Sorry for the late reply, I had a lot going on. Thanks for all the answers!
My subwoofer ist the Canton AS 85.2 SC, my headphone the Ultrasone PRO 900 and the speakers are the Mackie MR5 MKII (altough the speakers shouldn't be imporant, I want to use the headphone in conjunction with the sub).
Well, the main reason is that I want to feel the bass everywhere, not just in my head.
As stated above, I own the Ultrasone PRO 900, I don't think there are many headphones in its price range that have more bass ;)
But no matter of the headphone, I won't "feel" the bass without a sub.
I understand wanting to feel the bass, that reverberation in your stomach and chest but why use headphones and a sub and not just use speakers. The question could be reversed to "why do you want the sub on but NOT the speakers?" I just cannot understand any situation where you would want to do this, it will sound a long way from perfect as you wont be able to tell the headphones to not play the bottom end frequencies the sub is overlapping, it will sound messy and muddy at best.
I personally prefer gaming with a headphone and not speakers because of the details and Dolby Headphone.
We need to give you a fun pill so you can imagine how this might work
With headphones with a lot of bass rolloff, like the AD700s, I would imagine that setting the sub crossover at 50hz might allow it to fill in very well at those bottom frequencies for enjoying special effects in gaming and movies. Even if the texturing of that sub bass were decreased a little, tactile sensation adds a lot for special effects
Yep, exactly the reason why I want to do this ;)
What you describe definately does happen somewhat with my full range speakers + headphones when used simultaneously but judging from my 5.1 system with which I use full range speakers for front R & L with no muddiness (admittedly with a HF filter on the sub output) but I really can't see it being an issue.. especially when you have a degree of noise isolation from most headphones combined with the bass, mids and treble channeled directly into your ear canal while feeling the non directional sub bass from the sub.
Got me intrigued now, I'll test test my active sub (without the HF filter) with my headphones tomorrow and report back. :)
I would love to hear your result and your setup to get it working. Especially games would be very interesting :)
I hoped for a software/driver solution because replugging cables all the time will be very annoying, but there is probably no way, right?