the difference from the Quads, and like the Quads, they just disappear when listening. Unless you hear them you cannot comment on OB designs of the past, because what these speakers do, do right is sound real as the recording and alive like few speakers can, like panel and stats, they are an open window to the recording. They cost $5,000 and worth every penny and then some. 
Great post @phillb!

The significance of your point about Clayton using drivers designed and built specifically for OB use cannot be overstated. All professional loudspeaker designers/builders know the importance of that, and proceed accordingly. I’m sure there are some DIYers who have used inappropriate drivers (those designed for use in enclosures), but we’re not taking about them.

Danny Richie of course also uses drivers made to his specs, drivers made with electrical and acoustic properties tailored specifically for OB use. These include his woofers, tweeters, and NEO3 magnetic-planar tweeter. One difference between the designs of Danny and Clayton is Danny’s use of a minimum-width front baffle, partnered with the use of side "wings" to increase the front-to-back driver separation the large baffles used by Clayton inherently provide. In spite of their different approaches, Clayton’s design talent and resulting OB loudspeakers have received high praise from Danny.

Also good is your mention of subs not blending well with OB’s. Planar loudspeaker lovers have for decades dealt with that reality. No matter how good the box sub was, it sounded "separate" from the planar loudspeaker. In the 1960’s the 24" Hartley was used by many QUAD ESL users, Mark Levinson using it in his HQD (Hartley sub, double QUAD ESL’s, Decca Ribbon Tweeter) loudspeaker. Infinity used servo-feedback sealed-enclosure subs with their IRS and RS-1b speakers, and many other attempts could be cited.

There are numerous reasons for the difficulty of achieving the desired blending---which I won’t go into here, except in one regard:

In the 1980’s, Finnish company Gradient introduced an OB/dipole sub designed and built specifically for the QUAD 63. They followed it up with an OB/dipole for the ESL (aka 57). Though compromised by sub-par design, build, and maximum SPL, it showed the way. OB sub design flourished amongst DIY loudspeaker designers/builders, including a very young Danny Richie.

Meanwhile, Harry Pearson at TAS had come up with the idea of replacing the sub towers of the Infinity IRS with the bass panels of the Magneplanar Tympani loudspeakers, two 16" X 72" panels per side. Mated with the m/t panels of the IRS (which housed line-source arrays of EMIM and EMIT planar drivers), the sound produced was the finest many people have ever heard---to this day. Finally: full-range (except for the bottom half-octave: below 30Hz) reproduction, completely planar. Unfortunately, the resulting combo required a LOT of floor space, so was impractical for most.

Along comes Danny Richie. His GR Research company was started to sell loudspeaker kits to the DIY community, with an emphasis on OB design. GR Research was offering a number of OB loudspeaker kits, along with a sealed sub. Though very much liking OB bass, he resigned himself to the fact that it’s limitations presented a challenge he was unable to resolve to his satisfaction.

But then Danny heard about a company introducing a new (patented) servo-feedback woofer (Rythmik), which just happened to also be in the State of Texas (in Austin). Danny proposed to Rythmik designer/owner Brian Ding his idea of mating Brian’s servo-feedback woofer/amplifier with a woofer designed by Danny for OB use, a pair of the servo-feedback woofers installed in an OB/dipole frame.

As I’m sure you know (or have guessed), the product came to market. If you have heard the bass produced by the Magneplanar Tympani loudspeaker, you already know what to expect from the GR Research OB/Dipole Sub, but without the latter’s missing bottom half-octave (and massive power amp requirements!). For any OB or planar loudspeaker owner who wants not just more bass, but bass that sounds like it’s being produced by their loudspeaker, it is now available.
@mijostyn You and I shared some stats in our lives.   When I brought home the Acoustat X's, my wife let me know how ugly they were as she called them coffins.  Within a year I moved up to the Acoustat 2+2s which we had for about 5 years, the Martin Logan Monolith IIIs for 8 years.  My current wife (I'm was a widower) decided that they stunk as they were dynamic shy, muddy bass, head in a vise and bright sounding in a 25' X 20' X 11'6" room.  Four of my friends and acquaintances had Legacy Focuses so I bought a pair used in 1998.  Satisfaction for my wife and I appreciated them (although I longed for the Acoustat 2+2s).  After decades of upgraded electronics (2006 + 2019), cabling (as a beta-tester) and tweaks (Hallographs/HFTs/electrical type), I have a marvelous audio system.  The one thing I want to change are the speakers for high end types which will provide a more resolving and open soundstage in my custom built listening room.  Von Schweikert, Evolution Acoustics and now another friend suggested Usher and a San Diego speaker manufacturer whose name I forgot now are in the running.  I like Maggies and Soundlabs best of the planars and stats.   I've heard Emerald and several other boxless dynamic speakers at shows and they sounded good, weak bass and less dynamic than I'm used to.  I suppose a case could be made for them.   Legacy's "newer" baffleless speakers can sound good but most come with DSP which I don't want to use.  
"I’ve heard Emerald and several other boxless dynamic speakers at shows and they sounded good, with weak bass, and less dynamic than I’m used to".

You’re not talking about Spatial Audio speakers, they kill what you say on the faults of other older designed OB speakers. Time has marched on.

So far I owned EP KC IIs for a couple years, and now 3.4s (with outboard XOs) for over a year. I made 2 inexpensive improvements that paid HUGE dividends to the 3.4s

* I moved the XOs off the speaker bases which vibrate like crazy
* I replaced the crap jumper wires (from speaker binding posts to the XOs) with WireWorld internal speaker cables
Because my room is volumetrically quiet large by audio standards, I also have 2 SVS powered subs
I have owned Accoustat 2 + 2s and Maggie 3.5Rs. The Maggies came in a distant 3rd

fleschler, nice post, and kudos on the development of the rig over the years. I laughed when I heard your wife's criticism of the panels; spot on. Those are the weaknesses in comparison to other genres. I can appreciate panels, as I have reviewed a few and owned a few.

Thoughts on speakers to move to... You do realize that Legacy can make their speakers rather active or passive version for you. Read my review of the Legacy Audio Whisper and its other iterations that Legacy Audio did; I think there are three reviews of the process in total before the final speaker. My version, the DSW Clarity Edition has capability to be run fully passive, hybrid with active bass and passive mid/treble, or fully active with Wavelet. So, there are some options for you.

If you are interested in discussing with me the Aspen Acoustics Lagrange L1 (I own the preproduction model following demo, and I have already committed to ownership of the L1 production model based on the performance of the prototype. Owner's review will appear at Dagogo.com), I invite you to contact me. I reviewed the smaller Lagrange L5 MkII for Dagogo.com. You can see the L1 preproduction model that I own on the Aspen Acoustics website.

The Aspen Acoustics is what I consider a new genre, the DLT (Disproportionately Large Tweeter), and it's VERY legit. I love it as much as any genre of speaker I have ever heard, perhaps more than omni, line source or dipole speakers of comparable size. It's an amazing blend of openness and dynamic power. The L1 has LF comparable to the Legacy Audio V and Valor, not playing around. If you wish to discuss with me the speakers I have used, shown in my system, feel free. 

BTW, since you mentioned Legacy, the i.V4 Ultra Amplifier review is published. WOW, what an amp! I am loving what class D is turning into!  :)

Just got my x5's set up yesterday.  With only 12 hours of play time they sound very promising.  They have a big, expansive rich textured sound thus far.