Making Better Bass, Part 2: Subwoofer Phase - High-Def Digest: The Bonus View
Subwoofer setup and integration 101: sub crossover frequency, slope and phase for two channel systems - Acoustic Frontiers
What are the frequency settings for a subwoofer? I have a subwoofer with 4 different frequency settings. I need powerful, punchy bass. Should the setting be positive or negative? - Quora
How To Set Crossover Frequencies For Your Car Audio System