What Is Speaker Impedance and How Does It Work?

When buying audio peripherals such as speakers and headphones, have you ever wondered what that Ω symbol stood for ? For those who are unfamiliar with what it is, this symbol is called “ohms” and it is used as a measuring symbol for the impedance of an audio peripheral. 

You also probably heard about speaker impedance. But what is it and why should you learn about it? If you’re not familiar with the term, then having proper knowledge about it will greatly help you in correctly setting up your speakers for use. 

In this article, we will discuss everything you need to know about speaker impedance.

Ask the Editors: Can You Mix and Match Speaker Impedance? | AVS Forum
From AVS

What Is Speaker Impedance?

In technical terms, speaker impedance (and to some degree, headphones impedance) refers to the load an audio peripheral sends to a connected amplifier when in use. 

Note that when we are using any audio peripherals, the audio signals being sent from the audio source to the peripheral are electrical currents themselves (see “audio signal”). The word impedance is based on the output current of an amplifier, which is usually AC and not DC, as the latter is found on batteries instead. 

The amount of impedance indicated in an audio source such as your home theater main unit or even your MP3 player shows the amount of audio signal it sends as AC.

Meanwhile, the indicated ohms on your audio peripheral’s specifications indicate the amount of resistance it has from the AC being sent as audio signals. 

There is a chance that the audio peripheral would be damaged if it is used with an audio source with a higher ohms rating than itself; however, the chance of that happening is quite slim, unless the peripheral itself is faulty otherwise.

From GTGG

Resistance vs. Impedance: What’s the Difference?

You might be wondering if there’s any difference between the terms “resistance” and “impedance” in this case. Resistance is a part of an electrical circuit and is responsible for how hard it is to send an electrical signal through it. The more resistance present, the harder it is for the electrical circuit to send a signal.

But when it comes to the differences between the two, the simple answer would be there are no real differences. The only difference between them is how they are used. The term resistance is only used when referring to a circuit using Direct Current (DC), while the term impedance is used for circuits using Alternating Current (AC).

Therefore, when it comes to audio peripherals that are plugged into wall sockets, they usually have impedance. Meanwhile, audio peripherals using batteries such as lithium-ion have resistance instead.

Speaker Impedance in Technical Terms

In breaking down how speaker impedance works technically, do remember that it is basically an AC circuit that hosts a combination of DC resistance with any reactance on it. Thanks to that circuit and its contents, a speaker impedance can be established where it will affect how much current is drawn by the audio peripheral (i.e. speaker unit) from the audio source (i.e. amplifier) it is connected with.

One notable aspect of impedance is that it changes depending on the frequency. The reason for that is a single audio source contains a lot of frequency inside it, ranging from its voice (the vocals) up to the music it has. 

Therefore, in order for their speakers to be able to handle those changes, most manufacturers of audio peripherals have instead opted in for a “nominal” rating of impedance, speakers included. That said rating is the average of the lowest value of impedance, and it depends on what type of peripheral it is and various factors (i.e. speaker or headphones, its type, build, quality, etc.).

Two 4 ohm speakers wired to amplifier
From Amplified Parts

What Are the Commonly Used Ohms Ratings?

In the current market today, the commonly used ohms ratings for most audio devices are 4Ω, 8Ω, and 16Ω. Those ohms ratings are specifically used for speaker units, both individual and ones found in home theater systems and other devices such as desktop speakers.

However, when it comes to headphones, the ohms rating can range from a small 8Ω to a huge 600Ω rating, with 32Ω being the norm these days. Higher-fidelity (Hi-Fi) headphones and even some studio headphones have a higher ohms rating. See our guide on headphone impedance for more details.

Surprisingly enough, car speakers have their own separate ohms rating, due to their different setup, although the rating for this kind of speaker is very low. The ohms rating for most car speakers in the market today ranges from 2Ω to 16Ω respectively.

What Is the Importance of Speaker Impedance?

Knowing how speaker impedance works, you might still ask and wonder why it is important. Does it really matter in the long run? 

The simple answer to that is a big yes, as it will heavily affect the performance and lifespan of your amplifier unit. Do remember that impedance on a speaker unit determines the amount of current drawn from an amplifier that it is connected to.

In order to lessen the workload stress that an amplifier will be dealing with its technical lifespan, having lower currents being drawn out from it will greatly benefit it. 

Having more amounts of current being drawn requires more power, which burdens the amplifier unit more than necessary. That can eventually lead to the unit breaking down earlier than its expected end life as a result. That won’t be a good thing for consumers as that would mean that they would be needing to buy a new amplifier earlier than expected.

