If it is indeed loudness and not the effects of mastering as I previously pointed out, how do room acoustics come into play? Can you explain (in simple terms please) how room acoustics affect loudness levels...I'm not following that.
If the speakers couple differently to room modes. The standing waves can be slightly asymmetrical even in rectangular rooms due to difference in wall construction or presence of doors, windows, etc. I've seen plenty of examples of it. Obviously this affects the area where standing waves dominate the response, say under 300Hz.
It could be the recordings, your system, or your ears. You can rule out your ears by turning around and facing backwards from the stereo, thereby swapping left to right, ear wise. You can rule out most of your system by swapping the channels as close to the source as possible.
These days, in any room, in any system, if I can perceive imaging to be skewed towards the left, I'll wash the CD disc under tap water and then dab it dry with tissue paper and play in and it will usually cure the problem - snapping centre fill imaging right back to centre.
If I want a stronger remedy - the clear transparent cd jewel case still remains the best solution.
Sometimes, if I'm naughty, I bring a couple of CDs that I've wiped with a dry cloth earlier into a Hifi shop and ask them to play those discs. They never fail to make the system's imaging to become skewed towards the left.
