ALPINE SPS-M600 - 16,5 cm 2-way coaxial speaker. Great Sound on the Waves ! SPS-M600 – the Audiophile Experience on the Waves There is no substitute for a premium marine ready speaker in a wet environment! Alpine SPS-M600 16,5 cm 2-way coaxial speakers are specifically designed to add the ultimate listening pleasure to every maritime cruise. Designed for high power handling, these speakers are ready to embark on an expedition into great sound.