The M421 sets a new standard for low distortion, high impact bass reproduction. The M421 has a continuous power handling in excess of 12,000 W and measured peak output of 143 dBSPL at 4 m ground-plane, within its operating band. With a well-shaped response from 20 to 100Hz and a total weight under 500 lbs, the M421 delivers an unprecedented level of low frequency energy for its size. The revolutionary design features four, independently powered, 21 in. long excursion neodymium motor transducers. Specially designed 6.0 in. voice coils exhibit near linear force factor (Bl) through the entire range of cone motion. The drivers are configured in an isobaric assembly and coupled to an FEA optimized acoustic transformer. With integrated handles, casters, skids, travel dolly, and optional fly ware, the M421 is the most versatile and powerful sound reinforcement subwoofer to date.

The enclosure is constructed of multi-ply void-free birch hardwood plywood and is coated with a weather and wear resistant ProCoat™ polyurethane hybrid finish. Components in the front of the enclosure are protected by a flat grill made from perforated 11 gauge steel that is coated with heat cured epoxy powder. All rigging and hardware is weather protected with a heat cured epoxy powder coat finish.