The importance of matching headphones with audio sources in the pursuit of high fidelity audio.
Impedance is one of the basic specifications included with almost every quality pair of headphones and most audio sources (DAP, phone or amplifier). Everyone has seen the measurement, but I’m betting that few really understand the importance when making purchasing decisions.
One of the first questions you will see in headphone forums is if a dedicated amplifier will be needed for a new headphone purchase. Lots of opinions fly around, often contradictory, so let’s take a look at the science behind the answer.
The Basic Concept of Impedance
When describing impedance, there are several terms that you should aware of. When viewed as a simple electronic circuit, the impedance of the audio source may be written as output (or source) impedance, while the impedance of the headphones may be considered load impedance.
Headphone impedance is typically rated between 8-600 ohms, with a standard around 32 ohms becoming increasingly common. Audio source impedance is typically very low, often less than 4 ohms and approaching 0 ohms in many cases, but it may be as high as 120 ohms or more for specialized tube amplifiers, specifically output transformer-less (OTL) types.
Impedance Matching
Impedance matching is the interaction between the source impedance (the device the headphone is attached to) and the headphone impedance. To ensure the highest audio quality, the source and the headphones must pair well. As you may have guessed from the impedance range examples above, a match doesn’t mean ‘both the same’ but rather that they are ‘complementary.’
We will look at the rules around finding that perfect match in some detail below. For now, it is enough to understand that audio source and headphone impedances should not be equal and that headphones with different impedances will require different sources. Equal source and load impedance maximize the power we can transfer between the amp and headphones, but this typically reduces frequency bandwidth so it’s not what we want in high fidelity.
In general, low impedance headphones (which we will hereby define as below 50 ohms) are designed to work properly with portable devices, as they can efficiently reproduce adequate sound quality and volume from a low voltage device.
Conversely, high impedance headphones (50 ohms and greater) usually require robust amplification to perform their best.
Why are some Headphones High or Low Impedance?
Headphones with impedance greater than 100 ohms are typically older or professional studio specific designs. Pre-1990s receivers and pro audio equipment often used resistors to attenuate the speaker output power (wattage) to create a simple and inexpensive headphone circuit.
These headphone circuits consequently worked best with high impedance headphones. In some cases, high impedance headphones were designed to chain multiple pairs in parallel for pro studio applications. Without getting too heavily into the math behind it, the high impedance load preserves the source output voltage to be able to drive multiple pairs of headphones.
This was so prevalent that even as recently as 1996, the standard recommended source output resistance was 120 ohms, and went so far as to claim that source impedance had very little effect on the performance.
Stereophile did not mince words with their opinion of that standard and claim.
Most modern headphones are designed to appeal to as wide a market as possible, and that means they must play well on mobile devices. The sale of hundreds of millions of battery powered music players, including the ubiquitous iPod and more recently smartphones, has made lower impedance (around 32 ohms) headphones the norm.
Headphone Models with Multiple Impedances
Customarily, a particular headphone model is only available in a single impedance. Beyerdynamic is one of the few (if perhaps the only) major company that produces multiple versions of the same model, differing only by impedance: 32, 250, or 600 ohm versions of the DT880 and DT990 headphones, and 32, 80 or 250 ohm versions of the DT770.
As you can see the versions do not perform equally.
Steve Guttenburg of CNet explained:
If properly matched to an appropriate amplifier, it is possible to achieve an enhanced quality of sound with high impedance headphones, at least with specific designs like the Beyerdynamic models above. Please don’t take this to mean that excellent sounding low impedance headphones do not exist. This is just one company’s approach.
Headphone Sensitivity
Sensitivity (or efficiency) is a measurement of headphone volume at a specific power rating.
Headphone sensitivity is often measured at a specific frequency (1 kHz) at 1 mW of power. Sensitivity ratings are typically in the range of 90-105 dB (with outliers considered extremely sensitive or insensitive).
It would appear, with comfortable listening volume levels of 60-80 dB, a full 1 mW of power should seldom be required to achieve more than adequate loudness. But sensitivity ratings do not tell the whole story. We also need to take into account music dynamics and our amp’s total harmonic distortion (THD).
For highly dynamic classical music, the recommended dynamic range (the largest to the smallest intensity of sound that can be reproduced) is usually 20 db. An increase of 20 db requires that one hundred times the power be delivered to the headphones.
With that much dynamic range, a 1 mW nominal sensitivity rating can quickly become a 100 mW power requirement for the amp. Amplifiers will also generally produce more distortion as power is increased (although this isn’t universal). In that case, a requirement for 100 mW at low distortion may lead to an amplifier actually rated at 1 W+ (amplifier power specs are typically given at 1% THD).
How Sensitivity and Impedance impact Volume
Sensitivity and impedance are related but not causally linked. Both must be considered when pairing headphones and sources.
It is tempting to describe impedance as simply being resistance and use Ohm’s Law (Voltage = Current * Resistance) to illustrate, but Ohm’s Law is really only applicable to DC (direct current). If impedance was the same as resistance, comparing identical headphones that differ only in impedance would result in the higher impedance headphone always being quieter than the lower impedance one (given the same source voltage). However, this isn’t always so simple.
