Why not more popular?

Here is my Q have you heard a FR, single source driver? 
No, WEll you should. 

bdp24, maybe I am just an old guy and you do seem very informed but in my day open baffle meant just that and was not driver type limited. ESLs and planar magnetics are open baffle speakers and yes they are dipoles but so are any dynamic driver open to the rear. 

Next, if you think you can adjust the bass response of an open baffle woofer by adjusting the size of the baffle? Lets see, the wavelength of 100 Hz is about 10 feet. Any open baffle speaker of reasonable size is going to have bass cancelation issues regardless of the baffle size. That is just lay intuition. A driver with more surface area will produce more bass not a bigger baffle. So you see what Magnepan does with it's woofer panels. It makes the woofer diaphragms larger, many times the surface area of a 15" dynamic driver. But even with large diaphragms there are serious problems that prevent the production of adequately accurate and powerful bass in a room. Sound Labs has experimented with ESL subwoofers 7 X 7 feet, 49 square feet. Roger West is now working with old 30 inch EV drivers. Now he is a madman. 

Sand infill speakers have been around since the 50's. Warfdale I think was the first. If the final thickness of the enclosure wall is say 2" making a 2" thick MDF enclosure works just as well if not better. The primary resonance of a subwoofer is not the enclosure walls flexing, it is the entire subwoofer shaking. The way to stop this is to simply use opposing drivers in a "balanced force" configuration. The forces cancel out. Kef does this with the Blade, Magico with their big subwoofers. Boxes are easy to make but they make lousy subwoofer enclosures, better than an open baffle but that is about it. The ultimate subwoofer enclosure would be a sphere. Very difficult to build and apply. Next however is a cylinder. Wall stiffness second only to a sphere and easy to apply. Just stick a driver in each end and you have an opposing "balanced force" design in an enclosure that can be way stiffer than any box. No sand required.
I am a big fan of open baffle speakers using dynamic drivers in a 2 way configuration crossing down to an enclosed subwoofer. The open crossover can be made to look like art work. I recent heard a wonderful pair using Accuton drivers in a 1.5" thick quartz baffle board. Very cool looking. Instead of a stand they were hung on chains. What a great idea.

This is the thing I found out with an OB single baffle dipole, they are HARD to get even close. They sound wonderful, there is an immersion of sound, BUT the pole front to rear on the same baffle? THEN bounce off the front wall and it’s time aligned? HOW? It can’t be.

Dipoles on separate baffles the distance from the front wall to the back of the speaker, that is how deep and how far a speaker would have to be from the front wall. I notched the front pole to match the timing of the rear pole. You can’t do it with a common baffle. How the heck does GR do it? LOL.. You can’t! The best you can hope for it to mechanically slow the front pole and position the rear pole so close to the listening position the rear report won’t sound to far out of kelter.. NO WAY it’s gonna measure right.. BUT it sound DEEP and FULL..I could never get the sound stage right. there would be placement but no depth, then depth and no placement..

I tried until I was almost STUPID trying to figure that out with 123s.. They don’t work right.. LOL plane and simple.. Wound up on prozac because of those things..

Yes I have GRs OB servo system.. 3 doubles... Good stuff, BUT I been tinkering with direct coupling bass drivers, no passive crossover.. It actually works better for me and I'm using parts express drivers and a 300.00 Behringer 2496. I have better cone control and overshoot with class d 12k Behringer amps.. Took me a while to figure that one out... Stupid passive crossover in a bass system.. The dampening cannot work.. Short heavy copper. pretty simple.. direct coupled to heavy 12-15" drivers.. BACK it comes to center.. NOT in a forward position. Centered...

I owned quite a few floor standing monkey coffins/box speakers including; Nearfield Pipedream (10K prototypes), Genesis Vs (HPs personal pair), Usher 6371s...


and before all of those, Accoustat 2+2s with upgraded servo amps
and after the monkey coffins, Magnepan 3.5Rs, I found both of these to cut off the visual flow of my awesome multipurpose room.


I replaced the 3.5Rs with Emerald Physics KCIIs, with Clarity Cap upgrades, and wired with WireWorld OCC. Great for a regular size room, but mine is ~35 x 21 x 12. I tried to incorporate my SVS Plus and Ultra cylinder powered subs, but never could get a good seamless blend.

