What is a Driver
Whenever you are reading about a pair of headphones, earphones or TWS earbuds there is one thing that is conveniently mentioned and written in the specifications area, the Driver size. This is basically the diameter of the transducer installed in the headphones which in turn produces sound waves (by converting electrical signals to mechanical energy) which are then interpreted as music in our brains.
Earphones or earbuds usually have a driver size of 6 mm to 15 mm in diameter. On the other hand the driver size of headphones varies from 18 mm to 50 mm as the headphones are easily able to accommodate large transducers and accompanied magnets and motor systems.
While there are many types of transducers and drivers Moving-coil dynamic headphone drivers, are easily the most common driver type used. The other headphone driver types including balanced armature, planar magnetic, electrostatic and lastly piezoelectric drivers for bone conduction hearing.
Here we shall discuss about the most common driver type which is Moving-coil driver. Have a look below about the cutout of a driver to understand how it works.
The audio signal (electric signal) passes through the voice coil (moving-coil). It is a conductive wire. Furthermore audio signals are alternating currents which inturn varies the magnetic field in the coil.
As can be seen the voice coil is attached to the diaphragm from top which results in the diaphragm to move and vibrate corresponding to any coil movement which is actually induced by audio/electric signal. The magnet structure has a cylindrical cutaway in which the coil resides, it is suspended in such a way that it does not touch the magnet around it.
The pole arrangement is as follow. Interior of coil the magnetic pole is north. As you may have guessed to the exterior, it is south. This concentrates the magnetic field around the coil.
The main magnet is a ring shaped magnet as is often made of a Neodymium. This magnet is strong and is from rare earth material. This normally has the South Pole facing upwards and the North Pole downwards.
Basically as the current passes though the voice coil it induces a change in electromagnetic field. Subsequently it is pushed and pulled by the permanent magnet’s field corresponding to the changes in voice coils magnetic field. The result is the diaphragm movement therefore sound waves that represent the audio signal.
Why Size matters?
Well for the layman it can simply be said that large drivers can move large chunks of air easily. Large air movements mean that larger drivers can have more SPL (read bass). And since all things remaining same larger drivers need to move less than smaller drivers to move same amount of air. This basically means that larger drivers are more clean sounding.
The more air that is moved the greater the variation in sound pressure level. As a result sound waves are stronger and louder. This is particularly true of bass frequencies.
All though large drivers can easily move more air and create stronger bass, that is not the only criteria deciding how strong the bass or how loud the headphones are. Other factors such as driver material, impedance, tuning, chamber volume etc also play a crucial role in the final outcome.
Some of the best wireless headphones have a size of 40mm or there about.
Are bigger drivers better?
Although having larger drivers is good for producing louder SPLs. That is not the sole criteria which influences the outcome or output. Moreover smaller in-ear earphones having small drivers can sound louder and better than large driver equipped headphones. Proximity to ear, driver chamber volume etc also are pivotal factors which go in deciding what are the SPLs.
Further technicalities such as impedance, driver response, resonant frequency, damping characteristics so on and so forth are some of the factors that also influence the overall performance of the said driver in a headphone or earphone application.
Ideal size in earphones
As a general rule of thumb it is good to have earphones which have a driver with a diameter of 9 mm.
Similarly 40 mm diameter is a perfect size of drivers for anyone looking to buy headphones.
Best brands to consider
These are some of the more famous brands easily available and having good quality headphones, earphones and earbuds.