Here’s what Yamaha say:
The subwoofer, together with the midrange right and left satellite speakers, can reproduce a wide range of sounds, including everything from the resounding lows of the bass drum to the highs of the cymbals. Combined with stereo positioning, this generates a highly-realistic sound experience like that of acoustic drums. The MS45DR allows you to enjoy superb sound quality without an isolated feeling of headphones, providing open acoustic drum impression that you can share with family and friends.
The 20 W satellite speakers come equipped with 2 cm dome-shaped tweeters and 8 cm midrange speaker units, reproducing high-quality mid- to high-range sounds.
The satellite speakers can be mounted on electronic drum racks compatible with the 1.5-inch diameter pipes commonly incorporated into racks for electronic drum kits. Clamps have been added to the arms on the bottom, allowing for angle adjustment of the speakers. The 16 cm cone-shaped 20 W subwoofer speaker units reproduce accurate, low-range sounds of the bass drum and floor tom, delivering a powerful sound and feel that is perfect for realistic-sounding performances. In addition to a master volume that allows you to adjust the overall volume, a bass volume control on the subwoofer allows you to adjust the volume of the subwoofer alone, with simple controls that let you shape the sound. Included cables easily connect the MS45DR to electronic drum trigger modules. This simple system does not require complicated wiring, allowing you to complete a electronic drum monitor environment by attaching one cable each to the trigger modules, subwoofers, amplifier units, and satellite speakers.