Originally Posted by morijinal
Agreed. Filtering what exists makes sense. Amplifying what does not - does not. Don't get me wrong, I believe the EQ can cater to individual taste, and in some circumstances remove or amplify certain characteristics. However, you can only do so much when it comes to hardware. If a headphone isn't capable of pumping out sub-bass it can't be forced to. If they are capable of strong sub-bass they can be squeezed for every ounce they are worth if desired.
with EQ, filtering = amplifying. If you filter (reduce) all frequencies except the bass, and then increase the volume on your amp, the result is essentially boosting the bass frequencies. The reason you want to do it this way is to prevent digital clipping.
Now with sub-bass in particular, the reason you shouldn't boost those frequencies is primarily due to limitations of open dynamic headphones -- they inherently have increasing distortion below 100 Hz because the driver is moving freely, and with low frequencies this can and does result in over extension of the driver causing bass distortion.
This is the reasons ortho-dynamic headphones (LCD-2, HE-500) offer an improvement in the bass response, because they do not need to roll off the sub-bass frequencies to prevent distortion.