Open Baffle loudspeakers.

There are numerous production speakers that use little or no baffle. Here is a partial list:
Vandersteen 1C, 2Ce, 3a
Most electrostatics
Most magnetic ribbon speakers
MBL Radialstradters
Walsh models from Ohm, HHR, Decware, & Audio Physics

...and many more.

I have heard and/or owned a handful of the speakers listed above, and I have always preferred the sound of baffle-less speakers to other designs, especially in the lower price categories. When the budget is bigger, more inert cabinets that pricier speakers have can narrow the gap between baffle and baffle-less speakers considerably, IMHO.

The problem with open baffle speakers is the bass. The rear energy can wrap around and null the front energy. To overcome this, you need either wide baffles or U or H frames. Still, many OB speakers use 12 or 15", high Q drivers. Too high and they get sloppy. (ie. Carver Amazings)

Seems to be more popular among the DIY'ers and kit builders (GR Research) than commercially, not just because a decent box can be a PITA to build. The size and placement (at least 3' from back wall) are factors. Part of the reason for OB resurgence is the availability of subwoofers. Personally, I wouldn't tackle an OB project without DSP because what works for 50Hz might not work for 200Hz.

A popular choice of driver, including coax, is Eminence (particularly Alphas) but AE Speakers' dipole series look good.

As with any kind of dipole, what you lose in vocal "focus" you gain elsewhere.

There is a speaker designer in eastern Iowa that is designing some open-baffle speakers that sound promising while being inexpensive. He is talking about having it in kit form and also in finished trim. The guy's name is Jack Caldwell and he has a company named Holistic Audio Arts. Do a search on the name and it will pull up his info.
Best of luck.

The trick to OB's as Ngjockey said is DSP!!

I started out with a set of stock Hawthorne's...really good...kinda felt like I had my Maggies back but without that super small sweet spot!!

Then I bi-amped them with a Behringer DCX2496 and added subs...improved greatly!!

Next step...removed the Behringer for a DEQX...best move I have ever made in my audio swapping days...that thing is amazing...I'll never be without one!!! So simple with such great results, I just don't understand why people aren't eating them up!!

You can take a good speaker and make it really good or a really good speaker and make it great!!!

And mine are mounted on a 18" x 28" board 2' from the back wall with a slight tilt up...love it!! You don't have to be fancy but you now have the option to if you want...

Anyhoo...I betcha heard this before...once you go to an OB, you'll never go back to a box!! You'll always hear a box!!

My 2 cents :)

Nola speakers are open baffle in the mids and highs with a sealed box on the woofer only. Great sounding speakers!