11-27-2021, 10:07 PM
Overall, the answer is Yes. But, do you really want to?
First thing is to consider the "speaker" as 3 parts, the speaker, the power supply choke and the output transformer.
A replacement would have to take into consideration the parts and function lost with the original speaker. It would not be too hard to find a speaker that would mount in the original location, maybe with a gasket/adapter. Then find an OPT to match the radio's OP and the speaker's voice coil.
The biggest problem is the loss of the field coil that provided a magnet to the speakers voice coil but also provided a great deal of smoothing to the hum inherent to the poorly filtered power supply. Some would have you mount a large resister in place of the field coil. The resistor is going to get warm so it has to be of several watts rating. It will help a little with hum and it will drop the B+ to the proper voltage, but , since it is not a choke, the smoothing will be greatly diminished. Some would increase the size of the filter caps - then recalculate the drop needed in B+ and get a different resister. But this will only go so far. A 10uf cap in the first filter is about the limit. You could add another resistor and bump up the 2nd cap to maybe 30uf (this might be a little trial and error). Finding a place to mound a large choke would be the best for performance, but this is a tough install without mounting it to the cabinet or a spot on the chassis, drilling some "extra " holes in one or the other.
Anyway - do you really want to do that. I certainly would resist making so many changes to an old family radio. Unless it is done very neatly it is probably going to affect the value some. It also isn't going to sound like it did with the original speaker - It will probably sound better.
If it were me, I would continue the search for an original speaker. You're right, they are getting harder to come by. Which is another good reason to find one now rather than later. Somebody here might have one or one that is repairable (new cone or such).
Good Luck
Russ
First thing is to consider the "speaker" as 3 parts, the speaker, the power supply choke and the output transformer.
A replacement would have to take into consideration the parts and function lost with the original speaker. It would not be too hard to find a speaker that would mount in the original location, maybe with a gasket/adapter. Then find an OPT to match the radio's OP and the speaker's voice coil.
The biggest problem is the loss of the field coil that provided a magnet to the speakers voice coil but also provided a great deal of smoothing to the hum inherent to the poorly filtered power supply. Some would have you mount a large resister in place of the field coil. The resistor is going to get warm so it has to be of several watts rating. It will help a little with hum and it will drop the B+ to the proper voltage, but , since it is not a choke, the smoothing will be greatly diminished. Some would increase the size of the filter caps - then recalculate the drop needed in B+ and get a different resister. But this will only go so far. A 10uf cap in the first filter is about the limit. You could add another resistor and bump up the 2nd cap to maybe 30uf (this might be a little trial and error). Finding a place to mound a large choke would be the best for performance, but this is a tough install without mounting it to the cabinet or a spot on the chassis, drilling some "extra " holes in one or the other.
Anyway - do you really want to do that. I certainly would resist making so many changes to an old family radio. Unless it is done very neatly it is probably going to affect the value some. It also isn't going to sound like it did with the original speaker - It will probably sound better.
If it were me, I would continue the search for an original speaker. You're right, they are getting harder to come by. Which is another good reason to find one now rather than later. Somebody here might have one or one that is repairable (new cone or such).
Good Luck
Russ
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