Diy Subwoofer Kit: Build Super Subwoofer Room Under $500?!
Amazon.com: Arylic Subwoofer Amplifier Board,WiFi & Bluetooth Home Audio Amplifier Board for DIY Speaker Kit.Wireless Connection Multiroom/multizone Sync Play for Airplay DLNA - Up2stream Amp Sub : Electronics
How to Design Your Own DIY Subwoofer - TurboFuture