The IRX115S is an active subwoofer built around a 15-inch woofer with a 3-inch voice coil. Its frequency response runs from 35 Hz to 147 Hz (-10 dB), with a maximum SPL of 128 dB and a power rating of 1,300 W. A ported, tuned enclosure raises output and reduces woofer noise, and a high-efficiency amplifier helps protect the drivers.

System tuning is done with a few controls: selectable crossover points at 80 Hz, 100 Hz and 120 Hz, chosen to suit JBL IRX Series loudspeakers, plus a polarity switch to optimise the response in the room. The cabinet is made of MDF with a reinforced honeycomb bevel pattern and a reinforced grille. It weighs 65.3 lb and has ergonomic handles for transport.

Connections are two XLR/TRS combo inputs and two XLR outputs. A built-in standard pole mount lets it carry an IRX108BT, IRX112BT or other loudspeaker on top. Bluetooth streaming, dbx feedback suppression, ducking and EQ presets are available when it is paired with IRX Series powered loudspeakers.