I have a set of HK speakers hooked up to my MacBook, and there's only sound coming out of the left one. Here's the thing, though: the volume/tone controls from the right one (the one with no sound) are working just fine, and tracks that pan left and right (The Beatles' Taxman, for example) are being compensated through the left speaker. So basically, I'm getting mono sound out of one speaker. I tried hooking my iPod up to the speakers, but that didn't change anything. Oh, and when I hold the non-working speaker up to my ear, I hear the faint humming that is to be expected from a working speaker. And when I twist the jack around in the port, the sound crackles.