User Manual

Multichannel Monitoring Tutorial Booklet (M2TB) rev. 3.5.2

Masataka Nakahara : SONA Corporation

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because the ITU-R configuration, with its L/R spread of 60˚, is based on maintaining compatibility with

conventional two-channel stereo, its surround speakers were placed correspondingly further toward to the

front comparison to QUAD. If the naturalness of just the surround playback soundfield is to take priority

over the relationship between L/R and LS/RS, we can say that a placement of 135˚ (which uses the rear

half of the QUAD configuration) is a good placement.

3-3-1-3. 150°

If you require that the surround L and R have the same acoustical conditions as the front L and R, placing the

surround speakers at 150˚ will produce a placement that is completely symmetrical between front and rear

(However, to be precise, there must also be forward/rear symmetry in the shape and other acoustical

aspects of the room).

In such a placement, the L/R spread and LS/RS spread are identical, and it will be easy to move the sound

in a 360˚ path by surround-panning in a circle. This configuration is suitable when the front panning and

the rear panning are both important. We can say that while ITU-R is better at portraying a sound field, the

150˚ placement is better at localizing a sound image.

However, as the surround speakers are placed farther to the rear, the surround sound field will tend toward

monaural, and there will be a more distinct separation between the front and rear sound fields.

3-3-2. Diffuse surround

The most common method of creating diffuse surround is to use several surround speakers.

When multiple surround speakers are to be placed, it is important that the speakers be placed in the side

area (<135˚) and the rear area (>135˚) [Fig. 24]. This makes it easy to construct a monitoring environment

that provides the advantages of side placement and rear placement, allowing both a sense of stereo

separation in the surround (the advantage of side placement) and 360˚ surround panning (the advantage of

rear placement).

On the other hand, when the surround channels consist of multiple speakers, the sound intensity vector of

the LS and RS has been found to be located at the phantom sound image of multiple speakers [4][5]. For

example if speakers are placed at 100˚ and 150˚, the sound intensity vector when the LS or RS channel is

played will indicate the 125˚ direction, which is the same as if a speaker were placed at 125˚. If

compatibility with direct surround must be considered as a part of diffuse surround, you should consider

the positioning of the surround speakers' phantom sound images.

[Fig. 24] Two loudspeakers placement for each surround channel (Diffuse Surround)

135

150

side

rear

100