Trouble with right front speaker: crackling/popping sounds

[desktop]

I bought some Logitech Z506 surround speakers for my PC, but after hooking them up I found the front right speaker (the one with the thick black cord) was making a crackling/popping sound. So I took them back and got another set and the exact same speaker was again making a crackling/popping sound. I noticed that the only time it would make the this sound was when I played certain songs that had a very low bass beat, deep chord or certain timber to the singer's voice. Also, when there was no sound at all I could hear a distinct hiss in that speaker.

 

I thought it was odd that the exact same speaker would be bad in both sets I bought, so I was thinking perhaps it might be something else (a setting, or something). I took the second set back also, so right now I don't have any PC speakers, but before I buy another set I thought I would post here and see if I could get some help or advice so I can figure out what's going on.

 

Thanks