So understanding impedance isn’t as simple as considering load resistance. The source output impedance is an important factor as well. Loading of the transistors (or tubes) and bias (current) is also related. Amplifiers will tend to deliver more voltage into higher impedance loads because the output impedance is not zero.
With a high output impedance source, high impedance loads can provide more volume. An amplifier may be incapable of producing much power into a low impedance load if it is current limited, while it would be happy making plenty of power into a high impedance load. Different amplifier designs will all have unique specifications and abilities.
No wonder it is difficult to imagine what the results will be when we consider pairing headphones with a source. We can make educated guesses based on the specifications, but until you try it, you can never really be sure.
It is enough to know that source impedance, headphone sensitivity and headphone impedance are all factors that play into the resulting audio volume and performance.
Comparing Headphone Sensitivity and Impedance
To further complicate things, there is little consistency in headphone design with regards to impedance and sensitivity (even within a single manufacturer). There are low impedance headphones that are very inefficient and vice versa. Models with low sensitivity and low impedance. Other that are low sensitivity, but high impedance. High sensitivity, low impedance. Etc.
From the following chart listing a variety of headphone models with a range of impedances, it is easy to see many different sensitivities. It’s pretty obvious that these headphones have differing source requirements.
| Headphone Model | Impedance (Ohm) at 1 Khz | Sensitivity (dB) |
|---|---|---|
| Grado SR80 | 32 | 98 |
| Meze 99 Classics | 32 | 103 |
| Hifiman HE-6 | 50 | 83.5 |
| Fostex TR50 MkIII | 50 | 92 |
| Shure SRH 1840 | 65 | 96 |
| Audeze LCD 3 | 110 | 102 |
| AKG K1000 | 120 | 74 |
| Sennheiser HD650 | 300 | 103 |
| AKG K240 | 600 | 94 |
| Beyerdynamic T1 (gen 2) | 600 | 102 |
Frequency and Impedance
Obviously, a headphone driver is capable of reproducing a wide range of frequencies. A perfect driver would remain consistent across the full audible frequency range. Guess what? The typical headphone driver is far from perfect.
Resonant Frequency in Dynamic Driver Headphones
The voice coil in dynamic headphones is designed to properly control the driver and ensure good behavior at its resonant frequency. Resonant frequency is the frequency by which a material vibrates most easily – think opera singers shattering crystal with a sustained note.
Driver impedance is NOT linear with frequency for dynamic headphones.
Remember, most manufacturers state impedance at 1Khz in the headphone’s specifications. This impedance is likely significantly lower than at the actual resonant frequency for that driver. A frequency impedance graph for the driver illustrates a much more accurate picture. This resistance can multiply many times at the resonant frequency.
Dynamic driver headphones do not have a perfectly flat impedance response across all audible frequencies. However, some designs are flatter than others.
Planar Magnetic Headphones
Planar magnetic (also called isodynamic, magneplanar, or orthodynamic) drivers, basically an amalgam of electrostatic and dynamic drivers, act differently than typical dynamic drivers. They use an S-shaped pattern for the voice coil (unlike traditional circular windings) which tends to yield a low impedance.
However, much like dynamic drivers, not all planar magnetic headphones are the same. Some are easy to drive with low impedance and high sensitivity like the HiFiMan HE 400s (22 ohms – 98 dB). Conversely from the same company, the HifiMan HE-6 is notoriously inefficient and difficult to drive (50 ohms – 83.5 dB).
The largest departure from traditional dynamic drivers is in the impedance response. Planar magnetic drivers do not have peaks and valleys, and are very flat across all frequencies. Planar magnetic and dynamic headphones of similar ratings will often have quite different amplification requirements.
Source and Load Impedance
The load impedance of a pair of headphones plays an important role in an amplifier’s distortion performance. The operating voltage and current (or bias) chosen for transistors or tubes in amplifiers is optimized by the designer for low impedance loads, high impedance loads, or a compromise of the two.
Connecting a low impedance load, when the amplifier is optimized for high impedance, not only reduces power, it also increases distortion. Some amplifiers have multiple outputs or switches that allow them to adapt to multiple impedance loads and remain optimally biased.
The ratio of output impedance and load impedance changes also dramatically at the impedance spikes – those frequencies with the highest impedance for a particular headphone. This can result in poor control of the driver (damping), and possibly audible distortion at those frequencies.
For instance, many Sennheiser headphones have an exaggerated frequency spike around 100Hz. The Sennheiser HD6xx line can require high voltage (3-6V) at the spike, making it a poor pairing for many lower-powered mobile devices, but an ideal match for the Bottlehead Crack OTL tube amplifier characteristics (120 Ohm output impedance and high voltage).
In general: High impedance headphones require higher voltage sources. Low impedance headphones require higher current sources.
In general: High impedance sources provide high voltage but low current.
Equal impedance between source and headphones is good for portable power requirements, but not necessarily for sound quality.
