"Volume Boosters are out there, and this article will help you if you're frustrated with the poor audio from your old PC speakers. Don't hurry to buy new ones! A free software program can substantially improve the sound quality.
It is known that the frequency response of ideal speakers must be flat or almost flat. However, the frequency response of relatively cheap PC speakers is not flat at all. If you would measure the frequency response of your PC speakers, you could see a lot of resonance peaks instead of the flat response as it is shown by the gray line in the figure below. All that resonances are created by the mechanical parts of the speakers and, at some extent, by acoustic reflections in the room..."Wow, I never knew this problem existed, but it makes sense.