Microphones shootout. Road to Neumann U47

Thinking about the uniqueness of the Neumann U47, memorable sports performances, legendary tracks by musicians in their prime, and inventive minds that changed the world come to mind.

Why not make peace with the unicity of a moment, a performance, or an athletic feat? Why not draw inspiration from exceptional singularity to move forward and do better, rather than being tied to it with rogue nostalgia and lamenting not having lived in the right place at the right time?

The U47 is a unique microphone, designed to cope with what post-war Germany offered, namely a crumbling, non-centralized electrical grid, sometimes distributed in AC and sometimes in DC. It houses a purpose-built vacuum tube, the VF14, to power filaments at 55V but intentionally underpowered at 35V, fed directly from the only available power rail (105V at 40mA) through a resistor that dissipates about 3 watts and heats up like a crematorium oven (which is why it's often seen mounted upside down to prevent all this heat from damaging the PVC diaphragm, never used again since then).

No sane and normally functioning engineer would ever do something like this, and indeed, it's a case of making the best of a bad situation, technical flair, and a bit of luck here and there. None of the German designers sat down and said, "Now I'll build the best microphone in history." They made a microphone with what they had, produced about 6000 units, and then good night—VF14 gone, post-war era over, enter the U67, another unbeatable gem from Neumann, this time not due to the singular circumstances that led to its conception but for the technical boldness of its design.

Nevertheless, there are around thirty models on the market, from clumsy attempts to exquisite pieces. Since the hype keeps growing, I decided to compare those that come into my lab with my all-original 1960 Neumann U47. Above all, I aim to understand where and why there's always a missing piece to reach the real deal.

Today, I write about the two new contenders on the market, the Warm Audio WA-47 Tube and the Golden Age GA-47, which I carefully measured and listened to in the lab alongside Simone Coen (Chocolate Audio) and Valerio di Lella (Music Delivery). We'll compare what the manufacturers tell us with what we actually observed and heard, trying to convey our impressions.

Let's start with the listening test on vocals, with the usual mic placement as coincident as possible and the singer as centered as possible. Two takes, one soft and one with high vocal emission.

On a low-vocal-emission singing, the two microphones are almost comparable. The preference leans slightly towards the Golden Age for greater harmonic complexity and a better signal-to-noise ratio, a specification that becomes crucial on low-intensity sources. With a more powerful singing, the differences become more pronounced, and in our opinion, more in favor of the Golden Age. It tends to behave more faithfully to the original, responding to high pressures with a decent amount of harmonics that make it 'gritty' as we like it.

Between the two, the WA-47 is clearer. The Golden Age has a softer sound, more distant from the original 47 but perhaps more 'general purpose.

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These impressions are confirmed by the analysis of the frequency response, considering a full-band audio sweep at 1 meter from the source. Both clones fall short where the U47 excels, in that unique emphasis on the frequency range between 5kHz and 10kHz, which can sometimes be excessive (the U47 is NOT a general-purpose microphone). Another confirmation from the sweep responses is the additional brightness of the Warm Audio compared to the Golden Age, which lacks up to 5-6 dB in that spectrum compared to the original Neumann. Below 3 kHz, however, the three microphones are almost identical, at least in terms of frequency response.

The third analysis we conduct, subtle but crucial, is the harmonic distortion of the amplifier. The devil is in the details, and it is precisely on the harmonics that both microphones must make room for this unique and fortuitous combination of design and components that makes the U47 inimitable. The harmonic richness of the K47-VF14-BV8 combo is not replicated, not even close. Peace and goodwill.

As an incurable geek, I couldn't refrain from the technical analysis of components, assembly, and materials, and here's what I found:

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Warm Audio WA-47 Tube:

Chassis: Aluminum and power supply typical of overseas OEM’s.

Capsule: 47-style biased at 80V (an expedient that simplifies the circuit arrangement but alters the capsule's response, typically biased at 55-60 volts).

Tube: Current production JJ 5751 (a near equivalent to 12AT7), a dual triode with a slightly bright timbre.

Transformer: Custom AMI.

Components: Rather cheap, except for an output Solen capacitor.

Assembly: Industrial, PCB without solder mask (the traces will eventually oxidize).

Price: EUR 1059.

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Golden Age GA 47:

Chassis: Brass and iron basket, both crafted very well.

PSU: Original design.

Capsule: Style 67 (likely from Oktava), biased at 60V.

Tube: Telefunken EF800 connected as a triode.

Transformer: Dual-coil, unbranded.

Components: Quality.

Assembly: Handcrafted, somewhat naif wiring.

Price: EUR 1514.

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Are they beautiful microphones? Yes. Do they sound good? Yes. Do they sound like the Neumann U47? No.

Between the two, I appreciate the Golden Age more for several reasons, perhaps foremost because the brand's communication revolves around a new U47-inspired condenser microphone, while Warm Audio claims not to hear the difference between its young offspring and the old grumbler. We heard it, and how.

