When looking to buy a new piece of audio equipment or an electric instrument, we all start researching and reading about different specs and features. And if you’ve found yourself feeling lost among all these words and descriptions that you don’t understand at all, well, you’re definitely not alone. To be fair, it seems that retailers start listing all of these supposedly important things on their websites’ product pages without even knowing what they mean. It just makes them look more serious, with you ultimately buying the product because it has a lot of supposedly good stuff written about it.
What we want to look into here are headphones and, in particular, headphone impedance. Sure, you’ll be looking for headphones that would fit your personal preferences, but what does impedance actually mean for their overall sound?
What Is Impedance?
But before we get into it, we need to sort things out. There are actually a few different types of impedance in physics. And although one would immediately think that it’s the acoustic impedance, we’re actually talking about electric impedance, or the electrical signal impedance.
Of course, any type of impedance refers to some sort of resistance. In this case, it’s a deliberate resistance put onto the signal. In the case of headphones, it’s used to control the signal in order to give specific results and further enhance the sonic output and bring you the kind of sound that you need for particular settings.
Electrical impedance is actually a complex number and requires some basic knowledge of physics in order to understand. Technically, it’s the measure of the opposition within a circuit on a current when voltage is applied. It depends on the frequency of the sinusoidal voltage. Electrical impedance is expressed in the SI unit of ohms (or Ω). It should not be mixed with acoustic impedance, which refers to the actual sound and acoustic flow and is expressed as pascal second per cubic meter (or Pa•s/m3).
Overall, whether it’s headphones or an electric instrument, or any other electronic device, one thing always remains the same – the higher the impedance, the more the signal output is “restrained.” This can especially be noticed with guitar pedals, preamps, and different amplifiers, as well as amp heads and amp cabinets.
What Is Impedance In Headphones
When it comes to the headphones and the topic of impedance, it’s supposed to give specific results for specific settings, as we’ve already mentioned. As you already might know, headphones are, one way or another, connected to some sort of an amplifier. Be it a phone, an iPod, an old school mp3 player, your home entertainment system, your computer’s sound card, or anything else, they require some additional powered device in order for them to work.
The amplifier, of course, processes the signal before it goes into the headphones or speakers. And one of the things that are processed is the output capacity, with the ultimate goal of delivering optimal performance and sound. In short, the amplifier’s output impedance has to correspond with the headphone impedance. The general idea is that headphones should have an impedance that’s at least eight times higher than the one of the amplifier’s output. This particular ratio is referred to as the “damping factor” and it’s expressed as the headphone impedance divided by the amp’s output impedance.
Impedance In Practice: How Will It Impact the Sound?
The “perfect” setting includes headphones that have exactly eight times the impedance of the amplifier output. In case that it’s more than eight times higher, then you most likely won’t notice any difference, unless we’re talking about some really higher impedance levels. In case it’s much lower, then the results will be noticeable and the overall sound quality and the listening experience will suffer greatly.
If your headphones’ impedance is way higher than the one of the amp’s output, then you’ll notice a significant decrease in volume. In some cases, the sound might feel dull and too “deafened.”
And if we’re talking about the opposite setting, where the damping factor is lower than it should be, then you’ll experience a pretty unpleasurable sound quality, even if the ratio is even a little bit off. The resulting sound will have a lot of clipping or unwanted distortion.
What Kind of Impedance to Look for?
Of course, every amplifier or device has a specific type of headphones that will work for them. We can divide these devices into different categories according to how they work with different headphone types and their impedance.
For instance, if you’re using your standard battery-powered devices, like laptops, phones, tablets, and various types of portable music players, then impedance is usually anywhere between 16 and 50 ohms. The same could be said about the in-ear monitoring, the kind professional musicians use for live or studio sessions. In fact, these two types of headphones are pretty similar, with the only difference being that in-ear monitors can cover different frequencies better, mostly in the mid and higher range of the audible spectrum.
Then we have headphones that are intended for hi-fi devices, like home stereos and home entertainment systems. In this case, headphones should have an impedance of at least 60 ohms. Headphones intended for any kind of studio work should also have this same kind of impedance level. The same could be said about DJ headphones, which are similar to studio-oriented ones, although they come with some additional functionalities and design features.
To be fair, in almost all cases, you should not worry about the impedance and matching your headphones with your device. In case you’re looking for a new headphone set, there’s a high chance you’re in pursuit of something that will work with your phone or a laptop, and there are plenty of those available on the market. Pretty much the same situation is with hi-fi headphones, designated for more serious amplifiers, although it’s also not uncommon for these two categories to overlap in use.
You’ll probably need more time finding a proper studio or DJ headphones that would suit your needs. But even then, you should just know that regular smartphone or laptop headphones shouldn’t be used for serious studio work.