Headphone Jack Size, A Guide for Beginners

While wireless headphones and other devices are becoming more and more popular, using wired equipment remains. When it comes to wired headphones, there are headphone jack size differences to consider: sizes 2.5mm, 3.5mm, 4.4mm, and 6.35mm. Let's find out why jack sizes vary and which one is the right one to use in this headphone jack tutorial.

What is a headphone jack or headphone plug? The size difference

There are four very common headphone jack sizes available in the market. The size of headphone jacks refers to the diameter of the jack however, these connectors also differ when it comes to their lengths. Learning about the different sizes can help you find the right headphone that will work with your needs.

6.35mm headphone jack

The 6.35mm headphone jack is also called the ¼ - inch connector jack. This is a very common jack and it's often used in professional audio systems including headphone amps, digital converters, and professional use headphones.

This headphone jack is commonly used in electronic audio equipment like an electric guitar which uses a 6.35 TS patch cable. The connection comes with similar dimensions as the ¼ - inch headphone jack but has an extra conductor along the connector to create a TRS or tip-ring-sleeve than a TS or tip-sleeve connector.

The 6.35 mm jack is the largest and is also used in other professional devices like field recorders, audio interface devices, and mixing consoles. You can find audio connector adapters or plugs that help a 3.5mm female headphone connector connect to a 6.35mm male.

The sleeve of a 6.35mm jack is mostly made of polished metal but some high-end ones have gold-plated sleeves to reduce corrosion which can lead to signal loss in analog devices.

4.4mm headphone jack

The next headphone jack size is the 4.4mm jack. These are not as common as 6.35 and 3.5mm jacks but are able to produce balanced stereo sounds and clearer audio. If you haven’t seen a 4.4mm jack, these are sizes between the average 3.5mm and the XLR size.

Most 4.4mm jacks are used by professionals in the music-making industry, in the telecommunications field, and audiophiles. There are also a few digital audio players that offer connections for the 4.4mm and 3.5mm jacks.

The 4.4mm balanced plug called the pentaconn is a 5-pole plug with TRRRS schematics. This is used in the telecommunications and professional audio industries. More on the 4.4mm jacks as we explain the different wiring standards of headphone jacks later.

2.5mm headphone jack

The 2.5mm jack is known as the smallest and thus it has earned the name “sub-miniature” or the “sub-mini connector.” Also called a micro-jack, it was once a popular headphone jack but now, fewer and fewer devices are adopting its use.

There are two kinds of 2.5mm connectors or jacks. When using a device with 2.5mm ports, make sure that you are using the correct plug as you may damage the jack upon insertion. Always check your device manual as to the right type of connector or jack to use.

You'll find 2.5mm plugs and jacks in two-way radios or walky-talkies. There are also video cameras that still use the 2.5mm plug and jack. Some speaker-microphones like the Tait TP93/94 speaker mic also use the 2.5mm headphone jack.

3.5mm headphone jack

Of the different types of headphone jack sizes, the 3.5mm headphone jack is the most popular. Almost all analog wired audio devices and headphones have 3.5mm plugs. This 3.5mm is common in automobile audio connections located on car consoles. It is labeled as the AUX port when checking for connections.

The 3.5mm jack is also used in audio mixing consoles as well as other audio consumer products like smartphones, laptops, field recorders, tablets, and PCs. Traditional headphones used the TRS 3-pole 3.5mm jacks while those with a mic have the TRRS 4-pole 3.55 connection.

Because of newer and better audio systems, more and more smartphone makers are letting go of the 3.5mm jack. They now use lighting and USB-C headphone connectors to replace this headphone jack. Also, the use of wireless headphones and earbuds has paved the way for more devices to abandon the 3.5mm jack.

If you want to learn more about the 3.5mm jack, check out our article about it.

Using adapters simplifies the use of different inputs as various electronic devices use different inputs. For instance, an adapter that allows a 3.5mm jack to fit a 6.35mm port. This is the most commonly-used adapter. There are others like the 2.5mm to 3.5mm audio stereo adapter which allows you to connect a standard 3.5mm stereo headphone to a tiny 2.5mm device output.

The wiring standards of headphone jacks

Aside from the size, different headphone jacks vary when it comes to wiring standards. These standards refer to the way these jacks connect which affects the signals that they can use and send.

But before we discuss the 4 headphone jack wiring standards, let's get to know first the different headphone plug conductors. These components usually have 2 to 5 conductors namely the: Tip or T, Ring or R, and the Sleeve or S.

The Tip is the connector tip while the ring is the visible ring that separates the sleeve and the tip of the connector. The sleeve is a long ring or the long piece that determines the connector's diameter. All plugs come with two conductors which are the tip and sleeve. The number of rings or bands varies and these separate the two to avoid signal shorting. The plugs' toponomy is determined by the number of rings.

• Two conductors  - TS
• Three conductors – TRS
• Four conductors – TRRS
• Five conductors – TRRRS

Take note that the ring and the sleeve contact points come with the same diameters. As you describe plugs, start with the diameter of the sleeve conductor as this is the plug’s name. The ¼ - inch plug sleeves diameter measures 6.35mm. This rule goes for all miniature and all sub-miniature sleeves 2.5mm and the 3.5mm diameter sleeves.

