Jam Bookshelf Bluetooth Speakers (Black)Overview Enhance your sound system with the JAM Bookshelf Speakers. Designed to deliver bold quality sound from the 4 inch bass drivers, 0. 75 inch tweeters and rear bass port. The robust cabinet design reduces distortion and delivers a clear, rich audio experience. These are active speakers, so are great to go straight out of the box. Wherever you listen to your music, the kitchen, your bedroom or living room, these mains powered Bookshelf Speakers