Originally posted by janneman
Huh? If the bridge is properly balanced, there is no DC across the cap, right? Only AC, from the AC load current through the cap AC impedance.
Look at it half wave at a time. Depending how you connected AND the value of the cap. How big the reversal voltage will be will depend on the impedance of the cap for that frequency. The lower the frequency the larger the AC voltage drop across the cap the larger the reverse voltage at every haf a cycle. For example at 20 Hz 2,200uF cap has 3.6Ohms impedance. Your speacker is 8/4 ohms. It means you coud have up to half of the output voltage across the cap at every single moment (for 4 ohms speackers).
On the other hand if you use single power supply the cap will always see the same polarity voltage with different amplitudes across.