Sub-woofers are most common component of home theater systems and non-powered sub woofers or passive sub woofers are just perfect for your living room or hall. You will require an additional amplifier to power your sub-woofers. These sub-woofers are widely used in cars and have connections for speaker wires. What’s more, to prevent high frequencies to pass through the speaker cone, these non-powered sub woofers have a built-in crossover. The non-powered sub-woofers are generally used when a separate amplifier for your bass is needed.