Engineering:Bass management

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The fundamental principle of bass management (also called LFE crossover) in surround sound replay systems is that bass content in the incoming signal, irrespective of channel, should be directed only to loudspeakers capable of reproducing it, whether the latter are the main system loudspeakers or one or more special low-frequency speakers (subwoofers).[1] There are notation differences between the pre-bass-managed signal and after it has passed through bass manager. For example, when using 5.1 surround sound:

5.1 channels
Before bass management After bass management
FL - Front Left FL - Front Left
FR - Front Right FR - Front Right
C - Center C - Center
RL - Rear Left RL - Rear Left
RR - Rear Right RR - Rear Right
AW - Alternative Woofer N/A (incorporated into Sub)
N/A (bass can be in any channel) Sub - Subwoofer

As the table shows, the bass manager directs bass frequencies from all channels to one or more subwoofers, not just the content of the LFE channel. However, when there is no subwoofer, the bass manager would direct the LFE channel to the main speakers. This is the only time the LFE channel would not be sent to the subwoofer.

The key concept is that the LFE channel is not the "subwoofer channel".[2]

See also


  1. Elen, Richard (October 2002). "Bass Is Covered: A Dictatorial Approach to Bass Management in Surround Music Mixing". Surround Professional. 
  2. "What is the LFE channel?" (PDF). Information. Dolby Laboratories, Inc. 2000. Retrieved 2011-01-08. "LFE does not equal subwoofer" 


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