Rumble is the second hardware expansion module for the OP-Z. It's a built-in haptic sub-woofer, using high-definition vibro-tactile feedback and psycho-acoustic technology, allowing you to feel your music. When using rumble you will feel like you're holding and listening to a deep sounding sub-woofer. The frequency response 10–150hz is designed to maximise impact while minimising additional energy consumption. It also features a silent metronome mode, great when performing live to always know exactly where the beat is.