[iamdone]

I just did a test last night using AAC at 256 (iTunes for pc) and mp3 LAME (EAC high setting LAME 3.93.1). I didn't have my ety E4-S with me, so I used Senn. px200 and a Headsave Transit amp. I used the first 4 songs off Radiohead's Kid A for my sample.

The AAC has a slightly wider soundstage and creates a unique surround effect but the center sound doesn't sound right. It sounds like the left and right channel are being pulled apart just a bit. The vocals sounded a little in the background.

The mp3 sounded a little narrower but the vocal were more up front and it had a crisper sound to it. It sounded just bit harsh compared to AAC. Overall mp3 just sounded more enjoyable than AAC. AAC sounds like you added stereo seperator to it. This probably works great at lower bit rates but not a 256.

I also tested WAV files on the Ipod to use as the original. The three files sound almost the same when doing side-by-side testing but again, the problem can up with AAC. The center vocals are not as forward as WAV or mp3. If you are not using a headphone amp, I don't think you'll be able to tell the difference because soundstage placement is much harded to detect without one. The mp3s had just a little less (barely noticeable) dynamic range than the WAV but since the soundstage is the same, I prefer it to AAC. AAC seems to have almost the same dynamic range as the WAV. If they can correct the soundstage in future upgrades, then AAC would be the winner.

Also after listening to AAC a little more, I notice another problem. I causes the bobbles in the head feeling that I don't get from mp3s. It kind of makes you feel a little dizzy. I know crossfeed can fix this but you don't need this for mp3s.

 

[hempcamp]

I think the increased stereo separation (which is what gives you that bobblehead feeling) is actually a *good* thing, quality-wise. We wouldn't need crossfeed filters on high-end amps otherwise. So I don't think it's the AAC, I think it's the headphone/amp combo that is being more revealed by the AAC.

Hook your iPod to a high end amp/loudspeaker source and see if you detect the same "problem." You will probably see it the other way around that way.

--Chris

 

[iamdone]

Quote:

Originally posted by hempcamp I think the increased stereo separation (which is what gives you that bobblehead feeling) is actually a *good* thing, quality-wise. We wouldn't need crossfeed filters on high-end amps otherwise. So I don't think it's the AAC, I think it's the headphone/amp combo that is being more revealed by the AAC. Hook your iPod to a high end amp/loudspeaker source and see if you detect the same "problem." You will probably see it the other way around that way. --Chris

I does seem like it would be good thing but when I compared the soundstage width to the WAV file, it just sounded different. The mp3 sounded exactly the same as the WAV. Neither of those formats produced that dizzy feeling (I never suffered from this with cds or mp3s and can listen for hours and not get tired). Something is just a little off with the AAC (at least using iTunes to encode). I should be getting my Ety ER-4s back tomorrow, I'll retry this test again. The ety reveal so much more. I know the px200 were not the best for this test, but even with those headphones I could notice the slight differences side-by-side.

 

[Lando]

If you can, try a different aac encoder. If you're going to compare low bitrates, try throwing abr into the mix for mp3s. It sounds suprisingly good at abr 128, but vorbis sounds just as good at an even lower average bitrate.

 

[iamdone]

I think I'm done testing other than try different headphones. At the lower rate, I've heard AAC wins, so this was not worth testing. This is only a debate of sound quality at the higher bit rate. Even at this level, I could tell AAC would win if they corrected there soundstage. The main problem is the vocals. On WAV and mp3, they sound like they're front and center, with AAC they sound spread apart just a bit and almost in the center of my head.