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What is a Headphone? – Do You Really Know?

Most music lovers use it all the time, when listening to their favourite music. But how much do you actually know about this handy listening device? If you are learning to be a music producer or audio engineer, you might find yourself relying on alternative listening devices, apart from monitor speakers. Hence, the question we will ask today is – What is a Headphone?

As usual, we will go through various important topics surrounding the subject of discussion. Understand the basic principle in a headphone’s design, and find out how it impacts a user’s listening experience. We will also take a deeper look into the various factors that will affect the performance of headphones. Can’t wait to get started? Then, let us begin!

Introduction – Design PrincipleHeadphone Design

During the early times of telephony and radio, headphones are often recognised as head-phones. They are a pair of light and small listening devices that are designed with portability in mind, and are either attached on or around the head over the listener’s ears. Since they function by converting electrical signals to sound waves, they are also known as electroacoustic transducers.

Unlike a sound system’s loudspeaker (which projects sound openly, where everyone can hear), headphones are engineered to provide ample sound isolation, allowing users to listen to audio privately. Headphones are also sometimes called earspeakers or earphones. In order to hold the speakers in place, circumaural and supra-aural types have a band which goes over the top of the head.

Another type which is known as earbuds or earphones, consists of individual units that are plugged directly into a user’s ear canal. Headphones are often used to transmit audio signals coming from various sources such as an audio amplifier, FM radio, CD player, mP3 player, smartphone, video game consoles and electronic musical instruments. EarphonesWireless bluetooth technology can also be integrated into headphones.

In an effort to facilitate a more effective audio reception without causing a nuisance to others, radio pioneers together with radio telephone and telegraph operators became the first ones to use headphones within a professional capacity. The audio quality for the early headphones were not ideal, thus, the invention of high fidelity headphones was the next natural step to be taken.

Let us now have a look at the topics we will be discussing:

  • Real-world applications
  • Electrical characteristics

Real-World ApplicationsCD MP3 Player

Headphones can generally be used with most CD and DVD players, home theater systems, laptops, or portable devices (such as mp3 player, smartphone). There are also cordless headphones which do not require a cable to be connected to its source. Instead, radio or infrared signals (encoded using a radio or infrared transmission link, such as Bluetooth or Wi-Fi) are received by the headphones.

In the world of professional audio, headphones are often utilised by disc jockeys with a DJ mixer (for performance), and audio engineers (to monitor signal sources). DJs who work in radio stations also use headphones in order to monitor their own voices. However, the speakers will always be turned off to prevent acoustic feedback when talking into the microphone.

For music production applications, musicians and singers typically use headphones (in recording studios) while playing an instrument or singing along to a backing track or band. Headphones are also used in the military to monitor audio signals of various types.

Connector AdapterWired headphones typically use 6.35 mm (¼″) and 3.5 mm phone connectors. Take note that the larger 6.35 mm connector is normally used with “fixed location” home or professional sound systems. For most portable audio devices, the 3.5 mm connector remains the ideal choice. Adapters are also available if you want to convert between 6.35 mm and 3.5 mm connectors.

Electrical Characteristics

When looking for a headphone in the market, there are some factors that you need to look at. Hence, in this section, we will cover the two main electrical aspects of headphones. Do take note that, since most headphones are essentially small dynamic loudspeakers, the electrical characteristics of dynamic loudspeakers may also be applied to headphones.

Impedance

Depending on the model, headphones can have high or low impedance (typically measured at 1 kHz). Low-impedance is in the range of 16 to 32 ohms and high-impedance is about 100-600 ohms. The higher the impedance a headphone has, the more voltage (at a given current) is needed to drive it, resulting in a decrease in loudness of the headphones at a given voltage.

Headphone Amplifier

Photo by MMuzammils / CC BY-SA 3.0

A headphone’s impedance is a huge concern due to the output limitations of amplifiers. Most modern headphones today are driven by amplifiers, and headphones with low impedance presents a larger load. On the other hand, amplifiers are also limited in the amount of power they can supply, due to having output impedance.

The output impedance of an amplifier should be less than 1/8 that of the headphones it is driving (and ideally, as low as possible). This is to ensure an even frequency response, adequate damping factor, and undistorted sound. In the event where the amp’s output impedance is larger than the impedance of the headphones, a significantly higher distortion will be produced. 

Hence, headphones with lower impedance will usually be louder, with better efficiency. However, they will also need to be powered by a higher quality amplifier. On the contrary, higher impedance headphones tend to be more accommodating towards amplifier limitations, but produces less volume for a given output level.

Sensitivity

The measure of an earpiece’s effectiveness in converting an electrical audio signal into sound waves (audible sound), is known as a headphone’s sensitivity. It indicates a headphone’s loudness (dB) at a given electrical drive level. It is measured in decibels of sound pressure level per milliwatt (dB (SPL)/mW) or decibels of sound pressure level per volt (dB (SPL) / V).

Sound Level Meter

Photo by Alkarex / CC BY-SA 3.0

Never use high sensitivity headphones with power amplifiers, as this will lead to alarmingly high volumes and may damage the headphones. The highest sound pressure level is usually a subjective matter, with some sources recommending a maximum of 120 dB. However, the American Occupational Safety and Health Administration advises a peak level of 85 dB(A) to prevent future hearing loss.

On the contrary, the European Union standard (EN 50332-1:2013) suggests that a warning should be issued for any volume levels above 85 dB(A), and also recommends the peak maximum volume to be at 100 dB (defined using 40–4000 Hz noise), in order to minimise the chances of an accidental hearing damage.

Based on this standard, headphones with sensitivities of 90, 100 and 110 dB (SPL)/V should only be driven by amplifiers that are incapable of anything more than 3.162, 1.0 and 0.3162 RMS volts (at maximum volume setting) respectively, to minimise the risk of hearing damage. The typical sensitivity of headphones ranges between 80 and 125 dB/mW and is often measured at 1 kHz.

That should be a good basic summary of what you need to know about headphones. There are much more technical details to discuss, however I’ll leave that to future articles.

Do leave a comment or question below, and share this article if you like!

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Farhan

When I'm not rocking out to great music, I'd prefer to be sleeping on a field on a windy day =)

8 Comments

  1. You can look at the endless age of headphones and see how its been revolutionized through time and modern technology,
    I read this article and enjoyed the information, the product review, hone recordings, live sounds, and great content.. you did well,, thanks for letting me review it

    It was insightful and educational all in one

    • Hey there HB!

      Yeah, headphones and many other audio devices in general, have been through a lot of technological changes in the last few decades. It is my pleasure to be able to bring you informational articles that you may enjoy. Thanks a lot, and do come back for more!

      Cheers =)

  2. I was scanning through looking for a new set of headphones. Reading through your article I realized exactly how uneducated I am about a device I quote literally use every single day. I’m not a music producer or anything close, but I’m an avid music lover. What would you suggest for someone looking to get great quality from an android phone? Is there a difference I’m audio quality from headphones or is the difference more often noticed from the music device itself?

    • Hi Jennifer!

      The sound quality that you will get depends on a combination of the headphone itself, and also the music device. It’s never an isolated situation, where only one of the devices I have mentioned, is at fault. Try using the same headphone, and listen to the same music on various music players. You will hear a stark difference between any two audio sources, such as between a laptop and an mp3 player.

      For casual music listening across various audio devices, I would recommend Logitech Ultimate Ears. Here is one I recommend: Ultimate Ears 600vi Noise Isolating Headset

      Do take note that the on-cord controls only works with apple products.

      Thanks for dropping by!

  3. Glad you wrote this…it’s one of those things where you think to yourself, “Sure, I know what headphones are,” but do you REALLY? I am not very tech savvy despite the fact that I use them all the time, so I get lost with technicalities. It’s good to get back to basics because it is easy to take something that you use all the time for granted without really thinking about how and why it works. I actually need a new set of headphones for audio engineering. Do you have any suggestions on good ones to buy? Thanks in advance! 🙂

    • Hi Denise!

      Yeah, people love music and use audio products all the time, but most of them are unaware of its intricacies. I am very happy to know that you have benefited from this article. When choosing a headphone for audio engineering, you need to be sure that it is suitable for critical listening.

      Check this out: http://myaudioeducation.com/shure-srh840-review-yo

      Thanks for dropping by Denise, and do visit again sometime!

  4. Great information. Brings back memories of the old days of headphones. It sure has gone through many changes over the years, especially with the blue tooth enhancement.

    It’s also interesting how headphones can give you that real time experience by controlling what you can hear from your left ear and right ear. There are lots of games out there which takes advantage of headphone technology nowadays to make it sound like you are actually there in the game rather than playing the game. It also applies to music. It really makes you feel like you are at the live performance.

    Thanks for the information once again.

    • Hey Blame!

      Yeah, its incredible how much technology has impacted our listening experiences. I’m happy to know that this article has inspired you to think more deeply about headphones and audio in general. Do check back for more updates, and thanks a lot for dropping by!

      Cheers =)

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