Sound and audio are made of are created by waves within a range of frequencies. Humans naturally respond to the audible range of frequencies, and headphones are designed with their own range of frequencies that they are capable of producing.
What is headphone frequency response, and what is a good range? Headphone frequency response refers to the frequency-specific sensitivity of the output. Frequency responses show the range that headphones are capable of reproducing—a graph shows which frequencies are accentuated over others. The ideal range covers the audible sound range of 20 Hz – 20 kHz.
In this article, we'll examine headphone frequency response in greater detail and help you to determine the best frequency response for your own headphones and listening experience.
Related article: Complete Guide To Microphone Frequency Response (With Mic Examples)
Table Of Contents
- A Primer On Headphone Transducers, Sound And Audio
- What Is Headphone Frequency Response?
- Headphone Frequency Response Ranges And Graphs
- The Audible Range And The Human Frequency Response
- How Do Humans Hear Headphones?
- How Is Headphone Frequency Response Measured?
- Raw Frequency Response Vs. Compensated Frequency Response
- What Is A Good Headphone Frequency Response Range?
- Flat Frequency Response
- Coloured Frequency Response
- Impedance And Its Effect On Frequency Response
- Related Questions
A Primer On Headphone Transducers, Sound And Audio
Let's begin by quickly defining headphones, sound and audio.
Headphones are transducers that convert audio signals (electrical energy) into sound waves (mechanical wave energy). The audio signals are electrical representations of sound, while the sound waves are actual sounds that we can hear.
The audible frequency range of sound is widely accepted to be 20 Hz to 20,000 Hz for humans. This can be thought of as the frequency response range of our hearing. More on this in the section titled The Audible Range And The Human Frequency Response.
So both audio signals and sound waves are generally described as having frequencies between 20 Hz – 20,000 Hz.
An audio signal (that is not a pure tone) is typically made up of many different frequencies with varying amplitudes and transient characteristics. This electrical information is a representation of sound in an alternating current with the same frequency information.
For more information on headphones, sound and audio, check out the following My New Microphone articles, respectively:
• How Do Headphones Make Sound? (A Simple Beginner’s Guide)
• What Is The Difference Between Sound And Audio?
Headphones are designed to reproduce these audio signals as actual sound for the listener to hear. However, in the conversion, the reproduction of certain frequencies may differ slightly. The headphones may accentuate or deemphasize some frequencies of the audio signal in its sound production, altering the intended sound.
This is the essence of frequency response. Which audio/sound frequencies are the headphones capable of transducing, and which of these frequencies do the headphones naturally produce more of?
What Is Headphone Frequency Response?
Headphone frequency response refers to the frequencies of sound the headphones are capable of producing. It also involves the frequency-dependent sensitivity of the headphones or, put differently, the frequencies that the headphones will naturally produce more of (relative to other frequencies).
In other words, the frequency response is the measure of the magnitude of the headphone output compared to its input as a function of frequency. It illustrates how accurately the headphones reproduce each frequency of an audio signal in terms of amplitude.
Each pair of headphones has its own headphone frequency response specification. Typically this spec is included in the manufacturer's specs/datasheet.
This response is generally given as a range of frequencies the headphones are capable of producing.
Some manufacturers will include a graph to show exactly how the headphones produce each frequency through the range, but this is rare. To find this information, it is often necessary to seek out a third party that has conducted its own frequency response graph measurements.
So to put it simply: frequency response tells us which frequencies the headphones are capable of producing and which frequencies are over or under-produced relative to the intended audio signal.
Frequency response is typically given as a range the headphones are capable of producing from the lowest frequency to the highest frequency. More information is available via a frequency response graph, but these are typically produced by third parties rather than the headphone manufacturers themselves.
Although frequency response is often overlooked and/or taken for granted as an “unimportant specification,” it is actually one of the most important factors when it comes to proper sound reproduction. Stability, comfort, noise-cancellation, electrical impedance and sensitivity are also considered to be major factors. Still, the frequency response is perhaps the most important when it comes to the actual reproduction of sound.
Headphone Frequency Response Ranges And Graphs
The headphone frequency response range signifies the range of frequencies a pair of headphones is capable of producing.
The headphone frequency response graph shows us, in detail, the frequency-specific sensitivity of the headphones throughout their range.
