A guide to understanding headphones specifications ...but not only!  We also explain the different types of headsets, identify related health hazards associated with the use of headsets, and list the features to look for when making a purchase. 

The use of an appropriate headset  can even provide relief from distracting ambient noise while working or traveling.

Even if it's just an issue of getting better sound from your home theater receiver, a high-end headphones-pair offers a cheaper alternative to upgrading a speaker system.

Whatever your requirement, it always remain a pre-requisite to choose good quality headsets.

Unfortunately, many treat such a purchase with  a little bit of disregard - possibly because these represent a relatively small expense in comparison to  the rest of their AV gear.

The truth is that if you still want to enjoy the best audio experience from your AV receiver or CD player - it is essential that you have an understanding of what to look for, headphone-specifications, features, design options most suitable for your needs, in particular, the environment in which you will be using your pair, etc. 

Cheap headsets might be good enough for listening to your favorite CD while jogging, yet they are unlikely to deliver the same level of acoustic performance you enjoy with a good set of speakers.

Ok, one may argue that it is not right to compare different technologies, in that though these are somehow related, yet speakers and headsets are designed to cater for different needs.

On the other hand, one should be aware that with today's technology, it is still possible to experience music and movie audio with extraordinary clarity and image detail when using a pair of good quality-headphones combined with Dolby-Headphone technology. Hence, making the right purchase would surely make a big difference in your headphone-listening experience.

In this article, we take a look at the some of the most important issues to take into consideration when making a headphone purchase. With today's advancement in headset technology, the end customer is exposed to far more choices than ever.  We hope that the info contained in this article will help you get it right!

Headphones Basics - Choosing Your Headset

Dynamic or Static?

There are two basic types of headsets acoustic drivers: dynamic and electrostatic.

The dynamic-driver headphone use the same technology employed in dynamic-driver loudspeakers; these represent the most common type of speakers based on the use of a cone-type diaphragm attached to a voice coil.

In a similar manner, electrostatic headset drivers share the same electrostatic speaker technology where the diaphragm is no longer a cone but a thin sheet of stretched Mylar that is subject to varying electrostatic charge.

What ever the acoustic driver technology in use, the end-result is always a vibrating diaphragm that moves to displace air to create sound.

Electrostatic headphones are capable of delivering exceptional sound detail, especially in the high-end of the sound spectrum, with very low distortion; but these tend to be very expensive. In general, dynamic type headsets represent a more affordable solution - though high-end sets can be quite pricey too.

Comfort:

Whatever your listening requirement - late night music listening, watching TV, etc., it is important that your headset sits comfortably in place.

In particular, if you'll be listening for long stretches, look for headphones that come with a padded headband that can be adjusted to comfortably fit the size of your head.

Sealed, Open, Earbuds or  Canal phones?

Another basic issue is the type of headset design to opt for. If you are after a good solid pair of headphones, the solution is a sealed or open-air design, but for completeness shake, we will discuss all four.

Sealed  headphones represent the classic heavier and robust type of headset solution. These are necessary if you need sonic isolation - e.g. when listening in noisy environments or on the contrary, when working in a shared environment e.g. an office shared with others whom you don't want to disturb as a result of sound leaking out of an open design headset.

If you won't need the isolation of a sealed design to block out distractions, etc., open-air headsets deliver the best overall sound quality. A major advantage of the Open-air headset over the sealed type is their lightness, which makes them feel quite comfortable even following an extended period of use. These units are normally reasonably priced but tend to be quite fragile and may break easily.

If you want to go for the smallest sets ever, than Earbuds and Canal headsets are the solution to your needs.

Earbuds are tiny 'phones that fit into your outer ear, held in place by a lightweight headband or with small clips that attach to your ears. Extremely light - but if you want to enjoy the best sound, you need to find a set that provides a good fit to your outer-ear. Good sets tend to give excellent bass response that you not only hear but feel as well.

Canal 'phones are so small that they fit right into your ear canals; they require no headband or clips whatsoever. These sets provide an airtight seal in your canals, greatly reducing outside noise. Their main disadvantage is that their small cushions, which fit into your ear canals, will pick up earwax easily and quickly and so they must be cleaned or replaced regularly.

Portability:

Open-air, Earbuds, and Canal type headsets all form part of what are referred to as 'Portable headphones' in that these are all lightweight - allowing for ease of mobility.

