Bass management

A bass management system takes all the frequencies below a certain frequency (normally 80Hz) from the main channels, and the signal from the LFE channel, and mixes them together into the speaker that is best equipped to handle them. This is usually a subwoofer, but sometimes the left and right front speakers are used if a subwoofer isn’t available. The reason why this is done is to make use of the subwoofer for more than the occasional low frequency effect, since the subwoofer is there anyway, and to lower the effective response of the system to about 25 Hz.

When you encode to Dolby Digital, the LFE channel gets a +10 dB gain on playback from Dolby's decoder. This gives you the option of delivering some really powerful deep bass during playback, like in that earthquake sound effect in your recording. Consider also that this +10 dB of low bass can be added to any low bass that came out of the other 5 channels from redirection, so you realistically can deliver a sound from the subwoofer that is more than +20 dB above the sound from any other speaker.

What this means during mixing is that you would have to turn the analog gain to your subwoofer up 10 dB relative to the other 5 speakers, so that you hear the sound as it will be played back in home theater systems that use bass management, and you will get your levels set right in the mix.

Sonar’s bass management system allows you to monitor how a surround project will sound with bass management, so you don’t have to change the gain to your subwoofer during mixing. Sonar’s bass management system only applies to monitoring, and is ignored when you export your file.

To monitor with bass management

1.	If necessary, open the project you want to use bass management with.

2.	Go to Edit > Preferences > Project - Surround.

3.	Select the Monitor with Bass Management check box.

4.	Select an option in the Low Pass Cutoff (Hz) drop-down, and click OK.

 

See:

Surround effects