Note that headphones are typically designed to have two identical headphone drivers with identical frequency responses.
The frequency range is measurable by the manufacturer but is often meaningless to the consumer. It tells us only the frequencies the headphones are capable of producing but does not indicate the relative sensitivity of each frequency.
In other words, a theoretical pair of headphones could have a frequency response of 10 Hz to 40,000 Hz. This means it can produce frequencies within this range that exceeds the audible range of 20 Hz to 20,000 Hz on the low and high-end. By taking this range at face value, we'd assume that these headphones would likely sound great.
However, there's nothing to suggest that there couldn't be wild variability within this range. For example, the theoretical headphones could have a 40 dB dip in response between 1,000 Hz to 4,000 Hz. Sure, they are capable of producing sound in this range but do so very poorly. The resulting sound would be muffled and quite horrible.
A better, though less-flattering method of writing out the frequency response range would be to give a tolerance value. A tolerance value, written as +/- X dB, suggests that the response range holds true within this frequency-dependent sensitivity variability.
For example, we can trust a pair of headphones with a frequency response of 50 Hz – 25,000 Hz +/- 10 dB to be much more accurate in its reproduction of sound versus our previous 10 Hz – 40,000 Hz example.
With a frequency response graph, all this guesswork is taken out. These graphs offer much clearer information on how the headphones will produce frequencies within their response ranges.
To learn more about frequency response ranges and graphs, let's have a look at some examples!
|Headphones Model||Headphone Type||Frequency Response Range||Nominal Impedance|
|5 Hz - 21,000 Hz||45 Ω|
|Sennheiser HD 280 Pro||Closed-back|
|8 Hz - 25,000 Hz||64 Ω|
Planar Magnetic driver
|5 Hz - 50,000 Hz||200 Ω|
|6 Hz - 41,000 Hz||170 KΩ (given @ 10 KHz)|
Apple EarPods Frequency Response
The Apple EarPods (link to check the price on Amazon) are a popular pair of earbuds with a frequency response range of 5 Hz – 21,000 Hz.
Apple does not supply a frequency response graph with its EarPods. However, Inner Fidelity has tested these earbuds and has come up with the following graph:
Apple is featured in My New Microphone's Top 14 Best Earphone/Earbud Brands In The World.
Note that we're looking at the Top – Compensated and Averaged values in this section.
As we would expect from the relatively cheap mass-produced EarPods, the jagged frequency response graph shows us that the response is quite coloured.
The low-end drops off significantly below 100 Hz. This is common among earphones since their driver sizes are small.
So by looking at the graph, we infer that the EarPods are coloured and not very bass-heavy. They sound pretty accurate overall.
So a major factor to point out here is that, although the frequency range states the EarPods produce 5 Hz to 21,000 Hz, the graph shows us that this is far from the true picture.
Simply assuming consistent sensitivity between 5 Hz and 21,000 Hz would be a mistake.
Let's take a generous +/- 10 dB sensitivity variation in the EarPods' frequency range. With this deviation, the frequency range would come out as roughly 45 Hz – 12,000 Hz rather than the much better-looking 5 Hz – 21,000 Hz.
This is not to harp on the Apple EarPods specifically, though. Nearly all earphones tell a similar story when it comes to their frequency responses.
All that being said, this response curve is not fully indicative of a lack of bass response. The proximity and coupling between the drivers and the listener's eardrums increase perceived bass over regular head-mounted headphones and loudspeakers. Therefore, earphones can provide a stronger bass sensation while actually producing less low-frequency sound.
To test this, try gently pushing your earphones deeper into your ears and listen for the increase in bass.
As for the lower mids, the EarPods are quite flat, and their drivers will accurately represent the audio source.
There is a slight peak in the EarPods' sensitivity at 2 kHz. This boost helps bring out the character in most vocals and instruments. This is important to hear the audio's detail, particularly with earphones that are often used in noisier environments and during physical activity.
The EarPods, like the vast majority of headphones, has a high-end roll-off. This roll-off starts around 11 kHz. There is a resonance peak around 16 kHz before the high-end rolls off.
