Speaker Selector Switch Simulators

The speaker selector switch simulators presented here demonstrate how speaker selectors deal with speaker impedance and power distribution. Speaker selector switches are used to allow you to connect multiple speakers to your HiFi amplifier. They help to keep the total impedance safe for your amplifier. How do they do this? How do the different types work? How do they divide the power among the speakers? Read on…

These speaker selector switch simulators are ideal if you:

  • are thinking of buying a speaker selector switch and want to know the best type.
  • want to know how to use them better
  • would like to know the effect on impedance and speaker power with different settings.
  • like to know how speaker selector switches work

How to use the Speaker Selector Switch Simulators

Speaker selector switch simulators schematicThe speaker selector switch simulators below are based one a setup similar to this diagram. Only one channel of the amplifier is shown as speaker selector switches (and the simulators) treat both the left and right channels the same.

Basically you need to fill in the white boxes.

Start with selecting the minimum impedance your amplifier is designed for. Then type in the maximum RMS power your amplifier will produce at this impedance. This information is normally found in the “specification” of your amplifier User’s Manual.

Then type in the rated impedance of each speaker pair connected to the speaker selector switch. If you are using less than 6 speakers, simply type in “0” for the unused speakers. You can also make each speaker selector switch simulator act like a 2 way or 4 way speaker selector by using “0” for the unused channels.

The on/off switches next to each speaker simulate the on/off switch for each speaker zone on the speaker selector. As you turn each switch on or off the total load impedance and the power through each speaker is re-calculated.

Simulators for 3 types of Speaker Selector Switches

There are three main types of Speaker Selector Switches. There is a simulator for each type. Click on a button to go directly to that type.

Series Parallel Type Simulator Series Resistor Type Simulator Transformer Multiplier Type Simulator

Series-Parallel type Speaker Selector Switch

How they work: Series-Parallel type of speaker selector switches use switches to connect the speakers in a combination of series and parallel. Speakers 1 and 2 are connected in series, as are speakers 3 and 4.  Then each series pair are connected in parallel.

Pros and Cons: There is no power lost due to the switch.  They are not expensive. Can be used for 2-4 speakers. Do not work for all speaker/amplifier combinations. Normally recommended for 8 ohm speakers. If using three speakers, don’t turn the spare (4th) zone on, or it will disconnect the 3rd speaker (because there is nothing to be in series with).


Series Parallel Type Simulator Series Resistor Type Simulator Transformer Multiplier Type Simulator

Series Resistor type Speaker Selector Switch

How they work: When the “protection” switch is on, a resistor is placed in series with the speakers. The minimum load impedance will not go below the value of this resistor. Turning the “protection” switch off removes the resistor from the circuit.

Common resistor values used by different manufactures:
2.5 ohms: Niles
3 ohms: Sima
5 ohms: AVX, Monoprice, Parts Express

Pros and Cons: While the resistor takes care of the total impedance, it can also take a lot of the power. Therefore the resistors can get quite hot. Normally not recommend for higher powered amplifiers. The lower the resistor value, the less power loss through the resistor, but the less impedance protection offered.


Series Parallel Type Simulator Series Resistor Type Simulator Transformer Multiplier Type Simulator

Impedance Matching Transformer type Speaker Selector Switch

How they work:  Each channel has a transformer which effectively multiplies the impedance seen by the amplifier. For example if the multiplier is set to x2, a 4 ohm speaker will appear to be 8 ohms. The trade off for this is that the power available to the speaker is divided by the same factor.  Most transformer type of speaker selector switchers have a switch at the rear to set the multiplier to x1, x2, x4 or x8. In practice transformers are around 90% efficient – this simulator is based on 90% efficiency.  Most impedance matching transformer based switches also incorporate a separate 12 step volume control for each channel. This simulator also allows for different volume control settings.