The features to look for when choosing a good set of portable headsets depend on want you will be doing. For example, surely you do not want your set to come loose during exercising. Earbuds, in-ear headphones, and headsets with clip-on earpieces are designed with active uses in mind. Around-the-ear Earcups may also provide a more secure fit, and more isolation from outside noise, than an on-the-ear design.

Some Open-air headsets come in a choice of either behind-the-neck or no-headband design instead of the traditional over-the-head band; neither of these will mess up your hair while you listen to your favorite music!

Headphone Impedance & On-the-Ear Sensitivity:

Impedance: One issue that's especially important when choosing a pair of headphones is impedance. So called low impedance and high impedance pairs should not be intermixed.

Low impedance headsets may vary from 75 ohms up to about 150 ohms. Phones in this impedance range may be directly plugged into the headphone jack routinely found on recording and playback equipment.

Higher impedances sets normally have an impedance of around 600 ohms; these are more useful in studio installations where many units may be wired in parallel for studio monitoring applications.

The 600-ohm models are more rugged than low impedance ones in that the higher resistance coils are less susceptible to burn out than low impedance models. On the other hand,  high impedance sets require a higher driving signal to produce the same level of sound output in comparison to low impedance headsets.

This means that low impedance headphones will sound louder when plugged in devices with low output voltages such as portable CD players, etc. In reality, because of the limited power available from portable players, headsets for portable use should have a maximum impedance of 64 ohms.

Worth keeping in mind here that the lower the impedance, the more efficient headphones are in converting the incoming electrical energy into sound. On the contrary, the higher the impedance, the more electrical energy is required to drive the headsets tiny speakers.

Headphone sensitivity is usually stated as the in-the-ear sound pressure level (SPL) produced by one milliwatt (mW) of audio input.

We take a more detail approach to the issue of sound pressure levels further on in this article when discussing hearing damage. For the time being, it is sufficient to note that in reality, only a few milliwatts of power is needed to drive a stereo headset to very high listening levels.

Noise-Canceling Headphones:

Whether you do a lot of traveling, have to work in a distracting sound environment, or just live in a busy household, noise-canceling headsets can be godsend! These technological wonders incorporate sophisticated active circuitry which relies on tiny microphones to pick up the noises around you. The electronics inside generates an identical but out-of-phase signal that when played back in the headsets, helps to cancel and quiet the outside noise.

These headsets tend to be heavier than normal sets in view of the added batteries used to power their active noise-canceling circuitry. Should you decide to opt for this type of headsets, check battery life specs before you buy.

Wired or Wireless?

We fancy wireless headsets, but then it all depends what are your real needs.

Wired Sets: Unless you are going for a wireless pair, make sure that your wired headphones come with a long enough cord to enable you to hook your headset to your stereo or A/V receiver, PC, etc.

Ideally, try to avoid extension cords - it is easier to get entangled in something when moving around in your home theater room with a long cord between your headset and the AV receiver.

At the same time, the cord length itself should not be the deciding factor when choosing headphones - after all, one can always bridge the gap with a suitable extension cord.

Again, from a practical perspective, headsets with a one-sided cord - attached to one earpiece but not the other - help minimize tangles.

Wireless headphones open up a whole new world of listening possibilities. You can listen to your favorite music while moving around the house or yard — without carrying a portable player. And cord concerns are no longer an issue.

Models may use either a radio signal (RF) - most operate over the 900Mhz band, or infra-red (IR) technology. Models using RF may support a range of up to a few hundred feet - meaning that you can walk anywhere within the range and still enjoy a great sound. By contrast, models using infrared transmission work only if you stay within sight of the transmitter.

Since wireless headphones do run on batteries, models that include rechargeable types are more convenient and cost-efficient in the long run. If you decide to go for a pair of wireless headphones,  try to buy a set that automatically charges when on the stand with the battery still in place. Additionally, try to get an extra battery ready to swap over when the one in use runs out. (This applies to all battery operated headphones - not just wireless.)

Talking about re-chargeable batteries - try to avoid models using NiCd batteries. NiCad's are quite unsuitable for heavy use because they don't fully discharge because of the infamous memory effect. NiMh and Li-Ion do not suffer from this.