Generally speaking, you can keep this in mind when remembering the importance of speaker impedance:

  • Low impedance > higher current needed > increased amplifier load > results in more power needed
  • High impedance > lower current needed > decreased amplifier load > results in less power needed
From Labster Theory

There is a thing called “Ohms Law” which dictates the relationship between voltage, current flow, and resistance. That specific law can be applied when it comes to audio impedance. The law states that the flow of a current is directly proportional to the voltage it faces while being inversely proportional to resistance at the same time. The simple formula for it would be “Current = Voltage/Resistance”.

However, to make it simple to understand for the general audience, the thing to keep in mind is the generalization mentioned above. However, those two generalizations will only be true up to the point where the amplifier providing power cannot produce more current and power.

When that happens, either the amplifier’s fuse will blow itself up, the whole amplifier unit will die or the amplifier unit will be forcibly turned off by its protection circuit that is programmed to do so (just like an electric circuit breaker in one’s house). To avoid those things happening, never use an amplifier with a load impedance that is less than what is stated as the minimum (usually the minimum is 4Ω).

Why You Should Learn About Speaker Impedance

Just like when you are buying your first car or a new smartphone, you would like to know what the item you are going to purchase can do for you in advance. 

That is the same when it comes to buying a speaker unit (whether it is a standalone unit or part of an audio system), as it is better to know its specifications and performance output beforehand. You don’t want to immediately total your newly-purchased speaker after improperly setting it up and connecting to an incompatible amplifier.

In the current market today, most amplifier units (especially Hi-Fi ones) are commonly set up with an ohms rating of 4Ω to 16Ω respectively. That means that the amplifier unit with that rating can be used with a speaker unit that is rated with a minimum speaker impedance of 4Ω. You can use a speaker unit that is rated with a 4Ω, 6Ω, 8Ω, or even 16Ω with that amplifier. 

However, do take note that the higher the rating, the more power the amplifier will use during usage. But never use a speaker unit (or any audio peripheral for that matter) that is below the amplifier’s ohms impedance rating, unless you want to break either device as a result.

Does Lower Impedance Mean Better Quality?

It may have been stated several times in this article that having low impedance or using an audio peripheral with a lower or matching impedance rating to your amplifier is a great choice. 

However, does that mean that it will have a great quality by default? Unfortunately, that is not the case as the audio quality will still depend on its source and other factors, not the speakers and amplifiers alone combined.

Remember at the beginning that it has been mentioned that the impedance of the speaker changes depending on the frequency of the audio source. The indicated impedance rating shown on the audio peripheral is just an estimated rough average. 

However, do take note that an audio peripheral with a lower impedance rating such as 4Ω is perfect for those who want to hear what the sound engineers did to fine-tune a peripheral to their standards.

Impedance Switch: What Is It?

Some modern-day amplifiers and receivers have a dedicated impedance switch (usually located at the back of the unit), although it would be a stretch to call it a switch based on its looks alone. It instead looks more like a keyhole that you can find in your room’s door, as seen on the image below:

You will be needing a flat-end screwdriver in order to turn the switch to the desired impedance rating. However, there are other designs that are just simple knobs that you can easily turn with the grip of your fingers. 

However, do take note that this impedance switch isn’t a permanent solution when it comes to ensuring that your speaker and amplifier units would be perfectly compatible with each other in impedance rating. 

Generally speaking, it isn’t a flat setting, as it intentionally cripples the full capabilities of the amplifier or receiver using it. That means it will produce a low-quality audio performance as a result.

To avoid such a thing from happening, it is best advised to keep the switch at the highest settings and instead purchase a speaker unit that matches your amplifier or receiver’s impedance setting for the best optimal results.

Car Speaker Impedance

You may have a car of your own and wondered what is the difference in the impedance of car speakers from regular speakers? For one, it has previously been mentioned here that the setup of a car speaker is different from a regular speaker unit. Since a car speaker isn’t plugged into an electric home socket, it instead relies on the battery of the car it is hooked up with.

Usually, car audio systems are based on 12V DC, in order to be portable enough for the car battery to handle (along with other systems inside the car that share the same car battery as the main power source). Since there isn’t enough power in a regular car (unless modified), car speaker units rated at 4Ω are the norm.

Stock and factory-preset car audio systems with that kind of impedance rating allow it to pull more power from its stock amp without putting great workload stress into it. It eliminates the need for the installation of a dedicated amplifier with a higher load, which is only needed when you are installing a larger car audio setup.

From The Drive

Final Thoughts

Without this specific rating (along with its counterpart, resistance), many of us will surely damage most of our audio peripherals and devices without knowing it. Both impedance and resistance serve as reminders of the limits of our audio peripherals and devices. Additionally, both help consumers to know which components would work best with each other and simultaneously avoid what would be bad when paired up.

Knowing this audio technical term can greatly help you in properly setting up your audio system, whether it would be a home-based system, a mobile carry-to-go setup (i.e. mobile DAC amplifier units with connected headphones), or even getting the best setup for your car’s audio system.

You may also be interested in:

Leave a Reply