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S

SACD: Super Audio CD. Enhanced audio format with up to six channels of high-resolution audio encoded using DSD. Requires an SACD player. Multichannel also requires a controller with six-channel analog or proprietary digital inputs for full playback.
Sampling Frequency: How often a digital sample is taken of an analog wave. The more samples taken, the more accurate the recording will be. You need to sample at a minimum of twice the highest frequency you want to capture. For example, the 44.1-kilohertz sampling rate of a CD cannot record sounds higher than 22.05 kilohertz.
Scan Lines: The lines drawn by an electron gun in a CRT system to make up the picture. Drawn horizontally, from left to right, starting at the top left and working to the bottom right.
SDTV: Standard Definition Television. Lower resolution subset of the ATSC's DTV system. 480i is typically accepted as an SD signal. Digital broadcasters can offer multiple sub-programs at SDTV quality, as opposed to one or two HD programs. Digital satellite and digital cable often refer to the majority of their programs as SDTV, somewhat erroneously, as neither system has anything to do with DTV, though both, technically, consist of a digital 480i signal.
Sealed: See Acoustic Suspension.
Sensitivity: A measurement (in dB) of the sound-pressure level over a specified frequency range created by a speaker driven by 1 watt (2.83V at 8 ohms) of power with a microphone placed 1 meter away.
Signal-to-Noise Ratio: A comparison of the signal level relative to the noise level. Larger numbers are better.
Soft-Dome Tweeter: A tweeter that uses a soft fabric or plastic dome as the radiating diaphragm.
Soundfield: The total acoustical characteristics of a space, such as ambience; number, timing, and relative level of reflections; ratio of direct to reflected sound; RT-60 time; etc.
Soundstage: The area between two speakers that appears to the listener to be occupied by sonic images. Like a real stage, a soundstage should have width, depth, and height.
Source: A component from which the system's signals originate. DVD player, AM/FM tuners, and VCRs are sources.
Speaker: A component that converts electrical energy into acoustical energy.
Spider: Part of a loudspeaker driver's suspension that helps center the diaphragm and returns it to rest after being moved by an energized voice coil.
SPL: Sound-Pressure Level. Measured in dB.
Subwoofer: A speaker designed to reproduce very low bass frequencies, usually those below about 80 Hz.
Suspension: The elements that hold a loudspeaker driver's moving parts together, allows them to move, and helps return them to rest. Most commonly, these include the flexible surround around the outer rim of the driver and the spider on the underside of the diaphragm. See Spider.
S-VHS: Super VHS. Enhancement to regular VHS that offers improved luminance resolution. (400 lines or so.)
S-Video: See Y/C.