Yamaha DSP-AX2 EN - Manual (Page 55)

English
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Digital Sound Field Processing (DSP)
Understanding Sound Fields
A sound field is defined as the “characteristic sound reflections of a particular space.”
In concert halls and other music venues, we hear early reflections and reverberations
as well as the direct sound produced by the artist(s). The variations in the early
reflections and other reverberations among the different music venues is what gives
each venue its special and recognizable sound quality.
Yamaha sent teams of sound engineers all around the world to measure the sound
reflections of famous concert halls and music venues, and collect detailed sound field
information such as the direction, strength, range, and delay time of those reflections.
Then we stored this enormous amount of data in the ROM chips of this unit.
■ Recreating a sound field
Recreating the sound field of a concert hall or an opera house requires localizing the
virtual sound sources in your listening room. The traditional stereo system that uses
only two speakers is not capable of recreating a realistic sound field. Yamaha’s DSP
requires four effect speakers to recreate sound fields based on the measured sound
field data. The processor controls the strength and delay time of the signals output
from the four effect speakers to localize the virtual sound sources in a full circle
around the listener.
The DSP sound field programs can be classified in two types based on the sound field
processing method: programs that use early reflections only and programs that use
both early reflections and reverberation.
■ E/R (Early Reflection)
Each sound field is distinguished by the structure of the reflected sound. The increased processing capability of DSP technology enables
Yamaha engineers to incorporate even minute reflections with long delay times into the sound field data.
■ 4ch REV. (Four Channel Reverberation)
This type of program consists of early reflections and high quality digital reverberation processing. Reverberation is the most important
element for recreating the sound field of a church, for example. To recreate a realistic spatial sound image from reverberation data, Yamaha
has adapted the four-channel-output reverberation technology.
■ Illustration of the virtual sound sources and echo patterns
The virtual sound sources and echo patterns for the DSP sound field programs are shown below. The illustration of the virtual sound sources
shows early reflection sound only and the illustration of the echo patterns shows both reflected sound and reverberation.
RL
FR
RR
FL
Virtual Sound Sources
The center of these circles represents the virtual
sound source.
The size of the circle indicates the strength of the
virtual sound source.
The direct sound source
The listening position
Echo Patterns
Direct sound source
Early
reflections Reverbration
50~80 mSec