If you will be running speaker wire from your audio distribution amplifier or amplified keypad to the outside or even underground, you need cable that's rated for direct burial. Even if you don't actually bury the cable in the ground, it will better stand up to exposure to harsh outdoor weather conditions over the course of time.

Especially if you are installing one or more stereo-input dual-voice-coil single outdoor speakers that features dual tweeters like those pictured above, it probably makes sense to run 4-conductor cable like those pictured at the bottom of this page so you can experience two-channel audio, through a single cable, from a single speaker.

It's also nice to know that it you are going to be spending several hundred bucks on speaker cables to wire your whole house audio system that you can buy one single go-to cable that's both direct burial rated for outdoor and underground installation and CL3 rated for in wall and ceiling installation.