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I'm looking to buy this Cromwell but it looks to have an electro magnetic speaker (2nd photo) versus what it should have a permanent type magnet speaker (1st photo). Just looking for someone to confirm the 2nd photo is not correct. Also, can you just wire in an electro magnetic speaker in place of the permanent one like that? Thanks in advance.

No, the 2 speaker types are not interchangeable. However this could be a production change, as the amplifier would have to be set up to accept the dynamic (field coil) speaker, as the field supply is provided in the design of the power supply to the amp. The "magnetic" type of speaker as shown in your first photo is much simpler to drive, and does not require anything from the power supply, and in some cases, does not even require an output transformer. The "magnetic" type of speaker is of inferior sound quality.
I believe your dynamic (field coil) speaker is original to your machine.
To clarify your original post: The first photo shows a "magnetic" speaker with permanent magnet, and an armature that drives the speaker cone. The Second photo (the machine you are interested in) shows an early "dynamic" or "field coil" speaker. This has a voice coil (like all modern speakers) and an electro-magnet to generate the magnetic flux needed to work. Both were used during the year your machine was made, but are not interchangeable.

That Permanent Magnet speaker is an inferior design, using an armature arrangement. This style limits the frequency response and can be overdriven easier compared to an electromagnetic type. However, most of the time you won't be able to tell much difference unless there is a flaw in one or the other, or the volume is turned way up. You can replace the PM speaker with a period correct electromagnetic (electrodynamic) field coil speaker, by a simple modification to the power supply. Both of the Power Supplies you show appear to be the same. In the PM version, there will be choke coil or resistor in the main supply line that comes off the rectifier circuit. This coil or resistor circuit is usually characterized as a "Pi" arrangement when looking at it on a schematic (A filter capacitor, an inductive or resistive element, and another filter capacitor). That inductive or resistive element is what you disconnect and in its place connect the field coil of the speaker. If there is excessive hum, try reversing the field coil leads and then the voice coil leads. Before doing this, be sure the power supply is in top working condition to begin with, and be sure to have this work done by someone who is familiar with the hazards and workings of this equipment. Cheers, Russie

Just to clarify, the Electro-dynamic (field coil) speaker is the superior sound producer of the 2 speakers in your photo.

Victrola-Monkey wrote:I'm looking to buy this Cromwell but it looks to have an electro magnetic speaker (2nd photo) versus what it should have a permanent type magnet speaker (1st photo). Just looking for someone to confirm the 2nd photo is not correct. Also, can you just wire in an electro magnetic speaker in place of the permanent one like that? Thanks in advance.

The Cromwell came with the 10" cone speaker shown in your first picture, as was the Hyperion. I can't see in the service bulletins that the Cromwell was offered with the electrodynamic (104) speaker like the later Hyperion was.

Replacing the cone speaker with a 104 speaker could be done, replace the choke in the B+ line with the field coil of the 104 speaker. You might have to change the output transformer to make it right, one was a 1:1 the other was 25:1, not sure off-hand which was used with which speaker.

You could just pickup a 100-A speaker and put the unit back to original, and hope nothing else was hacked under the chassis.


Chuck