Hi @thenewelite
The problem may not be in the acoustimass, it could be in the media console or even the cable connecting the two.
Even though the other speakers work when connected to the console this doesn’t mean that the audio signals are being sent to or are being received by the acoustimass, if you get my drift.
Hearing a hissing sound at least proves that the power/amplifier section of the acoustimass may be OK.
On p.37 in the Troubleshooting guide (see link below) it details how to make a base module (acoustimass?) test wiring cable so that it can be tested to see if it is OK or not. At least by doing this you can prove where the problem is located.
Here’s a link to the [https://elektrotanya.com/bose_av321_troubleshooting.pdf/download.html|troubleshooting guide] for the system.
To download the file, when the sentence below the Document preview box changes from ''This file is downloadable free, of charge: '''...'''processing...'' to ''This file is downloadable free of charge: Download'', click on Download. Be patient it takes a little while to find the file.
Hopefully this is of some help.