Deep, throaty sounds require a largish speaker; 4" is the smallest practical size; a 5" to 6" one is even better (a Woofer is the best). If you have the space in your boat, this will do the business! 6 to 12 Volt supply; 1 Watt output capability; fully adjustable tone. Case size 53.5mm x 37.5mm x 23mm.