Yamaha DSP-AX2 ■E/R (Early Reflection), ■Recreating a sound field, Understanding Sound Fields, Digital Sound Field Processing (DSP), ■4ch REV. (Four Channel Reverberation)

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.

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■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.

Virtual Sound Sources		Echo Patterns
	The center of these circles represents the virtual	Direct sound source
				Early
	sound source.
			reflections		Reverbration
	The size of the circle indicates the strength of the
	virtual sound source.
			50~80 mSec
	The direct sound source
	The listening position

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