All speakers hiss to a certain degree when turned on. However, the sound usually disappears once an audio signal is sent to them. Hissing surround sound speakers can be caused by poor quality equipment that is not made to handle a high level of audio signals.
Bad Balanced Cable
Balanced audio cables minimise unwanted sounds that can be caused by electrical interference. They consist of three conductors, a positive signal, a negative signal and a grounding shield. The positive and negative signals carry the audio signal and change its polarity to reduce noise. If one of these three conductors isn't working, the signal isn't fully reproduced and it is accompanied by hissing.
Poor Gain Structure
Gain structure is how much an audio signal is boosted or "cut" (lowered) by a speaker as it moves from one speaker to another in multiple speaker systems. Speakers are made to handle a range of signal levels. If the signal is too high, the sound can be distorted; if it's too low, the speakers will hiss. Gain fixes this so that all speakers in a system emit sound. Analogue equipment can "cut" signals gradually as the volume becomes too loud for them to handle, creating a hiss. Low quality sound cards of digital sound mixers can have poor signal to noise ratios, which creates a hissing sound as well.
Headphone jacks or RCA jacks that do not fit connector ports snugly can cause hissing. Dirt or corrosion can act as a semiconductor and create distortion in the signal as well as a drop in its level, which causes hissing.