LFE+Main Subwoofer Mode Explained

I find there is quite a bit of confusion regarding the LFE+Main setting in Denon and Marantz AV receivers.  Some think it duplicates LFE from the subwoofer into the towers - but it doesn't do that.  So, what exactly does LFE+Main do, and should you use it?  Let's discuss.

• #entertainment
• #lfe
• #lfemain_or_lfe
• #lfemain_subwoofer_mode
• #lfemain_denon
• #lfemain_marantz
• #demon_bass_boosted
• #denon_bass_management
• #marantz_bass_management
• #low_frequency_effects_denon
• #low_frequency_effects_marantz
• #crossover
• #crossover_frequency_subwoofer
• #crossover_frequency_explained
• #crossover_frequency_home_theater
• #what_is_lfemain
• #bass_boost
• #duplicate_bass
• #home_theater_setup
• #home_theater_system
• #home_theater_subwoofer
• #bass_management