There are so many different brands, styles and prices of headphone that it can be very difficult to find a pair that is right for you. You might be wary of the trend for celebrity-endorsed headphones, but browsing the spec sheet doesn’t make things any easier. Headphone specs are complex, and very technical, and sometimes don’t even have any meaningful effect on sound quality.
In this guide we’ll cut through the jargon and show you what the key headphone specifications actually mean, and why — or if — they matter.
In-ear (canal) headphones, also known in-ear monitors, sit directly inside the ear canal. They have two main technical benefits. They sit closer to the ear drum, so can deliver excellent sound quality, and they also fill the entrance to the ear, so are effective at sealing out external noise.
In-ear headphones come with a selection of different sized tips so you can find one that fits your ear canal. Getting the right fit is essential for attaining best performance; using a wrong-sized tip will affect audio isolation and the earphones will be prone to falling out. In-ear headphones are extremely portable, so are most convenient for use on the go, or at the gym. Their smaller size, however, means they cannot compare in all-round performance to a larger set.
On-ear headphones, also called supra-aural headphones, rest on top of the ear. Like in-ear headphones, they direct sound straight down the ear canal, but don’t seal out external noises, and may also leak noise to those sat nearby. Many find them more comfortable than earbuds, and they are less likely to trap heat on your ears than over-ear headphones are. “Clamping” can be an issue, though, where they squeeze too tightly and become uncomfortable with extended use. It’s important to find a pair that fits well. On-ear headphones are a good compromise solution, with excellent sound quality (in higher end sets) and a good level of portability.
Over-ear or circumaural headphones encase the entire ear. Their increased size makes room for a larger driver, with louder volume and better bass performance. The driver is also positioned further away from the ear, producing a more spacious sound akin to what you hear from speakers. By covering the ear, these headphones offer good noise isolation, but they are a lot less portable than the other formats. Although it is no longer true to say that over-ear headphones are automatically better than other styles, circumaural headphones remain the audiophiles’ choice. You’ll also see headphones (over-ear ones especially) described as being either “open back” or “closed back”. This refers to whether the back of the earcups are open or sealed. “Closed back” headphones offer better noise isolation, and tend to have a more forceful sound similar to what you get from in-ear headphones. “Open back” headphones have more sound leakage and let in more ambient noise, but deliver what audiophiles often describe as a more natural sound.
The driver is the most important component in a pair of headphones. It turns an electrical signal into sound pressure — in other words, it creates the sound. There are different types of driver, but they all consist primarily of magnets, voice coils and a diaphragm. The components cause the diaphragm to vibrate, and these vibrations produce sound waves that our ears interpret as sound. apple drivers On the headphone spec sheet, the Driver indicates the diameter of the diaphragm, measured in millimeters. As a general rule (but not always true), the larger the driver, the better the sound, especially for bass performance. On over-ear headphones, a driver of 40mm or larger is a good bet. Since in-ear headphones cannot fit a large driver, a growing number take a dual-driver approach. Rather than having a single driver handling the entire frequency range, there’s one specifically for bass and another for the mid and high frequencies.
Sensitivity and Sound Pressure Level (SPL) are related terms, and either may be used on headphone spec sheets. They indicate how loud the headphones will go. Sensitivity shows how efficiently an electrical signal is converted into an acoustic signal. SPL is how sensitivity is measured, and is often displayed as decibels of SPL per milliwatt (although there is no absolute standard for this). Most headphones are within the range of 85-120 dB SPL/mW. To provide some context, regular city traffic is around 80dB, a shouting voice 105dB, and a jet taking off 130dB. The pain threshold for noise is thought to be around 120dB, while the Occupational Safety and Health Administration warns of the dangers of hearing loss with prolonged exposure to an SPL of more than 85dB.
Impedance is a measure of electrical resistance and is displayed in Ohms (?). In the simplest terms, higher impedance means more resistance, which means more power is needed to drive the headphones. Headphones designed for mobile devices tend to have lower impedance (below 32?), so they use less power. High-end and pro-quality headphones have very high impedance (300? or more), and require a dedicated amplifier to power them. The downside to lower impedance headphones is that, while they use a lower voltage, they require a higher current. An electrical current creates vibration, which in turn creates sound. The result is that lower impedance headphones may emit an audible background hiss. Impedance mismatch can also cause this and other performance issues. Mismatch can occur when using high impedance headphones with a smartphone, or low impedance headphones with a high-end audio system. It’s important to have the right type of headphones for the audio equipment you are using.