I recently bought some second hand speakers as my old set-up died. However, after roughly 30 mins of use the volume starts dropping and basically cuts out after an hour, increasing the volume works temporarily (audible volume and then continue to fade out still) and turning them on and off works the same. This happens both when plugged in on my phone (standard 3,5mm aux-in) and pc (RCA to aux on mobo). It's a 2.0 set-up, cerwin-vega model XD4. I just hope its fixable before buying some actual new speakers.