Zapco introduced the industry to great sounding Class D amplifiers some 10 years ago with the famous 9.0XD. In those days, the filtering and control systems needed to make Zapco sound quality in a Class D amplifier meant it had to be expensive and it had to be big.Today's technology, however, has allowed us to develop a line of great sounding full range Class D amps at an affordable price range and in a size that's an easy fit in today's smaller cars. Small car doesn't have to mean small sound, and you won't have to give up the back seat for an amplifier. And even motorcycles. In fact, at only 6.3" x 6.7", the ST2D is the ideal amplifier for a motorcycle faring. Small size, big power. And talk about POWER! This tiny little monster is going to give you 400watts RMS. With that kind of power in your faring, you're going to need louder pipes, and, since these little power houses are Zapco amps, you know they're going to sound great.Just like with the Z-Series and the ZX-Series, we kept the ST-D series simple. The feature set is kept to the essentials. They all have 18dB crossovers, speaker level inputs, and optional remote level controls, but, they don't have chrome or fancy paint jobs, and they don't look like hot rod engines or computers. They look like car audio amplifiers. We put our efforts (and your money) into great sound and reliable power.Even though they're Class D they have less than 0.05% THD+noise and 90dB signal to noise ratio. After all, loud is no good unless it sounds great as well. And these new amplifiers sound awesome. Audition one today and you'll know what we mean.Even though the 2ch, 4ch, and 5ch powerhouses have way more punch than you'd expect from such a diminutive chassis, we know you're going to want dedicated bass amps as well. And the ST-D series has 'em! You can choose 500 watts at 1 ohm or 1,000 watts at 1 ohm, and even the 1,000 watt amp is less than 10" long.Max RMS Power 500 Watts @ < 0.2%THD 1 Channel Low range class DPower @ 1Ω: 1 x 500 wattsRMS Rated Power @ < 0.2%THDPower @ 1Ω: 1 x 500 wattsPower @ 2Ω: 1 x 310 wattsPower @ 4Ω: 1 x 160 wattsMore about Zapco Power-Class-D 12V amplifier-Single channel 12V bass amplifier-Stable from 4 ohms to 1 ohm load-PWM MOSFET power supply-18dB octave crossover slope-80Hz sub crossover-30Hz Sub sonic filter-RCA Signal input and output connectors-4-way protection circuitry-thermal / over current / speaker short / DC-Tested voltage & THD: 14.4V & less than 0.2%-Dimensions in Inches : 6.7(W) x 2.2(H) x 7.5(L)The ST-500DM has 160w RMS @ 4 ohms, 310w RMS @ 2 ohms and 500w RMS @1 ohm. It has a 30Hz sub sonic filter and an 80Hz 18dB/octave Electronic Crossover.