Music/Recordings

[1] Home Theater & Stereo Channel Identification (DDD) 2:05
Left (Index 1), Right (Index 2), Center (Index 3), Subwoofer (Index 4), Surround (Index 5) channels, featuring almost the entire staff of Stereophile and Schwann Opus/Spectrum

Each stereo announcement is followed by 20 seconds of mono pink noise positioned in the appropriate playback channel. For those who like absolute accuracy, the sound-pressure level (spl) of the voices at the original session peaked at 100dB. The pink-noise level, however, should be around 85dB at the listening seat.

What you should hear: The pink noise should appear to come from the appropriate loudspeaker(s). It should sound like absolutely smooth rushing water with no band of frequencies sticking out more than any other. It should also not sound hollow or colored in any way. Neither its level nor its tonal character should noticeably change from speaker to speaker, though a Home Theater system's surround speakers will almost always sound quite different from the front ones. If the noise additionally comes from speakers other than the one mentioned in the announcement, then there is excessive crosstalk in your stereo system, or your Dolby Pro Logic decoder is operating improperly. Listen especially for a lurch in the image position at the start of each noise burst. Some decoders can take a noticeable time to assign the signal to the correct position. The levels of your Home Theater loudspeakers should be adjusted so that the noise signals give the same spls at the listening position. (Radio Shack sells a good a sound-pressure-level meter for around $30.)

[2] Stereo Channel Phasing (DDD) 0:34
In-phase (Index 1), then out-of-phase (Index 2), featuring almost the entire staff of Stereophile and Schwann Opus/Spectrum

Again, the stereo announcements are followed by pink noise, with the absolute levels as mentioned above.

What you should hear: In a conventional stereo system, a centrally placed listener should hear the image of the in-phase noise occupying a very narrow space centered between the loudspeakers. If the sound "splashes" to the sides at some frequencies, or the image is broadened at all frequencies, then there is something suspect in your system—most probably a loudspeaker or room-acoustic problem.

"This is the wrong channel!" Clockwise from top left: Molly Crenshaw, Tamra Fenstermaker, Gayle McGuinness, Sandra Solomon, Mary Olivera, Kathryn Golden, Laura Atkinson, Harry Atkinson, Thomas J. Norton, Steve Stoner, Richard Lehnert, Nancy Fay, and Maura Rieland rehearse their lines.

The image of the out-of-phase noise should not be centered; in fact, it should generally be very hard for you to point to where it's coming from. With some loudspeakers, however, the out-of-phase noise might appear to come from a point to the outside edge of either the left or right loudspeaker. If you don't hear these clear distinctions between in- and out-of-phase noise, or if you hear them reversed, try inverting the connection to one of your speakers.