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How beyerdynamic’s M Series Microphones Are Made

The M People By Sam Inglis
Published November 2023

The M People

We visit the German factory where beyerdynamic’s classic microphones are still handmade in exactly the way they always have been.

With centenary celebrations planned for next year, beyerdynamic have a good claim to be the longest‑established manufacturers of audio equipment in the world. Founded in Berlin by Eugen Beyer, their initial products included cinema loudspeakers, and as early as the 1930s they were already making microphones and headphones. After the Second World War, beyerdynamic relocated to Heilbronn, north of Stuttgart, where they remain to this day.

Eugen Beyer was a good friend of Georg Neumann, and the two had an informal agreement whereby their respective companies would focus on different design approaches. Neumann devoted himself to perfecting the capacitor microphone, whilst beyerdynamic specialised in electrodynamic devices: moving‑coil microphones, headphones, loudspeakers and ribbon microphones. The company’s track record for innovation in this field is second to none, and they still employ two full‑time staff devoted to prototyping and exploring new designs.

The path from ground‑breaking design to established classic was also a relatively short one for many beyerdynamic products. The iconic white, rectangular DT 100 headphones, for example, have been studio staples for decades, and few other microphone manufacturers can list as many genuine classics in their current ranges.

A rebranding exercise in the 1990s saw some of beyerdynamic’s studio microphones added to the TG (“tour group” or “touring gear”) line, with the M 88 and M 201 for example becoming the M 88 TG and M 201 TG respectively. This year, the range has been refreshed again. The TG appellations have been removed from the M 88 and M 201, and beyerdynamic are now promoting their classic designs as the M Series. The aim is to shift the focus back onto the timeless quality of these designs, and in particular, their heritage as studio tools. To celebrate the relaunch of the M Series, I was invited to Heilbronn to see how these classic mics are assembled — a process that, in some cases, has not changed for 60 years or more.

All Systems Go

Thorsten Bender is beyerdynamic’s Production Director.Thorsten Bender is beyerdynamic’s Production Director.

As Production Director Thorsten Bender explains, it is a key selling point of most beyerdynamic products that they are made in Germany, and for this reason, “system production” for professional headphones and the majority of microphones happens entirely within the plant. What this means, in effect, is that every aspect of manufacturing that makes a difference to the sound or the performance of a product takes place in Heilbronn, from the component level up. Of the 350 or so people employed at Beyer’s headquarters, 230 are directly involved in production, and the breadth of operations here is remarkable.

One thing that’s very striking about the beyerdynamic factory, and indeed those of other microphone manufacturers I’ve visited, is that the people building the products are all women. In fact, Thorsten says, there’s not a single man among the hundreds of workers employed in the manufacture of beyerdynamic mics or headphones. On joining the company four years ago, he was invited to try his hand himself and was politely told “You’ll make a better manager than a worker!”, and his experience is apparently typical: very few men, he says, have the fine motor skills required to reliably assemble small, complex and highly delicate items to an incredible degree of precision.

Even those who do have the requisite natural gifts require a fair amount of training and experience to get up to speed. A typical task might take four to six weeks to learn to perform competently, and there may be many such tasks in the production of a single item. To make production flexible enough, all factory operatives need to know how to do all of these tasks, so full training can take a year or more. The most specialised and most highly skilled workers of all are the five women who handle ribbon microphone production.

Vintage Modern

Introduced in 1957, the beyerdynamic M 160 ribbon microphone is the oldest product in the company’s current line‑up. When it was developed, it incorporated several technological breakthroughs that are still unique today. By stacking two short ribbons on top of each other, beyerdynamic were able to make the ribbon motor very small without sacrificing sensitivity. A unique corrugation process allowed the ribbons to move pistonically in response to vibration, while the addition of a plastic waveguide further increased sensitivity and improved the high‑frequency response. And by connecting the back of the ribbon motor to an acoustic labyrinth, beyerdynamic were able to modify its native figure‑8 polar pattern to give a hypercardioid response.

To corrugate and shape the ribbon, a small sheet of foil is clamped into this jig, with the excess cut away using a razor blade.To corrugate and shape the ribbon, a small sheet of foil is clamped into this jig, with the excess cut away using a razor blade.

Microphone Product Manager Milena Baur.Microphone Product Manager Milena Baur.The M 160 and its figure‑8 sibling, the M 130, remain in the beyerdynamic catalogue more than 60 years later, and are still produced almost entirely by hand, using the same toolings and techniques. The ribbons themselves, for example, are shaped and cut using an ingenious method I haven’t seen elsewhere. A small sheet of aluminium foil is clamped into a guillotine‑type device with flat jaws that form a template, stamping the distinctive corrugation pattern into the foil. A razor blade is then used to cut away the excess material, so when the jaws are unscrewed, the ribbon emerges precisely the right size and shape every time. Only one ribbon can be cut at once. Measuring perhaps 20mm by 2mm and impossibly thin, they have effectively no mass, so as Microphone Product Manager Milena Baur points out, ribbon motor assembly is definitely a job that can’t be done with the window open!

The M 160 motor is particularly complex, and is put together entirely by hand. Once the frame is bolted together, the first of the ribbons can be glued in place. This is done by eye, to an almost unbelievable level of precision — the clearance between the edges of the ribbon and the magnets is a 10th of a millimetre. Not only must the ribbon sit exactly centrally in the gap, but it must also be tensioned correctly, both of which are achieved by sliding the ends of the ribbon around whilst the glue is still wet. Once this is done and the glue is dry, a metal spacer is added at either end, and the second ribbon is glued in place, the gap between them being less than a millimetre.

