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Discussion Starter #1
I have (2) USA GP38s. The 1st loco has a Sierra Soundtraxx system installed in the fuel tank with the supplied speaker from Sierra. (A 2-1/2” round speaker made by Kobitone, 8 ohms, 0.5 watts numbered 49211). I wanted to trainline the sound into the 2nd loco when they run together. As a test… I connected a Phoenix speaker (A 2-1/2” round speaker, 8 ohms, ?? Watts, number SP-2.5SQ: 824-660) in parallel to the Sierra speaker. Well… the sound was coming out of both speakers for about 30 seconds when a puff of smoke came off the Sierra board followed by a bright glowing component. Needless to say … the board was cooked.




After reading about ohms on the Internet (should have done this first)… I discovered that hooking up two 8 ohm speaker in parallel changes the ohms to 4. I’m assuming the Sierra couldn’t handle this and blew.




Has anyone ever hooked up two speakers in one locomotive or trainlined the sound to a 2nd unit?




To add to the challenge… I noticed there is a place to mount a 2” speaker under the rear fan in the top of the locomotive. Is there a way to wire the sound board to run a speaker in the fuel tank and a speaker under the rear fan in the first locomotive so that the locomotive can run solo… but be capable to run a third speaker in the 2nd unit when both locomotive are operated together?




Can a Sierra card handle the power needed or would a Dallee 11 watt amplifier be needed?




I’m not very knowledgeable about this stuff (if I was, I wouldn’t have cooked the board ).




Any help or thoughts would be greatly appreciated!
Thanks, Russ
 

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Super Modulator
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Yes, you changed the impedence to 4 ohms and nuked the amplifier in the board.

Yes, I've used 2 speakers, when I do, I try to find 4 ohm ones and put them in series (8 ohms total)

If you can't do that, then two 8 ohm ones in series, but then you will get reduced sound levels.

Amp might help.

I'm guessing you want it REALLY loud.

Concentrate on more efficient speakers, will put out more sound at same power.

Regards, Greg
 

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The Soundtraxx is rather anemic when it comes to volume. They don't seem to understand that 1 watt tends to get lost when you are outside. If you want to use a Soundtraxx system, I would recommend an external amplifier too drive all of those speakers. Hooking up that second unit and then trying to run without it is difficult when you are trying to maintain a proper speaker impedance. When I do my F-3s, I intend to put a Soundtraxx in the A unit and the B unit. That way, speaker impedance will not change when I unhook the B unit.
 

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Discussion Starter #5
I was considering a sound card in each locomotive but was trying to save some money by having one card supply sound to 2 engines.
Russ
 

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I've run my Sierra at 4 ohms and it started motor-boating (sputtering), but never let the magic smoke out. Maybe we have different versions? Don't run these under 6-7 ohms minimum.
 

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The impedence rating of speakers is nominal at best. If you were to look at the plot of speaker impedence vs. frequency, you would see that the impedence varies all over the place. Also, different manufactures have different "habits" of measurement (that's as diplomatic as I can put it!).

So 2 different speakers, both rated at 4 ohms may have vastly different electrical characteristics. Add those variances to differences in speaker enclosures, supply voltage, volume, etc. and you can see that it's not necessarily an "exact" thing.

Regards, Greg
 
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