SVS Ultra bookshelf, Port hissing sound, based notes

MediumTech

Is it common for a port to hiss this way?
Edit 4/12/17, the problem has been found to be a "loose nut" in front of the volume knob.

Thanks to you all, and SVS customer service, in helping me to understand what "chuffing" is, and how to correct it.
        YouTube (Short URL)