SVS PB13-Ultra &ndash; 13.5-inch, 1000 Watt DSP Controlled, Ported Box Subwoofer with Variable Tuning (Black Oak) ...the PB13 will challenge you to find a single weakness... It reached the deepest notes with ease, and was very crisp and clear the whole time, without getting muddy or boomy. Did I mention it was smooth? It was oh so smooth.  Home Theater Shack Monstrous impact, yet delicate musical detailthe pinnacle of SVS technology and audio passion. Exclusive 13 Ultra Driver with unrelenting output delivering brutal output and subtle nuance. Sledge STA-1000D amplifier packing 1,000 watts of power (3600 watts peak dynamic power). Efficient, cool-running Class D power with 'green' standby mode. DSP controls and variable tuning with tuning with 20Hz, 16Hz and sealed settings to match any room. Ported box subwoofer.