The A5+s have a manual sleep mode that puts them into a low-power mode so you can leave the speakers on all the time. The A5+s sleep mode can be toggled by either pressing the sleep button on the A5+'s remote control or by pressing the volume knob in (you should feel it click); the light on the front of the powered speaker will slowly blink to let you know that the speakers are in sleep mode. 

For more information, be sure to check the A5+ Setup Guide.