Bass Management

Note

Some changes were made to channel labels and bass management in Device Console version 1.1.16. To avoid confusion, we recommend that you reset and rebuild all presets when updating to Device Console version 1.1.16.

Overview

The Bass Mgmt tab is used to configure the bass management filters:

By using this tab, each speaker channel can be set to have a high pass filter. In addition, its low-frequency content can be summed with the LFE channel to send to the subwoofer (or subwoofers).

Note that successful bass management requires sufficient gain in the subwoofer channel, due to the fact that the LFE channel is recorded at a 10 dB lower level than the speaker channels. If you have not already done so, refer to the earlier section LFE channel gain to align your subwoofer channel gain with the speakers.

Parameters

Frequency

Set the frequency of the high pass and low pass filters. The HPF slider sets the high pass filter corner frequency on the speaker channel: signal above this frequency is passed through to the speaker channel. The LPF setting sets the low pass filter corner frequency: signal below this frequency is summed to the LFE Mgmt channel.

Note that these filters do not create an abrupt change: there is a more or less gradual transition as determined by the filter type and slope.

Filter Type

Selects the type and slope of the filter. There are three types of subwoofer crossover filter with several slopes:

Butterworth (BW)

Available in 6, 12, 18, 24, 30, 36, 42, and 48 dB/octave, Butterworth crossover filters are 3 dB down at the cutoff frequency.

Linkwitz-Riley (LR)

Available in 12, 24 and 48 dB/octave, Linkwitz-Riley crossover filters are 6 dB down at the cutoff frequency.

Bessel

Available in 12 dB/octave only, a Bessel filter gives a more gradual roll-off through the crossover region.

Bypass

Bypass the respective filter. When "lit", the filter is bypassed. To enable the filter, turn this switch off.

LFE mix level and Mute

Set the mix level into the Bass Mgmt channel.

If enabling bass management, the mix level should be set to -10 dB for correct summing of the speaker signal with the LFE channel. This is needed because movie soundtracks have the level of the LFE (low-frequency effects) channel reduced by 10dB during mixing in order to accomodate the high signal levels needed on this channel.

If desired, the mix level can be changed from the standard -10 dB. For example, if the centre channel produces too much output from the subwoofer, set it to -12 dB.

The mix level is typically only set to 0 in the case where upstream equipment has already applied this gain adjustment on the LFE channel. This usually occurs only in upstream equipment with analog outputs.

Examples

Below are some examples of how to set the bass management for each channel.

Bypassed

This is the default setting. Both filters are bypassed, and there is no processing on this channel.

Bass management active

This is a typical setting for a speaker channel with bass management active:

• Both filters are enabled and set to 80 Hz Butterworth 24 dB/octave.
• The 10 dB gain adjustment for mixing to the LFE channel is enabled.

Setting the LFE channel

This is a typical setting for the LFE channel when using bass management:

• The high pass filter is left disabled.
• The low pass filter is enabled with a 120 Hz Butterworth low pass filter. (It is often recommended that the LFE channel be low pass filtered at 120 Hz in case there is any extraneous high frequency content on the soundtrack.) The 10 dB gain adjustment is not enabled.

A complete example

For reference, here is the complete screen with bass management set up for 7.1 processing. In this example, we have filtered the rear surrounds at 120 Hz:

Note also that the Bass Mgmt signal will need to be routed to the subwoofer on the Channel Routing tab. By default, Dirac channel 3 is processing the subwoofer channel, so we route the Bass Mgmt signal to Dirac-3.