If you are considering buying high quality headphones, you will very quickly come across the term “high impedance”.
This is because high impedance headphones typically deliver far superior sound – and unlike their low impedance peers, they do not distort or self-destruct if you connect them to audiophile level or DJ equipment.
High Impedance Headphones: What You Need to Know
Impedance is a measure of resistance to electric current, and it is measured in ohms: the higher the number, the more resistance there is.
In the world of headphones, low impedance is generally considered to be a number lower than 50 ohms. High impedance headphones can be 250 or even 600 ohms.
There are some crucial differences between low impedance and high impedance headphones. The first and most important difference is that low impedance headphones do not need much power to deliver sound, and as a result, it makes them ideal for applications where battery life is more important than sound quality.
For example, the amplifier in a typical smartphone is designed with 32-ohm headphones in mind. It may run much more resistant, but it does not get the best from them or from its battery.
The other really important point is that high impedance headphones really sound better.
Why high impedance headphones simply sound better
When you listen to high impedance headphones on a compatible hi-fi system or studio equipment, you will notice that there is a marked difference in the sound quality.
The sound stage is larger, the bass is more defined, and the individual instruments and voices are clearer and better positioned.
This is because the voice coil in high impedance headphones is designed differently from the one you find in low impedance models. Its wires are much, much thinner, and it allows manufacturers to wrap more wires more times and closer than they can on smaller models.
It does two things: it creates more magnetic force to move the diaphragm of the coil, which is the bit that actually produces the sound; and it makes the coil much lighter and more responsive. This means much lower distortion, better dynamics and more accurate sound reproduction.
Other specifications to study
There are some other numbers to consider when looking at headphones. The first is the frequency range and the second is the sensitivity.
The frequency range tells you how much of the sonic spectrum the headphones can deliver, and it is common to see 20Hz to 20kHz, which is the typical range for human hearing.
But some headphones are capable of much more, so for example you can see the lower limit as 8 or even 5Hz and the upper at 37 or even 44kHz.
The second number is sensitivity, which is measured in decibels of sound pressure level – abbreviated dB SPL. dB SPL tells you how many decibels of sound will be generated from one power unit, either 1 milliwatt or 1 volt, at a frequency of 1kHz.
The number effectively tells you how loud the headphones are, and the higher numbers indicate higher volume.
Just make sure you compare like with like: you need to know if you are looking at dB SPL / V, which is based on voltage, or dB SPL / mW, which is based on milliwatts.
Helplessly, some manufacturers only indicate dB without clarifying which measurement they are using. This can make it difficult to compare different models from different manufacturers.
Together in perfect harmony
It is important to match your headphones to the amplifier or other hardware you want to listen to. Headphones with too low an impedance can deliver hard, cutting distortion or may simply fail when connected to a high impedance output.
On the other hand, headphones with excessive impedance will struggle to produce the full dynamics and volume or may have inconsistent volume levels.
As a rule of thumb, if you are buying for use with a smartphone or similar device, look for low impedance headphones around the 32 ohm mark; If you are buying headphones for your existing or planned audiophile hi-fi hardware, or for recording studio hardware or professional DJ kit, high impedance is the way to go.
This is why some manufacturers offer the same headphones with different impedance levels: They make a 32 ohm version for maximum compatibility with standard audio devices along with higher impedance versions for audiophiles or studio use.