SDP1

About the SDP1

The Audio Research SDP1, introduced in the mid to late 1990s, is a solid-state surround processor that synthesizes rear and center surround channels from stereo sources to create a five-channel matrix from two-channel stereo. It preserves the purity of the front left and right channels by providing a hard-wired, straight-through path without volume control, ensuring no signal degradation. The SDP1 uses matrix derivations inspired by the Hafler surround method, adding rear channel delay and a center channel output to create ambient surround sound without discrete surround channel separation. It features level controls for left-rear, right-rear, and center channels, and five delay settings ranging from 25 to 45 milliseconds to optimize spatial effects. The processor is designed for use with full-range speakers and does not include built-in crossover networks for satellite/subwoofer systems. Its frequency response extends from 2Hz to 400kHz with distortion less than 0.01% at 2V RMS output, and it consumes 40 watts of power. Dimensions are 19" W by 11¾" D by 3½" H, weighing 11.5 lbs. The SDP1 is aimed at audiophiles seeking enhanced spatial sound without compromising the main stereo signal integrity.