Match for Best Performance
While it is extremely unlikely that anything catastrophic or destructive will occur with headphone and source impedance mismatches, sound quality can suffer.
Call it matching, pairing, synergy or just a case of plain old BFF, the source and the headphones must complement each other. As we touched on above, volume and sound quality can be greatly affected by impedance, requiring much more amplifier voltage to properly drive high impedance headphones, something that isn’t easy or possible to achieve with most portable devices.
High Source Impedance and Low Headphone Impedance Problems
There are real issues with the combination of high source output impedance and low headphone impedance. While often only found in the extremes of OTL tube amplification, this scenario creates higher harmonic distortion and noise, a low damping factor, and bass roll-off.
For every rule and scientific explanation you can read, it is easy to find contrary subjective user experiences that claim great success and impeccable audio performance against all odds. YMMV and read everything with a grain of salt.
Distortion
Typical solid-state headphone amplifiers often have VERY low output impedance (and high current). As a result, they work well with a wide variety of headphone impedances. However, pairing a headphone whose load impedance is lower than the amplifier’s source impedance will most likely create audible playback distortion.
This is why low impedance headphones are not recommended for high output impedance amplifiers, such as OTL tube designs like the Bottlehead Crack or Darkvoice 336SE. Stick with very high impedance headphones (200 ohms and up) for this type of amplifier.
Nwavguy explained that
Damping Factor
Damping factor is the amount of control an amplifier has over the driver. It is often described as the ability of the amplifier to control driver motion once the signal has stopped. Damping factor is most apparent in low frequency reproduction, where low damping can cause loose, boomy and indistinct bass, while high damping tends to make bass sound tighter and cleaner, but subjectively less warm.
Damping factor is measured as the ratio between the driver impedance and amplifier impedance, and is expressed in the format ‘2:1’ (where the first number is the headphone impedance and the second is the source output impedance) or as a single number ‘2’ (as in this case to represent the driver impedance).
Commonly a damping factor greater than 2.5:1 and nearer to 8:1 is considered optimal (headphone impedance 2.5x to 8x greater than the source impedance).
The term ‘rule of eighths’ is used as a rough guide. Divide the headphone impedance by 8, and that is the maximum source output impedance (32 ohm headphones / 8 = 4 ohm maximum source output impedance). In practice, it isn’t that strict a rule and often success can be had with a greater range.
This ideal is based on the theory that regardless of how large an impedance spike is in the headphone driver’s response, a high enough damping factor prevents the frequency response from varying more than 1 dB (not typically audible).
Bass Roll-Off
Bass roll-off refers to frequency response playback audibly decreasing towards the lower frequencies.
However, low-frequency response when matching headphones and amplifiers is a very complicated topic. Coupling between the amp and headphones (capacitors, transformers, etc) and the headphone’s inductive reactance below its resonant frequency also contribute to bass roll-off.
Low damping factor is commonly associated with bass ‘bloom’ or ‘boom’ around the headphone’s resonant frequency. In practice, this also leads to a perceived roll-off below resonant frequency (and a very measurable roll-off if the amp’s coupling or output impedance are poorly matched to the headphones).
Balanced vs Unbalanced Amplifier Impedance
A typical unbalanced (single-ended) headphone amplifier is what we’ve been discussing in this article. It derives its name from the relative impedance to ground of the two connections in each channel (hot or positive and ground or negative). Because the impedance to ground differs, we call it unbalanced.
A balanced output however, has two signal phases per channel. Each phase has an equal impedance relative to ground, hence the name balanced. The advantage of balanced connections over unbalanced connections is common-mode noise rejection.
Because any interference is imprinted equally on the two phases’ equal impedance, that common-mode interference cancels out. The usual approaches to driving balanced outputs can also impact audio quality because output impedance is effectively doubled.
“Balanced amplifier” is something of a misnomer. Balanced and unbalanced are types of interconnections between devices (like an amp and a headphone); these terms do not refer to specific amplifier architectures. Usually when you see the phrase “balanced amplifier” it is referring to a differential amplifier without shared grounds and balanced outputs.
A variety of sources and amplifiers and their output impedances:
| Device | Output Impedance (Ohm) |
|---|---|
| Chord Hugo 2 | 0.025 |
| Schiit Ragnarok | < 0.03 |
| Chord Mojo | 0.075 |
| Schiit Jotunheim | < 0.1 balanced or single-ended |
| JDS Labs Atom | 0.1 |
| Monoprice Liquid Spark | 0.1 |
| Fiio A3 | < 0.2 |
| Schiit Magni | < 0.3 |
| Apple iPhone 7 + adapter | 0.37 |
| JDS Labs Objective 2 | 0.54 |
| iFi xDSD | < 1 |
| iFi Micro iDSD BL | < 1 |
| Fiio Q1 Mk 2 | < 1.2 |
| Apple iPad Air | 1.6 |
| Fiio M6 | < 2 |
| iFi xCan | < 2 balanced, < 1 single-ended |
| Apple iPhone 6s | 4.5 |
| Burson Audio Play | 8 |
| Feliks Elise | 40 - 50 |
| Bottlehead Crack | 120 |
Conclusion
Let’s take a moment to summarize what we’ve discussed about impedance. It’s a complicated topic, but it doesn’t have to be confusing.