TS 

This 2-conductor plug transmits audio signals in mono. The plug's sleeve is the ground wire and returns path as the tip is responsible for transmitting the audio to the device.

• T – signal or transmission wire
• S – return path or the ground wire

Most TS connectors are short because if the cable is longer, audio signals could become distorted as the sleeve can pick up more noises just like an antenna. You’ll find TS connectors in 2.5mm sizes which are usually connected to musical instruments like acoustic guitars and other string instruments.

TRS

In a TRS connector, there is a ring in the middle of the tip and the sleeve. The ring is a conductor that produces a balanced or an unbalanced stereo signal or mono signal.

• T – this is the left channel signal
• R – this is the right channel signal
• S – this is the return wire

For a balanced mono output, the sleeve works as a return wire as the ring becomes the negative signal while the tip is the positive signal. To achieve an unbalanced stereo signal, the sleeve is the return wire or ground wire as the ring is the right channel and the tip is the left channel.

To achieve an unbalanced mono output, the sleeve is the ground or return wire as the tip has the audio signal and the ring the mic signal option. A TRS connector can accommodate an unbalanced stereo output.

The connector tip is connected to a wire that connects to the left headphone driver coil lead. Meanwhile, the ring is connected to the wire that connects to the right headphone coil lead.

The connector sleeve is connected to a wire which connects to the two negative poles of the driver coil. The wire comes with a soldered joint along the Y or on the earpiece as this is where the ground wire coming from the plug divides into two wires to connect to the two negative terminals of the coils.

TRRS

Meanwhile, the TRRS is very common as these introduce microphone conductors. TRRS is used with 3.5mm jack connectors and these abide by the standards of the Cellular Telecommunications and Internet Association or CTIA.

You can bet that your favorite electronic device at home has TRRS jacks like your laptop, smartphone, gaming consoles, and many other audio devices. The CTIA dictates the wiring diagram of the TRRS jacks:

• T – this is the left channel audio wire
• R – is the right channel wire
• R – is the common return ground and wire
• S - is the mic audio wire

The OMTP or Open Mobile Terminal Platform is an older mobile network operating standard set before CTIA. The OMTP standard referred to the sleeve as the common ground and return wire as one of the ring conductors as the mic audio wire.

The OMTP TRRS standard wiring scheme uses the tip as the left headphone, the ring for the right, and the other ring for the mic. The sleeve is used as a ground wire.

Some headsets use the TRRS connection while some don't. There are professional headsets that work with different connectors to transmit headphones and mic signals in a more versatile manner. Meanwhile, computer headsets and gaming headsets use USB connectors. Traditional and older desk telephones use RJ9 connectors. For headsets and headphones for new iPod models use Lightning cable connectors. 

TRRRS

There are three rings in a TRRRS conductor plug. It is a plug commonly used in rare 4.4mm pentaconn connectors. A pentaconn is short for 5 connectors. Despite its scarcity, TRRRS connectors offer balanced stereo audio signals through any compatible headphones or earphones.

• T – this is the left channel with a positive polarity.
• R – this is the left channel with a negative polarity.
• R – this is the right channel with a positive polarity.
• R – this is the right channel with a negative polarity.
• S -  this serves as the ground wire.

As you can see, the TRRRS has no return wire as each of the channels already have a positive and negative polarity. And because of the lack of return wires, TRRRS connectors offer amazing clarity with minimal crosstalk than other types of connectors.

Headphone jack compatibility

You must always use a compatible headphone jack and plugs to produce the best, high-quality sound. And to fully understand compatible jacks and plugs, you must first learn how audio signals are transmitted.

About mono audio signals and stereo audio signals

Audio signals are mostly transmitted to your headphones through a mono-aural or a mono signal or a stereo or a stereophonic signal. Stereo signals use left and right or 2 audio channels whereas a mono requires a single audio channel. Read the comparison guide about Mono vs Stereo.

A phone connector needs two conductors like the tip and the sleeve to carry mono signals. One of the conductors carries a mono signal and the other conductor is the ground to transmit the stereo signal. The headphone connector should have 3 conductors: one conductor acts as a left channel wire, the other conductor is the right channel audio wire and the third one is the return wire or the common ground.

With three conductors, the stereo signal seems to come from many directions as it uses two channels for natural hearing. In ordinary audio terms, this is the surround sound effect.

About balanced and unbalanced audio signals

Balanced and unbalanced audio is also utilized by headphones and most are designed for unbalanced audio.

To achieve balanced audio, there must be 2 signal wires with one wire transmitting positive polarity and the other one having a negative polarity. In unbalanced audio, there is one ground wire and another signal wire. The TRRRS connector is used to achieve balanced audio while the TRS connector is used for unbalanced audio.

From what you learned, there are four types of audio signals that may be carried using phone connectors: unbalanced stereo, balanced stereo, unbalanced mono, and balanced mono.

