Author: Veronica Sneesby Read time: 13 min
What is a CK12 Microphone Capsule?
Learn what the AKG CK12 capsule is and how its dual-diaphragm design works
A CK12 capsule is a large-diaphragm, dual-diaphragm condenser capsule. Its edge-terminated diaphragms, acoustic chamber design and ability to support multiple polar patterns made it one of the most influential capsule designs in recording history.
What makes the CK12 capsule different?
The CK12 is best known for combining several design features:
- A large-diaphragm condenser structure.
- Two sound-sensitive diaphragms.
- Edge-terminated construction.
- A multi-chamber acoustic design.
- Support for multiple polar patterns when used with suitable electronics.
- A brass-ring construction in the original historical design.
This combination gave the CK12 both tonal character and practical versatility. It could be used in microphones capable of changing polar patterns, allowing one microphone to work in different recording situations
How does a dual-diaphragm capsule work?
A dual-diaphragm capsule has a diaphragm on each side of the central structure. Each diaphragm responds to sound arriving from its respective direction.
The two diaphragms can be used together in different electrical relationships. By changing the polarisation and contribution of the rear diaphragm, the microphone circuit can alter how strongly the microphone responds to sound from the front, sides and rear.
This allows the complete microphone to produce different polar patterns, including:
- Omnidirectional.
- Cardioid.
- Figure-eight.
- Intermediate patterns between these responses.
The exact method depends on the capsule and the microphone circuit. A CK12 capsule does not independently select its polar pattern. It must be integrated into suitable electronics designed to provide the required polar-pattern control.
What are the main CK12 polar patterns?
Omnidirectional
An omnidirectional pattern responds broadly to sound from all directions.
This can produce a natural, spacious result and capture more of the room.
It can work well for:
- Room recording.
- Choirs and ensembles.
- Acoustic instruments in a good-sounding space.
- Natural vocal recordings.
Because an omnidirectional pattern captures sound from behind the microphone
as well as the front, the room has a significant influence on the result.
Cardioid
A cardioid pattern is most sensitive to sound from the front and rejects more
sound from the rear.
It is often useful for:
- Lead vocals.
- Acoustic guitar.
- Voiceover.
- Individual instruments.
- Recording in rooms that are less acoustically controlled.
Cardioid placement also creates proximity effect, meaning bass response
generally increases as the source is moved closer to the microphone.
Figure-eight
A figure-eight pattern responds to sound from the front and rear while
rejecting sound from the sides.
It can be useful for:
- Two-person recording.
- Blumlein stereo techniques.
- Mid-side recording.
- Ribbon-style room techniques.
- Deliberate use of front-to-back room sound.
The rear response makes microphone placement especially important. The sound
behind the microphone becomes part of the recording.
Intermediate patterns
A dual-diaphragm capsule can also support patterns between omnidirectional,
cardioid and figure-eight responses.
These intermediate settings can help an engineer adjust:
- The amount of room sound.
- Rejection of unwanted sources.
- Stereo recording width.
- The balance between direct and reflected sound.
What does edge termination mean?
In an edge-terminated capsule, the diaphragm is electrically connected at its outer edge. This leaves the central diaphragm area free to respond to sound pressure without a centre connection or central attachment interrupting its movement.
Edge termination is one of the design characteristics commonly associated with the original CK12 family, although it does not by itself guarantee a particular frequency response or tonal result
Why is the CK12 associated with an open or airy sound?
The CK12 is commonly associated with an open, detailed and airy character, with useful high-frequency presence and a spacious sense of room. Those descriptions are tendencies, not guarantees.
The finished sound depends on the exact capsule, diaphragm material and tension, chamber geometry, headbasket, circuit, transformer, tube or FET stage, and the position of the microphone in the room.
A well-tuned CK12-style microphone may capture vocal articulation and acoustic detail without sounding as mid-forward as some other classic capsule families. In a reflective room, however, that openness can also emphasise unwanted brightness.
The same microphone can therefore sound polished and dimensional in a controlled room but too forward or splashy in a lively space.
What changed in later CK12 capsules?
The term CK12 is used in more than one way today. It may describe:
- An original historic brass-ring capsule.
- A later capsule related to the original AKG design.
- A capsule fitted to a particular microphone generation.
- A modern reproduction or replacement capsule.
- A new design that follows CK12 principles without duplicating every original detail.
