AMR 130 Front Speakers Popping

I opened up the subwoofer from a AMR 50 speaker system and noticed that the power supply filter capacitor (4700 uF/25 V) was installed backwards (positive (+) lead connected to the negative (-) output of the diode bridge, - lead connected to the + output of the diode bridge. The diode bridge consists of four black, cylindrical devices with gray stripes around one end [of each of them]. The gray stripe marks the cathode or (-) lead). The + output of the diode bridge is the junction where the anodes (leads from the non-striped end of two of the diodes) are connected together and the - output is the junction where the cathodes (leads from striped side of the other two diodes) are connected together. This might be the source of the popping sound in your speakers (check it out and see). If it (the capacitor) is in backwards, re-install it the right way [if you can]. Otherwise, see if Polk can fix it (the subwoofer) for you. Incorrectly installed filter caps will [eventually] fail - sometimes with drastic results - if left that way!!