Most IEM cable connectors fall into four families: 0.78 mm 2-pin, MMCX, IPX and Pentaconn Ear. Check the socket on your earphone rather than the brand. One maker can use different connectors across its range, and two 2-pin sockets can still differ in how deep the pins sit. Match the socket, and any well-made cable will fit.
This guide is for anyone buying a replacement or upgrade cable for in-ear monitors. You'll learn how to recognise the common IEM cable connectors, what each is good and bad at, and which Null Audio plug to choose. If you already know your model, Find My Cable looks it up across more than 400 IEMs.
Key takeaways
- The 0.78 mm 2-pin connector is used on most custom IEMs and most current Chi-Fi IEMs, including Moondrop and Truthear.
- A 2-pin socket is either flat (flush) or recessed, and the Null Audio standard 2PIN (0.78) plug fits both.
- A qdc-style 2-pin plug has a raised shroud and won't seat on a standard recessed 2-pin socket.
- MMCX is used on the Shure SE series, Campfire Audio and older Westone IEMs, and can loosen after many swaps.
- FlexiPlug gives one cable 6 swappable tips, from 0.78 mm 2-pin to Pentaconn Ear.
What are IEM cable connectors?
An IEM cable connector is the small plug that joins a detachable cable to each earpiece. It sits at the earphone end, opposite the player plug. A detachable connector is the reason you can replace a broken cable instead of the whole earphone.
The connector is not the same as the player plug. The player plug is the 3.5 mm, 2.5 mm or 4.4 mm end that goes into your phone, dongle or player. You choose each end separately, and every Null Audio cable is built to order with the connector and plug you pick.
The connector matters for three reasons. It must fit the socket mechanically. It must keep a reliable electrical contact over time. And for 2-pin, it must be inserted with the right polarity.
Which IEM cable connectors are most common?
The table below covers the connectors you'll meet on most in-ear monitors. The last column is the option to pick in our configurator.
| Connector | How to recognise it | Common on | Choose at Null Audio |
|---|---|---|---|
| 0.78 mm 2-pin | Two thin pins side by side; the socket is flat or sunk into the shell | Most custom IEMs and most current Chi-Fi IEMs (Moondrop, Truthear, Kiwi Ears, Simgot), AAW | 2PIN (0.78), or Flat 2pin for flat sockets |
| qdc / “extended” 2-pin | Two pins inside a raised plastic shroud on the plug | qdc, older Ultimate Ears and Unique Melody, KZ “C-pin” | UE/UM/QDC 2PIN Legacy |
| MMCX | A round snap-on coaxial plug that rotates once seated | Shure SE series, Campfire Audio, older Westone, many universal IEMs | MMCX |
| IPX / T2 | A small snap-in plug with a flat face, similar in idea to MMCX | Current Ultimate Ears customs and UE 150–350, Westone MACH and Pro X, 64 Audio Aspire and some 64 Audio customs | IPX |
| Pentaconn Ear | A small round connector designed for many insertions | Acoustune and some other IEMs | FlexiPlug with the Pentaconn Ear tip |
Budget IEMs follow the same pattern. The Moondrop Blessing 3 and Truthear Hexa use recessed 0.78 mm 2-pin sockets. The Kiwi Ears Cadenza uses a flush 2-pin socket. The original 7Hz Timeless and the Tin HiFi T2 use MMCX.
How do flat and recessed 2-pin sockets differ?
2-pin is the most common connector on in-ear monitors. The two pins are 0.78 mm thick, but the socket comes in two shapes:
- Recessed: the socket sits slightly below the surface of the shell. Many Moondrop, Truthear and custom IEMs use this, as does the Simgot EA500.
- Flat (flush): the socket is level with the shell.
Our standard 2PIN (0.78) plug fits both. Choose Flat 2pin only if you know your socket is flat and you want the slimmest fit. On some custom IEMs with a flush-cut shell, a bulky 2-pin plug can press against the ear. Tell us, and we'll suggest the best plug.
Polarity on 2-pin
Polarity is the direction a 2-pin plug goes into the socket. Match the marked side of the plug to the marked side of the socket. Reversing it on one side puts that earpiece out of phase, which makes the stereo image sound hollow.
What is a qdc or extended 2-pin connector?
A qdc or “extended” 2-pin connector is a 2-pin plug with its pins inside a raised shroud. It is used by qdc, older Ultimate Ears and Unique Melody IEMs. A qdc plug won't seat on a standard recessed 2-pin socket, as Headphonesty notes in its Simgot EA500 review. Whether its pins are 0.75 mm or 0.78 mm is debated on forums, so we treat it as its own connector.
