Originally Posted by Toptube
I think it's because a decent set of headphones are fuller across the sound spectrum. Whereas most bass cabs have a frequency gap between what the main speaker covers and what the tweeter covers (if it even has one), these frequencies are often under represented.
Something like a Fearful with an extra mid driver would probably sound more like a good set of headphones.
The OP's primary issue IMO is that most of the Ampeg 410's I've played were incredibly uneven (which does NOT mean they won't sound great for some, but they surely won't sound like a good set of phones, which are designed to be very clean and accurate), with some mostly midrange, and others mostly low end. So, he is comparing (probably) one of the more voiced bass cabs out there to a much more transparent sound reproduction source.
If the OP really likes that clean, low distortion, wide tonality of a set of phones, IMO he has the right head and the wrong cab
Most of my rigs sounds reasonably close to the sound I get from my Café Walter headphone amp (very nice) and the BeyerDynamics990's. Not quite as pure, but quite close!