User Manual

ManualsBrandsYamaha ManualsDigital MixersYamaha 02R96VCM

Multichannel Monitoring Tutorial Booklet (M2TB) rev. 3.5.2

Masataka Nakahara : SONA Corporation

68 / 74

[Main channels]

• All-pass level 85 dBC

• Band level (1/3 octave) approx. 71 dB

[LFE band level (1/3 octave) ]

• Approx. 81 dB (+10 dB) DVD-Video, film

• Approx. 71 dB (+/-0 dB) DVD-Audio, Super Audio CD

[LFE all-pass level (20 Hz–120 Hz) ]

• Approx. 89 dBC (approx. +4 dBC) DVD-Video, film

• Approx. 79 dBC* (approx. -6 dBC) DVD-Audio, Super Audio CD

* When the LFE playback bandwidth is assumed to be 20 - 120 Hz.

Since the above all-pass levels are the values with the LFE playback bandwidth assumed to be 20 Hz -

120 Hz, you will need to apply a 120 Hz LPF to the monitor output for the LFE signal reproduced by the

subwoofer if you are relying on the all-pass level to make adjustments. Alternatively, the pink noise used

for adjustment could be bandwidth-limited with 120 Hz as the upper limit.

The all-pass level value is easily affected by the frequency response and playback bandwidth.

The low-frequency response, which is particularly liable to be affected by the acoustical character of the

room, is apt to become unstable. Furthermore in many systems, the main channel and sub-woofer differ in

their ability to reproduce the low range, and careful measurement and adjustment is necessary in order to

adjust the band level according to specifications (+10 dB, +/-0 dB). This means that in actual measurement,

it is desirable that not only a sound level meter but also an RTA must be used to check the level balance of

each channel in octave-band levels.

Using a sound level meter to adjust the all-pass level is a simple method of measurement in which

precision is guaranteed only if all speakers are in the ideal playback conditions.

In an environment in which bass management is being applied, +10 dB of gain is already being applied

before bass management (LFE bus), so the playback level adjustment must be performed after bass

management (the sub-woofer).

The 85 dBC value used up to this point is based on adjustments for a movie theater (SMPTE 202M-1998,

SMPTE RP200). In other words, by defining the relative value of the audio source signal level and the

playback sound pressure level, we can play back the same program anywhere at the same volume. When

this program is actually played back in this environment, a maximum playback volume of approximately

110 dB is obtained. Since it is not necessary to define the absolute level for other than movie theater

productions, the desired value may be used as the pink noise input level or the sound pressure level at the

listening point. The important thing is that the relative sound pressure balance be maintained. If you want

to play back at volumes typical of a household environment, it is good to make adjustments at about 79

dBC. Recently, however, the expression “85 dB of volume” is often used for the playback of multi-

channel productions regardless of media, and it is convenient to maintain an 85 dBC playback position as

the reference for a studio.

The value of “85 dBC” when playing back broad-band pink noise is a reference value that assumes the

speaker has a broad-band playback response of 20 Hz - 20 kHz. This means that in this case, the 1/3

octave band level of “71 dB” is the true playback level reference value. Since the LFE playback level is

given as a relative value (+10 dB, +/-0 dB) relative to the main channel band level, a simple comparison

of levels is difficult to make if the sub-woofer and the main speakers have differing low-range playback

capabilities. Due to considerations such as these, it is important to use not only a sound level meter, but

also an RTA to make measurements and adjustments in order to ensure reliable monitor adjustments. If

this is difficult, you can consider measures such as a simplified measurement using 500 - 2 kHz band-

limited pink noise. (However, this cannot be used for adjusting the LFE.) It is also useful to use the bass

management functionality temporarily to extend the playback range of all main channels to the full range

of 20 Hz - 20 kHz before making adjustments.