Pros and Cons: Can be used for most speaker/amplifier combinations. Are more efficient than series resistor type, and do not normally get hot. Can be designed for higher powered amplifiers. Provide individual volume control for each zone. Are generally more expensive.


Series Parallel Type Simulator Series Resistor Type Simulator Transformer Multiplier Type Simulator


If you need to buy a Speaker Selector Switch, here is a link to the range at Amazon (Note: if you purchase anything from Amazon (US) I get a small commission – thanks for the support)

How much power do I need?

The above speaker selector switch simulators may surprise you regarding how little power can reach the speaker when you have multiple speakers connected to your Hifi amplifier. Don’t get too stressed. People have been using these switches for many years with no problems. What these simulators show is that you don’t need a lot of power to fill a room with sound, especially for background music.

If you would like to explore more about how much power you need for each room in your house, you can use my Amplifier, Speaker and SPL Calculator

Other articles you may find useful:



  1. Hi, Geoff.
    Thanks for all the great switch simulators. I have a question about the series type switch. How is the power loss through the switch calculated. I tried to calculate it using Ohms’s law but am having trouble. How do we know what the voltage is at a particular load? We have the power at 4ohms, (80watts), and can therefore solve for voltage at that load, which is 17.89V. Do you use that same voltage for all the calculations? For example, 3 speakers in parallel with the 5ohm resistor in series give a total resistance of 7.67 ohms and the current would be 2.33amps according to ohms law I=V/R using 17.89V and 7.67 ohms . Therefore, P=V x I gives a power of 41.68watts and a loss of 38.3watts from the original 80watts. However, the simulator shows each speaker getting 9.3watts for a total of 27.9watts and a loss of 52.2watts. What am I missing? I also noticed in the simulator, if you have only one speaker at 8ohms and the 5ohm resistor engaged you get 49.2 watts to the speaker, but if you drop the speaker down to 4ohms you only get 35.6 watts. Seems counterintuitive. I would think at 8 ohms your would get less power than 4 ohms. Sorry, if this may be to complicated to explain here, but I am just curious am trying to exercise my brain with the calculations. Thanks.

    • Hi Don,

      The secret to your first question is that the voltage and current changes every time the total resistance changes. So your calcs are correct for 4 ohms, but when using a load impedance of 7.67 ohms, the total current will not be 2.33 amps but 3.23 amps (sqroot(80/7.67)) and the voltage will be 24.78 volts. Using 3.23 as the current, the power through the 5 ohms resistor will be 55.2 watts. Your calcs are correct, but you need to recalculate the current and voltage every time the load changes.

      In regard to the series connection, you are right, it is counter-intuitive. We are so used to thinking of speakers in parallel where the lower resistor takes more power, that the series connection plays with our minds. We need to think logically. As the power through a resistor is current(squared) x resistance, as the resistor value increases, so will the power.

      Thanks for making my brain sore by having to think through all this again:)

      hope this helps


  2. Hello Geoff,

    First off, thank you so much for posting this information. It’s been incredibly helpful, I’ve learned a lot. I’m putting together a multi-room system for my house. My plan is to have my Onkyo TX-NR656 drive the whole thing. The front A output will have 6ohm Elac speakers, the assignable B output will go to a Niles HPS-4 speaker selector. I will only have 3 pairs of speakers coming out of it. I’d like another pair of 6ohm Elac speakers then have 2 pairs of 8ohm speakers. I’d like In-line volume controls to the additional 3 sets of speakers. I’m fairly certain I will get decent sound of out of this set up, my real question is, will I damage any of the equipment? Any information would be greatly appreciated!!

    Thank you!!!


    • Hi Michael,

      I’m pleased you have found the site useful.

      It looks like you have it all sorted. I assume you mean “zone 2” when you talk about the B output. If that is the case, then you should be fine as zone 2 outputs are 2 separate amplifiers. The speaker selector you mention should be fine. While using it, you can use volume controls without impedance protection as the speaker switch will look after that you.

      Have fun with it,



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