Headphone impedance explained like you're five

Summary

This video script explores the concept of impedance in headphones, explaining how high impedance headphones require more power to drive and may need an amplifier, while low impedance headphones are easier to use with portable devices. It uses an analogy of garden hoses and water pressure to clarify the impact of impedance on audio circuits. The script also discusses the importance of matching impedance with audio sources for optimal sound quality and equipment safety, and touches on the subjectivity of sound preference beyond technical specifications.

Takeaways

• 🎧 Impedance is a measure of opposition to the flow of alternating electrical current in a circuit, composed of resistance and reactance.
• 🔊 High impedance headphones are harder to drive and may require an amplifier, while low impedance headphones are easier to work with and can be used with portable devices.
• 💧 The analogy of a garden faucet and hose is used to explain impedance, where hose diameter represents impedance and water flow represents loudness.
• 🌊 High impedance headphones require more voltage from the amplifier, leading to a lower current, while low impedance headphones require a higher current at a lower voltage.
• 🌱 The need for both high and low impedance headphones arises from different scenarios, such as using multiple headphones from a single source in a studio setting.
• 🎵 Traditional studio equipment, which operates at high voltages and low currents, pairs well with high impedance headphones.
• 📡 As technology evolved, portable devices with lower voltages but capable of delivering high currents made low impedance headphones more suitable for general use.
• ⚠️ Connecting low impedance headphones to a powerful amplifier can lead to equipment damage due to excessive current flow.
• 🔍 The output impedance of an amplifier should ideally be less than 1/8 of the connected headphones' impedance for optimal sound quality.
• 👂 Sound quality is not solely determined by impedance; other design factors and personal preference play significant roles.
• 📊 Impedance varies with frequency, and the ideal amplifier has an output impedance of 0 ohms, but in reality, it varies among devices.

Q & A

What does the term 'impedance' refer to in the context of headphones?

Impedance in headphones is a measure of the opposition that a circuit presents to the flow of an alternating electrical current, composed of both resistance and reactance. It is typically represented by the symbol Z.

Why might high impedance headphones require an amplifier?

High impedance headphones require an amplifier because they are hard to drive, needing a higher voltage to achieve sufficient loudness due to their resistance to the flow of electrical current.

How does the analogy of a garden hose and water source relate to headphone impedance?

The garden hose analogy represents the impedance of headphones, where the diameter of the hose corresponds to the impedance level, affecting how much 'water' (analogous to sound volume) flows through it.

What is the significance of Ohm's law in the context of headphone impedance?

Ohm's law, which states that current is equal to voltage divided by resistance, is significant because it determines how much current is needed to achieve a certain volume level in headphones, depending on their impedance.

Why are low impedance headphones considered easy to work with for portable devices?

Low impedance headphones are easy to work with for portable devices because they require less voltage and can handle higher currents, which is suitable for devices like smartphones that have limited power output.

What is the purpose of having both high and low impedance headphones?

The purpose is to provide options for different scenarios. High impedance headphones work well in situations where a single source needs to drive multiple devices, like in a recording studio, while low impedance headphones are better suited for portable devices.

How does the evolution of sound making devices affect the preference for low impedance headphones?

As sound making devices became smaller, portable, and cheaper, with vacuum tubes replaced by transistors and mains power by batteries, the preference shifted towards low impedance headphones that match well with these devices, which can deliver high currents at lower voltages.

What potential issue can arise when connecting low impedance headphones to a powerful amplifier?

Connecting low impedance headphones to a powerful amplifier can lead to damage due to the high current that would flow through the circuit, potentially overheating components and causing distortion.

Why is it important to match the impedance of headphones with the output impedance of the source device?

Matching impedance ensures optimal sound quality and safety of the equipment. A mismatch can lead to problems like muddiness, attenuation of certain frequencies, and poor electrical damping, preventing the full potential of the setup from being realized.

What is the '1/8 rule' mentioned in the script, and why is it important?

The '1/8 rule' suggests that for good signal transfer, the output impedance of an amplifier should be less than 1/8 of the impedance of the connected headphones. This rule helps minimize issues arising from impedance mismatches.

How does the frequency response of headphones relate to impedance?

Impedance varies with frequency, which means that even if the impedance value at 1 kHz looks good on paper, it might not translate to a good sound experience. The actual listening experience is more important than just the impedance value.

What advice does the script give regarding the choice between high and low impedance headphones for sound quality?