Some wireless headphones offer built-in processing of Dolby® Headphone and other surround formats, for powerful virtual surround sound effects. And if you want the best possible reception without fiddling with controls, look for wireless 'phones that provide automatic tuning.

But wireless headphones have their cons as well - more expensive than standard wired headphones especially if you opt for a high quality pair, battery life problems, interference,  and possible background noise. With some cheap models, periods of silence can be noisy; in general, expected sound quality from a good-quality set should be very similar if not better to that of an FM stereo broadcast.

Headphone Buying Tips

1. If you will be making use of your headphones solely with your home AV system, then go for the higher quality classical type of headset. The higher weight associated with these models would not be much of an annoyance since most probably you will be seated.

2. The standards you apply when purchasing headphones should be pretty much the same as those you apply when purchasing other AV equipment - after all, you will still want to enjoy clear sound with good bass response and least possible distortion irrespective of whether you are listening to your favorite music CD through a set of speakers or through a pair of headphones.

3. May be too obvious but often ignored - when making your purchase, make sure the cord terminates in a plug size that's compatible with the component or portable you'll be listening to. If it comes with a mini-plug and your equipment has a standard size socket, you would have to use an adaptor.

4. Some headphones include detachable parts, like ear cushions and cords that you can replace if you need to. This can be pretty handy especially with portable types.

5. Good fit and comfort are basic requirements for an enjoyable experience. The best headphones would be of little use to you if they do not fit properly - you simply would not be able to keep them on long enough to view your favorite DVD. Hence whenever possible, try before you buy.

6. This try-before-you-buy approach applies also to better analyze the headset acoustic performance.  Ideally, you should take a music CD with you from your own collection - after all, the best tools for evaluating headphones are music CDs and audio test CDs.

Audio Test CDs: Investing in a good Audio Test CD is surely worth it - both to assist you in your headset purchase as well as in setting up your audio equipment. When using a test CD in conjunction with headphones, simply skip loudspeaker specific tracks, such as speaker-setup tests). There are quite a number of inexpensive good audio test CDs around, including Stereophile TEST CD #2 and Stereophile TEST CD #3. A good headphone test CD should have pink noise tracks, an assortment of frequency sweeps as well as binaural tracks (or use separate binaural recordings). Alternatively, check our Guide to Home Theater Set-Up DVDs for more information of Set-Up Discs and possible alternatives that may be more suitable for your needs.

A Word of Warning...

Headphone Use & Hearing Damage

This article will not be complete without addressing the issue of hearing damage and headset use.

A good pair of headphones would normally deliver better sound quality at even higher sound levels than many inexpensive speaker systems can ever deliver.

This leads to many treating themselves by letting the volume up. Our advice - DO NOT do it!

Your ears can begin to suffer permanent hearing loss by sustained exposure to sounds over 85dB SPL - a level easily exceeded by most home stereos and portable music players. In reality, most headphones may easily exceed a 100dB sound pressure level.

But what does this 85dB SPL represent in real terms?

In order to answer this question, it is important for one to understand what this dB SPL measurement is all about.

db SPL is a ratio of the measured sound pressure level created by a sound source and the reference level; in this case, what is of interest as our reference level is the human hearing threshold. This is referred to as 0 dB SPL.

Noise measurements that take into account the human ear's sensitivity are referred to as A-Weighted dB(A). Interesting to note here that the ear's response to a constant level sound source varies with frequency - the human ear tends to be insensitive to low bass notes while it compresses higher sound levels - hence the use of a logarithmic scale to express sound measurements.

Taking 0dB reference as the threshold of human hearing, than 50dB represents very soft music, while soft popular music or a noisy office environment may very well reach 75dB SPL.

In comparison, a hair dryer or an alarm clock 1 meter away goes up to 80dB while traffic noise in a busy city junction already reaches 90dB SPL. This is already above the safe hearing level. Further up the scale, an ambulance siren measures 120dB SPL. A Jet takeoff gets up to 120dB - and may easily exceed 140dB if you are within a 25 meter distance.

Back to music listening - loud passages of music may easily exceed 100 dB while SPL during Rock Concerts and in Discotheques may go up to 110dB and more.

So think twice before raising the volume - your headphones may very well deliver unsafe high sound pressure levels even with minimal power input - risking permanent hearing loss.

Our advice: use your headset with respect, and you will surely have an enjoyable long-term headphone listening experience.

Last updated on 12^th May 2005