Customs Powered speakers for 53' Mercury

I have been working on an original radio for a 1953 Mercury that suffers from lack of volume. I have checked all the tubes on a tube tester and they all are good. This radio has a wire (that appears to be original to the radio) coming from the back of the radio that is hot (6V) when the radio is turned on. If I remember correctly some of the speakers in that era were not permeate magnets but rather electro-magnets that required a power source to amplify the radio volume signal. Does any one remember these speakers? Does anyone have a picture of that speaker? Any insight would be appreciated.

One other point of interest is that I have installed an aux input, that is used with a MPOW (bluetooth) for music from a cell phone. When that is used there is no issue with volume, in fact it works great at only half volume.

 

I rewired a '59 Caddy that each speaker took 4 wires. That was a long time ago, the only thing I remember from doing it was I'd connect evrything, turn the radio on and when nothing happened I switch it off, crawl back under the dash to switch the wires around. I did this 2-3times, got frustrated and just knew my first instinct was correct, crawled back under there - the caddy was big enough under the dash you could use a creeper - reconnected to how I originally had it and turned it back on without any result. I was sitting there frustrated, considering my options when the tubes finally warmed up enough to put out the most beautiful sound imagineable, I located the 'Cl***ic' radio station and heard Patsy Cline on there the way it was supposed to be heard. I've never heard anything better since.