The script suggests that for critical listening and transparency, headphones with higher impedance (around 250-300 ohms) might be a better choice, as they offer a better chance of matching with a wider range of sources. However, for general sound enjoyment, lower impedance headphones are recommended for better compatibility with various devices.

Outlines

00:00

🎧 Understanding Headphone Impedance

The first paragraph introduces the concept of impedance in headphones, explaining that high impedance headphones are harder to drive and may require an amplifier, while low impedance headphones are easier to work with and can be used with portable devices. Andrew, the narrator, aims to simplify the technical definition of impedance as the opposition to the flow of alternating electrical current, which includes both resistance and reactance. He uses an analogy of a garden faucet and hose to illustrate how impedance affects the flow of water (loudness), and how high impedance requires more pressure (voltage) and low impedance requires more water volume (current). The paragraph also touches on the historical use of high impedance headphones in recording studios due to their compatibility with traditional equipment.

05:02

🔌 Transition to Low Impedance Headphones

The second paragraph discusses the evolution of sound devices towards portability and the shift from vacuum tubes to transistors and from mains power to battery power. This technological change led to the development of low impedance headphones that are better suited for battery-powered devices, which can provide high currents at lower voltages. The paragraph warns against using low impedance headphones with powerful amplifiers, as this could damage the amplifier and headphones due to excessive current. It also explains the importance of matching the impedance of headphones with the output impedance of the audio source for optimal sound quality and equipment safety, introducing the 1/8 rule for ideal signal transfer.

10:04

📻 The Role of Impedance in Audio Quality and Equipment Safety

The third paragraph delves deeper into the importance of impedance matching for achieving the best sound quality and ensuring the safety of audio equipment. It emphasizes that while high impedance headphones are traditionally associated with professional use and may offer better sound quality in certain scenarios, they are not necessarily better in all situations. The narrator also discusses the challenges of finding a perfect match between headphone impedance and source output impedance, using examples of popular USB audio interfaces to illustrate the variability in output impedance and the corresponding ideal headphone impedance for each. The paragraph concludes by advocating for the use of one's ears as the ultimate judge of sound quality, rather than relying solely on technical specifications.

Keywords

💡Impedance

Impedance is a measure of the opposition that a circuit presents to the flow of an alternating electrical current, composed of both resistance and reactance. In the context of the video, it is crucial for understanding how headphones interact with audio equipment. High impedance headphones require more voltage to operate effectively, which relates to the need for an amplifier, while low impedance headphones are easier to drive with portable devices.

💡High Impedance Headphones

High impedance headphones are those with a higher resistance to electrical current, typically above 100 ohms. The script uses the analogy of a narrow garden hose to explain how high impedance headphones require a greater force (voltage) to achieve the desired flow (loudness), making them harder to drive without an amplifier.

💡Low Impedance Headphones

Low impedance headphones have a lower resistance, making them easier to drive and suitable for use with portable devices like smartphones. The script likens them to a wide garden hose, requiring less pressure (voltage) but a larger volume of water (current) to maintain sound output, illustrating their compatibility with devices that can supply high currents at lower voltages.

💡Amplifier

An amplifier is a device that increases the power of an electrical signal. In the video, it is compared to a garden water source or faucet, needing to exert more pressure for high impedance headphones or a larger flow for low impedance ones. Amplifiers are essential for driving high impedance headphones to achieve optimal sound levels.

💡Ohm's Law

Ohm's Law states that the current through a conductor between two points is directly proportional to the voltage across the two points and inversely proportional to the resistance between them. The script uses this principle to explain how the relationship between voltage, current, and impedance affects the performance of headphones and amplifiers.

💡Audio Circuit

An audio circuit is an electrical circuit designed to process audio signals. The video script discusses impedance in the context of audio circuits, emphasizing its importance in how electrical currents interact with the circuit components to produce sound.

💡Reactance

Reactance is the opposition to the flow of an alternating current in a circuit due to capacitance or inductance. It is part of the total impedance and affects how the circuit responds to changes in current at different frequencies, which is relevant when discussing the performance of headphones at various audio ranges.

💡Recording Studio

A recording studio is a facility for recording and producing audio. The script mentions recording studios as environments where high impedance headphones are beneficial due to their compatibility with traditional studio equipment that operates at high voltages and lower currents.

💡Portable Devices

Portable devices refer to electronic gadgets that are easily carried and used on the go, such as smartphones and portable music players. The video emphasizes the suitability of low impedance headphones for these devices due to their ability to work well with lower voltages and higher currents provided by batteries.

