I agree with Earl for the most part. I think a lot of what people percieve is psychological, especially when they expect an improvement. Sometimes, gains are much to small to be percieved, and sometimes there are no gains at all. There are lots of "tweaks" that fit this description. A guy buys an upgrade part or "mod" and puts it in, thinks he hears an improvement but measurements don't show anything. That's a case of expectations influencing perception, something that a blind test would show for what it is. Earl is saying that some things just aren't perceptible, and I am sure he's right. No surprise really.

But loudspeaker components are where I hear the most difference. If I use a good woofer with a shorting ring and replace a cheap one with a plain asymmetrical-flux ferrite structure, I can hear it right off. I can hear it as soon as I hit the door, just enter the room and I'll know, completely blind. So I know for sure I'll identify the JBL 2226 from the Chinese copy. I'd know the difference with a blindfold on from the next room over, it's that apparent. I'm pretty sure that's the case for all but the most casual listeners. Maybe some people that listen only to getto blasters and cheap car stereos might not hear a difference, but I'm pretty sure that everyone attending GPAF would be able to tell.