M-Series 7.7-inch Marine Tower Coaxial System for Enclosed Use (100 W, 4 Ω) - Titanium Classic Grille. Purpose-engineered and built for real marine duty, M-Series coaxial systems deliver maximum audio performance in any open-air boating environment. The oversized 7.7-inch design of the M770-TCX coaxial results in increased efficiency (more output for a given amount of power). Combine that advantage with long excursion and excellent power handling and you have a speaker system truly capable of playing loud and clear in a powerboat at speed. The M770-TCX coaxial is optimized to operate in a small sealed enclosure, such as a tower speaker system.