Evans EQ Bass Drum System. Diverse, versatile, innovative, flexible; your sound can be all of these things with the Evans EQ bass drum system. As a player, you understand how your sound has to contour to the style of music you're playing. The EQ bass drum system is your avenue to the many different tones and sounds you need. And what's more, with the use of the EQ bass drum system, your capability to fit every situation makes your abilities as a player all the greater.