Cardiod bass-horn, designed to extend the frequency range of the PalcoPlus system down to 30 Hz. This innovative sub-bass unit offers a distinctive, dual-transducer configuration using one 18'' woofer in a ported reflex configuration, and a second, 15'' woofer loaded by a folded horn.

The precise interaction of these two transducers permits the RAB1815 to radiate in a cardioid pattern from a single enclosure, with 15 dB attenuation at 180° from 40 Hz to 100 Hz, allowing much more bass reinforcement to be used for the public, even very close to the stage. Aside from creating a unidirectional polar characteristic, this design also provides the benefits of both bass reflex and folded horn systems: very deep bass, but with rapid response. The design also puts the actual cone movement of the two speakers in opposition on the same axis of the enclosure, assuring that the sub will not move.

The two transducers are purpose-built for the RAB1815. They are constructed with neodymium magnets and 4'' voice coils, and can boast an excursion of ±23 mm. Both woofers can handle up to 1600 W of continuous power, and the entire system is capable of delivering 136 dB SPL.

The cabinet is made of 18-21 mm birch plywood with chip-resistant paint. The RAB1815 weighs less than 60 kg, and is built to act as a base for stacked arrays of RA16 enclosures.

A single Neutrik 8-pole Speakon® connector provides simple and intuitive connection to the powered controller PLM6800 or to any other power amplifier, and helps to avoid mistaken connection to channels destined to the satellites during cabling.

A single PLM6800 can drive two RAB1815 units, otherwise each RAB1815 can be driven by a two channel amplifier with a rated output of at least 1600 watts per channel at 4 ohms.