First of all, you got some of the idea behind those files wrong.
20 Hz is the *bottom* of your hearing range. of COURSE it shouldn't be loud. your ears cant hear it as loud as it should be--they aren't made to.
Now, is there any point, from 20 hz to 400 hz, a sweep, that it suddenly gets WAY louder? or is it smooth, all the way up?
And those clicking artifacts.....they're probably in the mp3, or your sound card....
So, you've listened to them off of a portable, bass shy, off of a pc sound card, bass shy, what about off of a ministereo? (None of those should give it that much power...)
THEN, listen to it off of, oh, saaaaaay, a high quality Digital Audio Reciever. You know, the thingy that hooks up to your DVD player so you get DTS and Dolby Digital, the thingy that gets the radio and everything? Or, what about a DVD player or a big CD player? Try hooking it up to those.
Is it bass shy on a Led Zeppelin CD? Hey, Why dont you talk to some of us on ICQ or something? Like, get on, and add a few Head-fiers.....
Hey, anyone notice how Headroom's frequency response graphs show the SR-60 as having more bass than the SR-80? Wierd.