What is Headphone Impedance? | IMPORTANT DISTINCTIONS!!

Hi friend and Welcome!

What is Headphone Impedance? That’s quite a fully loaded question actually, but a good one nonetheless. Before we get into it, grab a snack, sit back and relax because..

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What is headphone impedance?

What is headphone impedance?

What I will bring you in this article

  1. Introduction
  2. What is Headphone Impedance?
  3. Low Impedance vs. High Impedance
  4. Current vs. Voltage
  5. Output Impedance
  6. Final Word

Now without further ado, let’s get rolling!!

Introduction

You may have been shopping for headphones and come across the dreaded impedance rating. Most of the time you wouldn’t give it a second thought with low budget headphones because it doesn’t really matter that much. Pretty much all of those cans are meant to be used with portable devices and buyers won’t even consider an amplifier because they either

  • a) don’t know what it is.
  • b) don’t care.
  • c) know they won’t need one.

While most lower budget cans don’t require an amp and don’t benefit from one, there are a few exceptions. The AKG K240’s are a prime

AKG K240

AKG K240

example. At 55 Ohms, they kind of hover in that weird gray area. They don’t sound that great plugged into a phone or laptop, but really come alive with an amp or even Your audio interface. The mid-range especially opens up and you realize why they’ve been a studio standard for so long. Check out my AKG K240 Studio Headphones Review!

But what is headphone impedance exactly?

What is headphone Impedance?

The definition is as follows: The combined resistance and reactivity the headphones present to the amp as an electrical load. Wow, that sounds like a bunch of hogwash. Lol. It’s basically a measure of how much your earphones or headphones resist an electric current (or more specifically, a change in current.

Low Impedance vs. High Impedance

When discussing varying impedance, generally speaking:

  • Low Impedance = between 16 and 32 ohm. This range works well with portable music players, phones, and other similar devices with weaker built in amplification. Low impedance headphones are more prone to blowouts when using a powerful amp, but can still sometimes benefit from one.
  • High Impedance = Over 100 Ohm. These require more power (or voltage) to achieve higher audio levels. They are both protected from the damage that occurs with blowouts, and can be used with an array of audio equipment.
  • Gray Area = 32 -100 Ohm. Headphones in the gray area may or may not benefit from an amp. It just depends.

Examples

  • Portable devices. Use the line output when available to hook up to an amp.
  • In ear headphones or earphones. Good efficiency. Rarely needs an amp.
  • Noise cancelling headphones. Do not need an amp because there’s a built in one already.
  • An amp with a DAC (Digital to Analog Converter) will improve your listening experience because there is better digital to analog conversion and processing power. My article on Bit depth vs. Sample Rate goes into this process more in depth! (no pun intended)

Use an amp with a DAC on:

  1. Your computer
  2. Your laptop
  3. Your tablet

Remember when I said the AKG K240’s don’t sound that good plugged into my laptop or phone? Because they benefit heavily from a DAC, and since my audio interface has one built in, I didn’t have to purchase a separate one. What does an audio interface do?

Focusrite Scarlett 2i2

Focusrite Scarlett 2i2

Current & Voltage

The reason higher impedance headphones have better sound quality is because they allow for more turns of wire to be used in the coil of the driver. What is a headphone driver? This results in a better motor system with fewer compromises, leading to a better overall sound.

Higher impedance headphones also require less current, reducing distortion. Because of this, they are also immune to output impedance differences between sources. But what exactly is current and voltage?

Current

  • Think of current as the volume of water in a bucket.
  • Think of voltage as the water pressure (PSI).
  • Think of impedance as the size of the hose nozzle.
  1. A high impedance headphone = Tiny nozzle. They need a lot of voltage (pressure) to function properly.
  2. A low impedance headphone = Is like filling a bucket with water. It requires more flow (current) but not a lot of pressure (voltage).

Output impedance

  • This is the impedance of the actual source you’re using, which can be difficult to find sometimes.
  • A perfect source = an output impedance of 0.
  • This means it will always deliver the same output into any load (headphone).
  • If the output impedance is not 0, the voltage produced by the source will be reduced when a load (headphones) is connected.
  • The higher the output impedance, the greater the drop in voltage at the load, in effect diminishing the quality of sound.

Basically, output impedance is one of the most common reasons that certain headphones can sound different when plugged into different amps.

What you need to know

  1. Most headphones work best when the output impedance is less than 1/8th of the input impedance.

Example:

Sennheiser HD600 @ 300 Ohms.

Sennheiser HD600

Sennheiser HD600

300/8 = 37.5 Ohms

So the output impedance of your amp/DAC should not be greater than 37.5 ohms when driving the 600’s. A popular option for the HD600 is the Schiit Magni/Modi combo. The Magni has an output impedance of less than 0.1 Ohm. This is the reason that it’s such a versatile amp. Remember what we said about a perfect source? As close to zero as possible. How to choose a headphone amp!

So

If you have a source with a high output impedance, this basically means:

  • The drop in voltage will be greater with lower impedance loads (headphones).
  • This drop can be big enough to make driving low impedance headphones difficult.
  • The greater the output impedance, the more likely there will be a discrepancy in the way your headphones receive the sound. This can manifest erratically depending on the headphone.
  • The greater the output impedance, the more likely the bass response will be affected in a negative way. For instance if the bass frequency was meant to sound tight and controlled with impact, it may actually sound muddy and/or boomy (less controlled). The bass will start to “roll off” at sooner at lower frequencies, compromising your listening experience.

Example:

Behringer UCA202. 50 Ohm output impedance. Struggles with 16-32 Ohm headphones.

Final Word

It’s rather important to take these things into consideration; especially the 1/8th rule. Why? Because if the output impedance is greater than an 1/8th of the headphone impedance, there will be undesirable variations in frequency response.

Examples:

  1. Weaker bass
  2. Glaring mid-range emphasis
  3. Muted high frequencies
  4. Odd phase characteristics

Basically this just means that the headphones will not sound as they were meant to. So be careful what you’re plugging those bad boys into! 🙂

Example:

audio technica ath m50

my audio technica ath m50’s in all their glory

My Audio Technica ATH M50’s have an impedance of 38 Ohms. My Scarlett 2i2 has an output impedance of less than 10 Ohms. Now this is a bit tricky:

38/8 = 4.75

The output impedance (10 or thereabouts) is greater than 1/8th of the headphone impedance. So will the M50’s sound bad plugged into the 2i2? Not necessarily, at least not to my ears, but they may not be at their best. The only way to find out is if I bought a separate amp/DAC and compared them. To my ears they sound pretty blazin’ though 😛

The point is this: Just be aware of what you’re buying as far as amps are concerned. I didn’t buy the 2i2 to amplify the M50’s. I bought it to power my studio monitors. What are studio monitors? Regardless, using the 1/8th rule will greatly aid you on your quest.


Well that’s about it for today my friend! I hope I answered the question of, what is headphone impedance?

Did I provide enough information? Are you confused? Enlightened? Appreciative? Let me know!

If you have any other questions, or felt that I left something out, leave a comment below or Contact me! I very much look forward to speaking with you.

All the best and God bless,

 

 

-Stu

[Xtr@Ba$eHitZ]

Be sure to check out my Reviews and Resources page for more helpful and informative articles!

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