I would take the person who repaird it last time and shoot them. This is a cross-over filter which is fed by AC from the amplifier but they have used polarized capacitors as replacements for non-polarized ones.
However, the first thing to check is the loudspeakers themselves, discionnect the filter first then run wires directly from the amplifier to the tags on each loudspeaker and feed some music through them. Don't turn the volume up too high, just enough to listen comfortably. The tone may sound horrible but you should hear clear sound from each individual loudspeaker unit. If any are silent or distorted, the loudspeaker itself is defective. If they are OK, the first suspect would be those capacitors. Replace them but with non-polarized types, the value shoudl be the sum of each of the ones in the group of 4 and the same as the single one, that is assuming the previous repairer used the same values as were originally there.
Brian.