Would it be possible to simply run a set of jumper cables from a powered diesel unit's speaker to a speaker in a dummy unit in order to get sound in the unpowered unit?
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Physically yes; the question becomes can the sound system amplifier board handle dual speakers under load. Our more astute electrical types will have to answer that question.
I'd probably consider a small audio amplifier module in the dummy unit to avoid overloading the sound board in the locomotive. It would be pretty simple to do.
I would just drop a Williams true blast II unit in the dummy for $30.00 It comes with everything you will need.
As long as you match the total impedance of the speakers to what it originally had it is fine. For example if the speaker in the power unit is 4 ohm, you could remove it and install an 8 ohm in the power unit, run 2 wires and install a second 8 ohm speaker in parallel (match + and - terminals). Total impedance would be 4 ohm. Running an amp with a higher than designed impedance should not damage the amplifier,however never go lower than the design,which might. You could therefore in this example then still run the power unit separately unplugged from the unpowered unit and get sound which may or may not be lower. If the new 8 ohm speaker is a quality one, efficiency may be a lot better than the original 4 ohm so volume may not be significantly reduced.
If the speaker is 16 ohm you could replace it with 2, 8 ohm ones in series.That was done in this tender in this post.
http://www.jcstudiosinc.com/BlogShowThread?id=621&categoryId=426
However if the harness was split between 2 engines there would be no sound unless the dummy unit was plugged in. You could add some kind of switch to the powered unit for a one or 2 speaker option but powered units are already pretty crowded.
Dale H
