Monoprice Outdoor Burial 8-inch Subwoofer with Dual Voice Coil (each) - Sycamore Series

You get a surprising amount of output from the subwoofer. So much so, than in a smaller patio setup, you'll have to turn the bass down on your equalizer. Get all 4 satellite speakers if you go with this. They aren't very expensive and going with 4 helps even out the sound around your patio and also helps them keep up with the subwoofer. Even though the speakers are weatherproof, I put planters over mine when not in use to keep them dry and hopefully live long lives. I wouldn't hesitate to recommend this to anyone. Its sounds much better than the price would suggest.

Hid one near the deep end of our pool that fills most of a pretty big back yard with a nice bottom end. You can feel it under water but is not harsh above. We decided to build a tiki bar on the opposite side of the yard 70' away and we needed good sound there, too. Now with both, we have great sound even at very low volume. When we really crank it, the windows shake and you can almost see a wave in the pool. No distortion, just good clean bass. We are running both on a 500W vintage Crown Amp. The other speakers have their own amp. We do not run the satellite speakers.