Amtec am731 3.1CH Comes with interesting features such as USB port and SD memory card slot, Bluetooth connectivity and also FM radio. Bluetooth Wireless Connection This technology allows you to connect the subwoofer to other devices without wires. So you can play your music collection and also amplifier other devices without cable connection. FM Radio In addition to listening to your saved tracks, you can also tune in to a radio channel and catch up with news or a radio show. The radio supports all the FM radio stations in your region. Adjustable Bass Levels The subwoofer offers a wide range of bass levels which you can easily adjust with a button on the control panel. You can also adjust it with a remote control which makes the whole task more convenient. USB Port and SD Memory Card Slot These features allow you to use connectivity devices on your subwoofer. The USB port allows you to use a flask disk and also USB cable and connect to other devices. On the other hand, the card slot allows you to use a memory card and play your stored music.