The clones, replicas, wannabes, pretenders—pick the synonym you prefer because any attempt to reproduce that unique peculiarity will be in vain. Not because there aren't skilled designers, but because that idea made sense in that context. It's the product of needs and circumstances that are now unrepeatable, and it's right for it to stay there, in the Olympus of singularities, alongside John Lennon's "Imagine" and René Higuita's scorpion kick in '95.

Joe Chiccarelli, Braingasm & The Pirate Sessions

“The ribbons sounded great on electric guitars and drums. Really big sounding with rich low end. Perfect for loud rock guitars. 
On drums the mics were well balanced and full sounded.
We also used the FET condenser on acoustic guitar and it delivered a clear and very forward sound.
The mics really helped out the sessions. We appreciate it immensely,
Well done.  Joe C”

— Joe Chiccarelli

Rome is like a big city with a small-town soul—you know it when the super-secret news of the day spreads from Salaria to Eur in just a couple of hours. "Oh, did you hear that Joe Chiccarelli is in Rome?"

If you're not in the sound business, you immediately think it's the new acquisition for AS Roma football Club. But if you are, the excitement is inevitable because Joe is a gem in the industry, with a résumé full of Grammys and stellar collaborations (from Frank Zappa to U2, Strokes, and so on).

Joe is at Forum Music Village, the most beautiful recording studio in Italy, created by “Il Maestro” Ennio Morricone, producing Morrissey's latest album (and probably dealing with all the tough nut to crack that our sad boy from Manchester might throw at him), in what he himself, once it's all done, has dubbed 'The Pirate Sessions.'

I schedule a meeting with him, to get to know him, have a chat, and, most importantly, to see if there's a chance to get him to try out some Braingasm microphones. He agrees, enthusiastically, and welcomes me during the soundcheck. He halts everything, asks for some time, and sits down to talk with me. "Hey, show me what you've got." He's a kind man, an artist, and a top-notch professional—the kind who doesn't need to prove anything to anyone, isn't resting on laurels, and is still open to discovery and experimentation.

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Joe takes my Deluxe 47 and sets it up as a mono room mic on the drums. He cranks up the gas (on the Neve VR Legend at the Forum), starts tweaking with Gain, Compressor, and EQ, squeezing out every nuance from the microphone. He gives a thumbs up, smiles approvingly, and continues the check. I finally relax and introduce him to the Braingasm Vintage Ribbon.

Joe adds another dose of enthusiasm and tells me he'll try it on Jesse and Boz's guitars.

At this point, I'm already completely satisfied. I leave just before becoming a pain in the neck, telling him we'll meet again after everything is done to pick up the microphones and get some feedback.

I come back just before the teardown, Moz has already been repatriated, and Joe is finishing up some things. I find my Ribbon on Jesse Tobias's Divided by 13, and Joe tells me he used it throughout the session, replacing his usual Royer R 121. He also really appreciated the Deluxe 12 on the acoustic guitars.

Session Test Microfoni a Condensatore

Holidays? Pokémon? Pornography?

Much better. A total session where we roll out the entire Braingasm catalog alongside the finest microphones in circulation.

The goal of this test isn't to determine who's better or worse, but simply to listen, evaluate, and discuss nuances, tones, spatiality, and attitude, setting an upper limit and understanding 'how far we can go' in designing a good studio microphone.

We spent a very nerdy day at Avalon Studio in Montefiascone, in the company of Luca Gentili and Alfio Scoparo, listening to all the Braingasm condenser microphones on vocals, guitar, and drums, comparing them with the best from Neumann, Schoeps, and AKG.

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This is the list of microphones we tested:

Neumann U 47 - 1960

Neumann U 67

Neumann U 87 Ai

AKG 414 ULS

Schoeps CMC 5

comparing with our Tube 47 and Soviet 67 , plus the J-FET’s Deluxe 12, Deluxe 36, Deluxe 47

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We can't wait to share all the news for the upcoming year, including a new lab, collaborations with the best artisans in Rome, and projects in the pipeline such as studio outboard gear and preamps...

Meanwhile, enjoy your holidays. It's been a year full of achievements, all thanks to you incurable enthusiasts.

See you in September,

Rock 'n roll

Teo.

Neumann large diaphragm condenser microphone capsules.

While sending some condenser capsules to my trusted workshop for restoration, I realized I had in my hands the history of studio microphones:

An original M7 and various editions of the K87 and K67, all genuine Neumann/Gefell specimens, the reference sound of music production from the '50s to today.

Fascinating, inimitable, beautiful even just to look at. These capsules are the result of meticulous and distinctive research by German engineers, and if they have had no rivals for over 60 years, the reason is simple: they sound damn good.

