Physical Headphone Types Explained
Headphones are sort of like shoes: There's an element of utility (different shoes for different uses); an element of comfort (heads and feet come in different sizes and shapes; a poor fit is no fun); and style (both are worn and seen by others). Each headphone type has advantages and disadvantages in sound quality and effectiveness in various modes of use. There are also some physical variations within each type, for example in the way they are secured to your head (headbands around the back of your neck, loops that go over your ears), all of which will be covered in the appropriate sections below.
Headphones come in many shapes and configurations, but there are fundamentally five basic physical types of headphones, which are characterized by the size and shape of the ear-piece and how they physically interface and acoustically couple with your ears...the topic of this article. Other methods of classifying headphoneswhich will be discussed in depth in other articlesare by acoustic principle (sealed, open, noise canceling), by the type of acoustic driver used (dynamic, planar magnetic, electrostatic, etc). We can ignore driver types and noise cancelers for the moment, but it is important for the following discusion to know about the fundamental differences between open and sealed headphones.
Open headphones allow the free escape of sound from behind the driver and/or through the earpad, closed headphones have a sealed chamber behind the driver and/or tightly seal around or on the ear. An open headphone doesn't suffer from some of the acoustical resonance problems in the rear chamber or in the trapped air space between the headphone and head that sealed headphones have to contend with, but they also don't seal you away from outside sounds. Open headphones can sound more airy and spacious, but because you can hear your surroundings they need to be used in quite spaces like your home or office. Sealed headphones tend to sound more congested and closed-in, but because they provide some isolation from outside noise they can be used in noisier environments. In most cases below, we'll address both open and sealed versions of these physical headphone types.
Understanding the Ear Diagrams
This article is all about how the headphone acoustically couples to the ear, so we'll have to have a good way to diagram that relationship. The above picture of the ear on the left will be used to show where the headphones make contact and couple with the ear, and the diagram on the right will be used to show the exact physical relationship. The diagram to the right is a cross-section of the ear at the level of the tragus, and its position is shown by the red line in the picture at the left.
This is a good point to note that ears come in a pretty wide variety of shapes and sizes, and headphones that are comfortable for one person may not be for another. Generally speaking, the smaller the headphones are, the more likely they will be to have comfort and ergonomic problems for some people. Circumaural headphones don't touch the ears, so they will most likely deliver comfort broadly; supra-aural headphones rest on the ear and comfort and acoustic seal will vary depending on the shape of the users ears; in-ear monitors are very small and are quite likely to be uncomfortable, so a variety of tips are usually included for the user to explore for best seal, fit, and comfort.
Alrightythen, let's have a look at the different headphone types...
Circumaural Headphones (Full-Size, Around-the-Ear, Over-Ear)
Headphones are quite an unnatural way to hear sound. When listening to speakers and natural sounds, the sound waves bounce off our torso, head, and ears in a way that causes the sound to be significantly changed before arriving at our eardrum. This is perfectly natural and we're accustom to these changeswe need them for sound to be perceived as natural. Headphones bypass a lot of those reflections and as a result can sound quite different and unnatural compared to speakers. Because circumarual headphones rest around the ears with the driver positioned next to the ear but not touching it, they provide the closest facsimile to the way we naturally hear sound of all headphone types. As a result, the very best sounding headphones tend to be circumauralin very general terms, of course, because headphones of most types can be both very good or very poor.
On the other hand, because of their larger size the acoustic volumes created (the air space captured between the headphone and ear, and in the housing behind the driver) are larger than other headphone types. This provides opportunity for disturbing resonances to occur at lower frequencies than other headphone types, and the potential for a significantly uneven frequency response in the region from about 2kHz and above (low-treble). One method to combat these resonances is to open up the space behind the driver to the outside environment and allow the sound to easily escape the enclosure. The world's best sounding headphones are almost always open (acoustic principle) headphones. (See this InnerFidelity article for examples of great headphones of this type.) The disadvantage of open headphones is that people around you will be able to hear your music, and you will be able to hear the noises in your environment. As a result, open circumaural headphones are best suited for a quality listening experience in the quiet of your home or private office space. Audio pros will appreciate the fidelity and clarity of the best headphones of this type for mastering and editing work in quite rooms.
