I finally got the ABX to work - managed to get 6/7. I don't know how i got one wrong because there was a very clear sound difference between the wav and the mp3 with the timbre of the bells. The mp3 sounded duller and less bright/harsh than the WAV.

Whilst i could tell the difference, it doesn't mean that the mp3 was bad - in fact it was more comfortable to listen to.
the MP3 was converted straight from the WAV with high quality 320kbps joint stereo CBR Mp3.

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By saying this you strike me as a "sennheiser type" of guy.

Congratulations to everyone who is doing successful (or unsuccessful) ABXs, assuming they did it properly (like not cherrypicking test results and making sure the sound levels are identical).

I am a big fan of lossy (despite having everything in FLAC format anyway), however if you can ABX it reliably then more power to you, you have proven that the differences exist, that you know what they are and can perceive them. It's the people who say something like "the file was COMPLETELY RUINED!" and refuse to do any ABXing that are annoying.

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I have found very little information as to the why of it, I only know that it seems to be a by-product of compressing music.

I noticed it the first time with "More Human Than Human" by White Zombie because the iPod's lousy EQ made the issue stand out even more. A quick fix with MP3Gain and the problem was gone.

A lot of people use programs such as Vorbis Gain, MP3Gain, AACGain, ReplayGain, etc, not just to normalize but to reduce the distortion caused by clipping which is a by-product of encoding music to a lossy format.

"It was the weirdest orchestral balance I'd ever heard. The gentle woodwind chords that begin Mendelssohn's incidental music to A Midsummer Night's Dream were as loud as the climactic "Wedding March" that ends the piece. The radio broadcast was obviously being compressed to hell." -- John Atkinson http://www.stereophile.com/asweseeit/727/index.html

Clipping depends largely on the type of music, Most rock music is recorded at the highest dB levels possible to begin with, thus the act of ripping to a lossy format will push the dB levels over the edge and cause distortion. For a lot of other types of music that aren't recorded at extremely high dB levels, it won't be noticeable.

Most Lossy Codecs tend to strip the highest and lowest frequencies from the music, figuring that most people won't be able to hear those frequencies to begin with. I'm no expert though, and I can only prove my theory by the fact that there IS a difference to my hearing and by lowering the dB levels the music sounds a lot better. I also tend not to be the only one who notices the difference, I've run across a lot of threads both here and over at hydrogen audio where people have expressed the same concerns and have found that lowering the gain fixes the issues.

I was looking for information on that as well.

Saves me some time looking I guess. Thanks.

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Note that what Atkinson is talking about in this quote is dynamic range compression, not the reduction of file size using a lossy compression. Though the title of the article includes the word "MP3" and he goes on to discuss MP3s generally, the part that you quote does not suggest that dynamic range compression is related to MP3 compression.

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An isolated 6/7 is by no means a conclusive result, especially since you thought you could easily tell the difference. It may be worthwhile to run the test again, ideally with a reasonable number of tries (for example 8 tries if you're making no mistakes or 12 to 16 if you made a few bad calls).

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6 out of 7 is, what, 90% confidence? That's enough to satisfy most people, I would imagine.

OK, I did the ABX test and now I admit that there is a difference after all. But guess what? The mp3 sounds BETTER than the wav file.

lowpass rocks!

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I wouldnt at all be surprised some people find that. There are certain things about good lame encoding which can be very very pleasing to the ear. I think sometimes it can even 'soften' the music, taking out some of the harshness of the piece which could possibly be an annoyance in certain cases.

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6/7 gave me 6% chance of guessing according to ABX.
The one time i got it wrong i only listened to A and X and nothing more...all other times I did it properly listening and comparing all 4.

Yes, I do like the sennheiser sound as I love my HD595s - especially for gaming and movies.
I was using MDR-sa5000s to do the test which as we all know, their 2.5khz spike probably meant that cymbals would be the obvious place to notice a difference. Even though I know the sa5000s are better I still enjoy the sennheiser sound greatly.

The WAV was almost shrieking and had so much more intensity than the MP3. Sure, that 'raw passion' might be accurate, but if I'm going to be listening to music in the background whilst writing an essay I don't want to have that harshness.

ultimately you have to decide why you are listening to music - are you trying to produce a pleasurable sensation in your head, are you trying to study music and practicing your trasncription, do you want to feel alive with the music, do you want to hear everything so you get something new, do you want to just have something comfortable? If you can't appreciate what WAV, or MP3 do for you in different circumstances then that is a shame. I generally listen to get the more emotional side - i.e. close my eyes and listen for the sublime and feel as if i'm on fire and I'm not sure whether the Mp3 stops me from doing that even though i know it isn't quite right (even if that is circular since we're defining 'right' as the wav by definition)

Perhaps the best analogy I can think of is the 'eastern european' orchestral sound versus something that you might hear in the US or London. I heard the chisinau national opera tonight as they are local in oxford and they had the same 'sound' as I heard in Prague or you might hear on some eastern european Naxos recording. Compared to my recordings and the music I've listened to in western europe it sounds awful to my ears - I can ABX them perfectly if i could - but you have to appreciate that sound is not perfect however good your kit is and different ways of hearing the same music might be quite good. By all means don't be happy with a poor orchestra, or a crap music player and 65kbps MP3, but it can fulfill some need or other.

I was just doing informal testing, using iTunes to encode different versions of the same song at different bitrates. I started with 32kbps, just to make sure I wasn't tone deaf. Sounded like crap, coming thru a pillow, then a pool of water, then ear protectors, then another pillow! Moved on to 64, vocals still sucked, but instrumental wasn't as bad. Then to 128, not so bad. If I didn't know any better, I'd stick with this and call it a day. I didn't go higher than this, as the dramatic increases in quality seemed to have halted. Just wanted to point out that if needed, 128kbps Mp3s I could live with, and that I didn't hear an extreme difference between that and ALAC; I did hear difference, just not a big one.

I believe the itunes mp3 encoder is not that great. So it would be a better idea to encode to itunes aac or lame mp3.

VBR will always be better theoretically. I would store V2 at least because you will regret it later on when you might be able to hear the difference.