💡Electrical Damping

Electrical damping is a concept related to the control of distortion in audio signals, especially for low-end frequencies. The script explains that proper electrical damping ensures that the speaker membrane stops moving when the signal ends, preventing unwanted distortion. This is closely related to the impedance match between the headphones and the source device.

💡Signal Transfer

Signal transfer refers to the process of conveying an electrical signal from one component to another without significant loss or distortion. The script discusses the importance of impedance matching for effective signal transfer, using the garden hose analogy to illustrate how mismatched impedance can lead to weak or inadequate audio output.

Highlights

Impedance is a measure of opposition to the flow of alternating electrical current in audio circuits, composed of resistance and reactance.

High impedance headphones are harder to drive and may require an amplifier, while low impedance headphones are easier to work with and compatible with portable devices.

An analogy is used to explain impedance, comparing headphone amplifiers to garden faucets and headphones to garden hoses with varying diameters.

High impedance headphones require higher voltage and lower current, whereas low impedance headphones need higher current at lower voltage according to Ohm's law.

The need for both high and low impedance headphones arises from different scenarios requiring different audio setups, such as recording studios versus portable use.

Traditional studio equipment, which operates at high voltages and lower currents, pairs well with high impedance headphones.

The evolution of sound devices towards portability and the use of transistors and batteries has led to a preference for low impedance headphones.

Low impedance headphones are a better match for battery-powered devices, requiring higher currents but lower voltages.

Using low impedance headphones with a powerful amplifier can potentially damage the equipment due to the high current flow.

The importance of matching the source and its load for optimal sound quality and equipment safety is emphasized.

The output impedance of an amplifier should ideally be low to ensure compatibility with a range of headphones.

A high output impedance from an amplifier can lead to signal transfer issues and a less than optimal listening experience.

The '1/8 rule' suggests that the output impedance should be less than 1/8 of the connected load's impedance for good signal transfer.

High impedance headphones may be better suited for critical listening and transparency due to their wider compatibility with various sources.

Low impedance headphones offer better compatibility with a range of devices but may not provide the same level of sound quality as high impedance headphones.

Impedance is just one factor in sound quality; other design considerations also play a significant role.

The video concludes by emphasizing the importance of personal preference and using one's ears as the ultimate judge of sound quality.

