EH Scott Radio Enthusiasts

The Fine Things are Always Hand Made

So I have this speaker in my collection: 

Operating it would require just 4 leads, two with a field voltage and the two VC leads. But this doesn't look anything like the extension speaker shown in the AW23 manuals:

Any ideas on what I have here?

Kent

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Also, there is no output transformer on it (even though it is labeled that way), the two "P" leads go to a 19 ohm VC.

Kent

Is it possible that it doesn't need an output transformer since it uses the main speaker output transformer. Just thinking

John - Yeah, the VC can easily be connected similarly to the extension speaker diagram. The field is the puzzler, where would we ge a good field supply for this?

Kent

Is that just a regular AW-23 speaker, missing the pedestal base and output transformer?  I've never been into my AW-23, so I may be making an uninformed statement. 

Alex - Yes, it came in a base just like an AW23 speaker but with no plugs on the base.

Kent

My thought would be that the field would connect in parallel with the main speaker field. Any other thoughts from the group?

Kent King said:

John - Yeah, the VC can easily be connected similarly to the extension speaker diagram. The field is the puzzler, where would we ge a good field supply for this?

Kent

Connecting the field in parallel with the main field coil is a bad idea unless the field is one with a high value like 2.5k for two reasons.  One the +250 volt supply will rise to +325 volt or more.  Second the fields of Jensen A12 speakers need about 10 to 12 watts of power to deliver clear bass.  Now the current will be divided between the two fields meaning both the main speaker and extra speaker will be under powered.  You may successfully got mushy bass from BOTH speakers!

A much better way is mount a 1:1 isolation transformer with a bridge rectifier and filter capacitor to the speaker frame and power from AC line.  You only need a 20VA transformer...I think you can get everything from Mouser for less $50.

bob

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