Great big bottom.
JBL's idea with the STX800 Series was to offer the professional touring musician or the enthusiastic hobbyist with a commitment to great sound an alternative to light-duty portable PA speakers without making the commitment to full-size line array tour sound systems. JBL's promotional literature for this series states its place in the market beautifully: "Our goals at the inception of this project were simple: Offer a high performance, high density system solution in a truck-pack friendly format. Develop concert-worthy floor monitors and side fills that could affordably complement any touring sound system. Deliver an affordable, great sounding subwoofer that could reproduce true low frequency at elevated sound pressure levels." The JBL STX828S Dual 18" Bass Reflex Subwoofer is the ultimate low end manifestation of this design concept.
A dual 18" high power subwoofer system in a front-loaded, vented enclosure designed for maximum low-frequency performance. The STX828 has an optional wheel kit. Two drivers give 2,000 watts of continuous pink noise power handling, 4kW program and 8 kW peak.