Transcripts

if you spent more than 10 minutes online

reading about headphones you probably

ran into the term impedance and when it

comes to headphones you quickly learn

that some headphones are high impedance

which means that they are hard to drive

and they might require an amplifier and

some headphones are low impedance which

makes them easy to work with and they

will work great with your phone with

your portable devices and for some

people that's all they want to know but

if you want to actually learn more and

understand what impedance is then you

are in the right spot because my name is

Andrew Andrew and if you watch my

channel you know that I only have one

t-shirt but I am on a mission to search

this entire wonderful Universe for

answers to the most important questions

and explain these answers to you like

you are five so let's learn all we can

about audio impedance and see how it

relates to audio circuits impedance is a

measure of the opposition that a circuit

presents to the flow of an alternating

electrical current and it is composed of

both resistance and reactance and it is

typically rep represented by the symbol

Z or if you want to put it differently

you could say that impedance is sort of

the resistance in the world of

alternating currents because usually

resistance works for DC well impedance

is basically the analog for alternating

currents now this is the official

definition and you know it's great if

you understand it but I think it doesn't

make things very easy to grasp for most

people anyway so here's what we're going

to do you're going to need to pull your

imagination and put it on the table cuz

we're going to put it to work we're

going to think about a typical audio

circuit but instead of thinking of a

headphone amplifier and a set of

headphones we're going to think of the

headphone amplifier as being a garden

water source or garden faucet and the

headphones will be a garden hose the

diameter of the hose would be equivalent

to the impedance of the headphones and

the water that flows through the end of

the hose would be equivalent to the

loudness of the headphone so the more

water flows through the hose the louder

the headphones are high impedance

headphones would translate to a narrow

hose which would constrict the flow of

water and as our impedance gets higher

the hose gets narrower and narrower and

this makes the amplifier work a lot

harder the amplifier or our garden water

source now needs a lot more pressure it

needs a lot more Force to push the water

through to get a good flow so that we

get a good amount of loudness so the

water pressure the force with which the

amplifier has to push this signal to go

through the impedance of the headphones

would be equivalent to the voltage the

amount of signal that's flowing the the

amount of water that gets through the

end of the hose would be equivalent to

the current of the signal we can see

that in the case of high impedance

headphones the amplifier needs to

operate at a higher voltage to have

enough strength to push the signal

through the opposition that the

headphones provide and because of Ohm's

law that states that the current is

equal to the voltage over resistance

this naturally leads to a lower current

on the opposite side low impedance

headphones would translate to a wide

hose one that barely opposes to the flow

of water so now there's not a lot of

water pressure needed but instead a huge

volume of water needs to flow through to

keep a steady flow so when working with

high impedance headphones amplifiers

need to push a high voltage with little

current but when working with low

impedance headphones amplifiers need to

push a high current at a low voltage and

this is all because of ohms law but if

we stop for a moment and think about it

why do we need both High impedance

headphones and low comp headphones why

do we have these two sort of Standards

we're back in our garden but we're going

to add multiple water hoses this time

because let's say we want to wet

multiple corners of our garden

simultaneously adding together multiple

narrow hoses works fine because if the

Water Source has enough pressure

initially the pressure dropped from all

of the extra other hoses shouldn't be

too severe and the water consumption

should still be well below the limits of

the Water Source but adding together

multiple large diameter hoses wouldn't

be as trouble-free because because each

hose individually now requires a lot of

water and likely the Water Source won't

be able to Output this total required

amount which is very high now and

therefore there will only be a weak

stream of water coming out of each of

the garden hoses and this is definitely

a bad setup you never want to have

multiple low impedance devices connected

to a source in parallel but High

impedance headphones work very well in

such scenarios where just one source

needs to drive mult multiple of them and

this is a typical scenario for example

in a recording studio that's tracking an

entire band being high impedance these

headphones will require higher voltages

but they won't draw a lot of current and

coincidentally this was a great pairing

for most of the traditional TW based

studio equipment that was generally used

in recording studios and this equipment

worked by Design at high voltages and

lower currents and therefore headphones

needed to be high impedance to play nice

with them back then the standards for

professional headphones in terms of

impedance es were somewhere between 600

and 250 ohms and as our technology

evolved sound making devices got small

portable and cheap and vacuum tubes got

replaced by transistors and Main's power

supplies got replaced by batteries and

batteries work at relatively lower

voltages but they can deliver High

currents when needed so circuits were

adopted accordingly and now you

basically had a new huge Market of

potential buyers that wanted to get

headphones that played nice with their

portable new fancy devices and thus the

transition to low impedance headphones

began if you remember from Oh's law

earlier low impedance headphones require

higher currents but lower voltages so

they're basically a great match for

battery powered devices if our band

earlier were to use low impedance

headphones instead of high impedance

headphones with a very powerful

amplifier this could be a recipe for

damage the very low impedances of the

headphones would combine to an even

lower total impedance which wouldn't be

able to resist the high power of the

amplifier so a lot of current would end

up flowing in the circuit components

inside the amplifier could overheat and

even get damaged and the volume knob

won't be very useful because just

turning it a tiny bit would lead to a

very loud sound one that's unpleasant to

listen to it could end up melting the

drivers inside the headphones because of

all of this extra current which would uh

overheat the coils inside and then the

membranes could end up making some very

unnatural movements because of the high

power signal all all matching together

the source and its load is very

important for both sound quality and the

safety of the equipment so this is the

main reason why we have high impedance

and low impedance headphones so we can

achieve a good match no matter the

scenario in which we find ourselves High

impedence headphones work great when

Daisy changed to a single suitable