- There are two types of impedance (measured in Ohms): headphone impedance and source impedance. Impedance matching between headphone and source is done to ensure a good combination of sound quality and sufficient volume. A match means ‘complimentary’ not ‘equal’.
- Pairing a headphone with an impedance of 2.5-8 times higher than the source impedance should yield good results. This recommended ratio is commonly known as the ‘rule of eighths’ and contributes to proper driver control (damping factor). Pairing a headphone with an equal or lower impedance than the source will likely result in unpredictable (poor) sound quality.
- Sensitivity is also an important factor in headphones, and is a measurement of loudness at a certain power input (usually given as decibels per 1 mW). While sensitivity and headphone impedance both influence volume, they are not linked. Headphones vary greatly in impedance and sensitivity and both must be considered when selecting an appropriate amplifier.
- Sensitive (100 dB+), low impedance (8-32 ohm) headphones will typically pair well with a portable source (such as a phone) without much benefit from a separate amplifier. Less sensitive (less than 95 dB), and/or medium to high impedance (more than 50 ohm) headphones will typically benefit in sound quality and volume with a more robust amplifier than a phone (or portable device) provides.
- Headphone impedance ratings can be misleading because dynamic headphones vary in impedance at different frequencies and are not flat in response (the rating is for a single frequency). Planar dynamic drivers do not suffer from this problem and are flat in impedance across all frequencies.
- Higher impedance headphones require more source voltage (something portable devices are not good at) and lower impedance headphones require more source current (something OTL tube amplifiers are not good at providing).
- While some high impedance headphones are made to an elevated standard (such as utilizing thinner voice coil wires) and can be capable of lower distortion, higher impedance does not necessarily equate with better sound quality.
NwAvGuy tells us that “…a “perfect” source has an output impedance of zero ohms. This means it will always deliver the same output into any load.” Since we live in the land of compromise rather than perfection, we have to make educated decisions when selecting an amplifier for our headphones.
Luckily, there is almost a guarantee that someone out there has tried and written (or YouTubed) about their experiences with the combination of headphone and source you are considering.
Now you know to disregard or be skeptical when you hear that “impedance is unimportant” when considering new headphones or amplifiers. Contrary to some opinions, it’s not all about sensitivity. Those folks have probably never considered the audible impacts of source and headphone impedance matching.
Personally, I occupy a very specialized niche of the headphone world. I own (and love) a Bottlehead Crack OTL amplifier. This means that my headphone choices are VERY limited when selecting an appropriate pairing; there are very few 200+ ohm headphone options. Luckily it sounds so good that I’m happy to live with the limited selection.
Of course, it does require that I own a few solid-state amps (as well) for all those other low impedance, low sensitivity headphones that I can’t resist. The sacrifices we must make for a hobby!
Congratulations it is really interesting article
Thanks for the kind words! Cheers!
Was confused about the impedance thing. Glad I found this article. It was very helpful.
Great write up.
Thank you for this review. I have enjoyed reading this a lot.
Just a heads up the part “Voltage Is Important” is wrong:
Headphone measurements are taken with a constant voltage source. If what you said about impedance spikes requiring more voltage was true we would see a dip in the frequency response at the impedance spike resonant frequency. However usually we can see a bump or “high point” instead.
Dynamic headphones are actually more sensitive at the impedance spike because the same constant voltage into the higher load impedance (less power delivered) produces around the same amount of sound pressure level as equal amount of constant voltage into lower nominal impedance outside of the impedance spike.
+1
You are right, reading that paragraph it seems that the headphone amplifier need to know the impedance curve of the headphone. If the headphone shows an impedance spice at a certain frequency it means that it will require less current to reproduce that frequency. An amplifier should offer zero impedance output and infinite current capability (at better) in order to force the required voltage on the load. Reading the paragraph one could suppose that headphone should be current driven.
That section doesn’t quite work and doesn’t come across as intended. I’ve submitted revisions to the entire section. Thanks for pointing that out!
Very helpful! Now i see. Thank your for taking your time and writing the article. Have a good day!
Great ride in the world of impedances and thank you for clarifying the importance of choosing the right device for or needs.
Very well explained!
Very helpful!
I recommend others to read this.
Great day to you!
Steph
Amazing article, thank you!
So much information, and moreover the kind of information that tends to be overlooked now that we all focus on just the “main” numbers in the specs sheets. I’ve always been curious about HOW different headphones match with different amps, now I finally got a more comprehensive insight on WHY, too.
Great article! unfortunately I am still unsure if my mixer/interface (Yamaha MG10XU) will properly power the DT770 and DT990 250 ohm versions. Yamaha Specs state:
– The Actual Source Impedance – 110 Ohm;
– For Use with Nominal – 40 Ohm Lines.
Thank you so much in advance if you reply to this.