Note that these high-end roll-offs are common because headphones sit close to your ears, and so high frequencies sound louder than they actually are. Typically, high-end frequencies dissipate quickly in the air between loudspeakers and our ears, but this is not the case with the proximity of our ears and the headphone drivers.
To compensate with the naturally increased high-end, headphone manufacturers often design a high-end roll-off into their headphones' frequency responses.
Bass boosting also achieves a similar effect while bringing up the perceived loudness of bass frequencies. This is important because headphones do not produce the visceral type of bass that loudspeakers produce (the bass you can feel in your body).
Sennheiser HD 280 Pro Frequency Response
The Sennheiser HD 280 Pro (link to compare prices on Amazon and B&H Photo/Video) is a prevalent pair of closed-back circumaural (over-ear) headphones with moving-coil dynamic drivers. They have a published frequency range of 8 Hz – 25,000 Hz.
The Sennheiser HD 280 Pro is featured in the following My New Microphone articles:
• Top 5 Best Moving-Coil/Dynamic Headphones Under $100
• Top 5 Best Closed-Back Headphones Under $100
• Top 5 Best Circumaural (Over-Ear) Headphones Under $100
Sennheiser does not publish a frequency response graph for its HD 280 Pro headphones. However, we can see the graph of these headphones below as calculated by Inner Fidelity:
Sennheiser is featured in the following My New Microphone articles:
• Top 13 Best Headphone Brands In The World
• Top 14 Best Earphone/Earbud Brands In The World
• Top 11 Best Microphone Brands You Should Know And Use
• Top 11 Best Soundbar Brands On The Market
Note that we're looking at the Top – Compensated and Averaged values in this section.
We can see above that the Sennheiser HD 280 Pros have an excellent low-end response and a relatively flat/natural-looking frequency response curve.
These headphone drivers will recreate their audio signals with excellent clarity between about 20 Hz and 2 kHz before the high-end roll-off begins happening.
What this tells us is that the bass response of the HD 280 Pro is nice and strong, and the bulk of the audio will be accurately reproduced for our listening pleasure.
The slight dip in sensitivity around 100 Hz helps to reduce the “boxiness” of the sound.
The high-end roll-off is fairly consistent save for a noticeable peak at ~9 kHz. This peak centred at ~9 kHz aids in high-end clarity while giving the 280s their character. However, a relatively sharp peak in the middle of a long high-end roll-off may also colour the sound of the headphones too much and is generally considered a negative trait.
Audeze LCD-4 Frequency Response
The Audeze LCD-4 (link to check the price at B&H Photo/Video) is a pair of high-end planar magnetic headphones with an open-back circumaural fit. The LCD-4s have a frequency response range of 5 Hz to 50,000 Hz.
Once again, Audeze does not publish a frequency response graph. The following graph is from the research conducted by Inner Fidelity:
Audeze is featured in My New Microphone's Top 13 Best Headphone Brands In The World.
Note that we're looking at the Top – Compensated and Averaged values in this section.
The Audeze LCD-4s boast the flattest low-end-to-mid-range frequency response of the 4 headphone examples in this section. This allows for generous perceived bass response and clarity in the mid-range of the headphones' sound.
The high-end roll-off begins just above 1 kHz but is relatively flat at -15 dB above 4 kHz. Of course, there are resonant peaks and dips in the high-end response, but this is natural in headphone design. Overall, the high-end is well-represented and attenuated properly to achieve a balanced sound for the listener.
STAX SR-007 Frequency Response
The STAX SR-007A Mk2 (link to check the price on Amazon) is a pair of electrostatic headphones with an open-back circumaural design and a published frequency response range of 6 Hz – 41,000 Hz.
The STAX SR-007A Mk2 is featured in My New Microphone's Top 5 Best Electrostatic Headphones.
STAX does not have a frequency response graph for its SR-007 Mk2, but Inner Fidelity has published the following frequency response graph:
Stax is featured in My New Microphone's Top 13 Best Headphone Brands In The World.
Note that we're looking at the Top – Compensated and Averaged values in this section.
As we can see, the SR-007 has both a low-end roll-off and a high-end roll-off.
The result of the above frequency response, along with the specialized amplification of the SR-007, yields an amazingly transparent sound that represents the audio signal with great clarity.
