Before we start looking at headphone sensitivity it is necessary to understand – what is a headphone and how does it work? Then we can move on to understanding – what is headphone sensitivity?
Headphones allow you to listen to music or watch a movie without disturbing the people around you. Most of us like to listen to our music loud and must have good sound quality. A common problem is that the sound can be distorted. This is the reason we look at headphones sensitivity.
Headphone styles
There are many types and varieties of headphones. A popular and recommended headphone is an over-the-ear headphone that is well-cushioned, with a closed-back, and completely covers the ears. These are connected to a metal or plastic adjustable headband, allowing the headphone to fit comfortably and be properly placed over both ears.
Take a look here if you want to understand Open Back vs Closed Back Headphones.
A headphone consists of one or two transducers (converts a signal in one form of energy to a signal in another) usually mini speakers.
As headphones direct sound directly to the ears in an enclosed environment. Factors such as frequency (this range applies to the tone and pitch of the sound you hear) and Sensitivity (which applies to the volume of sound produced) or loudness are of great importance.
Most headphones show actual impedance and sensitivity specifications. Some go further and show maximum / clipping levels which will be explained later and frequency response. These specifications define how each unit will work with an audio system.
From an audio system perspective, important specifications are power output, impedance, and clipping levels.
The loudness of a given headphone is directly related to the Impedance and Sensitivity of the headphone. It is therefore important to understand what Impedance and Sensitivity are, as they are co-related and you will know whether your headphones sound best when matched with a smartphone or a dedicated amp.
You will also have a better idea of how loud your headphones can go to avoid damaging your hearing.
This is especially important with children so look at the Best Noise-Canceling Headphones for Kids.
Impedance
Impedance is very important in that it gives a good indication of what will be needed to play a specific set of headphones. It can be argued that it is one of the most important factors to use in deciding what will be the best set of headphones to buy.
Headphone impedance defines how much electrical resistance a headphone provides to an audio source’s signal. This is measured in ohms (Ω) which often range between 8 and 600 ohms depending on the model of the headphone. It indicates how much power a specific headphone will require to obtain a reasonable listening volume.
It is important because the higher the ohms the more power the headphones will require. It means that certain power sources such as smartphones won’t be able to produce the power to produce a clear and loud enough sound.
The impedance that can be played off a smartphone or notebook to ensure an acceptably loud sound with good sound quality is between 20 to 40 Ω. An acceptable volume may be achieved using a smartphone on headphones with an impedance of 45 to 1000 Ω but using a portable amp will certainly increase the power and therefore improve the volume and quality of sound.
Any headphones with an impedance exceeding 1000 Ω will require an amplifier.
The question is asked: Why choose headphones with a higher impedance? Where portable amps or stronger amplifiers are required and thus cannot be easily carried around with you when you can use a headphone with a low impedance that will produce a loud enough volume with good quality sound by using completely portable smartphones.
High impedance headphones are capable of reproducing a much more defined and crisp sound that is closer to the actual sound. For that reason, High impedance headphones are used in sound recording studios.
Sensitivity
A Sensitivity rating indicates how effectively a headphone converts an electrical signal into a sound signal. The Sensitivity rating indicates how loud the headphones will play at a given power level.
This measurement is given in decibels of Sound Pressure Level per milliwatt, or Db SPL/mW, and is based on a 1Mw input signal. One Mw is in thousandths of a Watt, or0.001 Watts.
The sensitivity of headphones is usually in the range of 80 to 125 dB SPL/Mw. A Sensitivity rating of 86 dB is considered fairly low while a dB above 110 can be considered to be too high and can lead to hearing loss.
High Sensitivity
Sensitivity can also be referred to as Efficiency or Sound Pressure Level. (SPL). The Sound makes waves in the air which is how you can hear it. The higher the volume the higher the pressure and therefore there is more chance of causing permanent hearing damage.
For example, if a headphones sensitivity is 126 dB SPL/Mw this will mean that 1mW of power will generate 126 dB SPL/Mw. This is above the danger level for SPL and if listened to at that level even for a short time it could lead to loss of hearing.
A sensitivity rating must be matched with the output level of an audio system. A system with a low output level using a low sensitivity headphone will result in a low SPL. If the amplifier level is increased meaning that a higher output level is now sent to a low sensitivity headphone, it will result in distorted sound due to amplifier clipping.
Apart from a high sensitivity making the sound get too loud, the hiss of your amplifier and electrical noise will occur.
Amplifier Clipping
Amplifier clipping occurs when an amplifier attempts to deliver an output voltage or current beyond its maximum capacity. This causes waveform distortion. Headphone specifications will generally not show clipping levels. The audio source equipment might indicate the level at which the headphone amplifier begins to clip.
Final thoughts
Trying to match a pair of headphones with an amplifier or smartphone can be a complicated and technical process. If you have a basic knowledge of what impedance and sensitivity is, you will be able to match a pair of headphone with either a smartphone or an amplifier.
For example, A headphone with specifications of 30Ω and 90dB can easily be used with a smartphone.
Now that you understand the concept better, you will be able to select the perfect headphones for your needs and buy with confidence.
