hunterj :
l1ghtm4st3r :
It's strange to have them not make any noise when they're first turned on.
I had a similar problem with my BX5 D2's, turns out the signal it was receiving from the power outlet was not clean enough.
I found the solution was to buy a ground loop isolator.
Interference must be coming from somewhere in your system as that's the most popular cause for hissing noises and so an isolator will take the signal, clean it up then deliver it to your speakers for them to use.
Give it a shot, let us know how it goes.
Yea they also don't make noise if I plug the 3.5 mm direct into my iPhone. Might just go ahead and get an audio interface such as the Scarlett 2i2.
Definitely sounds like a ground loop problem then. You wouldn't get anything from your iPhone as it's DC current so no hissing sounds or anything.
Not sure the Scarlett would actually solve your problem.
http/www.amazon.com/Raptor-GL15-Ground-Loop-Isolator/dp/B0009O19LQ/ref=sr_1_2?ie=UTF8&qid=1420231467&sr=8-2&keywords=ground+loop+isolator
This is more along the lines of what I was thinking of.
I imagine you want to buy the 2i2 to be a recording device, but I don't think it's actually got a ground loop isolator to clean the signal. If anything, it will record just perfectly but your speakers will still play back sound with the hissing.