If speaker replacement is because "it sounds different" then it's not the speaker; in fact, it's extremely unlikely to be a speaker issue unless someone poked it with a stick. Most likely it's the filter capacitor(s). Most of the original capacitors might still be fine if the radio has been in regular periodic operation, but the filter capacitors (usually a tall "aluminum can" near the tubes) take a bigger hit. When they go bad (and they will) then the radio will hum or buzz loudly or not work. If it sounds more like static or frying bacon then it's likely a resistor. r/audiorepair or r/VintageRadios can be of assistance.