What is Frequency Response?


If you’ve ever purchased a pair of speakers, headphones or even earbuds, you will have noticed there is a frequency response range noted in the description or specification sheet. Some manufacturers even boast about the frequency response range of the product with terms like full-range or full frequency response. 

In this article, I’ll give you the full rundown on what this means and how to apply your new knowledge of frequency response range to make better purchasing decisions.

What is Hertz?

Hertz (Hz) is the unit of measurement for one frequency cycle. There are a few multiples of Hertz but the most relevant to consumer audio is kilohertz (kHz). Kilohertz represents the thousands multiple of the frequency spectrum or 103 Hz. For example, instead of writing 1,000Hz we write 1kHz (or 1k among audio professionals). 

For the purposes of this article, we won’t go into too much detail on Hertz but if you are interested in learning more, you can do so here

What Frequencies Can We Hear

Before we get into equipment, it’s important to know our own limitations as human beings. The average human being can hear audio frequencies between 20Hz and 20kHz (20,000Hz). 20Hz being the lowest bass frequency and 20kHz being the highest treble frequency. For the most part, we can hear frequencies very close to either end of the spectrum however, as we get older, we start to lose the higher frequencies. 

Frequencies below our 20Hz threshold can still be felt. Most earthquakes produce frequencies below 20Hz. So although we can’t hear below 20Hz, we can definitely feel the frequencies. 

Here is a simple frequency breakdown for the hearing ability of human beings.

Frequency Description Frequency Range
Sub-bass20Hz to 60Hz
Bass60Hz to 250Hz
Low Mids (Low Mid-Range)250Hz to 500Hz
Mids (Mid-range)500Hz to 2kHz
High/Upper Mids (High/Upper Mid-Range)2kHz to 4kHz
Presence4kHz to 6kHz
Brilliance6kHz to 20kHz

Here’s that information reflected on a graph. The first graph deals with the sub-bass, bass, low mids, and mid-range frequencies. The second graph also shows mids along with the high mid-range, presence, and brilliance.

Frequency Response Graph 1 - Outeraudio
Frequency Response Graph 2- Outeraudio

What We Can Hear in Relation to Audio Equipment

20Hz to 20kHz is referred to as full range in audio equipment because it’s the full range of our ability to hear. So a product which produces full range is ultimately ideal, right? It’s a little more complicated than that.

A full range specification from a manufacturer can be a little smoke and mirrors. In other words, any speaker or headphone can produce a frequency response of 20Hz to 20kHz however, without seeing the actual frequency response graph or actually listening to the product, you won’t know the true audio characteristics. 

A product might produce 20Hz – 20kHz but with more bass and less treble or lots of treble and only a little bass. In both scenarios, the products have the same full range frequency response but each produces the frequencies differently.  

How to Read a Frequency Response Graph

Often a manufacturer will indicate in the product description or specification what frequency response a speaker or headphone is able to produce. Often you will see full range or 20Hz to 20kHz.

In an ideal world, a manufacturer’s full range specification of 20Hz to 20kHz would look something like the graph below.

Frequency Response Graph 1

The graph above is what a typical 20Hz to 20kHz product specification would look like. The orange line represents the product’s frequency response if every frequency was produced exactly the same. Awesome right! This product produces all the frequencies we can hear, at exactly the same volume. Unfortunately, it’s not as simple as that and you’ll probably never come across a product with this straight line from 20Hz to 20kHz in consumer audio equipment.

Now let’s take a look at the graph below. These are two different frequency response range displayed on the same graph. Both are 20Hz to 20kHz but completely different!

Frequency Response  Graph 2

This is where you get the “aha moment”.

Now you can see, both of these frequency response ranges are 20Hz to 20kHz, or full range, but in theory, will sound completely different. Let’s look at these two lines in more detail and I’ll explain what is happening.

Firstly, the orange line indicates a massive bump at 1kHz of around 9dB. This is considered the mids or mid-range. 9dB is a huge difference and whatever equipment this orange line represents would sound terrible. You would hear very loud vocals, guitars, and some brass instruments. Nothing would be very clear and the sound would be harsh on your ears.

The blue line is pretty flat until you get this massive dip of -6dB at 100Hz. In this scenario, you would actually hear a pretty balanced mix except when it came to the bass. Around 60Hz – 150Hz is where you get punch and definition from your kick drum, bass guitar, and other bass instruments. With this product, you would hear some bass but it would be very weak and lack any power. If you were only listening to the spoken voice, you probably wouldn’t notice the bass dip all that much, but add instruments and you’ll probably be underwhelmed with the bass.


So now you start to get the picture. A 20Hz to 20kHz frequency response on a product means very little. Until you see a frequency response range on a graph like the ones above or, hear the product itself, a frequency response range is written in the description is too vague to mean anything and should not influence your purchase. 

Next time you are purchasing a speaker, headphones or other audio products, see if the manufacturer supplies a frequency response graph with the product. You will find cheap imported products will happily display a 20Hz to 20kHz frequency response in the product description but almost never publish this information. In contrast, a high-end or professional audio manufacturer will either publish this information on their website or in the user manual. 

Frequency response range help give an idea of a product’s capability but you can’t take the numbers at face value. If a product states it produces 20Hz to 20kHz, do some digging, find a user manual or check the manufacturer’s website. 

Also, check out reviews to see what your fellow consumers say. Quite often people will be fairly descriptive about what they could and couldn’t hear. 

Ultimately, it comes down to putting the product to the test and listening before you buy something. This is not always easier to do when shopping online however, Amazon sometimes offers a 30-day money-back guarantee on electronics products.

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Author: Matt Hallowes

Matt has worked as a sound engineer and tour manager since 2003. His work as a sound engineer includes both live production and venue installations. With a passion for the industry, Matt shares his knowledge and expertise with us.

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