[MrFixr55]

Hi StoneyD,

I have put a PM Dynamic speaker into a Philco Model 20 with good results. You can install directly into the cabinet without hacking the cabinet up. You do have to hack the speaker. At the 4 speaker holes, cut a notch into the frame to make the holes into an open U. This and 4 washers will allow you to mount the speaker into the cabinet.

To deal with the field coil, merely place a 3.1K (a 3K will do fine) 5W resistor across the field coil leads. Temporarily transfer the transformer to the new speaker (most speakers have mounting points) or fashion a bracket to mount the transformer onto the speaker. There will be a mismatch as modern speakers are usually 4 Ohm or 8 Ohm and the Model 20 speaker is about 1.5 Ohm. However, for testing purposes, you should be OK. I used a Hammond 125D (I believe) which had 5KOhm Plate to Plate impedance and this seemed to work just fine.