Car Speakers Shut Off When I Turn Volume Up?

i have a 95 honda with 2 amps and a capasitor. speakers in car meaning driver side and pasenger side front and rear speakers shut off after i turn the volume up past the halfway point but my subwoofer that are conected to a seperate 2nd amplifier keep playing i replace the fuses on the amplifier they were good but i replace them anyways and i also cleaned the batery terminals where the amps are conected i duno what else to do any ideas