Hi,

Difficult to solve your problem with no detail of implementing your export. Some points to check.

1 - Do you listen the vocals on your PC with the same speakers?

2 - What player do you use (WMP, Realplayer...)?

Are you sure that your player doesn't use style or effect : equalizer, style : rock, jazz...? All tuning must be neutral. Try to use Magix Music Editor or  Audacity with no effect to check the sound of your export.

Or simply drag and drop your Wav export in a new project of MMM. Check if all fx are out and all tunings are neutral : equalizer, fx etc... How is the sound?  

3 - In what format have you record your vocal? Use Wav.

4 - What export format do you use : mp3, wav? Check with wav format.

5 - Try to export vocal only without music (mute the instrument tracks)  and check it, applying the above recommandations.

Regards