Channel Crossover And LFE
Dear Gary: Big thumbs up to you all from down-under on such an excellent magazine; there is never a day that goes by that I’m not pulling out Widescreen Review to read over for the umpteenth time while on my commute to work; waiting for the next issue. Recently I was lucky to upgrade to the Denon AVR-3805 and have a question for you on the LFE channel and the crossover to the surround channel. The processor allows you to apply a crossover point that gives, as best can be, a blend between those loudspeakers that are set to small and the subwoofer. My question is, by setting this crossover, say at 40 Hz, does this limit the overall output of the LFE channel to the 40 Hz setting, or is the LFE channel fixed to a higher figure and is passed through unchecked, regardless of the crossover used for the small speakers?
John Barsby, Sydney Australia
Contributing Editor John Kotches Comments:
In a correctly implemented bass management system, the crossover for a loudspeaker defined as “small” has no effect on the LFE channel. The content provider is responsible for utilizing a low-pass filter beginning at 120 Hz in the LFE channel during soundtrack creation and prior to its encoding for inclusion on distribution media. The output of a properly implemented bass management system would be the low-pass filter from each loudspeaker defined as “small,” plus the LFE channel (including its pad) with no additional filtration. There are some products on the market, which allow the end user to define a low-pass filter on the LFE channel (such as my reference Meridian processor), but if you are trying to reproduce the soundtrack as intended, the bypass (or no filter) setting should be utilized even when the manufacturer allows for such an option. To the best of my knowledge, your AVR-3805 should not have such an option.
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