Sound issues, headphones AND external speakers

[gmq]

I am attempting to use harmon kardon external speaker set with my t510 (which I recently bought in good condition used), and am having very limited sound. The set has an external amplifier. The sound can only be controlled from the computer, and doesn't get to even a third as loud as it has on all other laptops/desktops these speakers have been used with, morever the external volume controls (located on top of one of the satellite speakers) does not work up or down. The headphones were playing loud enough and could be controlled from the wireless headphones and then stopped doing so not too long after receiving the computer. They now play this in and out highly staticky, skipping, choppy sound that is intolerable.

I hope these problems ring an obvious bell to someone. Thanks very much!