The low-end roll-off passes 20 Hz (the lowest point of human hearing) at -10 dB, so the headphones will still produce low-end with some clarity. As for the high-end, the reductions in sensitivity give the SR-007 a natural-sound high-end without compromising precision.
The Audible Range And The Human Frequency Response
The audible range of human hearing is universally accepted to be 20 Hz to 20,000 Hz. However, through ageing, damage, or an otherwise non-ideal sense of hearing, many people may have a more limited range.
That being said, we are not equally sensitive to all frequencies within our ranges of hearing. This frequency-specific sensitivity we have in our hearing is portrayed well in the Fletcher-Munson curves shown below:
- Sound Pressure Level: the change in localized pressure in the medium (air) caused by sound waves measured in decibels (dB SPL).
- Frequency: the cycles per second of a pure tone sound wave.
- Phon: a standard measurement for perceived loudness/intensity of pure tone, psychophysically matched to a reference frequency of 1 kHz.
As we can see above, much greater sound pressure levels are required at low-end frequencies for us to hear the low frequencies. The same is true with the high-end frequencies, though not as extreme.
In other words, we are less sensitive to sound frequencies at the low and high-ends of our hearing range.
In fact, we feel these frequencies more than we hear them. When projected loudly through the air, deep bass will rumble our bodies (think of a miked-up kick drum in a live venue). Similarly, the high-end frequencies actually have little harmonic content but allow us to hear the “airiness” or “brightness” of sound.
We are naturally most sensitive to the midrange where much human speech takes place. Take note of the natural increase in sensitivity around 4 kHz that coincides with speech intelligibility and sibilance.
This section shows that not only do headphones have frequency responses, but our own ears do as well. In fact, if we have hearing damage in one ear, our two ears will actually have different frequency responses.
Microphones, speakers, and other transducers that deal with sound and audio will also have frequency responses.
To learn more about microphone frequency response, check out my article The Complete Guide To Microphone Frequency Response (With Mic Examples).
How Do Humans Hear Headphones?
Headphones interact with our eardrums in interesting ways.
Let's think about it. Headphones are essentially small loudspeakers placed just outside your ear or even within your ear canal (as is the case with earphones). Unless someone is whispering into your ear or you press your ear near or against a sound source, you'll rarely experience sound in nature like you do when wearing headphones.
To learn more about the differences between headphones and earphones, check out my article What Are The Differences Between Headphones And Earphones?
This proximity is at the root of some interesting interactions between headphones and our general sense of hearing.
Let's begin with bass. As we learned by looking at the Fletcher-Munson Curves in the previous section, humans feel bass more than they hear it.
Whereas loudspeakers and subwoofers push large amounts of air to produce a bass response, headphones rely more so on proximity, coupling to the eardrum, and bone conduction to produce perceived bass.
Loudspeakers are much more capable of producing the large movements of air required of bass frequencies. If we stand in front of a loud subwoofer, we can feel the bass.
However, we wouldn't want to put our ear up to a loud subwoofer since it would likely cause damage.
Headphones, then, must produce bass differently in order for us to perceive the bass in the sound.
The relatively small diameters of headphone and earphone drivers are naturally worse at producing large amounts of bass frequencies compared to larger loudspeakers.
For more information about headphone driver size, check out my article What Is A Good Driver Size For Headphones?
So headphones rely on their proximity in order to produce their perceived bass response. Note that the following points apply to the general interaction between headphone drivers and eardrums across all frequencies but can be used especially to explain bass frequencies.
The proximity of the headphone driver to the eardrum means the driver (headphone speaker) doesn’t have to move as much air to produce a decent bass response when the headphones are worn properly.
Many headphone/earbud form factors create a sealed (or at least a semi-sealed) enclosure with the speaker on one end and the eardrum on the other. This coupling of diaphragms allows the bass frequencies to have more of an effect on the eardrum and a greater perceived loudness.
The sound vibrations in the headphones physically vibrate our skull and the tiny bones in our inner ears, which send signals to our brain that help us perceive the sound frequencies. This is known as bone conduction and is particularly effective with bass frequencies.
Though all headphones provide some bone conduction, it is circumaural (over-ear) and bone conduction headphones that provide the most. They both press against our skulls and can, so their bass frequencies are more easily perceived.
