How to: Install a subwoofer and amplifier, Crossover to increase bass for better listening - YouTube
Pure Bass Subwoofer Second-Order Crossover Speaker Frequency Divider DIY Home Theater - buy Pure Bass Subwoofer Second-Order Crossover Speaker Frequency Divider DIY Home Theater: prices, reviews | Zoodmall
Can I build a speaker crossover from scratch? - Quora
The Subwoofer DIY Page v1.1 - Projects : The "Mini-Me"
Crossover For Subwoofer Circuit Diagram
External Passive Crossover for Subwoofer - YouTube
How To Design A Crossover For A DIY Speaker || Part 1 - Crossover Design Intro - YouTube