It must have been sometime last year during my epic loudspeaker design project (in testing phase) that I noticed, to my shock, that when I played “Something For Kate’s” track “California” (from there album “Desert Lights”) using my Nexus 7 tablet as source, I enjoyed it a whole lot more than if I listened to the CD (from which the the tracks were downloaded) directly.
I remember at the time it somewhat stunned me, but I didn’t think much more of it until today, when it finally struck me as to why that might be. As with much over limited material these days, clipping is a pretty common place event and that particular CD is no exception.
The presence of clipping is the key to answering the question. Clipping introduces wide-band noise into the signal chain, which lossy compression schemes like mp3, or ogg vorbis for that matter, simply can’t encode accurately, so the upshot is that the information lost out of lossy encoding the clipping ends up smoothing it out and making it sound less distorted. You can clearly see this at work in the time line of the “California” track in the samples I show below.
Clipped segment in “California” track as is on CD
The same clipped segment in “California” track after being converted to mp3 format
Looking at CD case (click on it to get a bigger view) you’ll see a clear and extreme clipping event in the content, which is evident from the ruler flat top of the signal. Now look at the same event after being converted to mp3 and you’ll see that although it still looks like clipping, it is no longer ruler flat and has sharp edges smoothed out. It is the sharp edges that give rise to the wideband noise that makes the clipping sound so obviously bad.
The general finding following from this behaviour is that any content that conforms to loudness wars playback levels will generally always sound superior as an mp3 rather than the unadulterated and more accurate CD source, not because the CD format is bad, but because the mastering is rubbish and the CD shows it up as such, whilst the lower Fi mp3 has a harder time of showing up the defects.
Given the entrenched nature of the loudness wars mentality, the only reasons you should consider actually buying a CD version of commercial music is to have a backup and to have the enjoyment of looking through the liner notes and artwork. You should probably set about transferring it to your mobile phone / tablet to actually play the content and not bother with the CD at all, other than for a definitive backup of the material.
If the music business wanted to continue selling CD’s more than downloads, the wholesale participation in the loudness wars did them no favours. That participation has essentially destroyed the aspiration of Hi-Fidelity to such an extent that you would be mad to even consider it if you are into popular contemporary music. Perhaps if you are into classical music but even there I’ve notice with horror how loudness levels are being pushed higher.
Perhaps the only reason to consider a Hi-Fi purchase these days is for home cinema reasoning where quality recording technique is still practiced and appears to be the entrenched (thankfully) approach.