I replaced the KCIIs with EP 3.4s (12" concentric woofer with 1" polyester dome tweeter), which sound seamless down to ~ 40hz and blend much better with the SVS subs, but when I moved them out from ~6ft from the front wall to 7.5ft that freed them to come fully alive. IMO, the 3.4s will more than satisfactorily reproduce 95% of music we all enjoy in a more normal sized room. Quite the bargain if you can find them. There are a couple bigger EPs for sale in the classifieds


My subs are ~ 10 years old, and Im sure SVS sells vastly better subs now, but even theirs are expensive. What to do? Next up for me is EP 2.8s, which uses all carbon fiber drivers; a 12" concentric, plus 2 @ 15" subs per speaker. That should take me over the top

In summation; OBs are capable of life like reproduction at a reasonable price, and cost a lot less to ship

@mijostyn: I expected to see the response in your paragraph number one, but not from you ;-) . Yes of course, planars are technically open baffle (though there have been some ESL’s made in sealed boxes). My statement was made in response to the post in this thread claiming that "Open baffle is basically a version of what Martin Logan has been making for years."

If that’s true (and it’s not---the factory-built OB’s from Spatial Audio and Emerald Physics use dynamic---cone---drivers, as do the DIY kits from GR Research---though some with a magnetic-planar NEO3 tweeter---and Siegfried Linkwitz.), you could make the same claim about planars dating much further back than Martin Logan, all the way back to the QUAD ESL, introduced in 1957. Then the KLH 9 a little later, the Magneplanar Tympani I in the early 70’s, Sound Labs and Acoustat in the 80’s, and numerous others. Why single out the Martin Logans?! Martin Logans claim to fame is the curved ESL (designed by Roger Sanders) and the ESL/dynamic woofer hybrid (or at least popularizing it).

As for baffle size and dipole cancellation, of course that cancellation cannot be completely eliminated by increasing the front-to-back driver distance alone (that’s what Infinite Baffle is for ;-), but you can lower the frequency at which cancellation commences somewhat by doing that. What Siegfried Linkwitz and Danny Richie do is use an H-frame to create the front-to-back driver separation instead of a flat baffle, as the frame provides more resonant-free sound than does a "normal" flat baffle (an un-normal one is the 2-1/4" thick one made by Ric Schultz of EVS, mentioned above) . The depth of the H-frame is limited by the "cavity" resonance inherent in each of the frames enclosed spaces (the deeper the frame, the higher the frequency at which cavity resonance becomes audible). Both Siegfried and Danny limit that depth to around 14".

To further minimize the dipole cancellation inherent in dipoles, both Siegfried and Richie incorporate the 6dB/octave shelving circuit I mentioned above (commencing at around 100Hz, I believe). Siegfried does it in his digital filters, Danny had Brian Ding of Rythmik put it in the A370 plate amp that comes with the OB Sub kit---analog, of course.

The reason full-range planars are so big is for the reason you state---their bass output is restricted by the relatively-limited (compared to dynamic woofers) ability to move air: the thin Mylar film only moves back-and-forth a tiny distance. OB/Dipole dynamic woofers are also less able to move as much air as a sealed or vented sub, so more of them need to be used. The Linkwitz and basic GR Research use a pair of woofers (the former 10", the latter 12"), but GRR also offers a 3-woofer version. Plus, you can make multiple H-frames and stack them. What Danny does at Hi-Fi shows (and in his own listening room) is use OBs at the front of the room, and a pair of sealed subs at the rear. That set-up won GR Research "Best Bass At The Show" award several years running at RMAF (as reported in show reports in TAS and elsewhere).

Clayton Shaw at Spatial Audio and most DIY’ers go a different way: using a pair of 15" drivers on a big flat baffle. When you do that, the midrange driver (if any) and/or tweeter will also be on that baffle. For better or worse: Danny Richie is particularly adamant that it is for the worse (though he holds Clayton and his speakers in high regard).

As with everything in audio, there are trade-offs made in all loudspeaker designs. You have to pick your poison, find the loudspeaker at your price-point which gives you the most of what you are looking for. OB’s are one choice, planars another (ESL, magnetic-planar, or ribbon), horns, and of course normal dynamic (cone and dome). Infinite baffle are REALLY out-of-fashion, though they may come back in when kenjit introduces his version ;-) .