Each capsule characterizes a condenser microphone according to its distinctive tone, and although the design of the amplifier circuit continues to change (tubes, transistors, back to tubes, with and without transformers, etc.), our favorite large-diaphragm capsules survive this constant evolution. It's now more a son of marketing than real technical needs.

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This is an M7 capsule, a large-diaphragm condenser from Neumann/Gefell dating back to around 1957.

The design is the work of engineer Georg Neumann himself, who, perhaps somewhat unwittingly, revolutionized the way we record and listen to music with this project.

The double membrane is made of PVC (Poly-Vinyl-Chloride), a liquid polymer plastic deposited on a glass support to create an extremely thin membrane, approximately 8 - 10 micrometers thick.

Unlike modern Polyethylene membranes (such as Mylar and Hostaphan), which also come in thicknesses of 3 or 6 microns, PVC is much more challenging to work with and is more prone to degradation over time. For this reason, it's very difficult to find an original M7 capsule that has retained its characteristic tone.

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In the 1960’s a new capsule was introduced, called the K67, the beating heart of the new Neumann condenser microphone, the U67.

As Telefunken ceased production of the VF14 tube (Neumann was the sole buyer, and the costs for the factory were no longer sustainable), engineers set to work to launch a new condenser microphone model, the U67, which quickly became the reference microphone in recording studios worldwide.

The transition to Mylar had already occurred between the M7 and the K47, as well as the membrane mounting system (screwed instead of glued). Additionally, unlike the K47, which shares the same drilling pattern with the M7, the new backplate has an innovative design. These features give the microphone a sound very different from its predecessors. The K67/K870 is the same capsule found in modern U87 Ai studio microphones.

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At the end of the 1960s, with the advent of transistor technology, a new studio condenser microphone, the famous U87, was introduced.

For various design improvements, a new capsule called K87 was introduced. It shares the same drilling pattern as the K67, but this time divided into 2 electrically isolated backplates. In fact, it's the only capsule with 4 contacts instead of 3 (2 membranes and two fixed electrodes). In essence, the K87 is exactly a K67 with the two backplates isolated (this means that if the two electrodes of an 87 are electrically contacted, a 67 is obtained, but the reverse is not achievable).

Missing from the lineup are the K47 and K89, mounted respectively on U47/M49 and U89.

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The capsule is the beating heart of a microphone, being largely responsible for its tonality and often the component that determines its final cost, at least for the handmade condenser microphones we design and produce at the Braingasm laboratory. For more refined tastes, we choose M7 capsules (Thiersch Red Line in Mylar or original Microtech Gefell PVC) for projects in the style of the U47, or Tim Campbell for projects in the style of Elam or C12.

Some of these K67 and K87 capsules that will be restored are part of an ambitious project in collaboration with a highly talented sound engineer with whom we are designing custom signature models. Stay tuned!
 

The fine art of building a ribbon microphone - Pt.1

'The tool is half the master'... always true, whether you're a carpenter, a farmer, or a surgeon. In our case, the right tools are indispensable, and the ribbon microphone doesn't forgive.

We're working on a micrometric scale; the aluminum ribbon is 1.8 microns thick. To give you an idea of what we're talking about, here's a list from Wikipedia that illustrates the order of magnitude in question with some examples:

1-10 µm: Typical diameter of a bacterium

1.55 µm: Wavelength of light used in optical fibers

6-8 µm: Diameter of a human red blood cell

6 µm: Anthrax spore

7 µm: Thickness of a spider web thread

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Cutting a bacterium in half is already a difficult concept to visualize, let alone being careful not to damage its edges, crumple it, or make it fly away with a sigh, and so on.

For an easy-to-imagine comparison, consider that household aluminum foil has a thickness ranging from 40 to 80 microns, which is almost 50 times greater than our microphone ribbon.

But cutting is just the beginning of the work. Once the ribbons are cut correctly (4 mm wide and 100 mm long), the next phase is corrugation. This system allows the ribbon to expose more surface to the sound field than a flat ribbon. It also increases its elasticity and resistance.

We proudly present our super vintage (and, above all, artisanal) machine for corrugating the ribbon, built with used Meccano parts.

The next phase, once the ribbon is cut and corrugated, is its placement inside the structure, called the motor.

The ribbon motor is a simple mechanical system consisting of two permanent magnets glued to a metal structure.

We'll cover the housing and tuning phase in another post. For now, let's conclude our beloved scientific talk.

The ribbon microphone exploits the physical law of electromagnetic induction, the same wonder of physics that brings dynamic microphones and loudspeakers to life. In practice, the aluminum ribbon is suspended in a strong magnetic field and vibrated by the surrounding sound field. Due to this physical law, a tiny electrical current is generated at the ends of the ribbon, consistent with the incident pressure wave. This current is then extracted, converted through an output transformer, and made available on the microphone's balanced output.

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