Simplest definition of Impedance in Headphones or Earphones
Just like any other electronic items, headphones & earphones have their own resistance to the electric current flowing through it's circuitry. Measured in ohms, most of the today's consumer headphones and earphones have impedance of 32 ohms.
Let's dive deeper to understand, what exactly is Impedance
Well, we would not get into very technical things related to Impedance but try to explain you it's meaning with respect to your listening preferences as an amatuer music lover.
Since Headphones & Earphones are electronic gadgets, they follow the laws that are applicable to electricity.
Now, impedance is an electrical quantity that plays a pivotal role in how well your headphones perform. When electricity tries to pass through a headphone, it encounters some resistance.
If that still was very technical for you, let us give you an example.
Say, you want to move a motorcycle or a car from standstill position. To move, their engine will have to produce enough energy to propel the vehicle forward.
Depending on many factors like road's inclination, condition of the road, wind etc or even the weight of the vehicle and its occupants, the amount of power required will vary to move the vehicle ahead. Hence, logically speaking, the vehicle's engine must have enough power to take into account all these resistances and move ahead.
Hope it's making sense till now?
Now, all headphones & earphones have an inbuilt resistance to the audio signal passing through it depending on the quality of it's material, especially the metal.
There are many factors responsible for this, right from the size and type of the driver used to the kind of components inside to the whole circuit.
The source providing the audio signal, which typically can be your smartphone but it can be an amplifier too. It also has to overcome its own set of resistances to provide the audio signal. However, just for sake of simplicity, we'll stick to resistance of the headphone only.
Now, when you consider all those reasons (read resistances) that a current or audio signal (which really is a form of electricity) needs to face, in order to make sure audio plays out from the headphone end - that's Impedance.
So what exactly you should look for under Impedance while buying Headphone or Earphone?
Simply put, if your main source of power for the Headphone or Earphone is going to your smartphone, stick to lower Impedance (8-32 Ohms).
And if you're going to use a dedicated amplifier for the Headphone, for e.g. DAP, Music System or Headphone Amplifier, then you can opt for headphones with higher impedance.
Note that higher the impedance, higher will be the power consumption.
Bonus Gyan
And yes, even wireless Bluetooth headphones and true Wireless earbuds have inbuilt amplifiers for this exact function. When you charge these devices, you're basically charging the amplifier inside them.
Headphones & Earphones have an impedance that is typically between 8-600 ohms. Nowadays, 32 ohms is quite common for an impedance rating.
Most headphones we see around, can easily be powered by the inbuilt amplifiers inside a smartphone or DAP.
However, headphone impedance are seen to rise as they get more and more serious to cater to very audiophile-centric or professional demand.
Impedance matching is an important aspect of a headphones' functionality.