Sealed or closed circumarual headphones are much more susceptible to problems with resonances in the enclosure behind the driver, but they can also provide a sanctuary against outside noise when listening. Be forewarned though, isolation with circumaural headphones can vary widely. Ports in the rear enclosure used for bass tuning and "leaky" pads used to make bass response more consistant with changes in pad seal will reduce isolation in sealed headphones. On the other hand, those measures will make the headphone sound better. A sealed headphone with very high isolation that simultaneously sounds very good is very hard to achieve.
Circumaural sealed headphones are a good choice for: quality listening in moderately loud environments; studio work for audio pros and artists; and in situations where sound leakage from the headphones might disturb others. This type of headphone can work okay in portable and travelling applications, but their larger size may make them too bulky for convenient use, and higher isolation from outside noise can be had with in-ear monitors and noise canceling headphones. In this case, sealed on-ear headphones should be considered for their smaller size.
Supra-Aural Headphones (On-the-Ear, Ear-Pad)
Supra-aural headphones have pads that rest on the outer part (pinna) of your ear. Pads can be donut shaped (as in the diagram above), but may also be flat pads covering a donut shaped foam with holes in the pads for sound, or just foam pads...or in a few cases, no pads at all. Like the circumaural type above, on-ear headphones come in both sealed and open acoustic designs. Sealed designs will usually use real or synthetic leather covered pads; open types will usually be fabric covered or just plain foam pads.
Generally speaking, supra-aural cans are less expensive, smaller, lighter, and easier to stow and transport conveniently. The small size and weight of this type offers opportunity to attach these cans to your head in numerous different ways including headband straps that go around the back of your neck (for runners and women who don't want to muss their hair) and clip-ons that attach directly to your ears without a headband (great for action sports when helmets are used).
Because this type of headphone rests against the folds and ridges of your pinna (outer ear) the acoustic seal is not as reliable as it is with a circumaural headphone, and leads to more variability of performance in bass response and isolation than full-sized headphones. Smaller earpiece enclosures mean resonance problems occur higher in frequency and are less likely to color low-treble response, but the smaller size also creates limitations on acoustic control techniques by designers. While it is generally accepted that the pinnacle of headphone sound quality is achieved with expensive full-size headphones, at $250 and below price-points on-ear headphones can be very competitive and will sometimes sound as good or better than full-sized cans at the same price.
The small size and weight of these headphones coupled with the multiple ways they can be mounted to your head allows supra-aural cans to be specifically designed for a wide variety of uses. Supra-aural, sealed headphones make for great general purpose portable usefolding features allow you to easily store them in backpack, desk drawer, briefcase and purse, and most manufacturers now include mic/remotes on the cable for duties as a cellphone headset. With the very light weight and ability to securely attach to your head, many supra-aural headphones are specifically designed for exercise, sport, and other active uses. On-ear headphones are great for kidswe recommend open designs with foam pads so that kids will more likely remain aware of their surroundings and traffic, and you'll also be more able to monitor how loud your children are listening and help them keep it to a safe level.
Supra-Concha Headphones (Categorized generally as On-Ear)
While generally lumped into the supra-aural category by retailers and headphone enthusiasts, acoustics engineers recognize supra-concha headphones as a different class. These headphones forgo the more reliable sealing opportunity of the entire outer ear, and attempt to seal primarily against the inner bowl of the ear (concha). Headphones are available in both open (foam pad) and sealed (leather pad) versions in this type, but sealing against the concha is difficult and quite unreliable. Really good sounding super-concha headphones are few and far between. Fortunately, headphones of this type are primarily bought for their convenience and very small size.
