SERIES vs PARALLEL: Speaker Impedance Explained

September 18, 2020

In this post, you’ll learn about speaker impedance when connecting multiple speakers to a single amplifier channel. I’ll briefly explain what impedance is. I’ll help you find the impedance specifications for your amplifier and speakers.

By the end of this post, you’ll understand how to calculate total impedance when connecting multiple speakers to a single amplifier channel.

If you are designing a sound system and want a FREE guide to the most important speaker specifications, download the FREE Loudspeaker Technical Specifications Guide.

What is speaker impedance?

For the purposes of understanding speaker impedance in this post, you can think of impedance as the property of a speaker that resists (or impedes) the flow of energy from an amplifier.

Speakers with higher impedance present a greater load to the amplifiers that power them. Speakers with a lower impedance present a lesser load to an amplifier.

Amplifier & Speaker Impedance Specifications

It’s important to consider the impedance specifications for both your amplifier and your speakers. 

Each speaker will have a nominal impedance rating, either on the back of the speaker or in the technical specifications online. A speaker’s nominal impedance is usually 2, 4, 8, or 16 ohms. 

Written on the back panel of the amplifier or in its technical specifications, you’ll find the impedance rating of your amplifier. The impedance rating of an amplifier usually ranges between 2 ohms and 16 ohms. 

The following sections will help you to ensure that the load presented by your speaker or your speakers falls within the range of your amplifier’s impedance rating. 

Calculating Speaker Impedance

You can find calculators online that will help to quickly determine the load presented by your speakers based on the impedance of each speaker in the circuit. You can find a useful speaker impedance calculator here

It is, however, still beneficial to learn the formulas for determining impedance so that you get a better understanding of how impedance works. 

Impedance with a Single Speaker

Connecting one 8 ohm speaker will present an 8 ohm load to the amplifier. 

As long as 8 ohms falls within the range specified by your amplifier’s specifications, your system should work without any problems.

Calculating the total impedance of multiple speakers will depend on if the speakers are connected in a series or parallel circuit.

Impedance with Multiple Speakers in Series

When you connect multiple speakers in series, you simply add the impedance rating of each of the speakers together.

Two 8 ohm speakers in series present a 16 ohm load to the amplifier. 

Connecting a 4 ohm speaker and an 8 ohm speaker in series will present a 12 ohm load to the amplifier. 

How to Connect Speakers in Series

To connect speakers in series, wire the positive terminal of the amplifier to the positive terminal of the first speaker. Then, wire the negative terminal of each speaker to the positive terminal of the next speaker. The negative terminal of the last speaker will connect to the negative terminal of the amplifier, completing the series circuit.

Impedance with Multiple Speakers in Parallel

When connecting multiple speakers in parallel, calculating the total impedance is a bit more complicated. 

If all of the speakers have the same impedance, you simply take that impedance rating divided by the number of speakers being connected. 

For example, connecting two 8 ohm speakers in parallel will present a 4 ohm load to the amplifier. That’s calculated by dividing eight ohms by two speakers.

If the speakers in the parallel circuit do not all have the same impedance rating, you’ll need to use a different formula. 

To calculate the total impedance of a 4 ohm speaker and an 8 ohm speaker connected in parallel, I’ll plug the numbers into the formula like this, which gives us a total impedance of about 2.7 ohms. This would be too low for most amplifiers to operate at without overheating.

How to Connect Speakers in Parallel

To connect speakers in parallel, wire the positive terminal of the amplifier to the positive terminal on each speaker. Then, wire the negative terminal of the amplifier to the negative terminal on each speaker.

I also wrote these guides on speaker polarity (positive vs negative) and speaker crossovers. Check them out to make sure you are connecting your speakers correctly for optimal performance!

If you are designing a sound system and want a FREE guide to the most important speaker specifications, download the FREE Loudspeaker Technical Specifications Guide.

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