Source but often times because of the

higher required voltages such suitable

sources are not necessarily portable so

high impedance headphones are great in a

studio but maybe not so great for for a

portable setup where you want to use

your mobile phone as a source or any

sort of other portable music player this

doesn't mean that you can never ever use

high impedance headphones with portable

devices some might be very well suited

to drive high impedance headphones but

it's not a guarantee you need to try and

see how a certain combination works but

if you want something that is guaranteed

to work with portable players with

phones then you should look towards low

impedance headphones and the headphones

will get nice and loud and sound as the

manufacturer intended on such devices so

overall it's great that we have the

option to choose what works best in

different scenarios but as an audio file

you're generally interested in getting

the best sound quality possible so in

this case should you get high impedance

headphones because since they're meant

for the professional Market they have to

sound better right it's not that simple

because purely based on impedance it's

impossible to say that some headphones

will sound better compared to others all

of the other other design considerations

play a huge role in how some headphones

sound you can have good sounding low

impedance headphones and bad sounding

High impedance headphones and besides

the impedance of the headphones

themselves you also have the output

impedance of the source that's driving

those headphones with our garden water

source being our amplifier the output

impedance of this amplifier would be the

inverse of the size of the faucet to

which we're connecting our hoses or our

headphones so a low output imped would

translate to a big diameter faucet with

a strong output stream and this is

perfect this is what you always want to

have because to such a big faucet you

can connect both large diameter hoses

and small diameter hoses and you'll get

great results in all cases so it's

actually the ideal scenario you want a

low output impedance at all times a high

output impedance translates to a very

tiny faucet which is a huge problem

because it forces you to only connect

very narrow hoses if you want to achieve

good good signal transfer or a good

stream of water a good flow of water if

you connect a very large diameter hose

to a very tiny faucet you're just going

to have a very weak trickle coming out

the other end there actually is a rule

of thumb that tells us that if we want a

good signal transfer the output

impedance of an amplifier has to be less

than 1/8 of the impedance of the

connected load otherwise these

mismatched impedances can lead to

problems which you might or might not be

able to hear but they will prevent you

from getting the most out of your setup

it's hard to say exactly what will

happen because it can vary from device

to device from situation to situation it

can also vary in intensity it will

probably be something related to

muddiness certain mid- frequencies or

high frequencies can get attenuated

sometimes quite bad there's also the

concept of electrical damping which is a

mechanism of controlling the Distortion

of especially low end frequencies in a

nutshell a properly damped speaker

membrane will stop moving as soon as the

signal reaches zero in a poorly damped

driver the membrane will continue moving

even after the signal has stopped

leading to distortions and deviations in

the frequency response and electrical

damping works best when the 1/8 rule is

being followed so overall it's very

important to have a good match between

the impedance of the headphones and the

output impedance so that you're not

impeding your gear from providing you

with the best sound quality possible the

ideal amplifier has an output impedance

of 0 ohms and the higher this output

impedance is the higher the impedance of

the connected load has to be for a good

signal transfer and in the real world

you can imagine that output impedances

vary quite a bit for example if we look

at some popular USB audio interfaces we

can see that while the Motu M2 has an

almost perfect output impedance of 0.06

ohms the Steinberg ur22 Mark I has a

whopping output impedance of 91 ohms

while the lowest acceptable headphone

impedance for the M2 is 0.48 ohms the

ur22 Mark I needs headphones with an

impedance of at least

728 ohms for a perfect signal transfer

so perfectly following the 1 rule with

the uh Steinberg is practically

impossible because you can't really get

700 plus ohms headphones right but still

the higher the headphone impedance the

more you can minimize the problems that

may arise from the uh not perfectly

matched setup and many other devices

also have higher output impedances

because it's just simply a cheap way to

make a headphone out really and

therefore if your goal is indeed

critical listening and

transparency I think it makes sense to

argue that headphones with a higher

impedance like 250 ohms 300 ohms around

that sort of value are a better choice

because they allow you to have a better

chance at following the 18 rule with a

wider range of sources if pure sound

quality is what you're after again if

transparency is what you're after but

they can also come with their own range

of problems because impedance is just a

piece of the puzzle and you know some

devices might lack the necessary power

to get such headphones to be loud for

some individuals they simply won't get

loud enough you know I I don't think

that's a healthy way to listen to

headphones at such loud levels but still

I can understand this is a problem and

it complicates the setup you're now

looking into amplifiers or USB dongles

you can use right so if you want to stay

away from this if you just want General

sound enjoyment if you care about sound

quality but don't care about staying as

true as possible to the recorded Source

I'd say getting some lower impedance

headphones like 80 ohms or lower is

actually a better choice because you'll

get better compatibility with all of

your devices and what you might be

losing from not following the rules

might not even be that important because

we're humans we're subjective we argue

that dust on a vinyl or tape flutter

makes things sound better and more

organic compared to a pure digital

recording and things are never black or

white even if we did learn a ton about

impedance in this video we barely

scratched the surface impedance is very

complex the more you look into it

usually in Spec sheets or on paper they

give you the value at 1 khz but

impedance varies with frequency even if

something seems very wrong on paper it

could end up not sounding wrong to your

ears as all mixing and mastering

Engineers will tell you in this audio

world you should always use your own

ears they should be the ultimate judge

even if on paper it's not such a great

setup or it's not such a great match if

you enjoy the sound that was the initial

purpose anyway right and with that out

of the way this is now the end of the

video and thank you very much for making

it this far it was a long one I know but

hopefully now you know a little bit more

about headphone impedance to help you

navigate this uh sea of audio

information and if you're still feeling

curious maybe you want to watch another

video if not totally fine I'll see you

around take

care