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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 the DSP-AX1.
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. 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.
The center of these circles represent the virtual sound
source.
The size of the circle indicates the strength of the
virtual sound source.
The direct sound source
The listening position
Virtual Sound Sources
Echo Patterns
RL
FR
RR
FL
Direct sound source
Early
reflections
50~80 mSec
Reverbration