How to use Headphones and Speakers at the same time
Take a closer look at the use of wireless headphones and speakers Treblab N8 Perhaps this will not solve the problem, but the sound quality will be at its best. Their main advantage is that you can forget about the wires and take them with you wherever you want.
if your speakers aren't part of the unit (that is... they plug in just like your headphones...) you can get an audio splitter. Then it is possible to plug them both in, since there is now two jacks.
Depends on the hardware setup. If you mean a computer, in some cases you can change certain settings, but I dont know what, sorry.
Most stereos you cant.
In some speakers it is possible to use it both, just insert the headphones lightly(half) just make sure that the sounds on the speakers would not lose.