There are four common headphone jack sizes; 2.5mm, 3.5mm, 4.4mm, and 6.35mm. There are different types, that combined with the different sizes are used for different audio applications. The outside diameter of the sleeve conductor is measured to determine the headphone jack size.
Before starting to discuss the different headphone jack sizes it is necessary to understand the difference between a headphone jack and a headphone plug.
A headphone jack is a fixed port electrical connector that is used to transmit and receive audio analog signals between the headphones and the device. The headphone jack usually comes installed in the equipment while the headphone plug is connected to a cord attached to the headphone.
The headphone jack is the female port installed on the devices, and the headphone plug refers to the male plug at the end of headphone cords.
If your headphones are permanently wired, the end of the cable has a plug. Your audio player, smartphone, laptop, etc., has a headphone jack that you plug your headphones into. When you insert the plug into the jack that connection becomes complete.
To avoid confusion, I will refer to the port (female connector) as the Headphone Jack and the (male connectors) as Headphone Plugs.
What Makes a Headphone Plug?
The headphone conductor consists of three different components:
- Sleeve (S) – Can be confused with a ring but is longer and determines the diameter of the connector.
- Ring (R) – Separates the tip and the sleeve.
- Tip (T) – This is the tip of the connector.
Each conductor has a sleeve and a tip. The difference between plugs is the number of rings. If it has one ring, it is a TRS connector or a three-conductor plug. If the conductor has two rings, it is a TRRS connector four-conductor plug.
How Do Headphone Jacks Connect?
For a plug and a headphone jack to connect correctly, they must have the same wiring schematic and the same headphone jack size.
In order to get audio in our headphones, jacks have a digital to analog converter which then converts digital audio signals from the audio device into analog audio signals which get converted as sound energy When you connect a plug to a jack that connection becomes complete.
To get audio signals the cords attached to the headphone plugs create an electrical circuit, thus making it possible for the signal that is in AC to be transmitted to the headphones which then converts the signals to sound.
How Audio is Transmitted
Audio signals are transmitted to the headphones via a Mono signal or Stereo signal. A Mono signal uses one audio channel whereas a Stereo signal uses two audio channels. (left and right)
A phone connector needs two conductors to carry a Mono signal. A tip and sleeve. One conductor carries the audio signal while the other conductor acts as ground.
To carry a stereo signal, a headphone connector must have at least three conductors. A left channel audio signal wire, a right channel signal wire, and a common ground/return wire.
Because it utilizes two channels the stereo signal creates the illusion that the sound is coming from different directions which simulates “natural” hearing.
If you want to go wireless, take a look at The 10 Best Bluetooth Transmitters.
Balanced vs Unbalanced Audio
Most headphones make use of unbalanced audio that is wired as having one signal wire and one ground/return wire and is achieved by TRS connectors.
Balanced audio is achieved by TRRRS connectors that have two signal wires, in which one carries positive polarity, and one carries negative polarity. This creates quality stereo sound.
Types of Headphone Plugs
There are four types of headphones plugs that are often used on different devices. The names of the plugs indicate how many conductors the plug consists of.
Here is a guide to In-Ear vs On-Ear vs Over-Ear Headphones.
TS Connectors
The TS (Tip-Sleeve) type of connector is the simplest type of headphone plug and features 2 conductors. The sleeve acts as a ground, and the tip is responsible for the audio signal transmission.
TS connectors only transmit unbalanced mono audio signals and perform best with short cables. They are mainly 2.5mm headphone plugs and are used with guitars and instruments or headphone connections.
If long cables are used audio distortion may be experienced. This is because the sleeve picks up noise along the way just as an antenna does.
TRS Connectors
TRS (Tip-Ring-Sleeve) connectors have three conductors. The addition of the ring allows the audio signal to be a balanced mono system. The tip and the ring are responsible for the negative and positive signals while the sleeve serves as the return wire.
It can also be an unbalanced stereo signal with the tip responsible for the left channel signals, the ring for the right channel signals while the sleeve serves as the ground-return wire.
A headphone with the TRS connector means these headphones can be used for stereo sound without a microphone or mono sound with a microphone signal. The TRS connector is mainly used to carry unbalanced stereo signals and uses a 3.5mm plug
To get unbalanced mono, the sleeve acts as the ground/return wire while the tip carries the audio system, and the ring is an option to carry the microphone signal.
TRRS Connectors
TRRS (Tip-Ring-Ring-Sleeve) connectors are equipped with four conductors. These connectors comply with the standards set by Cellular Telecommunications and Internet Association (CTIA)
The TRRS connector supports unbalanced stereo audio with a microwave signal added at the same time. These connectors are often used with computers, smartphones, and video game consoles due to users being allowed to have stereo sound with the microphone signal.
The tip and the two rings are responsible for the left and right channel audio signals and the ground return path. The sleeve serves as the microphone signal wire.
TRRRS Connectors
TRRRS (Tip-Ring-Ring-Ring-Sleeve) connectors are equipped with five conductors and support balanced stereo signals and carry balanced stereo audio to compatible headphones.
Tip: left channel audio signals (positive polarity)
Ring: left channel audio signals (negative polarity)
Ring: right channel audio signals (positive polarity)
Ring: right channel audio signals (negative polarity)
Sleeve: serves as ground
Due to there being positive and negative polarity wires for left and right channels it is possible for the TRRRS to manage without a return wire because they connect to the headphone system
TRRRS connectors achieve more clarity as the lack of a return wire reduces crosstalk and produce a high sound quality which is why the connectors are used in professional music production gear.
If you are going the wireless route but want volume, check out the 10 Loudest Bluetooth Speakers.
Headphone Jack Sizes:
2.5mm
This is the smallest headphone jack size there is. Also called the sub-miniature or sub-mini connector. It is sometimes referred to as the 2.5mm micro-jack. It is losing its popularity as manufacturers are now using the mini-jack in their designs for smartphones.
They are mainly used for mono headphones and for video cameras.
3.5mm
These are the most common size for headphones. 3.5mm jacks are used for both TRS and TRRS style systems and are used with most laptops, smartphones, portable audio players, and tablets. Headphones with a microphone will utilize the TRRS 4-pole 3.5mm connector.
Apple has removed the 3.5mm from its iPhone 7 and other companies may follow suit but the 3.5 mm jack is still the top choice for many audiophiles looking for high-quality sound.
4.4mm
These are relatively new and not as common even though they carry balanced stereo and the audio is clearer using TRRRS connectors. They are mainly used in professional telecommunications and audiophile industries.
6.35mm
Commonly known as the ¼ inch connector, it is the largest jack size and is relatively bulky. It is used with headphone amplifiers, digital to analog converters as well as audiophile-grade headphones.
Adapters
While headphone jack plugs normally come in single format versions, adapters can be used to make use of different inputs that an electronic device may have. The 3.5mm to 6.5mm is the most common adapter available.
Adaptors are made to help connect different Aux cable sizes. You can find Lightning to 3.5mm Jack, Micro-USB Type C to 3.5mm Jack, etc. Many adaptors are available. You must make sure you choose the right one for your use and connection.
In Conclusion
As much detail as possible has been included to explain how audio is transmitted from jacks to headphones.
By understanding the use of conductors and the various ratings of connectors and the purpose of the different sized headphone Jack sizes will help you to make the correct decisions when looking for headphone plugs or an adaptor to use when your headphone does not fit in your new acquisition.
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