Simple Impedance Calculation for Speakers in Series
Do you need a calculator to determine the total load impedance of speakers in series? Probably not. The calculation to determine the total impedance of speakers in series is easy. Simply add the impedance of each speaker to get the total impedance.
Example 1: An 8 ohm speaker in series with a 4 ohm speaker = 12 ohms.
Example 2: Four 4 ohms speakers in series = 16 ohms.
So if calculating the impedance of speakers in series is so simple, why do we need a calculator? My point exactly. I’ve always thought there is no need for such a calculator. After all, most people can add 4+8 and get 12 as the answer. However I’ve had some requests for such a calculator. Hopefully the power sharing calculations are the driving force for these requests and not the total impedance calculation.
Below is my calculator for 2, 3 or 4 speakers wired in series. Although I’m not sure why you would want to connect 4 speakers in series, but if you do, this calculator will help.
Simply type the impedance of each speaker into the white boxes (or use the drop-down values). Use N/A for unused speakers in this calculator. The total impedance will be calculated for the entered speakers.
Also calculated for each speaker is its percentage share of the amplifier’s output power. This is useful as power sharing is a consideration when using speakers with different impedance.
“Power Differential” is the final calculation of the top section. This calculates in dB (decibels) the power level difference between the highest and lowest power as it is shared across the speakers. This shows the power level difference when using speakers with different impedance.
Amplifier Power Calculator
The bottom section of the calculator helps in matching the speaker combination with your amplifier. This is not necessary if you only want to know the total impedance and/or the power ratios.
However if you are connecting these speakers to your amplifier, it may be helpful to input the amplifier power and the associated speaker impedance. In the specifications for your amplifier, it should say something like :
Amplifier power: 80 watts continuous average power @ 6 ohms (2 channels driven, THD 0.08%, 20Hz-20kHz)
This tells you the maximum continuous power the amplifier will deliver into a 6 ohm load is 80 watts. In the calculator below, for this example, you type in 80 for the power and 6 for the impedance. Be aware, some specifications state RMS power rather than continuous power. These are effectively the same.
The calculator will display the effective power of the amplifier for the calculated total impedance of the series speakers. Also displayed (under each speaker’s power %) is the actual maximum power the amplifier will supply each connected speaker. A comment on the suitability of the calculated total impedance for your amplifier is also provided.
Note: the calculated output power for the amplifier is based on a theoretical “ideal” amplifier. In practise, your amplifier may produce slightly more power.
This calculator will help you understand the total speaker load on your HiFi amplifier. For a better understanding of this and what to do about it, read the articles How do I Connect Multiple Speakers to my HiFi Amplifier and How to wire four HiFi speakers or How to connect 2 speakers to one amplifier or watch the video in the article Understanding Speaker Impedance. .
Also see How Multiple Speakers Share Power for further details about the percentage power calculations. For more details about the effective amplifier power at higher impedance loads, see How Impedance Changes Amplifier Power.
If you need further advice on connecting speakers in series, please read the FAQs before submitting your question.