[Reece]

Seems that (some) early moving-coil speakers, especially those with the spider screwed into the center of the pole piece, had a kind of stiff action and didn't have all that good bass response and so the power supply didn't have to have the best filtering, and since larger filter caps were expensive...could be that the speaker, the speaker mounting, and the supply filters were all serendipitously ideal for the situation.

I think I read somewhere another idea about cleaning out those capacitor blocks: put them in the freezer for a while and the tar is easier to chisel out. Does that ring a bell?