User Manual

Multichannel Monitoring Tutorial Booklet (M2TB) rev. 3.5.2

Masataka Nakahara : SONA Corporation

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3-8-1. Comb filtering: Distance difference > 8 mm

If the same sound is played back from two speakers whose distance to the listening point differs by 8 mm

or more, dips will occur in the frequency region below 20 kHz. A distance of 8 mm corresponds to a

minute time difference of approximately 0.025 msec when converted by the speed of sound, and can be

caused not only by differences in physical distance, but also by the rigidity of the speaker, the wiring, and

electrical delay produced by equipment.

3-8-2. Haas effect: Distance difference > 30 cm

This is also called the “precedence effect,” which is the phenomenon that causes the perceptual sound

source to be strongly localized around the closer of two sound sources. The distance difference at which

the Haas effect appears depends on the type of signal, but in general is greater than 30 cm. A monitoring

environment in which the Hass effect is occurring may experience problems such as failure of the sound

image to move smoothly when panning occurs. For example if the surround speakers (LS, RS) are placed

more than 30 cm closer than the front speakers (L, C, R), the sound source movement when you

surround-pan from surround -> front will not be heard smoothly because the perceptual panning is pulled

strongly toward the surround speakers.

Another problem is that in a diffuse surround environment, the surround coverage area may not be wide

enough, causing the perceived sound image to be located only around the nearest surround speaker.

3-8-3. Crossover with the sub-woofer: Distance difference > 1 m

If there is more than 1 meter of difference between the distance from the sub-woofer to the listening point

and the distance from the other speakers to the listening point, dips are likely to occur in the combined

response.

Severe dips occur in the region of the sub-woofer cutoff frequency.

If the monitor system uses bass management (discussed below), special care must be taken to avoid

significantly impairing the frequency response of the main channels.

If the above monitoring problems occur, you will need to reconsider the speaker placement, and try

adjusting the speaker phase (in particular, the sub-woofer).

If improvements cannot be expected from the above adjustments, it will be necessary to apply electrical

delays to each speaker.

In addition to delay, designing your monitor system so that an attenuator or GEQ (PEQ) can be applied to

each speaker often provides useful ways to adjust the monitoring response.