Using The Reverb Program | Lexicon, Inc. |
Sound in Space: A Short History of Stereo and Surround, Continued
affordable
In the early 1990s Dolby Digital, DTS, and MPEG surround arrived. These systems provided discrete digital signals for each channel and a separate Low- Frequency Effects (LFE) that provided very low frequency sound effects. Squeezing 5.1 discrete digital channels into a recording involved some data reduction, but the reduction schemes used psychoacoustical principles to make the resulting artifacts less audible. Dolby Digital soundtracks were the first to make the transition from movie theaters to the home, via laser disc. With the advent of DVD, whose popularity rapidly eclipsed laser discs, Dolby Digital and DTS tracks became more widely available for home theater.
The discrete digital technologies require specialized hardware for playback, and the original source material cannot be recorded on home tape recorders, VCRs, or broadcast over conventional broadcast equipment. More importantly more and more consumers were installing surround sound systems in their homes, and there was a great need for a technology that would allow standard two channel recordings to be reproduced in a surround system. Not with Dolby Pro Logic, which narrowed the front image and provides a monaural surround signal, but with a system that offered a wide front image over a large listening area, and the listener envelopment present in the original recording location.
To solve both problems Lexicon developed LOGIC7 matrix technology, which provides a method for releasing surround recordings on standard stereo compatible CDs. More importantly, LOGIC7 and LexiconLogic provide a method of playing the millions of standard two channel music recordings with all the advantages of discrete surround.
LOGIC7 also allows Dolby surround films to be played with a wide frontal image and full rear envelopment. LOGIC7 encoded recordings can be broadcast or played on any currently available reproduction equipment, and yet they provide full five channel surround on a device with a LOGIC7 decoder, and decent four channel surround when played with Dolby Pro Logic. LOGIC7 uses matrix technology to compress the spatial aspects of a recording so it can be delivered on a two channel format. There is no data
reduction of the sound waveforms themselves, so the sound quality can be very high.
Competing with LOGIC7 and the current
Algorithms
Random Hall
Random Hall is a hall effect with gradual
The early reflections are user adjustable in amplitude and delay. Some skill is needed to set useful reflection patterns. Since the reflections are adjustable, they are not randomized. Once set, the reflection pattern is fixed. The pattern can be expanded or contracted in time using the "Delay Master" control, and the overall level of the pattern can be set with the "Early Level" control.
The most important user parameters for Random Hall are the level controls – the "Early Level" and "Reverb Level". Early Level is a master control for all the early reflections. Lowering the control to zero eliminates the reflections, and their associated sense of distance from the sound source. The "Reverb Level" control is a master control for the late reverberation. With this control you can set the exact amount of reverberance and envelopment.
The apparent size of the space supplied by the late reverberation is set with the Shape, Spread, and Size controls. Of these controls the Shape and Spread are the most natural. As Shape is raised from zero to about 30% the onset of the late reverberation goes from abrupt to gradual. The effect on the apparent size of the space is quite dramatic. Spread has little or no effect until Shape is at about a quarter of its range, at which point Spread affects the length of both the buildup and sustain. At this point, the sustain will be approximately the time value indicated by the Spread display, in milliseconds. At still higher settings of Shape, a secondary sustain appears in the envelope at a lower