Whoa, now that's timing... my GF just bought an MP3 player (Creative MuVo?) this weekend... the ripper that comes with it rips MP3s (or WMAs) at about 8x-10x speed... got bro and I into a conversation about audio compression (for those who don't follow my posts - bro and I have differing opinions on audio, I'm a technician, he's a musician) and we did some moderately scientific testing recently on MP3 vs Redbook.

Same selections played back on three different sets of transducers - my Axioms (2xM3s, VP150, 3xQS4s w/STF-2), my Edirol monitors (MA-20Ds) and his Sennheiser cans (sorry, I don't know the model) from 2 different sources - MP3s played off a CD-R in my DVD player through the TOSlink (optical) connection, Redbooks played through my H/K carousel (FL8550) over the S/PDIF (coaxial) connection. MP3s were encoded at 128Kbps with Fraunhofers CODEC & through whatever Creative's software uses and at 256Kbps through Fraunhofers CODEC.

Method: listener sat in the sweet spot eyes closed, luckily both sources were pretty close in gain so we didn't need to pad either source to match levels. Tester would randomly mute the receiver (for Axioms), turn down the Edirols (run through the stereo outs on the receiver) or the headphone level, cue up one of the tracks and play about 5 seconds of a random selection, mute, and restart.

-The Fraunhofer codec at 256K did very well against Redbook (subjectively) but was still picked out of the lineup more often than mathematically "null".
-Fraunhofer at 128K was easy to determine but subjectively didn't sound that bad until you heard it "against" redbook or the higher bitrate.
-The Creative encoder might as well have been AM radio.

Also, the Axioms seemed to be the easiest to make the determination on (though I did have to deal with bro's constant b****ing that they were too bright - sorry bro, next time bring over your 1-way paper cone 80s era towers!) with (to my surprise) the Edirols being second and the Sennheisers third... I would have thought having the music pumped directly against my eardrums would have been better than this pair of $250 powered nearfields.

Also, I had a much easier time of it than bro did (he's got hearing damage from his years on stage) and once you put the high and low bitrate/quality tracks onto the MP3 player and played them through a pair of consumer headphones (whatever Sonys GF has - not the included Creative earbuds - I can't wear them!) most of the extra quality was lost. By the time you take your heart beating in your ears into consideration while jogging (her) or cycling (me) it's probably a wash.

Again, not exactly as scientific as it could be, but more than anything, it was a way of getting a "blinder" listening test between the compression methods. Of course, since he's a Mac guy, he wants to add in AAC and a bunch of other variables if we do it again.

Bren R.