Open Baffle. Why are they mostly limited to DIY?

@gnjtack. you are SO right about the OB sub and dipole speaker pairing being a great one. There are a number of us Maggie/Eminent Technology/Quad speaker owners using a pair of the GR Research/Rythmik OB/Dipole Servo-Feedback Subs with them. But as you said, it is a DIY product, the woofers and dedicated servo amp available as a kit only. However, there are a few woodworkers making flat pack OB frames to install the parts in, the flat packs pretty easily assembled.

Linkwitz Lab offers it's own OB/Dipole sub as part of complete OB speakers systems, but again as a kit only. The top model is tri-amped, the consumer required to provide three stereo amps (or six mono), including the one for the woofers. That can get expensive!

seanheis1, an open baffle sub, or even woofer, has advantages and disadvantages in comparison to boxed ones, whether sealed, ported, or infinite baffle. No enclosure resonances (though even the baffle, if insufficiently engineered, can itself be resonant), no room loading in the side-to-side plane (due to the figure-of-8 radiation characteristics of all dipoles, even at low frequencies), both making possible less boomy sound. But the stopping and starting characteristics of the woofer driver is a determining factor as well.

The disadvantages include the less-maximum-output-capability of OB designs. Once again, the intrinsic capabilities of the driver is a prime determiner in the quality of the sub or woofer.

Now, imagine taking the intrinsic advantages of the OB woofer, and combining that with the benefits of servo-feedback, long used in some very high quality woofer systems (including the bass columns of the Infinity IRS and RS-1b loudspeakers, as well as the well known subs of Velodyne). Such was the thinking of Danny Richie of GR Research, who specializes in OB speaker design, when he learned of the new servo-feedback system by fellow Texas resident Brian Ding, designer and owner of Rythmik Audio. The two put their two big heads together, and the result is their State-Of-The-Art OB/Dipole Servo-Feedback Subwoofer, the only such design in the world, co-marketed by both companies.

To your point, seanheis1, OB's are thought of only in terms of having all cone-type drivers, but some of the best actually use at least one ribbon, magnetic-planar, or similar type driver, usually a tweeter of course, in combination with a cone woofer. And many OB enthusiasts are also planar fans, some having a pair of those as well as OB's. I mean, planars are just OB's with non-cone drivers!

And snapsc, you're exactly right, OB ownership places the same demands upon one as do planars---3 to 5 feet minimum from the wall behind them.

One incorrect thing said above is that OB's require a lot of power. Actually, one thing OB users like is the design's generally high sensitivity. Many owners pair them with low-power single-ended amps. One exception is the Linkwitz OB's, which require not a lot of power over-all, but a separate power amp for each driver. A fairly complicated x/o is a big part of his designs.