When selecting headphones for a particular job, there are many different specifications, attributes and general terminology for them What do they all mean?
Even if you understand what these headphone specifications mean, it is not always clear what difference it may make in practice. Sometimes it may be important - other times not.
Understanding the headphone specifications and terminology can help you cut through all the sales literature, or help talking to a sales assistant when buying a pair of headphones.
Open & Closed Back Headphones
One of the first things seen in the description for many headphones is that some are described as being open back and others are closed back headphones.
With closed back headphones you have a trade off.
Fully closed will isolate more sound (for the listener and away from any bystanders) because of less ambient interference. But, as sound is about air pressure – with a speaker moving the air in front of it to create sound, and by default the air behind it will move as well.
If that air can’t move as freely (being fully closed creates a build up of pressure), it will affect the movement of the speaker and therefore affect the fidelity of the reproduction. Whether that difference is notable by the listener is another question.
Headphone Frequency Range
One of the key attributes to look for in a pair of headphones is the frequency range they can deliver.
Essentially the greater the range of frequencies the headphones can reproduce, the more accurate their sound. Human hearing is generally considered to be 20-20,000 Hz.
While most people can only hear frequencies from 20-20,000 Hz, some headphones actually reproduce 3-40,000 Hz. This is because infra- and ultrasonic frequencies are not heard—they are felt.
This creates the richness of live and studio-quality music experiences—an experience lost with compressed digital files or some other headphones.
Whichever headphones you end up choosing, you’ll want to see at least 20-20,000 Hz range (or greater), although depending on the particular make up of the inner workings of those headphones (drivers, type of metal in the cables etc.), the precise reproduction of those frequencies might differ, creating marginally different sounds for discerning ears.
Headphone impedance & ohms
If you remember physics lessons back at school, electrical resistance (measured in ohms) is related to wire width. The thicker the wire the less resistance (as there is ‘more space’ in the wire for the current to flow through – think of it like water in a pipe, the narrow, the harder to get through).
Therefore speakers / headphones made with thicker wire need less power to drive and can therefore go louder, but that thicker wire (which is coiled around and around at the back of the speaker cone) is therefore heavier and means the speaker cone moves less freely, thus affecting it’s reproduction of the sound.
Conversely speakers / headphones made with thinner wire will move easier, but will need more power. Crudely speaking, lower impedance (less than 100 ohms), needs less power to drive, therefore can get louder; higher impedance (250 ohms), better sound but more power needed. Real world examples would be, less than 100 ohms – iPods, laptops, field recording; 250 ohms – hi-fi installations, studio monitoring.
And the end of the day in an ideal environment, 250 ohm headphones will sound better and more natural. If power is an issue and you don’t have a headphone amp, you could consider something like one of these: