full range open baffle

There are a ton of 3". I've been working with the fountek fr88ex lately. Not open baffle though. Sounds reasonable for a 3" full ranger. Depending on your budget, I've heard to CSS EL70 in a bass reflex and it was great. Lots of bass which may come in handy being an OB. 4" though and about $100 a pair. Tang band has lots of selection. I have a pair of 3" prototype tang bands. Serial numbers 1 and 2. So I can't tell you the model. But the were not quite as good as the fountek. Had a slightly rising measured response compared to the fountek. That's typical of tang band I believe. Very cheap though. They can run as low as $20 a pair. I'd sell my protos for that much.

If you have $100 to spend, the el70 or chr70 would be best as they have a beefy bottom to counter baffle step and OB.

That's not physically possible. Good sounding open baffle speakers take at least a couple drivers and baffle widths, equalization, and ample displacement (which you don't get from full-range drivers, especially small ones. 22cm and 5mm Xmax is a good start to reach a conventional sub-woofer).

I say that having heard a variety of open baffle setups (and built Linkwitz Orions) including a $40,000 pair of Feastrex field-coil drivers with and without woofers on Nelson Pass's big baffles (Nelson is a super cool guy and analog whiz but that's not enough to crutch a flawed concept into acceptable sound).

Your problem is that dipoles roll off at 6dB/octave with output matching a monopole at .17 * v / D with v the speed of sound (1130 feet/second) and D the path length difference between both sides of the driver to listener which is baffle width on a flat baffle. At .5 v/ D the reverse polarity rear wave (from the acoustically small drivers) is delayed a full 180 degrees producing a 6dB peak and beyond that you end up with a multi-lobed polar mess approaching the null at .75 v / D and beyond until driver directivity precludes an acoustic dipole response.

Baffle widths need to be small to avoid the polar response problem and you need multiple widths with multiple drivers and/or equalization to get the bass.

That's not possible.

If you want to play with full-range drivers, the small Fostex drivers work great in tall thin back-loaded horn enclosures. Output levels are severely limited from the low displacement but they sound natural and have some bass.

If you want open baffles accept that it will take equalization and 2-3 drivers until you can use a sub-woofer for the bass.

Definitely a good idea to re-think that. Listening nearfield like you plan would have helped, but it would have still been an issue. The full range forum on www.diyaudio.com has a lot of good designs like you describe.

I have similar speakers to the ones Drew described (Linkwitz Orion) and agree with everything he says.

However, I just built a much simpler two way OB for the bedroom using an 8 inch mid and tweeter. Because I don't listen loud in bed, the 8 inch has enough xmax for me to run it all the way down to 50Hz.

But it does need EQ as described.

Consider a back-loaded horn unless you're limited to computer-speaker sized micro cabinets. That gets you SPL from minimal driver excursion over much wider band-width than a ported enclosure which is pretty important given how little full-range drivers give you to work with (under 1mm; I'd guess a longer voice coil is too inductive and would roll-off the high frequencies).

^ Mark audio FRers have around 4mm xmax.