Open baffle speakers

In application, very impressive.

They would be a perfect project for me. I never finish anything. 

Open baffle speakers have many virtues, very deep bass is NOT one of them because the front and back waves of the drivers are out of phase and bass frequencies wrap around the speaker and cancel each other.  One could use subwoofers or box woofers for the lower frequencies, but, depending on your taste and priorities, the bass without such augmentation can be good enough.  I've heard PureAudio Project open baffle speakers that, for my taste, have enough bass without augmentation.  The "small" version has twin 15" woofers, and the taller version has four 15" woofers.  I consider this brand's speakers to be among the very best for the money.  

I've heard some other open baffle speakers with quite large baffles and some with sides that go backwards to effectively extend the path length for front-back  interaction, but these tricks only reduce cancellation.  

They became popular because, if well designed, they sound phenomenal. Yeah, you'll probably want a sub, but in all honesty, you'd probably want a sub no matter what type of speakers you run.

+1 @coralkong I’ve heard Spatial speakers on several occasions and they never sounded bass shy even without subs — on the contrary the bass sounded excellent. 100% agree almost all box speakers benefit greatly from a couple subs as well so that’s not a deterrent to owning an open-baffle speaker in my book. As always there are trade offs either way, but when you can get that level of sound/openness/efficiency without the considerable expense and additional weight of an having to build/ship a heavy, inert box it’s not hard to see why open-baffle designs offer some significant advantages. I could live very happily with what I’ve heard from these designs and may well own some in the future.