(1) The ability to localize the individual instruments, voices, or other sound sources when listening to a stereophonic recording is called imaging. Accurate imaging with two channels is almost impossible, requiring both channels to have identical gain and frequency response, the two loudspeakers to be within 1dB of each other in frequency response and the phase must be identical. In addition, the listener must be precisely between the two speakers. The lack of accurate imaging with traditional, two-channel stereo has lead to three-channel (LCR) and higher-channel audio recording and reproduction in an attempt to improve the listening experience. Contrast with stereo spread.
(2) The resulting output of a D/A converter is a stair-step waveform that contains a great deal of high-frequency distortion. To reconstruct a smooth replica of the original signal, the stair-step is passed through a steep lowpass filter called an anti-imaging, or reconstruction filter.
See quantization error.