Like most other electric guitars, the majority of basses have solid bodies; they need an amplifier to boost the signal so your audience can hear it. You can't just plug your bass into any Peavey or Marshall and expect perfect results; you need an amp that's designed for bass guitar. Bass amps focus on the bottom end, with an emphasis on low frequency response. The speakers are bigger so that you can feel the low notes of that driving beat. Remember, it's the amplifier that drives the speakers, so if it doesn't produce great sound the speakers won't either.