Excessive noise within a passive speaker system can be caused by many of the components which make up the system, especially if this is an older system. It is worth trying to define the sound further which may give you a better clue of which steps to investigate before ruling your speakers as being the issue.
There are three types of noise you are likely to come across when working with an analogue/passive speaker system. Pops and clicks, Crackling or hissing/hum, below you will find a little explanation of common causes for these with recommendations of further sections to check.
Pops and clicks
These will usually be associated with surface noise from vinyl, if you are using a turntable as your audio source please start by following the steps in the article “Why are my speakers producing pops and clicks?”.
Crackling may suggest there is a loose connection or some interference within the system, please start by following the steps in the article “Why are my speakers producing crackling?”.
This is quite commonly linked to noise within components of the system or a ground loop, please start by following the steps in the article “Why are my speakers producing hiss/hum?”.