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Discussion Starter · #1 ·
I have a factory stereo multiplex adapter from a later year for my 65 chevelle. I want to connect more modern speakers to it, but in the radio tech section, the advice is to keep the speaker impedance at 10 ohms. The front speakers that I am using are rated at 10 ohms; I have two sets of speakers that I could use for the rear; one is rated at "4-8 ohms" as stated on the back of the speaker, the other set is rated at 4 ohms. Can I put a resistor in the wiring to get the resistance to 10 ohms safely? What type of resistor would I need and how would it be wired? If I can't do that, would an 8 ohm speaker be safe for the rear speakers when I am using 10 ohm speakers in the front?

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65 Danube Blue MALIBU 4 door wagon, 350/330hp crate with GM Performance Parts serpentine belt system, 700R4, factory air with Vintage Air conversion, factory am/fm stereo, tilt wheel.
 

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Just remember that a speaker is a dynamic load as far as impedance is concerned. Hook an ohmmeter to the unit at rest, and it'll never read what's on the sticker. While connected, press (gently) on the cone and the meter will range all over the place. An 8 ohm speaker will work fine, in an application calling for 10 ohms. It's nearly within the +/- 10 percent tolerance of the other components in the system.
If you're going to install a resistor, it should be installed in series, or in line with the positive lead. Not across the leads.

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'64 El Camino
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Jim,

Haven't forgot about you. Will post a diagram a little later.
 

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Okay Jim,

I'd recommend, for simplicity, to wire the additional speakers you want in series with the rears that are currently in your wagon. This will also prevent excess wear on the factory output circuitry in the radio and multiplex adapter.

 

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Discussion Starter · #5 ·
Thank you for the diagram, what if I just want to put a couple of 4 ohm 3 way 6x9's in place of what is already there? Do I have to add a resistor to the line to make it closer to 10 ohms? What kind of resistor would I need and how would that be wired?

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65 Danube Blue MALIBU 4 door wagon, 350/330hp crate with GM Performance Parts serpentine belt system, 700R4, factory air with Vintage Air conversion, factory am/fm stereo, tilt wheel.
 

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<BLOCKQUOTE>quote:</font><HR>Originally posted by JimN:
Thank you for the diagram, what if I just want to put a couple of 4 ohm 3 way 6x9's in place of what is already there? Do I have to add a resistor to the line to make it closer to 10 ohms? What kind of resistor would I need and how would that be wired?

<HR></BLOCKQUOTE>


Jim, I need you to clarify; are you saying you only want (2) 6X9 speakers in your rear for the left and right channels? So basically you want to leave the 10 ohm speakers up front, but in the rear, run (2) 4-ohm 6X9 speakers, correct?

Have to make sure, as it affects what I recommend.
 

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Jim,

Go to a Radio Shack store and purchase (2) of the following: Catalog # 271-120, 8 ohm, 20 watt non-inductive resistors.

You'll then have to wire each one in series with your modern 4 ohm 6X9 rear speakers. This will "bump-up" the DC resistance the audio ouput circuits will see, thus they will act like a current limiting resistor for less work on the radio and multiplex. Simply splice them in-line with the + lead of each speaker;

 
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