Take care
Sometimes all you can do is just try it!
can an audio interface work as a headphone Amp?
Great article thanks, there’s so much confusion and misinformation going round on this topic.
+1
really interesting, but it is indeed a complicated topic… Especially now that we are in lockdown (covid19) it is hard to go and try out combinations… My wife really loves the look of the Decware CSP3 but I still have no clue if this will work with the Focal Elegia and Focal Stellia that we have.
I reached out to decware to ask but if anyone has a view, would love to hear it.
Thanks
excellent article. which amp they recommend for some HD 650. I have seen several options but I want them to recommend me about the 100 usd that I can buy. Thank you
JDS Lab Atom.
Hi, Thanks for the article!
Would love you help..
I’m trying to understand my Focusrite 2i2 1st gen – headhones amp.
On link 1 the they say “headphones with a maximum impedance of 200 ohms.”
On link 2 (3rd gen but probably the same for 1st gen) it’s said: “<1Ω "
I don't want to damage my low impedance headphones.. is it ok to use 32ohms headphones? (It seems they work fine on it)
Also I wanted to buy Hifiman he4xx which is 35 ohms by some sites, and few people on the internet said that the Scarlet 2i2 is too weak and can't drive them properly.. what do you think?
Link 1: https://support.focusrite.com/hc/en-gb/articles/210708269-What-impedance-headphones-should-I-use-with-my-audio-interface-
Link 2: https://focusrite.com/en/usb-audio-interface/scarlett/scarlett-2i2
Thank you very much
Hi. The output impedance of your device is less than 1 Ohm and supports headphones up to 200 Ohms (or another way to put it, between 1-200 Ohms). So your 32 Ohm headphones are easily within that range.
Remember though, figuring it all out is not as easy as just impedance ratings, as the sensitivity of the headphones and the power of the amplifier must also be factored in. The HE4xx are rated as sensitivity: 93 dB, and impedance: 35 ohms. The only thing we don’t know is the power of the amplifier in the 2i2. The HE4xx are planar magnetic drivers, and as a general rule, planars benefit from power. The folks who have actual experience with the pairing may be giving you good advice.
But in all honesty, sometimes you just have to try yourself to see if it will work and sound good.
Hi,
Thanks for an interesting article.
I’m trying to figure out the best match for a Zoom H5 Handy Recorder.
The specs for the headphone out are:
PHONE OUT stereo mini jack (20 mW + 20 mW into 32Ω load)
Which pair of headphones would be the better match?
– DT 770 32 ohm
– DT 770 80 ohm
Thank you vey much.
It will likely drive either one, but the 32 ohm is a safer bet.
Fantastic article. Really brilliant.
I have a Rega Aethos integrated amp with following specs for headphone stage:
Headphone output:
No load 12.5 V
32 Ω 2.7 V
54 Ω 4 V
300 Ω 9 V
Source impedance 109 Ω
Given high “source impedance” figure, am I locked into higher impedance headphones? If so, can you suggest a few good ones, since such phones seem to be harder to find. I’m a real beginner when it comes to phones, but need a nice set since our kids are all home from college studying on-line and things need to be quiet.
Thanx very much for your help.
Glenn
It’s not so much ‘won’t work’ rather more likely ‘sounds better with’. Typical recommended high impedance pairings include:
Beyerdynamic DT880 (600 Ohm)
Beyerdynamic DT990 (600 Ohm)
Beyerdynamic T1 (600 Ohm)
Sennheiser HD580 (300 Ohm) Note the new HD58X model is 150 Ohm.
Sennheiser HD600 (300 Ohm)
Sennheiser HD650/HD6XX (300 Ohm)
Sennheiser HD800 (300 Ohm)
Thanx very much for your help. I like “less analytical” sound so it’s my understanding, although I’ve never heard any of these selections with my own ears, that the Beyer would, more likely than not, not be a good choice. Is this correct?
Hi,
Loved the article, I got a basic understanding of Impedance and Sensitivity. I still have a number of questions.
1. You mentioned a lot of impedance mismatch when the source goes more than 2.5-8 times the Headphones, But what happens if the source is say <1ohm and the impedance of headphone is 18, in this the source is quite a lot lesser than 8 times. BTW, I am using planar headphones.
2. What are the ideal amp settings I should look out for if my headphones are low impedance and low sensitivity eg, 93.5dbW at 18 ohms? These are quite hard to drive, so it needs an amp for sure, now, what are the specs of the amp itself I should be concerned about? a quick check on the power output page of headphonesty gave me a required 45mW to power it and an amp I was looking at has 30mW+30mW(32ohm). what exactly does this mean? how do I calculated the output power this amp would deliver for 18ohm?
3. There is also a mention that low impedance headphone require higher current, now to my understanding this doesnt really matter right, whatever the source is? it just means if I am using a portable device its going to drain more battery? if that isnt the case, what should I look out for to make sure this isn't an issue.
Sorry for the long post and any stupid questions if there are, I just want to run my headphones at the right settings to experience what exactly they are capable of and will help a lot in the future. Thank you.
