[Ronin61]

Will a speaker from a philco 37-660 fit and work in a philco 36-645K ? Are the same speaker.

[Ron Ramirez]

No. The 37-660 speaker has a field coil resistance of 2200 ohms, while the field in the 645's original speaker (H-21, by the way) has a field of only 435 ohms.

Here are speakers that would work in your 645K:

H-21 - 97H, 97D, 97X, 640X
H-26 - 37-650X, 37-650PX, 37-665X, 37-2650X - 460 ohm field, close enough
H-30 - 37-9, 37-10, 37-11 - 480 ohm field, close enough

[Ronin61]

Thanks Ron looks like I have a bad field coil and I'm searching for a replacement.