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| WA-CX12 open on the bench, click to enlarge |
What Is the WA-CX12?
The WA-CX12 is a multi-pattern tube condenser microphone built to emulate the AKG C12’s natural, balanced sound. It’s a versatile workhorse, ideal for recording vocals, acoustic instruments, and room ambience, with a design that pays homage to the original’s aesthetic and sonic character. Warm Audio’s goal was to make the C12’s coveted tone accessible, using premium components and meticulous engineering to deliver professional-grade performance at a fraction of the cost of vintage alternatives.
If you've experimented with DIY builds using donor bodies like the Apex 460, the Warm Audio CX-12 is nothing like those others. The moment you pick up the CX-12 you can feel a big difference, the CX-12 is a beast of a microphone weighing in at two-pounds and seven-ounces (mic only). The body is larger, longer and machined from brass, beautifully finished too, it's like a microphone work of art. Inside you'll find premium components and that big, meaty, old school AMI output transformer, made in Kansas. A larger output transformer in a tube mic like the WA-CX12 typically enhances low-end depth, high-end clarity, and overall headroom, delivering a more open and neutral sound. A smaller transformer trades some of these qualities for a more colored, character-driven tone, which can be equally valid depending on your creative goal. The Gotham cable Warm Audio uses for all their tube microphone connections feels tough and durable, deserving its reputation in the world of premium quality wire and cable.
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| CX-12 Output Transformer, click to enlarge |
WARM AUDIO CX-12 Technical Specifications
- Frequency Response: The WA-CX12 boasts a frequency response of 30 Hz to 20 kHz, capturing a wide range of sonic detail. Its response is mostly flat up to 2 kHz, with a slight dip followed by a gentle treble boost between 5-10 kHz, giving it a smooth, open top end and vibrant midrange. This profile enhances clarity without harshness, making it flattering for vocals and instruments alike.
- Pickup Patterns: The microphone offers nine polar patterns—cardioid, omnidirectional, figure-8, and six intermediate patterns—selectable via the external power supply. This versatility allows it to adapt to various recording scenarios, from solo vocals to stereo miking techniques like Mid-Side or Blumlein.
- Technology and Components: At its core, the WA-CX12 features a custom edge-terminated, all-brass CK12-style capsule, designed to replicate the original C12’s dual-backplate design. The capsule uses a 6-micron gold-sputtered Mylar diaphragm for sensitivity and detail. A premium 12AY7 vacuum tube provides warmth and harmonic richness, while a custom TAB-Funkenwerk (AMI) USA output transformer ensures a full, natural sound with robust low-end and polished highs. Premium capacitors and a no-solder-mask PCB minimize noise and crosstalk, enhancing clarity.
- Diaphragm Size: The WA-CX12’s large-diaphragm capsule measures approximately 34mm in diameter, consistent with classic C12-style designs, contributing to its ability to capture nuanced performances with depth and presence.
- Tube: The microphone employs a hand-selected 12AY7 vacuum tube, chosen for its low noise and warm, musical character. This tube complements the capsule and transformer, adding a creamy texture to the signal path.
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The History of the AKG C12
The AKG C12, introduced in 1953 and produced until 1963, is one of the most revered microphones in recording history. Designed by AKG in Austria, it was a large-diaphragm tube condenser with a groundbreaking CK12 capsule—a dual-backplate, edge-terminated design that allowed nine polar patterns via a remote switch (the S12 controller). The C12 used a 6072 tube and a custom transformer, delivering a sound that was transparent yet warm, with a smooth top end and clear midrange. Only about 2,500 units were made, making originals rare and highly sought-after today.
The C12 was a studio staple at places like Abbey Road, where engineers used it on everything from vocals to orchestras. Its ability to capture natural, uncolored sound with a touch of elegance made it a go-to for mid-20th-century recordings. For example, Geoff Emerick famously placed a C12 in figure-8 mode to record Paul McCartney’s bass amp for The Beatles’ Sgt. Pepper’s Lonely Hearts Club Band, capturing both the direct sound and room ambience. Its versatility and pristine quality cemented its status as a legend.
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| CX-12 Vacuum Tube, 12AY7, click to enlarge |
Why Was the AKG C12 So Popular?
The C12’s popularity stemmed from its innovative design and exceptional sound. The CK12 capsule was a marvel, offering flexibility with nine polar patterns while maintaining consistent frequency response and sensitivity across them. This made it adaptable to countless recording scenarios, from intimate vocals to distant room miking. Its sound—open, airy, and balanced, with a gentle high-frequency lift—flattered a wide range of sources without sounding hyped or artificial. The tube circuitry added a subtle warmth, enhancing its musicality.
