I was looking at frequency scans of a friends CD rip in comparison to mine today and noticed in his rip the frequency range was much higher than my own. I use 320 preset insane. I'm guessing he uses custom parameters to achieve this. Here's a couple pics of what i mean.
friends rip:
[a href="http://imageshack.us/photo/my-images/23/example1m.png/" target="_blank"]
--lowpass
Beware though that changing this can occasionally reduce quality, so its often better to let LAME decide on the lowpass filter settings.
Yeah... With lossy compression, if you make one thing "better", something else* is getting "worse". I don't know what's getting worse, but something has to give. You are forcing LAME to waste bits/bytes encoding high frequencies that you can't hear when the rest of the music is masking those high-frequencies. That means bits/bytes are taken away somewhere else.
At 320kbps you can probably increase the frequency range without noticing any difference, but you are almost always better off letting LAME make the decisions rather forcing it to do something. At lower bitrates you are more likely to hear the damage when you start mucking with LAME's carefully-optimized psychoacoustic model.
* Most compression artifacts that you hear don't show-up with simple noise, distortion & frequency response measurements. It would be fairly easy to make an encoder that "looks good" when measured & graphed, but sounds bad...
--lowpass
Beware though that changing this can occasionally reduce quality, so its often better to let LAME decide on the lowpass filter settings.
I figured it was using a lowpass filter but couldn't be sure. I'm also guessing he used --lowpass-width. Thanks for the help, i do understand it could reduce quality was just a bit curious as to how exactly this was done.