When I bought my Mac MINI the monitor I purchased had built in speakers but the volume was very low and even though I have all of the volume slides almost in their max position I could barely hear anything with sound. So I ordered a set of plug and play speakers that have a usb plug as well as a direct plug to the back of the computer. Again all of the slides are at the max position and the lights are on on the speakers so it appears that they are getting power but alas the sound level is exactly the same as before. Any ideas?