Speaker Time Alignment
For optimum playback, the mastering engineers who create CDs need to anticipate the speaker configuration over which the music will be reproduced. In stereo, that configuration is simple: two identical speakers ideally set an equal distance from the listener. In a multi-channel sound, the ideal is slightly more complex. Multi-channel Super Audio CD is designed to conform to an international standard, called ITU-R. This envisions that the listener sits in the exact center of a circle of five identical speakers, with each speaker occupying a specified position in the circle. (For the Low Frequency Effects or LFE channel, the subwoofer can be flexibly placed outside the circle.)
The ITU-R circle makes a great reference for studio engineers. But few home environments can accommodate exactly this setup. Even if you did have five identical speakers all the way around, the rectangular shape of most rooms would make it difficult to place all five speakers at equal distance from the listening position.
Center
LF
30° 
110°
| Reference |
Left surround | Right surround |
Mastering for Super Audio CD multi-channel sound assumes that speakers will be placed according to the international ITU-R standard.
To resolve the problem, Sony provides a special Digital Signal Processor (DSP) that adjusts the arrival time of each channel with delay in 900- microsecond increments. Because most people can't make the mental leap from microseconds to speaker distance, Sony calibrates the delay as distance, in 30- cm (1-foot) increments. Each 900 microseconds of delay "moves" a speaker back 30 cm (1 foot). In this way, Speaker Time Alignment adjusts the "virtual position" of each speaker, enabling you to synchronize the arrival time of sound for all five speakers. You can even change the perceived distance of the subwoofer in relation to the other speakers. With Speaker Time Alignment, you'll experience multi-channel sound as it was meant to be heard. You'll get the effect of correct speaker placement, even if your actual placement is far less than correct!
ES DVD Players 2005, Version 4.0 | Page 29 |