Later manufacturing approaches used different materials and mechanical methods, including versions associated with PTFE, commonly called Teflon.
These changes reflected practical issues such as manufacturing complexity, consistency, material availability, reliability and cost.
As a result, “CK12-style” is often the most precise term for a modern capsule that recreates the architecture or sonic intention of the classic design rather than claiming to be an original vintage component.
| Capsule family | Broad design association | Commonly associated character | Typical pattern context | Important qualification |
|---|---|---|---|---|
| CK12 | Dual-diaphragm, edge-terminated, multi-chambered design. | Open, airy, detailed and spacious. | Multi-pattern operation when paired with suitable circuitry. | Historic and modern CK12-labelled capsules can differ substantially. |
| K47 | Large-diaphragm capsule family associated with classic U 47-style microphones. |
Often described as full, solid and present. | Commonly cardioid or switchable variants, depending on the microphone design. |
“K47” covers multiple historical and modern implementations. |
| K67 | Dual-diaphragm design associated with the Neumann U 67 family. | Detailed, controlled and adaptable to circuit equalisation. | Multi-pattern operation in suitable microphone designs. | The capsule response is shaped by the microphone circuit and acoustic system. |
These descriptions represent broad design and tonal associations rather than fixed rules. Diaphragm tension, backplate geometry, acoustic equalisation, electronics, transformer, headbasket and microphone placement can all affect the final sound.
Is a CK12 capsule a good choice for a microphone build?
A CK12-style capsule can be a strong choice for a C 12- or ELA M 251-inspired build, particularly when the design calls for multi-pattern operation and an open, detailed presentation.
Compatibility must be checked rather than assumed. The capsule’s physical mount, wiring, polarisation requirements, circuit, headbasket clearance and power supply all need to suit the build.
BeesNeez Pro Audio manufactures CK12-style capsules in Australia, including brass multi-chambered versions and variants using insulated aluminium diaphragms.
How is a CK12-style capsule used in recording?
Vocals
A CK12-style microphone can suit vocals when you want intelligibility, air and a clear sense of space.
Begin at a moderate distance with a pop filter, then listen for sibilance and room reflections. Moving closer may increase intimacy and low-frequency proximity effect, but it can also exaggerate plosives and make the top end feel more assertive.
Acoustic guitar
For acoustic guitar, try aiming toward the 12th fret rather than directly at the sound hole. This can preserve string detail while reducing excessive boom.
If the recording sounds too bright, change the angle or position before reaching for equalisation.
Piano, strings and overheads
The CK12’s associated clarity and transient detail can be useful on piano, strings, drum overheads and room microphones.
Multi-pattern operation can help you alter the balance between direct sound and room sound. In cardioid mode, the microphone reduces pickup from the rear and captures a more focused sound. Omni mode can produce an open, natural result in a good-sounding room, while figure-eight can be useful when sound from both the front and rear is intentionally part of the recording.
Room and ambience recording
The room becomes part of the result.
A CK12-style microphone may reveal attractive ambience in a balanced acoustic environment, but it will also reveal flutter echo, harsh reflections and background noise. Listen to the room before choosing the pattern.
Common CK12 misunderstandings:
“Every CK12 capsule sounds the same.”
No. The name identifies a design family or historical association, not a single universal frequency response.
“The capsule alone creates the C 12 sound.”
No. The capsule is central, but the complete microphone system also includes the circuit, transformer, headbasket, power supply and mechanical construction.
“A dual-diaphragm capsule is automatically multi-pattern.”
No. Multi-pattern operation requires compatible circuitry and control voltages.
“A modern CK12-style capsule is an original AKG CK12.”
Usually not. A modern capsule may recreate important mechanical and acoustic principles while using different materials, manufacturing methods or tuning.
“Airy always means better.”
No. Air and detail can be valuable, but the best choice depends on the voice, instrument, arrangement, room and desired mix position.
Summary
A CK12 capsule is a historically influential dual-diaphragm condenser capsule design associated with the AKG C 12 and other classic European microphones.
Its edge termination, brass-ring construction and multi-chambered acoustic geometry helped provide flexible polar-pattern operation and the open, detailed character often linked with CK12 microphones.
The most important practical lesson is that a capsule is part of a complete microphone system. The circuit, transformer, headbasket, tuning, room and placement all shape the recorded result.
