Stereo & Electronics - I am having a problem with my radio in my firebird. The volume will just go down

On my wifes firebird there is a problem with the radio, as soon as you drive for a minute the volume goes down and as I turn up the volume it works for a second then goes right back to the same thing. I hooked up another radio last night and it has the same problem. Any idea what this could be. It has the stock radio and has 2 added speakers in the back for a total of 6 speakers.

And if it helps the rear in the hatch area speakers are tied into the rear speakers.

does ur car have steering wheel controls, maybe they are stuck or jacked up

No it does not. I am clueless on this one

try unhookin rear speakers could be overloadin the amp

I did that still the same problem.

Could it be a bad ground.

I think it is fixed one of the rear speakers was grounding out shorting out the radio. Thanks for the help guys