In the lows much of what you hear is room related. To improve transient response and make a better bass presentation, removing room interaction a big part of it. Geddes gets room averaging below 100Hz by using multiple subwoofer locations, and this solution works quite well, as you average not only the frequency response, but the associated resonance times. For instance, the corner location might excite a mode with a long delay time, but if that sub is only one of many, and the others don't excite it, then only a small portion of that frequency is contribution from the modal response.
Horns also work, by ensuring that you get the wavefront before the rest of the room does, and limits the excitation energy applied into the room for a given on-axis SPL, but in the bass, this means very large devices indeed, and all the associated complexity and cost.
Which leaves us one more option, the open baffle. This would be a very good choice, but most JBL woofers are not suited to it. JBL likes strong motors, which means low Qts, and accordingly, a lot of damping at Fs. The older 2213/123A woofers work exceedingly well for OB, as they have both a low Fs and a high(ish) Qts. There's an abundance of information on the use of OBs at various resources online. Here's a project using that woofer OB.
http://www.enjoythemusic.com/diy/031...pen_baffle.htm