User Manual

Multichannel Monitoring Tutorial Booklet (M2TB) rev. 3.5.2

Masataka Nakahara : SONA Corporation

55 / 74

[Filter Types]

The type of filter used (Butterworth, Linkwitz, etc.) depends on the matching between the type of low

pass filter and the response of the main speakers.

Example: For small types where the main speaker is attenuated below 80 Hz.

• LPF “Linkwitz” fc=80 Hz, -24 dB/oct

• LPF “Butterworth” fc=80 Hz, 12 dB/oct

In this way, it is desirable for the specifications of the high-pass filter to be selectable according to the

response of the speakers that are used.

The bass management controller shown in [Fig. 35] is a type that is frequently used in consumer players

and AV receivers. When this type of bass management controller is used, the upper limit of the LFE

playback bandwidth is determined by the crossover frequency of the main channels, as shown in [Fig. 36].

Since the crossover frequency is generally set to 80 Hz, bass management controllers such as shown in

[Fig. 35] will limit the LFE playback bandwidth to 80 Hz. In contrast, DVD-Video and film allow LFE

signals up to 120 Hz to be recorded and played back, and DVD-Audio and Super Audio CD allow full-

range recording and playback. In a production workplace where it is necessary to reproduce all of the

playback bandwidth that can be recorded on the media, it is necessary to use the bass management

controller shown in [Fig. 41]. This type of bass management controller has two low-pass filters — a low

pass filter for the main channel crossover (LPF1) and a low pass filter for the LFE (LPF2) — and allows

the cutoff frequency of LPF2 to be changed as needed. Most professional bass management controllers

are of the type shown in [Fig. 41].

Example) - LPF1, HPF fc-80Hz

- LPF2 fc=120 Hz (DVD-Video, movies, etc.), Through (DVD-Audio, Super Audio CD, etc.)

- AMP +10dB (DVD-Video, movies, etc.), ±0dB (DVD-Audio, Super Audio CD)

Whether this type of bass management controller maintains +10 dB of gain for the region above 80 Hz

(DVD-Video, movies) will depend on the room acoustics ([Fig. 42]), but it is an effective bass

management controller for previewing and for work that requires all of the signal recorded on the master

to be checked, such as when mastering or authoring.

During the mixing production process, on the other hand, acoustical operations that would allow signals

above 80 Hz (which carry a sense of localization) to be present in the LFE signal are normally avoided,

and a low-pass filter at fc=80 Hz is usually applied to the master signal of the LFE. In this case, it is

possible to use the bass management controller shown in [Fig. 35].

[Fig. 41] Bass management controller (2)

LFE

AMP

HPF

LPF2

HPF

SUB

LPF1