I purchased a 2005 XLR, with 4K miles last month. Its XM antenna was still in box; and I had dealer install it and replace OnStar with new digital system. XM audio is significantly weaker than FM/others; I have to remember to turn down volume before changing from XM to FM, for fear I'll blow out the speakers. FM reception is weak - in/out for nearby stations - where I didn't remember it to be before the installations. I thought might be related to installation. I left with dealer on Friday, only to have it returned with a note and an attached GM Bulletin 1837884 saying, "this is a normal characteristic of the system" on 2004-6 XLR and 2005-6 Corvette. I don't know if the tech checked the recent installations at all. It seems incredible that such system performance would be "normal." (It's not normal on our STS or Chevy pickup.) I've searched XLR forums without finding any reference. Is this typical of radios in your XLRs? Appreciate any info or recommendations. . . John D, Weatherford, TX.
my 2005 is the same as yours in the xm department only mine was in it when purchased new. when switching from fm/cd/dvd to xm the audio is terrible, really sucks. I dont really care for the xm any way and have sirrius in other cars, i have even taken my sirrius from my pickup which works off of a fm transmitter and ran it in my xlr through the fm and it sounded way better than the stock xm radio. just my 2 cents!
Sadly, it is normal.
It is particularly noticeable on XLR. It actually has to do with the input and output level matching on the receiver and the radio. As far as I can tell it wasn't done properly and there is a really noticeable difference as you can see.
You can make adjustments on the audio controls to help it but you can't get rid of it.
It is not related to the installation or anything your dealer did.
I have talked to the Brand Quality Manager for this carline about this issue. Short of GM spending oodles of money redesigning and replacing the radio there is nothing you can do and I wouldn't count on them doing that.