Outdoor speakers will create good sound in a small area near your home. For the best audio effect, we recommend installing the left and right speakers at a distance of about 3-4 meters. Do not try to cover more space. Moving them further apart, you will lose sound quality. Besides, speakers must be parallel to each other. For the user to get the desired sound, the speakers must aim at the listening position.
For an outdoor speaker installation, a 15 AWG multi-strand copper cable will be more than sufficient for lengths of the order of a few meters (depends on the distance to the receiver). You can buy this at any usual DIY store. The multi-strand wire is more flexible and, therefore, easier to work while setting up an outdoor sound system than rigid cable, and it helps to avoid any skin effect at high frequency.