The Bose® SoundTouch™ SA-4 amplifier works with the following Bose indoor and outdoor speakers, as well as most other speakers.

Indoor speakers

301® Direct/Reflecting® speaker system 201® Direct/Reflecting speaker system
161™ speaker system Virtually Invisible® 791 in-ceiling speakers
Virtually Invisible 191 in-wall speakers Acoustimass® 5 Series III system
Acoustimass® 3 Series IV system

Outdoor speakers

251® environmental speakers 151® SE environmental speakers
Free Space® 51 environmental speakers