To learn how headphones produce bass in more detail, check out my article Do Headphones Have Subwoofers & How Do HPs Produce Bass?
Any headphone drivers worth their money will produce mid-range frequencies accurately. This is true of all driver types though balanced armature types may be a bit more narrow-banded.
For information on all headphone driver types, check out my article What Is A Headphone Driver? (How All 5 Driver Types Work).
As for high-frequencies, all well-designed drivers can be tuned to produce high-end that extends beyond the audible range. Regarding the form factor design, earphones and open-back headphones are more typically effective than closed-back headphones.
The short wavelengths of high-end frequencies will cause more phase cancellation than their longer counterparts as they bounce around the headphone enclosure. This is less of a concern with earphones and more of a concern with headphones, particularly those with closed-back ear cups.
For further reading on closed-back headphones and their open-back counterparts, check out my article The Complete Guide To Open-Back & Closed-Back Headphones.
It's also worth mentioning that sound is naturally “EQed” by your body as it reaches your eardrums.
With headphones, the physical makeup of your head and particularly the open space of your sinuses will provide some acoustic gain for mid-range frequencies.
The concha, which is the smaller cup in the outer ear around the entrance of the ear canal, focuses sound into the ear canal. It is designed to be particularly effective between 2 kHz and 5 kHz, which is where speech intelligibility occurs.
Additionally, the length of the ear canal provides the opportunity for modal artifacts to occur. These peaks will generally happen at about 3 kHz, 9 kHz and 15 kHz, though they are largely dependent on the shape of the ear in question.
These are but a few biological ways in which the sound we hear will differ from what the headphones actually produce. These factors may add to the confusion about headphone frequency response but are worth knowing nonetheless.
How Is Headphone Frequency Response Measured?
So far in this article, we've made basic interpretations of multiple headphone frequency responses by looking at the compensated and average graph lines of the Apple EarPods; Sennheiser HD 280 Pro; Audeze LCD-4 and STAX SR-007 headphones.
How are these frequency response graphs measured?
Well, it's actually quite complex. Perhaps that's why most information on headphone frequency response is provided by third parties rather than by the manufacturers themselves.
A few resources to check out various headphone frequency response tests are:
Headphones are unlike regular loudspeakers, which typically have their frequency responses measured with a measurement microphone in an anechoic chamber.
Unlike loudspeakers, headphones cannot be measured with normal measurement microphones in an acoustically dead environment. Rather, they must be measured as if they are being worn by a theoretical listener.
In other words, they must be coupled to a microphone that mimics the acoustic characteristics of the ear. This adds complexity to the measuring process but yields a closer estimation of what typical eardrums will hear when listening to the headphone drivers.
Dummy heads that simulate the human head and ears are used in headphone frequency response measurements. The microphones inside these dummy heads have similar responses to human eardrums, which are quite different from the responses of measurement microphones.
Note that the frequency response of the measurement microphone in the dummy head needs to be taken into account when calculating the response of the headphones.
The measurement takes place by first placing the headphones on a dummy head. A sweeping sine wave audio signal is then sent to the headphones. This audio is at a consistent amplitude and sweeps across a wide range of test frequencies (typically wider than the audible spectrum of 20 Hz – 20,000 Hz). The exact specifications of the frequency response are determined by the testing party.
Since the sweeping audio is at a consistent level, any differences between the microphone's pickup and the mic's frequency response would be due to the inherent frequency response characteristics of the headphones.
It is up to the testers to maintain uniformity during their tests and to perform tests redundantly to produce as accurate a final result as possible. This may require:
- Utilizing the same audio source and equipment (dummy head, measurement microphone, headphone amp, etc.) set up in the same way (except for the headphones being tested, of course).
- Performing the tests at various amplitudes to measure the response at different sound levels from the headphones.
- Repositioning the headphones on the dummy head for a more averaged response rating.
- Utilizing different dummy heads in different tests to further redundancy when necessary.
Each headphone is typically measured and re-seated multiple times to ensure redundancy and accuracy in the test. The final frequency response plot is given as the average of those multiple measurements.
But it's not that easy.
The dummy heads, like our own heads, have their own resonances and “natural EQs” that colour any sound that reaches the internal microphone. This colouration was touched on briefly in the previous section.
