Raise the very first slider (the brown one) on this one   http://mynoise.net/NoiseMachines/desertedSoundscapeGenerator.php   Some of my headphones were able to output the very low frequency rumble (HD600), some did not produce any sound, or only harmonics when the volume is boosted...

Dear Head-Fi'ers,   I set up a new page that hopefully will help you evaluate headphones, online, and determine which one offers the best performance when comparing different pairs. Feel free to comment.   http://www.audiocheck.net/soundtests_headphones.php   Happy sound checking!