1. Less is bad. More is good. 1:1 ratio is not desired. 1:8 or 1:800 is ok.
2. I’d look for a far more powerful amp for headphones that difficult to drive. Like 10x + more. 30mW is not a powerful amp. For instance the XDuoo C5D Plus is 1000mW at 32 Ohm and still portable.
3. Current in this case speaks to amplifier power rather than battery.
Hi Trav,
Thanks a lot for taking your time to reply.
I think I’m clear except for the third point.
So if I were to use a smartphone to use the Headphones I mentioned the volume is low and if I use a iFi Hip Dac – the volume is fine, where does current play a role here? In the sense through the Dac/amp my phone can still output the necessary power right for a give Dac/amp? What are the specifics I need to take care?
Hi Ravi
I think google might be the best bet to do some reading on the differences between amplifier current and the current rating for a battery/charger.
However, in this case, the phone (source) just needs to feed a ‘line level’ output to an external amplifier (which basically any headphone output can do). Or the source has a USB output (nothing to do with amplifier current) to an external DAC.
On the battery side of things, an external DAC/Amp with an internal battery should not drain the source battery.
Hi Trav, Great article. I hope you won’t mind a novice question: Does the Rule of Eight applies to monitor headphones for portable recorders like Zoom H5? When it specifies phone output as 20mW+20mW into 32ohm load, does it means headphone like Audio-Technica ATH-M40x (15Hz-24KHz, 98db, 35ohm) and ATH-M50x (15Hz-28KHz, 99db, 38ohm) will have audible difference from the recordings in the device? Look forward to your enlightenment. Thanks.
I have a DT 990 pro 250 ohms. I work in a MacBook Pro 2018. What can I do to improves the headphones response?
An external Headphone Amplifier is your best solution, but in order to have it you need a DAC too, so DAC+Amp stack or 2 in 1.
One of the best is Topping DX3 Pro and would be perfect for your DH 990 Pro
The only problem with DX3 Pro is that the new V2 (LDAC) has an Output Impedance of <10 Ohm which is not great with lower Impedance Headphones and especially In-Ears if you will ever want to have in the future.
Thank you so much, Lifu.
Check out my xDuoo XD-05 or xDuoo XP-2Pro reviews. Both have plenty of power for the DT990 and built in DACs.
thanks brother.
So if you have high impedance headphones, but a low impedance amp (THX 789; 1 ohm output impedance) is there a way to increase the output impedance of the amplifier? How hard would it be to make an impedance matching circuit that you would put in-between the amp and the headphone?
I studied about transmission lines and impedance matching in an electrical engineering course in college. Is it really that hard to make an adapter?
For what purpose?
Are you referring to the DT880 600 Ohms that is best paired with 100 Ohms output impedance amps?
Or are you just trying to modify the frequency response?
Like you said, many integrated amps from the past use a simple resistor between the speaker and headphone output. E.g. my Denon PMA-720A (a model from the late 80ties) has such a resistor of 120ohms. My Teac A-H300 has resistors of 390 ohms. Should such resistors be considered as part of the amps output impedance, or added the headphone’s impedance, when we look at the matter from the perspective of damping factor.
In the living room I use the Teac in combination with a BD DT880-600, as well as a Custom One Pro-16 ohms. The latter i use when e.g. my wife is reading a book while I listen to some music without disturbing here. In some cases the bass on the COP gets too boomy for my taste, I wonder if these 390ohm output resistors have anything to do with it. In the past I tried bridging these resistors, but that resulted in hum being audible in the cans. Apparently this amp can’t drive cans properly without the output resistors.
Your Custom One Pros can be customized for bass with the little sliders on each side, that’s why I bought them!
As I understand it, I believe without resistors, you’d have full speaker power to the headphone jack which would blow up your cans and eardrums
Hi, I’m really glad to find this content after many days of research.
I need a headphones recommendation for ALTO ZMX 122 FX, which I am using on my M-Audio Delta 1010LT’s monitor outputs. The Main Mix output of the Alto is connected to a pair of KRK Rokit 5 RPG2 and I am struggling to match a pair of headphones for the Headphones out on the Alto.
This Alto specification states as All other output = 120 Ohm. What are my headphones options in this case?
Hello! Thank you for this article. I have some short questions:
1. I have A&K SP1000M ( bal. output is 1 ohm and unbal. Output is 2 ohm) and I’m planing to pair it with Campfire audio Ara which is 94db and 8.5 ohm of impedance. Is it good match? I would like to hear every detail of Cliff Burton baselines on Metallica first albums.
2. Campfire audio Ara specs:
10Hz–28 kHz Frequency Response
94 dB SPL @ 1kHz: 7.094 mVrms
8.5 Ohms @ 1kHz Impedance
Features
Dual High Frequency Balanced Armature Drivers + T.A.E.C.
Single Mid Frequency Balanced Armature Driver
Quad Low Frequency Balanced Armature Drivers
Beryllium / Copper MMCX Connections
Machined Titanium Shell
Tuned Acoustic Expansion Chamber™ (T.A.E.C.)
