while listening to my system, during a song I noticed the bass went neutral & the instruments disappeared into the back of the room
Is this correct? This wasn’t something that happened who knows when and then you noticed, this is something that actually happened WHILE you were listening???
Because what I said about the protective circuit is based on this one statement. That this is something that happened during a song. Everyone else’s ideas would be things that happened whenever, who knows, and then you just happened to notice it.
If its something that happened suddenly and during play then it has to be either a protective circuit that tripped or your receiver has a problem. Which by now if its been off and on again then it won’t be a circuit and Houston, we have a problem.
To check this out disconnect all but one pair of speakers. See how it sounds with just one pair. If your receiver has multiple speaker terminals then check that one pair with each set of terminals. Then disconnect that pair and do the same with the next. And so on, until you have confirmed all speakers work properly when connected one at a time. Then if they all work individually connect additional pairs of speakers one pair at a time checking each time to see how they sound.