In an era when recording technology was rapidly evolving, the C12 stood out for its reliability and versatility. Studios like EMI and Decca relied on it for critical sessions, and its use on iconic records by artists like The Beatles, Frank Sinatra, and Ella Fitzgerald gave it mythic status. Its scarcity after discontinuation only fueled its allure, with vintage units now fetching $10,000-$30,000 or more on the secondhand market.
Notable WA-CX12 Users
While specific high-profile users of the WA-CX12 are less documented due to its relatively recent release, Warm Audio’s microphones have gained traction among modern engineers and artists. The WA-CX12’s design targets the same applications as the original C12, and user reviews praise its performance on vocals, acoustic guitars, and drum rooms. Professionals like Bryan Woolbert, a producer and engineer, have lauded its smooth mids and airy highs, comparing it favorably to vintage C12s and other high-end clones. Studios adopting Warm Audio gear often cite the WA-CX12 as a go-to for vocal sessions, particularly for pop, rock, and jazz.
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| Inside the WA CX-12 case, click to enlarge |
Is the WA-CX12 Popular?
The WA-CX12 has carved out a strong niche since its debut. It’s not as ubiquitous as, say, a Neumann U87, but it’s gained a loyal following among home studio owners, independent producers, and even some professional facilities. Its affordability—offering C12-like quality for under $1,000—makes it a standout in a market where comparable tube mics often cost two to three times as much. Online forums like Gearspace show mixed but generally positive sentiment, with users appreciating its smooth, balanced sound, especially in cardioid mode. Its versatility and build quality have helped it compete with other C12 clones from brands like Telefunken and Peluso.
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| CX-12 Power supply, connection and power supply side, click to enlarge |
Warm Audio’s reputation for delivering value has boosted the WA-CX12’s appeal. Reviews highlight its ability to rival pricier mics, with some engineers choosing it over their boutique tube models for certain tasks. Its popularity is growing, particularly among those who prioritize vintage-inspired sound without vintage price tags.
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Warranty on the WA-CX12
Warm Audio provides a one-year warranty on the WA-CX12, covering defects in materials and workmanship. Some retailers, like Vintage King and Sweetwater, extend this to two years as part of their own policies, offering extra peace of mind. The warranty reflects Warm Audio’s confidence in the mic’s build, which includes hand-inspection at their Austin, Texas headquarters.
Epilogue: A Modern Classic
The AKG C12’s limited production run of 2,500 units makes originals a treasure for serious collectors, with prices that put them out of reach for most. A vintage C12 in good condition can easily cost as much as a used car, and even then, finding one is a challenge. Fortunately, the internet age sparked a DIY microphone movement, with enthusiasts reverse-engineering classics like the C12. Companies like Warm Audio have taken this passion mainstream, crafting modern clones that deliver remarkable fidelity at accessible prices.
The WA-CX12 is a testament to this ethos. It captures the C12’s organic tone—warm lows, clear mids, and silky highs—with enough authenticity to satisfy discerning ears. That’s why I couldn’t resist grabbing a stereo pair. Whether tracking vocals, pianos, or room sounds, the WA-CX12 brings a touch of vintage magic to my recordings, proving that you don’t need a museum piece to make music that resonates.
Thanks for reading High on Technology, Good Music To You!
©April 2025 by Mark King, It's not ok to copy or quote without written permission from the author.
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| I must say, I do really like the tweed storage case the CX-12 mic system comes in |
- 12AY7:
- Also known as 6072A in some contexts, but distinct from the 6072.
- Lower gain (mu ≈ 40-45) compared to tubes like the 12AX7.
- Warmer, smoother sound with less noise and a more gradual breakup, making it ideal for clean, musical applications.
- Commonly used in modern mic designs (e.g., Warm Audio WA-CX12) and guitar amps for its balanced tone.
- Plate voltage typically around 250V, with a heater current of 150mA (series) or 300mA (parallel) at 6.3V/12.6V.
- 6072:
- A specific dual-triode tube, often associated with the original AKG C12 microphone.
- Slightly different electrical characteristics, with a focus on ultra-low noise and high linearity for studio-grade audio.
- Gain is similar to the 12AY7 but optimized for microphone circuits, with a design emphasizing clarity and transparency.
- Rarer and more expensive due to its historical use in vintage gear.
- Electrically compatible with 12AY7 in some circuits, but subtle differences in plate resistance and transconductance affect tone and performance.
