Not sure, so let's run through some basic troubleshooting.
CMD+R, type in mmsys.cpl in the Run dialogue box. In Sound, press Playback tab, right-click your speakers and select Properties. Should be an Enhancements tab and usually there's a loudness equalisation option. Try tick that, then Apply/OK. Any better?
If there's no update available, try right-click and select Properties. Then Details tab and select Hardware IDs from the drop-down Property list. Copy & paste the values as a response to this, then I'll have a look online and see if there's an update elsewhere. Also if you were to do this, please advise of the Driver Date & Driver Version -- this can be found in the Driver tab on the Properties menu.