Headphones

home

post separation

Headphones exist in many forms and shapes ranging from small ones that are pushed in the ear canal to quite large ear-speakers that hang on the sides of your head.  We can divide them in several groups. IEM (In Ear Monitor) are not ‘suited’ or liked by everyone and have foam tips and are inserted IN the ear canal (Intra-aural). CIEM’s (Custom moulded In Ear Monitor) is a more specialised IEM and it must be custom made by the manufacturer. You will need to have a mould made by an audiologist or other qualified person which is sent to the manufacturer and they make an earpiece that fits exactly in your ear.   It is obvious CIEM’s are thus more expensive and can only be used by the one who had them made while lEM’s with foam tips can be used by most people. Not everyone is comfortable with things tucked away in the ear canal. CIEM’s in general have a better sound quality because of the fit. a small ‘leakage’ of air can already result in the bass being completely gone.
DSCN2428Another common form is the earbud which rests in the outer ear. Because the shape of ears not being equal some people may have problem getting a good seal and thus these earphones may sound bass-less to some while other people hear plenty of low, so not suited for everyone. Try to audition these headphones if you can but most vendors won’t provide that service which makes them kind of a gamble. Buying from an online store where you can send them back within a couple of days if they don’t work for you may be the best way.  DSCN2430The ear-clips are models that are placed between ear-buds and the smaller on-ear earpad type of headphones and are clipped behind the ear via a plastic or metal clip and have an earpad-style driver being pressed against the ear. Not everyone finds them comfortable and the comfort is also very dependent on the brand/type. next type is the small earpad type headphones (supra-aural)  that come with some portable equipment, in DSCN2288airplanes, hospitals and are quite cheap in general. They have foam ear-pieces and rest on the ears connected by a thin, metal or plastic, headband. More luxurious versions exist. Another very similar headphone is the on-ear with a usually more sturdy quality and earpads that provide a good seal or have foam pads. Some of these clamp hard to create a good seal and may become uncomfortable very quickly. NOT recommended for people wearing glasses as the ears are pushed against the head with the ear-rests of the glasses between them.. quite painful. DSCN2236Next in line is the over-ear (circum-aural) headphone that has pads that rest on the head and doesn’t touch the ears. These are the most comfortable ones but may get quite hot in warm whether.  Another type of headphone, but a quite rare one, are the ear-speakers that do not seal around the ears but sortoff hang next to them. Quite large and need a lot of power. These headphones do not have deep bass extension and cannot have it because of acoustic ‘rules’ that prevent that.

Power ratings range from merely a few milliWatt (mW) to several Watts. Portable equipment usually can not provide more than just a few mW while desktop amplifiers can provide higher amounts of power. Portable amplifiers in general can provide output powers up to tens of mW or even 100mW. The lower power headphones are the ones for portable use like IEM’s (In Ear Monitors) and CIEM’s (Custom moulded In Ear Monitors). The small earbuds usually can handle more power and have an average rating around 50mW. headband and earclip headphones in general are specified with ratings varying around 200mW while (semi) professional headphones are often rated at a few Watts. This is because these headphones also double as small speakers when lying around on consoles or hanging around the neck. Ortho-dynamic headphones, in most cases, also have power ratings into the several Watt region and can be driven from loudspeaker amplifiers even.

Resistance or more exactly impedances of headphones can be between 8 Ohm and 2000 Ohm.  The impedance of a headphone is important as it determines how much voltage is needed to reach a certain power level (S.P.L). Lower impedance headphones in general are better suited for portable equipment as they require just a small amount of voltage but relatively larger amounts of current. The impedance ‘range’ for low impedance headphones is between 16Ohm and 64 Ohm. Higher Impedance headphones are more suited for usage with desktop equipment and usually have a range between 120 Ohm and 600 Ohm. Headphones with impedances between 16 Ohm and 120 Ohm can also be used with desktop amplifiers but the possible ‘synergy’ could be less. This depends on some of the traits of the used amplifier. The output resistance of the amplifier can be the limiting factor in these cases.

So when looking for a headphone it is important to know if you want to use it with portable equipment (playing directly from them) or for primary use at home driven from mains fed equipment. Note that higher impedance headphones that are not primarily intended for portable use can still be used with portable gear but only when a suitable portable amplifier is used.

