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Shop Speaker Setup (Ohms)

post #1 of 3
Thread Starter 


I am needing some assistance with figuring out my speaker configuration and the correct ohms to aim for. I've read several posts but I am still not confident that I understand it.


I have 6 speakers. All 4 ohms. I want 4 on the corners and two on the front wall. This is in a shop so looks/quality doesn’t really matter - I just won't to ruin the speakers or the amp. All of what I have is cheap reused stuff but I still don't want to unnecessarily blow anything.


My amp is the Pyle PTA2 Mini 2x40W (bought on Amazon)

From the documentation:

The speaker impedance can be ranged from four to eight Ohms for the general stereo output. The total speaker impedance must be at least four Ohm per channel


I am using the 4-Way Stereo Speaker Selector from Radio Shack.


I would like to be able to choose any combination of the three sets of speakers:



Front corners

Rear corners


From the speaker selector documentation:

Impedance Chart

The chart shows the impedance for all possible combinations of 8-ohm speakers.

Speaker Sets On                          Impedance

A, B, C or D                                           8

A + B                                                    16

A + C                                                    4

A + D                                                    4

B + C                                                    4

B + D                                                    4

C + D                                                    16

A + B + C                                              5.3

A + B + D                                              5.3

A + C + D                                              5.3

B + C + D                                              5.3

A+B+C+D                                              8



This chart is what has me thrown off. I didn't know if I could just halve the impedance from the chart or not since it's for 8 ohm speakers.



What would be the recommend setup given the items I have?

post #2 of 3
I think you may have a problem here, unless you are wiring the speakers in "series". If you are using a speaker switch that does not have impedance protection circuitry, than adding speakers to the "on" position is adding them in "parallel" and the resulting impedance will be lower, not higher.

4ohm + 4ohm in parallel is approximately 2ohms and will blow your amplifier.

I'd suggest you consider a better speaker switch....on with impedance protection which limits the load seen by your amplifier to 4ohms or more.

post #3 of 3
Thread Starter 

Thanks! Sounds like exactly what I need.

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