You can make electrolytics work but they have to be biased correctly! I don't know why, but for some reason most speaker manufacturers don't do this. The problem is that electrolytics can't be reverse-biased. This is supposed to be why you use non-polars. But non-polar caps are merely two electrolytics assembled back-to-back. The problem is not solved- now you have distortion of the waveform in both directions!
The solution is simple. Get two caps of the right value (in this case 47uf). Put them back to back but keep the connection where they meet available. Attach a 100Kohm resistor to that connection, and connect a couple of 9V batteries in series to that resistor and the minus connection of the speaker. If the back to back connection is the negative side of each cap, attach the negative side of your battery power supply to that as well.
What you will find is that the distortion associated with electrolytics is gone! You will also find that they can keep up with expensive film caps for an embarrassingly low price :)
The batteries will last for their shelf life. You could of course replace them with a small power supply. As long as the caps are biased at a voltage greater than that of the incoming signal, its all good.