The connector's number of conductors determines the kind of audio signal that the plug can transmit. To get balanced mono, you need a TRS connector to carry the audio signal. For unbalanced stereo, a TRS connector is required. For balanced stereo, you need a TRRRS connector. With more conductors, more signals may be transmitted.

Now that you have a general idea about unbalanced and balanced signals that phone connectors can carry, you may now understand better why some headphone jacks are compatible with certain plugs.

What headphone jack is compatible with a type of audio plug?

As we mentioned before, headphone jacks and audio plugs should have similar wiring schematics to work together. However, there are times when a headphone jack and an audio plug are compatible despite their conductors are not a match. Also, there are headphone jacks and audio plugs of the same size but are still not compatible.

A 3.5mm TRRS microphone plug with CTIA standards will work with a 3.5mm TRS jack as these come with similar wiring diagrams.

An unbalanced 3.5mm TRRS headphone plug will work with a 3.5mm TRRS jack as the sleeve of the jack is designed to carry microphone signals is wired to the ground of the TRS connector of your headphone.

TRS plugs and TRRS jacks will work together as the ground wire will connect.

A TRRS headphone jack with CTIA standards won’t work with a TRRS headphone plug with OMTP standards. Take note that the tip and the rings of the two jacks are very similar.

Jacks with the CTIA standard will not work with plugs with the OMTP standards.   

How to find out if your headphone jack is compatible with a plug?

Although it's best to find out by plugging the jack into a plug and listening for audio, this technique should not be used. Doing so can severely damage your jack or plug and cause sound distortions. Also, an unpleasant sound may be produced which can hurt your ears.

It's best to check your device's owner's manual to find out about compatible headphone jacks and plugs. You may use a connector as we mentioned above but this can also severely alter sound quality.

Other types of headphone connectors

Aside from the 2.5, 3.5, 4.4, and 6.35mm jacks, there are new headphone jacks and connectors available.

• Lightning connectors – instead of the headphone jack, Apple uses Lightning connectors. This is also known as the charging ports of iPhones.
  
  
• USB connectors – many smartphone manufacturers decided to let go of the traditional headphone jack and use the USB connector instead. Because of this, newer and more efficient USB-type C headphones have become more popular.
  Aside from USB type C headphones, there are units that use USB Type-A connectors. You can check out headphones with microphones from Logitech.
  
  
• XLR connectors – many professional headsets and headphones use XLR connectors. These headphone units have removable cables to allow different connections including the XLR connector. (here are details about the different of XLR and  TRS )

FAQ

Here are the most frequently asked questions about headphone jack sizes and their corresponding answers.

• Are the headphone jack and audio out the same?
  These are different terms as the headphone jack can output audio that will work with headphones. Meanwhile, audio out can output mono signals that may be balanced or unbalanced. These are not compatible with headphones as these don’t have the ideal output voltages to be compatible with headphones.
  
  
• Can you plug a speaker into a headphone jack?
  You may plug a speaker into a headphone jack but this is not advised. The speakers have to be stereo and should be able to take the impedance and voltage levels of your headphone out port. If you plug a speaker that's only for speaker-level audio into a headphone port, the results won't be pleasing at all. You may also end up damaging the jack as well as the output of the device.
  
  
• How can you tell if you have a 3.5mm jack?
  You know that you have a 3.5mm jack if you plug this into a device like a smartphone, laptop, TV headphone jack, etc. If you're unable to hear any audio then try connecting the headphone to another device.
  
  
• What is a 2.5mm headphone jack?
  A 2.5mm headphone jack is a small and round connector that’s used to accept a pin-like plug on a phone headset. You can use a 2.5mm headphone jack with other devices as well as this can support a microphone or stereo sound speakers. This depends on how many connector rings you have on the headphone jack and plug.
  
  
• Is a 3.5mm jack similar to AUX?
  The design of an AUX connector and a 3.5mm headphone jack is the same but the AUX connector is compatible with all audio while the headphone jack is only suitable for headphones.
  
  
• Do all laptops come with a 3.5mm jack?
  Many computers and updated laptops have one audio jack ideal for headphones and mic. This jack is compatible with wired headphones with 3.5mm TRRS plugs designed for integrated audio jack systems. Lately, laptops and smartphones are doing away with the 3.5mm jack to make way for thinner and more efficient headphone connectors.
  
  
• What is the size of a laptop audio jack?
  The standard size of a laptop audio jack is 3.5mm. This size of the jack is also found in notebooks, recording devices, mobile devices, and laptops.
  
  
• What is the “universal audio jack?”
  The universal audio jack is a four-contact jack and plug that allows the interconnection of mic and stereo signals in an audio system.
  
  
• What type of audio jack should you use for headphones?
  The 3.5mm audio out is the standard audio jack on headphones as well as speaker systems. These connectors will plug into the headphone port and have a green color plastic sleeve.

Last Words

Headphone jack size varies in diameter, diagram schematics, and compatibility. Knowing the different types of headphone jacks will help you find the right one that will match your device. This reduces damage to your device as well as the jack you will plug in. Also, getting to know these basic audio information helps you use different connectors and plugs for different devices, instruments, and audio equipment.

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