It's curious. When I sit on my vibrating love seat (home made version of the vibrating board thingy) and play with headphones I swear the sound of the bottom end becomes louder. Switch off the seat and the bass is thin and reedy, turn it on and it once more sounds rich and full. But here's the thing - I can't hear the seat when I'm wearing headphones. At all. So I'm feeling bass and my brain is telling me I'm hearing it.
I don't understand the science at all, perhaps someone else can shed light.