With all the different frequency responses and resonances to take into account, things get complicated pretty quickly. How do testers come to find an accurate frequency response result?
Testers must compensate for the inherent resonances in the dummy head. This is generally done by finding the “target curve” of the dummy head.
The target curve essentially represents the nature of human hearing as defined by the resonances of the synthetic dummy head. It acts as a sort of reference line to help us further understand the response of the headphones by showing us the peaks and valleys that will be inherent in the microphone capture.
In other words, if the headphones were perfectly flat in their production of sound (producing all frequencies at the same amplitude during the test), then the resulting frequency response curve would be that of the target curve.
The Harman target response is commonly used, which measures the response of the internal dummy head microphone to a carefully calibrated stereo pair of monitors in a critical listening room.
The multiple tests I alluded to previously are averaged out. This average is called the raw response.
Testers subtract the raw response data of the test from the target curve to get a better idea of how the headphones will sound to the listener when worn. This new curve is known as the compensated curve and gives us a general idea of how a pair of headphones will sound when worn properly.
Raw Frequency Response Vs. Compensated Frequency Response
We saw multiple lines in the frequency response graphs shown in the section on Headphone Frequency Response Ranges And Graphs. The top lines showed the compensated and averaged headphone frequency response, while the bottom lines showed the raw frequency response for five different headphone positions.
Let's have another look at the frequency response graph for the Sennheiser HD 280 Pro headphones:
The raw frequency response data is taken from the microphone measurement during testing.
Raw frequency responses are converted to compensated responses by applying the target/compensation curve. This compensated response is the flattening of the headphone's raw frequency response by deducting it from the target response (attainable by various methods).
Though some experienced viewers may be able to read the raw frequency response graph of a pair of headphones and understand how they'll sound, it is simpler to read the compensated graph to get an idea of how the headphones will sound when the listener actually wears them.
What Is A Good Headphone Frequency Response Range?
A good pair of headphones will have a neutral frequency response and reproduce the audio content as it was intended by the producer/engineer.
Again, this neutral frequency response is not absolutely flat though there isn't exactly a standardized compensation/target curve. Each party that tests for headphone frequency response may have a slightly different compensation/target curve in which they reference real-world headphones.
When it comes to frequency response range, so long as a pair of headphones is capable of reproducing sound in the audible range of 20 Hz – 20,000 Hz, it is considered good. Having this range means it will produce all frequencies in the audible range of human hearing.
However, many professional headphones have frequency response ranges that extended well below and/or above the range of human hearing.
Is there any advantage to having headphones capable of producing infrasound (below the audible range) and ultrasound (above the audible range)?
Though infrasound and ultrasound frequencies might not be heard through our sense of hearing, they can certainly be felt. We naturally hear and feel sound waves, and so, in theory, headphones with extended frequency response ranges can ultimately enhance the listening experience through hearing and feeling.
Note that a seemingly good frequency response range does not necessarily mean that the headphones will sound good. First, “good” is subjective, and an extended range could have some nasty resonant peaks and dips in the actual response that would lead to poor sound quality.
To continue on the point of subjectivity, the best headphone frequency response is somewhat genre-specific. For example, Dubstep may benefit from the added bass response, while Baroque would likely sound best through a more accurate response.
To recap, a good pair of headphones should easily produce audio frequencies between 20 Hz and 20,000 Hz. Extended frequency responses may improve the sound quality of the headphones via our sense of feeling. Different listeners and genres will often benefit from flat or coloured headphone frequency responses.
Let's discuss flat and coloured headphone frequency responses in more detail here.
Flat Frequency Response
A flat frequency response means that the headphones will reproduce all frequencies in the audible range with equal sensitivity.
Of course, this does not mean that the headphones will produce white noise, which is made of all audible frequencies at equal amplitude.
Rather, the headphones will reproduce the audio signal with exact precision according to the audio signal's frequency profile.
Achieve an absolutely flat response is impractical in headphone design and may not even be wanted.
This accuracy may seem desirable, but in practice, it is not. Headphones will nearly always benefit from a boost in their bass response.
This is because of the way headphones produce bass and how we perceive this bass.
