Logic77Two possibilities.
The most likely possibility is that the signal level is not matched between your source and your speakers. If you're using unbalanced input, e.g. from an audio jack on your phone through the splitter, then you may need to switch the input sensitivity between +4dBu and -10dBV. There should be a section on the back of the speaker labeled "Input Sensitivity" where you can toggle this.
The less likely possibility is that your input source's DAC really sucks and you need a better input source.
RaymondblHi there - I am copying my reply to a similar problem above :)
From what you are describing, it sounds like you have ground loop loop interference. From what I understand, it occurs often when the source input and monitors are powered from the same source - ie the same power strip.
What you could try is to have the monitors running on a different power strip to the PC/ DAC if possible.
NB: Different at the wall too - so different wall sockets.
From what I've read and understood from conversations from someone working at a my local musical instrument and equipment store, that should clear up any buzzing or interference.
If that doesn't help, then sorry - I don't know enough to give a somewhat educated opinion.
Good luck!