Hello guys, thanks for all the help. Your postings have proved to be useful to many people. I will now present a problem and I hope that some of you might know the solution from past experiences. My speaker is Altec Lansing ADA890 THX Certified (4.1 speakers) and my soundcard is Creative X-Fi. It all started when suddenly it stops producing sounds. The power LED on the subwoofer is green indicating there is power in the unit. One strange thing that I noticed was the reading on the LED display at the front speaker (where you can control Volume, Bass, Treble). Normally it reads STEREO, STEREO X2, QUAD, PROLOGIC (depending on your preferred sound setup). Now it reads DOLBY DIGITAL HD (blinking) but with no sound. I unplugged the wire connecting it to the soundcard and plugged it onto my MP3 player and it still detect DOLBY DIGITAL HD (still no sound). Can you all give suggestions on what might causing it to behave that way and if possible how do repair it? I have been trying to find circuit diagram for this speaker but to no avail. I already bought a 2.1 Klipsch Promedia but I still like the sounds from my Altec Lansing and I really want to have it in working condition again. Thanks. Play it safe!

Look at the device manager first for any yellow or red marks. The event viewer might have a related error too.

hi on the ADA sub box, press the diagnostic button, the speakers should play a tone If so the ADA unit is working properly, check your cables etc to the pc. btw Dolby HD is eax3, have you set your sound card up to out put something the ADA cant decode?

Thanks for your wonderful suggestions. First of all, FYI I tried connecting the speakers to my Creative Muvo MP3 player to test it but still it does not produce any sound. I have opened the subwoofer casing just to look inside if it short circuited somewhere. Do you think the subwoofer is the unit controlling the decoding function or is it contained in the front speaker with the knobs? Play it safe!