have you checked to see if connection(inside) the speaker cabinet are secure, and that the cross-over's are intact, blown or shorted crossover can also cause static, loss of sound or low sound. However having said that it could be the woofer itself, removing the woofer and fill will allow inspection, you can also test the woofer you think may be blown, by connecting to the other speaker you said is working properly, if it still has low sound then you know its the woofer and not a short somewhere
My friend had the same problem with a set of Jamo S-807, was getting limited sound from woofers, turned out to be the crossover had shorted out, he sent the crossover out for repair or replacement(not sure which) but that solved the problem. Hope that helps.