The efficiency of headphones also varies considerably. The efficiency of a headphone basically tells you how much power is needed to play with a certain loudness (SPL =  Sound Pressure Level).
Some headphones play pretty loud with just a few mW already and thus have a high efficiency (given in dB/mW or other quantities). Other headphones need quite a lot of power to reach the same SPL and thus have a low efficiency.

There are also different types of drivers. BA (balanced Armature) drivers are found in (C)IEM’s, as well as dynamic drivers. These types of headphone provide an excellent attenuation from outside noises and is why you often see musicians/singers wearing CIEM’s as monitors during their performance. Most headphones, however, have dynamic drivers with a voice coil and a small membrane. They exist in many different sizes and made from different materials and are also called ‘moving coil’ drivers. Another type of driver is the ortho-dynamic driver which is a flat (planar) membrane sandwiched between strong magnets with holes between them and a coil etched on the membrane. A variation of this type of planar drivers is the electrostatic driver and the electret driver.

Some very rare and exotic transducers (drivers) are bone-conduction drivers and air-motion transformers. A subset of the moving coil type headphones is the Noise cancelling headphone which has an amplifier built in and 1 or 2 small microphones in the earpiece. These microphones are used to ‘cancel’ the sounds coming from the outside or at least lower certain sounds to a great extend. They need batteries to operate and cannot cancel all types of outside noise but are great on airplanes and busses in filtering out humming or constant noises. A headset is another variation and can be earbud, IEM, supra- or circum-aural type and is basically a normal headphone with a microphone attached. Used by gamers and on the go connected to a mobile phone/smartphone.

DSCN2435Open, closed or semi closed (or semi open) headphone types exist and it is important to decide which one you want/need. Open headphones (earbuds as well) leak sound to the outside world and let sounds from the outside in and certainly the cheaper versions could sound better to most. Semi-closed DSCN2147headphones leak less sounds to the outside world and let in some some as well but noticeably less than fully open ones. Closed headphone are literally closed and they leak far less if any sound to the outside world and also let in little to almost no sound from the outside world. Not every type does this equally well (mostly caused by the pads (cushions)) and if you want maximum isolation it is wise to look around. Cheaper closed headphones can exhibit a ‘cuppy’ sound. The better ones can sound equally good as it’s open cousins. Noise cancelling (NC)  headphones can also provide good isolation from outside noises only to be surpassed by IEM’s. IEM’s can provide even better isolation and  CIEM’s and are the best choice when seeking total isolation.

The frequency range is another important factor BUT most manufacturers just mention 20Hz- 20kHz and handily forget to mention how many dB’s of graph colorationdrop-off it has at those values nor do they mention within how many dB the SPL varies within that frequency range. So a headphone specified to have a range from 4Hz to 35khz may very well have less bass and/or highs than a headphone specified to have a range between 40Hz and 18kHz for instance. BUT… it may also be the other way around. Basically the spec will tell you very little UNLESS they mention the – xdB points or within how many dB it varies. The only way to find out is by interpreting frequency plots of headphones AND understanding WHAT is important and what not.

Distortion figures are another factor and again in this case also manufacturers mostly quote ‘nice’ figures obtained at a frequency the headphones perform best. They are never given at the harder frequencies nor are the number of harmonics and their content over a wide frequency range given. The only way to find out is to look for websites that perform their own measurements.

Sealing issues:
Some people trying out / owning headphones may find their evaluation of their headphone(s) differs considerably from those of other users.
Before blaming it on the headphone(s) find out if you aren’t plagued by fit/seal issues.
ON-ear headphones have the biggest chance of having a bad seal as well as over-ears with large diameter earpads or stiff earpads.
The shape of your head, amount / type of hair and ear-shape may be causing a bad seal in combination with some headphones.
If this is the case TEST if you are getting a good SEAL with your headphone(s).
Especially when there is less bass than ‘expected’ or the sound is nasal or otherwise ‘coloured’ in a way that isn’t usually described.
To test for seal simply press the earcups more firmly on your ears. When the sound changes dramatically (most obvious in the bass) then experiment with other pads and or clamping force to address that issue, or find another headphone that doesn’t have sealing issues.

 

post separation

home

post separation

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s