Intra-Concha Earphones (Ear-Buds)
Aaaaak! The dreaded ear-bud has, in general, the worst audio fidelity of all headphone types. (Devices of this type, and in-ear monitors below, are customarily referred to as earphones rather than headphones.) This type of earphone rest in the concha bowl of your ear, with very little opportunity to form a seal; all earphones of this type are considered open. While most ear-buds sound horrible and are more likely to cause hearing damage with their uneven response and lack of bass that causes many people to turn them up far to loud, there are some that perform quite well for specific uses.
The most famous ear-bud of all time are the little white earphones that came stock with your purchase of and iPod or iPhone. Apple has done a splendid job designing these earphones and they are among the best sounding of this type. Apple's main requirement for these earphones is that they're cheap enough to give away with devices, and good enough sounding to provide peolpe with a quality listening experience. Apple's new EarPods are their latest take on ear-buds, and they too are very good for a low cost earphone of this type. If you have Apple ear-buds made in the last few years, you'll really have to purchase a different type of headphone to substantially improve the quality of your listening experience.
One application where intra-concha earphones are particularly well suited is for exercise, sports and active applications. The best of the exercise ear-buds will be sweat and water resistant, and will feature various methods for securing them to your ears. Some will use headbands, others will attach with loops around the ear or small nubs that lock them into the upper part of the concha bowl. You will find both intra-concha and in-ear monitor versions of these earphones. Because in-ear monitor versions will block out a lot of outside noise they work well in the gym and other noisy indoor environments. Ear-bud style exercise earphones are better for running, bicycling, or skateboarding outdoors as they allow you to continue to hears the sounds around you and will be safer in traffic. You must make an effort to consciously pay attention to those sounds, howeverlistening to music can be highly distracting, and that can be very dangerous. Please be safe, many people are killed by inattentional blindness when wearing headphones.
InnerFidelity has reviewed very few headphones of this type as the sound quality is so often poor, but some of our favorites include the Yuin PK-1 for quality reproduction, and the Sennheiser/Adidas Sport earphones for exercise.
Insert Earphones (In-Ear Monitors, IEM)
In-ear monitors are the smallest of all headphone types. They seal and affix themselves in your ear with a small tip inserted into your ear canal. Headphones of this type can sound astonishingly good because the acoustic space between the IEM driver and your eardrum is so small that it can be accurately modeled by engineers and relatively easily designed for high-fidelity. On the other hand, IEMs bypass almost all of the normal human hearing system and none of the natural reflections from the pinna of your ear are heard. These reflections, and how they change as you move your head relative to the sound source, are used by your brain to locate where sound is coming from and give you a sense of space and sonic image when listening to music. Because these sonic cues are completely missing with in-ear monitors, the sound image tends to be smaller in your head than when listening to circumaural headphones. The best of these earphones deliver such resolution and transient response that even though the sonic image is smaller, it can be very well defined and precise.
In-ear monitors are almost always considered a sealed earphone as they require an air tight seal to deliver good bass response. If you have an IEM and are not getting good bass response your tip might be too small to form a seal in your ear canal, or it might be too large and is folding up on itself making a leaky seal. Experimenting with the tips that came with your IEMs may solve the problem. Comfort can also be an issue with IEMs as our ear canals and surrounding area of the ear is very sensitive. Again, trying different tips is likely to yield a more comfortable fit. Many find the after-market tips by Comply provide an excellent seal and very good comfort.
In-ear monitors provide the highest amount of isolation from outside noise of any headphone type. They are very good at providing a quality listening experience in the loudest environments and work well for air and plane travel, mowing the lawn, studying in bars and cafeterias, and the like. Again, be very careful to remain visually aware of your surroundings in traffic and around metro train stations, inattention can be very dangerous.
In addition to generic fit IEMs with little rubber tips, there is a class of in-ear monitors that can be custom made for your ears. These custom IEMs (CIEMs) can range in price from about $400 to $2000, and the sound quality of these devices can be almost as good as the best circumaural headphones. CIEMs are commonly used by audiophiles for portable listening applications, and by musicians as stage monitors.
Recommendations for this type of headphone can be found on InnerFidelity's Wall of Fame pages for in-ear monitors.
Next up for Headphone 101 is a deeper look a the acoustic principles of open and sealed headphones.