The very compact (1 foot sq) PSB Speakers SubSeries HD10 has the performance of a much larger subwoofer and is perfect for people who want performance but do not want to give up a large area of their room to do it. To overpower the laws of physics the HD10 uses Dual Opposing Heavy Passive Radiators to “fool” the HD10 cabinet into behaving as a much larger enclosure with much larger, longer ports. The results of this design should be obvious to all: Deep, powerful, high impact reproduction of even the most challenging soundtracks and musical performances from a subwoofer less than a fourth the size of conventional solutions of equal ability.