KZ's “C-pin”, used on the ZSN Pro, ZSN Pro X and ZS10 Pro, is a qdc-style connector. So is the socket on the Simgot EM6L. For all of these, choose UE/UM/QDC 2PIN Legacy, or the qdc tip on FlexiPlug.
MMCX and IPX: snap-on connectors
MMCX
MMCX is a snap-on coaxial connector that lets the earpiece swivel. That makes fitting over the ear easy. The downside is wear. Audio-Technica lists loose fit, overly tight fit and dropouts when rotating as common MMCX problems. If that happens, the socket on the earphone or the plug on the cable may need replacing.
A few makers use their own recessed or keyed MMCX variant that a standard plug won't fit. Examples are the Sennheiser IE 300, IE 600 and IE 900 and the Etymotic ER4SR and ER4XR. Sony's IER-M7 and IER-M9 use an MMCX-type socket that sits deeper. We make dedicated plugs for these.
IPX (T2)
IPX is a small snap-in connector used on current Ultimate Ears custom IEMs, such as the UE Live. Our IPX plug also fits T2 sockets, such as Westone MACH and Pro X and Ultimate Ears UE 150, 250 and 350. The 64 Audio Aspire uses IPX, and 64 Audio customs use IPX or flat 2-pin. See the Ultimate Ears, Westone and 64 Audio guides.
Brand-specific connectors and Pentaconn Ear
Pentaconn Ear is Nippon DICS's earphone connector, designed to stay reliable over many insertions. Acoustune and other makers have adopted it (Porta-Fi; Pentaconn). Choose FlexiPlug with the Pentaconn Ear tip.
Some makers use their own connector. We make cables for these too:
- Audio-Technica A2DC, on models such as the ATH-E70 and ATH-LS70iS: choose A2DC. See the Audio-Technica guide.
- JH Audio: 4-pin with the bass adjuster on the cable; choose JH w Bass Control. See the JH Audio guide.
- Sennheiser IE series and IE PRO: each has its own option. See the IE series and IE PRO guides.
- Sony IER-Z1R, FitEar and Etymotic ER4: dedicated options. See the Sony and Etymotic guides.
Own more than one IEM? Use FlexiPlug
FlexiPlug is our interchangeable connector system: one cable, with swappable earphone-side tips. Current tips are 0.78 mm 2-pin, IE300/600/900 MMCX, IPX, A2DC, qdc 2-pin and Pentaconn Ear. It suits anyone who switches between IEMs with different connectors.
If you only need one connector, a fixed plug is simpler. Brevity Pro starts at USD 49, uses four 26 AWG 5N copper wires, and its default 2PIN version ships within 2 working days. Browse every option in all IEM and headphone cables.
Connectors do wear. Our repair service can replace damaged connectors, and products bought within 3 years qualify for flat-rate repair from USD 30. Details are on the warranty page.
How do I find my connector for sure?
- Look your model up in Find My Cable.
- Read the full IEM cable connector guide.
- Or send a close-up photo of the socket to sales@null-audio.com, or through our contact page, and we'll tell you which plug to choose.
Frequently asked questions
Is 0.78 mm 2-pin the same as qdc 2-pin?
No. A qdc or extended 2-pin plug has its pins inside a raised shroud, and it won't seat on a standard recessed 2-pin socket. qdc, older Ultimate Ears and Unique Melody IEMs use it, as do KZ C-pin models such as the ZSN Pro. At Null Audio, choose UE/UM/QDC 2PIN Legacy for these.
Will a 2-pin cable fit both flat and recessed sockets?
The Null Audio standard 2PIN (0.78) plug fits both flat (flush) and recessed 2-pin sockets. Choose Flat 2pin only if you know your socket is flush and you want the slimmest fit.
Why does my MMCX cable crackle or cut out?
MMCX connectors can wear after many connections. Audio-Technica lists loose fit, overly tight fit and dropouts when rotating as common MMCX problems. The socket on the earphone or the plug on the cable may need replacing.
Does it matter which way round a 2-pin cable goes in?
Yes. Match the marked side of the plug to the marked side of the socket. Reversing one side puts that earpiece out of phase, which makes the stereo image sound hollow.
Can one cable work with IEMs that use different connectors?
Yes, with FlexiPlug. It is a Null Audio cable with swappable earphone-side tips: 0.78 mm 2-pin, IE300/600/900 MMCX, IPX, A2DC, qdc 2-pin and Pentaconn Ear.
Do IPX cables fit Westone and Ultimate Ears T2 sockets?
The Null Audio IPX plug fits current Ultimate Ears custom IEMs and also T2 sockets, such as Westone MACH and Pro X and Ultimate Ears UE 150, 250 and 350. The 64 Audio Aspire also uses IPX.
Sources
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