PVD Black Stainless Steel Spout
Black Screws
Can I take this or you recommend another IEMs?
> Since we live in the land of compromise rather than perfection, we have to make educated decisions when selecting an amplifier for our headphones.
Only in the mobile space. In the past few years, we’ve seen a number of low-impedance, low-distortion, and high-powered amps capable of driving everything on your headphone list to high volumes. There is no advantage *at all* to high amp impedance except as a crutch for power delivery. That should be the lede for this multi-thousand-word article.
Thank you so much for this great insight. Still a bit confused, but it makes sense. I‘m trying to pair a mixing/mastering headphone with my 8-40 ohm output on my yamaha 01x digital mixer, to get better results in mixing.
I think i’ll have to read this content again to get the proper understanding of the impedance. Not that the article is bad, heck article is awesome. Its me that couldn’t understand in the one go xD. BTW informative article.
Guess your not the only one..????
Excellent article, I wanted to ask you if I have a source impedance (headphone output) of the boss me70 guitar multi-effect of 44ohm, which beyerdynamic pro 770 are better the 32ohm or the 80 or even the 250?
Thanks a lot .
You stated the coil wiring of a speaker can be. 018, (18 thousandths of one inch) ‘half the width of a human hair’.
A human hair is typically. 002, two thousandths of an inch, making the wiring nearly 10 times the width of a human hair.
The quote states 0.018 mm, not inches.
Thanks for the catch! You’ll have to take it up with Steve Guttenburg, as it was a quote. 🙂
Steve Guttenburg of CNet explained:
“The impedance of a headphone is largely determined by the driver’s voice coil, and for Beyerdynamic’s high-impedance models the voice coil’s wire is super-thin, just 0.018mm, half the thickness of a human hair. Beyerdynamic’s Senior Product Manager Gunter Weidemann explained…
Hello Trav, nice artical. some of it helps but I ride a motorcycle and wear a helmet and can’t get the music loud enough to hear the music at speeds over 40 mph. I use a SanDisk ”clip sport go” and wired ear buds 16 ohms sensitivity of 120 dB. The SanDisk is unspecified specs but has a pre gain setting from 0-12.0 dB. I have been looking at the portable headphone amp but they come in different ohm levels, 16-150 ohms and 16-600 ohms. I need help in figuring out what will work best without throwing a lot of money at it. I’ve tried helmet speakers and wired ear buds and the sound level is the same. Thanks.
The best thing you can do is to isolate the external noise, rather than increasing volume to drown it out. I’d be worried about hearing damage by prolonged loud listening. Try finding a pair of IEMs (likely with foam ear tips) that have high isolation and snugly fit in your ears like ear plugs. If the outside noise is effectively blocked, then it shouldn’t take too much power to hear them. My old Shure E3C IEMs with foam tips, literally cut from ear plugs, are my go to set for lawn mowing or similar loud activities. They physically block the outside noise, rather than drown it out, and all I hear is the music.
Great article! Super clear and to the point.
Good luck if you’re looking at the numbers on the boxes and do the math. Go to the shop and try on the headphones is the only way to tell which one is better. More money is not always better. I have a $300 Bose, $500 SHure, Sony, $100 Tascam – is the worst, the over emphasized sounds on the mids gave me headache and irritating feeling after three songs, weight like a brick on my head- Technics, Apple. Recently, I asked my son to let me try Logitech headphones and OMG! it’s the best of them all. I ran out and bought one for myself the G432 was on sale for $50, it’s the best sound I’ve ever and I couldn’t believe music can sound that good and I’ve been missing all these years. They’re well balanced mids, highs, and lows, not one sound is over powered the others. I listened to Youtube for two hours. I only took it off because I thought I was over doing it.
Very educational and enjoyable reading.
Thank you for this very important article.
George
Cheers! Glad you enjoyed it!
I have a (low impedance ?) balanced Hifiman Sundara paired with a SingXer SA-1. Is there a best, appropriate, recommended setting: High Gain or Low Gain ?
Also: it’s got a Hi-Z/Low-Z selector. Best setting ? Thanx!
It isn’t really that easy I’m afraid. It always depends on the specific amp/headphones as to what works best. The best thing you can do is experiment and go with what sounds best to you.
This article may be of some help.
Your Custom One Pros can be customized for bass with the little sliders on each side, that’s why I bought them!
As I understand it, I believe without resistors, you’d have full speaker power to the headphone jack which would blow up your cans and eardrums
Great article thank you. I’ve been trying to figure out why some headphones ($40- $50 ish “electronic store” headphones like Sony etc) sound awful with my digital pianos or keyboards, but sound fantastic with a pc or iPad. The ones that have sounded good with my pianos have been the music store “studio” headphones, even if they are only $30 ish? Would this be due to the impedance being different?
Thanks!
That may well be the case, although your personal sound preference may lean heavily towards a less v-shaped or commercial tuning and towards a flatter studio sound. As well, the amp circuit in your keyboard may be significantly different than a typical headphone output on a ipad or computer.
