Compression, I'm referring to really bad compression irritates me something fierce to the point I won't listen to the song.
I don't have many cds that I can think of that are really bad. One that many audiophiles are probably aware of is Vapor Trails by Rush. The thing is you may not be aware of bad compression unless you know what it sounds like.
Another good example is from a TV. When I visit at my parents place they usually have the TV on. The sound coming from the tiny TV speakers is compressed along with elavated volume. I find that while I'm trying to visit I am being irritated by the compression from the TV.
I don't have that problem with my TV, except for those annoying commercials. That's when I mute the sound or change channels.
