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Wiring speakers Track and electrical/DCC
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Active Member 59 posts melusi Active Member 59 posts
melusi

I am fitting a sound decoder to an Athearn  GP-50 . (Blue Box).The size of the shell is too small for a standard speaker so I decided to fit a twin mini speaker set.

My question is, do I wire them in series or parallel?

Peter
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janreimers Active Member 69 posts
janreimers

Melusi, Please state the ohm

Melusi, Please state the ohm rating for the decoder and the ohm rating for your speakers. 

 

JR
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lexon Prolific poster 1,211 posts
lexon

Wiring speakers

Usually in series. Look at the below link. Look in Curriculum and SoundTraxx. He has loads of good DCC and sound info. Bruce use to own Litchfield Station, a very good DCC company.

http://www.mrdccu.com/

Rich
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melusi Active Member 59 posts
melusi

rating

Not sure of Decoder rating but came with a 32ohm speaker. My twin speakers have an 8ohm each rating.

 

Peter

Peter
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melusi Active Member 59 posts
melusi

Speakers

Thanks Rich. 

Peter

Peter
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Kevin Rowbotham Prolific poster 2,336 posts
Kevin Rowbotham

Speaker Impedance

Ohms law states that: current = voltage ÷ resistance.

Therefore if the resistance goes down, then either the voltage or the current must increase (usually the current). Either way, this puts an increased strain on the power supply of the amplifier.

For example, if you disconnect your 32 ohm speaker from your amplifier and connect 2 X 8 ohm speakers wired in series, (resistance in series circuits is additive) for a total impedance of 16 Ohms, the resistance goes down. Less resistance lets more current flow and so the amplifier will have to deliver more power to the speakers (current or voltage) - which it may not be designed to do.

IMO, the idea is to get as close to the supported impedance of the amplifier, as possible.  Amplifiers are often rated for a range of impedance.

Note:  I am not sure if this is the case with your decoder or not.  Contacting the manufacturer regarding what impedance is safe, might be prudent.


 

~Kevin

Appreciating Modeling In All Scales but majoring in HO!

Not everybody likes me, luckily not everybody matters.
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Michael Tondee MRH Author 5,521 posts
Michael Tondee

Maybe an oversimplification

But wiring two like value speakers in parallel will half the impedance. so for two 8 ohm speakers, the load is 4 ohms. Wiring two like values in series will double the impedance so for two 8 ohm speakers the the load is 16 ohms. Obviously wiring in series will get you closer to the impedance you want but as Kevin suggest, I'd check with the manufacturer and see what range of impedance the decoder will tolerate.

Michael

 

Michael, A.R.S. W4HIJ

 Model Rail, electronics experimenter and "mad scientist" for over 50 years.

Member of  "The Amigos" and staunch disciple of the "Wizard of Monterey"

My Pike: The Blackwater Island Logging&Mining Co.
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Prof_Klyzlr Moderator 7,950 posts
Prof_Klyzlr

Dear Peter, Fastest way

Dear Peter,

Fastest way home.

- the Digitrax decoders come with a 32ohm speaker because that's what the decoder power amp circuit is rated for.

- Ergo, the Impedance (that's the technical term") for the power amp output circuitry can be safely assumeed to be 32 ohm.

- general rule : you can connect a speaker driver (or array or speaker drivers) which Exceeds the power amp Impedeance, but it's risky to connect a speaker or array with Lower impedance.

- Speaking Specifically: the guys over on the Digitraxx-sound Yahoogroup have successfully connected down to 8ohm loads onto the digitraxx decoders, with the Known Condition that tje Master Volume must NOT be run at Full. (With an lower-than-reccomended speaker load, turning up the Master Volume is like deliberately "turning up the volts" into a short circuit! Circuitry damage follows!!!)

- given that *the decoder wants a safe 32 ohm load (IE has a reccomended impedance of 32 ohms) *connecting 2x 8ohm speakers in parallel gives a total load of 4 ohms *connecting 2x 8ohm speakers in series gives 16 ohms total load The "closest match" would be to run your 2x 8ohm speakers in series, And be _very_conscious_ that the Master Volume CV MUST NOT be lifted above 50% without EXTREME CAUTION!

Happy Modelling,
Aim to Improve,
Prof Klyzlr

PS when connecting the speakers in series, start with Red - speaker - black - red -speaker - black This should ensure the speakers are "in phase" electrically. (IE when the speakers get a positive-going audio signal, the speaker cones both "jump" in the same direction). Depending on the enclosure and acoustics of the install, you may find that messing with the speaker connections/"relative phase" may affect (possibly to the better) the sonic response of the speakers.
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lexon Prolific poster 1,211 posts
lexon

Speakers

Digitrax has a series of decoders that use 32 ohm speakers. Rather common knowledge.

You would need to put 4, 8 ohm speakers in series.

A couple electronic suppliers sell small speakers with different impedance's. I think Mouser and Digi-Key as I remember looking up 32 ohms speakers for someone some months ago.

I have heard a similar issue with LokSound 100 ohm decoder speaker outputs.

Rich
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