Loudspeakers and subwoofers have large drivers that push lots of air to produce the low-frequency long-wavelength bass sound waves. As we've alluded to previously when discussing human hearing, these bass sounds are felt more than they are heard.
The sensation with headphones is completely different as the bass is only perceived by the brain as sound.
Rather than pushing lots of air right next to our eardrums (which would cause permanent hearing damage at high volumes), the relatively small drivers of headphones rely on other methods and working principles to induce a sense of bassiness.
The first is proximity. A bass source close to the ear does not dissipate within the medium (air) nearly as fast as a distant bass source.
The second is bone conduction which allows the vibrations of the headphones to travel through the bones of the skull to reach the inner ear. The inner ear vibrations cause electrical signals in our brain that allow us to effectively “hear” the bass.
The third is coupling with the eardrum, which allows less driver diaphragm movement to have a greater effect on our hearing.
For more information on headphones and perceived bass response, check out my article Do Headphones Have Subwoofers & How Do HPs Produce Bass?
But in order to produce this bass response in the relatively small-diaphragm drivers of headphones, there often needs to be a sort of built-in “bass boost” in the headphones.
So the audio source is effectively bass boosted to allow the headphone drivers to produce a more powerful-sounding low end.
Flat headphone frequency responses, therefore, will sound quite thin relative to their low-end boosted counterparts.
Coloured Frequency Response
Coloured frequency response is the opposite of flat frequency response. It has certain frequencies better represented than others.
The bass accentuation discussed in the previous section is a prime example of coloured frequency response.
Practically all headphones are coloured due to their high-end roll-offs. However, some headphones are considered more coloured than others.
A pair of headphones is considered more coloured if it has notable peaks and dips within its frequency range.
Impedance And Its Effect On Frequency Response
Headphone impedance is a critical specification to understand as it is directly correlated to nearly all aspects of headphone driver performance.
Electrical impedance is essentially defined as the amount of difficulty an alternating current will have when flowing in a circuit.
In other words, we can think of impedance, and electrical resistance applied to alternating current.
A higher impedance circuit will require a greater amount of voltage to allow the same flow of current.
But what does this have to do with headphones? Well, it has to do with both headphones and the audio sources they are connected to.
With headphones, we're interested in maximal voltage transfer between the audio source and the headphone drivers rather than electrical power transfer.
Therefore, we're looking for impedance bridging rather than impedance matching. Impedance bridging essentially means that maximal audio signal transfer will happen between a lower-impedance source and a higher-impedance load. In the case of headphones, the headphone jack output is considered the source and the headphone drivers are considered the load.
Impedance matching happens with equal source and load impedances. This maximizes the power transfer between the source/amp and the headphones. However, it typically does so at the cost of frequency bandwidth.
Essentially with proper impedance bridging, we can have ideal signal transfer and optimal headphone performance.
However, headphone impedance is often frequency-dependent. This can be shown in the impedance graph of the familiar Sennheiser HD 280 Pros shown below:
As we can see, there is a spike in impedance around 70-80 Hz. This peak, in theory, would alter the frequency response of the headphones if the source impedance was wildly different from the nominal impedance of 64 Ω.
Impedance generally has more of an effect on the overall headphone volume than it does on frequency response. That being said, impedance peaks centred around a certain frequency could cause lower headphone volume in and around the peak frequency.
How do I choose good headphones? The best way to choose the best headphones for you is to listen to them. It is a good idea to choose an audio mix you're familiar with and listen via an audio source you plan of pairing with the headphones, but this isn't absolutely necessary. Know your budget and test the headphones not only for sound quality but for fit/ergonomics as well.
Related article: Are Expensive Headphones (Or Cheap Headphones) Worth It?
Is bass high-frequency or low-frequency? Bass audio/sound is made of low frequencies in the audible range of human hearing. The sub-bass range is generally described as 20 Hz – 60 Hz, while the bass range is 60 Hz – 250 Hz. Note that these lower frequencies have longer wavelengths.
Related article (source): Fundamental Frequencies Of Musical Notes In A=432 & A=440 Hz
Choosing the right headphones or earphones for your applications and budget can be a challenging task. For this reason, I've created My New Microphone's Comprehensive Headphones/Earphones Buyer's Guide. Check it out for help in determining your next headphones/earphones purchase.