Hi TomJ,
Here's a quick method to test if your Hsu's auto wake-up feature is not working or perhaps working erratically.
First, disconnect all cables from your subwoofer except the AC power cord.
Use any portable music player--CD, iPod, MP3 and run an adaptor cable from the headphone output (stereo mini-plug) to an RCA male plug, and connect it to the line-level input of your subwoofer. Make sure the sub isn't totally off, then play any music with the output volume on the music player at half to 3/4 output. Your sub should "wake up" and you'll hear deep muffled bass.
You can use one channel of any audio CD player or the analog audio output from a DVD player.
If the sub doesn't wake up even when you increase the output level of your music player to maximum, then there's something wrong with the sub's auto-wakeup circuit.
Regards,
