SVS unveiled the SB-4000, PB-4000, and PC-4000 4000 series subwoofers back in November. These reference quality subs replace their popular 13-Ultra series, with a level of change which is quite dramatic from the previous generation. Alterations were made to the cabinet and 13.5? driver, but the electronics received the most benefit with the introduction of a 50MHz Analog Devices Audio DSP with 56-bit filtering, discrete MOSFETs, and 1200 watt ?Sledge STA-1200D? amplifier. Each of the models offer a different implementation of these fundamental elements with a sealed (SB), ported (PB), and ported cylinder (PC) option available. Which one you choose will depend on preference, and available space ? these subwoofers are massive. Sealed subs tend to have a cleaner and more balanced sound than their ported counterparts, which provide a throatier BOOM. Coupled with a smaller footprint, this often makes them a better choice for most mixed use environments. So when offered the chance to review one of the new units, I opted for the SB-4000.