Bob Carver has always been a speaker designer who thinks outside the box, and also one who tends to ignore so-called experts when they tell him something can’t be done. As the founder of Phase Linear in the 1970s, Carver in the 1980s, and, more recently, Sunfire, Bob has been proving “experts” wrong for over 40 years. A great example of his unconventional thinking is the Sunfire True Subwoofer, first launched some 15 years ago. Using a brute force approach, this design bent the rules that traditionally defined how much bass you could get from a given size of driver and enclosure, in the process creating what has gone on to become one of the most imitated subwoofers of all time. Now that same mindset has been applied to creating the Dynamic Series SDS-12 — a lower-cost brother for the True Subwoofer, with an asking price 75% less than the original. To deliver loud and deep bass with a small sub, you need an extra-rugged driver that can stand up to huge excursions (the amount that it moves in and out) that get measured in inches, rather than a few millimeters. The cabinet also needs to be built like a tank, as big driver excursions mean that the enclosure will be pummeled by pogo stick-like shifts in internal air pressure. The catch is that it’s really expensive to build such a robust and powerful sub. So for the Dynamic Series subs, the challenge was to figure out how to keep costs down without too drastically diluting the original True Subwoofer’s winning formula. Step one was to make the sub a little bigger. It might seem counterintuitive that a bigger sub can be cheaper, but even a small increase in internal volume significantly reduces the pressure variations inside the box. The upshot here is that, instead of needing a cabinet and driver with Abrams tank-level build quality, you can squeak by with something closer to Humvee-like toughness. The demands on the amp are also reduced, so rather than needing the True Subwoofer’s 2,700 watt amp, you can get by with one that cranks out a mere 300 watts (600 watts peak). Step two in Sunfire’s cost-trimming exercise was to add a downward-firing 12-inch passive radiator. This further eased the internal pressure, reducing stress on the active driver and amplifier while increasing output. These two changes combined translated into a cabinet that’s roughly two to three inches bigger all around than the True Subwoofer EQ12. That might not sound like much of a size difference, but with cabinet walls that are noticeably thinner, the internal volume of the SDS-12 is actually substantially greater.