Hello, I am trying to convince myself if I need to update the amplifier of my audio interface, I will continue to investigate a lot these days. But for now I would like to ask you (if you see my comment), if there is any chance that it can successfully pair these two headphones that I have with my interface. Thank you, I have read the entire article but I still have my doubts.
Sennheiser HD 6xx
BD Dt 880 250 ohms
Presonus 1810
Presonus 1810
Potencia máxima 150 mW/channel (60Ω load)
Respuesta en frecuencia 20 Hz – 20 kHz (ganancia unidad)
Rango dinámico 103 dB (A-ponderado, 1 kHz, ganancia unidad)
THD + N 0.250% (1 kHz, 150 mW, ganancia unidad)
Impedancia (rango de funcionamiento) 32Ω a 600Ω
SPECIFICATIONS Dt 880 250 ohms Beyerdynamic
Transducer type . . . . . . . . . . . . . . . . . . . Dynamic
Operating principle . . . . . . . . . . . . . . . . Semi-open
Nominal frequency response . . . . . . . . . 5 – 35,000 Hz
Nominal impedance. . . . . . . . . . . . . . . . 250 Ω per cartridge
Nominal SPL . . . . . . . . . . . . . . . . . . . . . 96 dB SPL
Nominal T.H.D . . . . . . . . . . . . . . . . . . . . < 0.2%
Power handling capacity . . . . . . . . . . . . 100 mW
Sound coupling to ear . . . . . . . . . . . . . . Circumaural
Nominal headband pressure . . . . . . . . . 3.5 N
Weight (without cable) . . . . . . . . . . . . . 295 g
Length and type of cable. . . . . . . . . . . . 3 m / single-sided
coiled cable
Connection . . . . . . . . . . . . . . . . . . . . . . Gold plated stereo
mini jack plug (3.5 mm)
and 1/4" adapter
(6.35 mm)
Massdrop x Sennheiser HD 6XX Headphones
Color: Midnight blue
Transducer principle: Open, dynamic
Frequency response: 10 Hz – 41 kHz
THD: < 0.05%
Nominal impedance: 300 ohm
Cable length: 6 ft (1.8 m)
Connector: ⅛ in (3.5 mm)
Weight without cable: 9.2 oz (260 g)
Made in Romania
Hi. Without having tried it, I expect that it may be a bit underpowered for those two higher impedance headphones. It appears rated at 150 mW/channel (60Ω load), and it is normal for an amplifier to have significantly less output power with higher impedance loads (250/300 Ohms).
My headphones are the Beyerdynamic DT 770 Pro – 80 ohm — and I’m just trying to figure out if they will sound good on this tube amp I’m considering but they give the headphone output in a range (Headphone output for impedance: 8 ohms – 32 ohms) – That’s literally what it says. So will my headphones sound good or not? All these articles seem to imply that the figure should be a single number and not a range. I assume the amp has the ability to detect whats plugged in…but just going by the numbers, what do you think?
Hi. You are asking a bit of an impossible question. “Will they sound good or not?” If the manufacturer recommends a range and you disregard this recommendation, then you get what you get. It may work fine (meaning to your expectations), or not. No way to really tell unless you try.
Amps are best suited for a range of headphone impedances and sensitivities – not a single number – and not one that the amp ‘detects.’ Remember that dynamic driver headphones do not have a perfectly flat impedance response across all audible frequencies – a 32-ohm headphone may be 100 ohms at resonance. It varys with the music you play.
If there is anything to take away from the article is “it depends.” Nothing is a hard-fast, universal rule, and paying attention to just impedance and ignoring sensitivity, or just load impedance and ignoring source impedance, or any other variable won’t paint the full picture. Many variables change the sound.
Almost any combination will make sound, how ideal that sound is to your ears is entirely subjective, and some will be happy with a setup that breaks all the “rules.”
Hello team,
I have reciver 1970 year Yamaha CR1000, I am looking for dynamic stereo headphones with immaculate sound quality. Reciver impedance for head phone is 8ohms (or higher ), these are recommendation from manual. I want spent between 100 /200 gbp on headphones. Could you please recommend one? Does headphones impedance ideally need to be 2.5 -8 times higher than amplifier impedance for best listening experience ? Please advise. Kind regards Bartlomiej
Your Yamaha was built at a time when higher headphone impedances were expected. Check out some of the 120 Ohm+ Sennheisers or Beyerdynamics as a start.
i finally finished reading this and i still dont understand much 😅
Concentrate on the bullet points in the conclusion… the important stuff is all in there. 😉
Hi. I have a question can I pair my Steinberg UR22C with beyerdynamic dt 990 pro 250 ohm Headphone?
Will it work to make sound? Almost definitely. Will it be ideal? That depends on the output specifications of the amplifier.
omg after awhile I just gave up…why are these impedance articles always so ridiculously and unnecessarily long-winded? About 99% of people looking up these articles don’t give a flip about what impedance is and the math and yadayadayada. Just tell us the gist what’s better/worse and what we should look for. You should be able to do that in a simple paragraph or two.
Give the bulleted list in the Conclusion a go.