[JohninCR]

I'm very happy with the Warrior 15's that I picked up for $20 ea.  My only complaint is
that 2 of the 6 required a little tweaking with a razor knife where they got a little sloppy
with glue.  I plan to dope the cones heavily to bring down the Fs and really stiffen them
up, but they're quite extended and I won't use them anywhere near the upper range limit.

Just to clarify something that TMinus attributed to me, I believe pro type woofers are an
excellent choice for OB bass because they are designed to exceed Xmax without problem.
You have to be more careful with subwoofer type drivers because typically their Xmax and
mechanical limit are closer to equal, so banging noises and potential driver damage are
more likely when driven near their performance limit.  Pro drivers are designed for abuse.
In addition the much greater Xmech than Xmax gives usually gives you some usable
excursion beyond Xmax.  Sure there's probably some extra distortion, but it's better than
the ugly banging noise of hitting the back plate.

[tminus]

That's 0.25 inches or 6mm.  My concern is whether or not that is point-to-point,
since 3mm is typical of that size and efficiency pro-woofer.  Xmech is a concern for
anyone going for high dynamics, so the occasional very deep and strong note doesn't
damage the driver or cause that nasty banging sound.

John did say Xmech is a concern of his, not Xmax, like I eroneously misquoted him as saying.  My bad.  I do stand by my statement, however.  OB is an inefficient architechure for making deep bass.  Not that it can't be done.  I am not making that argument.  The LF driver must often times work twice as hard as it otherwise would to make the same SPL mounted in an architechure that stores some energy i.e. some kind of box.  The danger of over-excursion increases, the lower the frequencies.  Duh! You might be thinking.  But my point is that it is true to another order of magnitude, per se, when the driver is operating in OB.

That's all my point is for hum4god.  If I were looking for a driver to make deep bass on OB, I would look for high excursion, big cone drivers preferably with a higher Qts.  One way to overcome the 6db loss in the lower frequencies before eq is added would be to choose an underdamped high excursion driver mated to a current amp or an amp and cables that, together, act to sufficiently damp the driver. 

"Even though a dipole requires a 6 dB/oct boost towards low frequencies, it takes little power to drive it to maximum excursion at its lowest bass frequencies. Amplifier power could be an issue as frequency increases, where it requires higher cone acceleration to reach Xmax. Thus SPL is limited by driver volume displacement at the very lowest frequencies and becomes amplifier limited as frequency increases."

"Realistic bass levels can be obtained from dynamic drivers in open baffles, not from panels. For extreme SPL requirements the number of drivers could get very large and, therefore, below 50 Hz they are more economically replaced by sealed box subwoofers."

                                                                                                         Linkwitz

Another way (to get deeper OB bass) is to put 4 woofers with a Silver Iris on an 8' baffle.  There's lots of good choices.  Even not precluding using box subs.  But if you're sold on deep OB bass, I think the argument for using high excursion high eff low damped drivers below 30-50hz on open baffles can sove issues before eq is needed, and add to sensitivity and economy (possibly fewer drivers, amplification, eq, cabling, ect).

Happy New year,

Patrick