A worker inspects the alignment and tensioning of the ribbon assembly in an M 160 motor.A worker inspects the alignment and tensioning of the ribbon assembly in an M 160 motor.Every other aspect of ribbon‑mic production is carried out by hand to a similar level of detail, exactly as it has been since 1957. The baskets, for example, are made in‑house from layers of steel mesh — three for the M 130, four for the M 160 — optimised to protect the ribbon from wind blasts without colouring the sound. The M 160’s tubular body houses the acoustic labyrinth that helps to shape the polar pattern, which is an equally complex design. Construction of the M 130 is even more involved, thanks to the large spring‑like structure that provides the magnetic flux return path around the motor. Every individual M 160 or M 130 is the result of several hours’ work, and given that this takes place in a high‑wage economy such as Germany’s, it’s surprising that these mics are still as affordable as they are. The unique design and skills involved in their manufacture also mean that, until now at least, no‑one has been able successfully to copy them.

M & M

The beyerdynamic M Series also includes a measurement microphone, the MM 1; two small‑diaphragm capacitor mics, the MC 930 and MC 950; and two very well‑known moving‑coil mics, the M 88 and M 201. Sadly, the MC 840 large‑diaphragm mic was discontinued a few years ago.

All of these mics boast a lengthy history, with the M 88 and M 201 dating back to the ’60s and ’70s respectively. And they all share with the ribbon models the fact of being very largely handmade. Both capacitor mics use the same capsule: a conventional, but not simple, true capacitor design that is built up by hand, even down to the process of attaching the diaphragm. To give you an idea of the fine tolerances at play in microphone construction, the only difference between the cardioid MC 930 and supercardioid MC 950 is the inclusion or otherwise of a single spacing washer — this alone is enough to modify the polar pattern.

Being phantom‑powered capacitor mics, the MC 930 and 950 have active circuitry, and this is one aspect of production that is highly automated. Printed circuit boards for these and many other beyerdynamic products are produced on high‑tech machines: a pick‑and‑place robot populates the boards with surface‑mount components before wave soldering fixes them in place. Even in this very modern, automated environment, though, there’s still a role for human hands and eyes. Larger components such as the MC mics’ switches must be attached manually, and as well as electrical testing, each completed PCB goes through a rigorous checking process whereby a scanning machine flags up visual discrepancies between the unit being tested and a reference sample, and a worker judges whether these are significant enough to merit rejection.

Keep On Moving

Like the ribbon mics, the M 88 and M 201 are still made in exactly the same way as they always have been; and, once again, it’s a highly skilled, labour‑intensive process. Although both are moving‑coil dynamic mics, the diaphragm of the M 88 is more than twice as wide as that of the M 201, and the two microphones are therefore more different in sound and application than their specs might suggest. As in the older headphone designs (see box), the diaphragms are formed from a polyester film called Hostaphan which, fortunately, is still available today. Once cut and formed into the appropriate 3D shape, this is heat‑treated to set it, whereupon the voice coil can be attached — by hand, naturally.

The entire transducer assembly is quite complex, incorporating the acoustic labyrinth that controls the polar pattern as well as a second humbucking coil and an inductor to minimise noise and interference pick‑up. One of the most crucial and challenging moments in the assembly process is that of attaching the diaphragm, with its voice coil glued in place, to its mount. The voice coil must sit precisely in the middle of a narrow circular gap, so that it can move freely yet be close enough to the surrounding magnet to generate a healthy signal level.

Even processes such as fitting the protective gauze and name bands to the body of the MC mics are carried out by hand.Even processes such as fitting the protective gauze and name bands to the body of the MC mics are carried out by hand.

There are dedicated test environments on the factory floor for some models, but ribbon mic performance needs to be checked in a full‑sized anechoic chamber.There are dedicated test environments on the factory floor for some models, but ribbon mic performance needs to be checked in a full‑sized anechoic chamber.The use of strong magnets within these mics introduces production difficulties of its own. Because the metal must be magnetised prior to construction, there’s a constant risk of ferric dust and debris being attracted, and it only takes a tiny particle of iron to compromise performance. Thorsten Bender says that Beyer’s designers have experimented with magnetising the metal in situ after construction, but so far they haven’t been able to achieve satisfactory results.

Testing Regime

A stringent testing regime is fundamental to quality control. For each M Series model, beyerdynamic have a library of ‘golden samples’ from different eras that serve as references; these themselves are tested at regular intervals and, if necessary, recalibrated or replaced with new ones. Each and every production mic is measured and compared against these references to give the individual plots that are supplied to buyers, and many individual components and sub‑assemblies are tested before final assembly. It’s all part of a culture that values the company heritage without being enslaved by it. beyerdynamic haven’t stopped innovating, most recently in the consumer sphere with their high‑end Xelento in‑ears, which use a single full‑range dynamic driver rather than the more usual balanced armature design. But they know the value of their established designs, and they are keen to reiterate that any changes they are making in relaunching the M Series really are purely cosmetic.

What only a manufacturer such as beyerdynamic can offer is long‑term consistency: the knowledge that if you buy an M 88 or an M 160 today, it’ll sound exactly like the one you used in 1978.

The microphone market has changed out of all recognition since the M Series models were first introduced, and as Thorsten Bender acknowledges, good quality microphones have become a lot more affordable. But what only a manufacturer such as beyerdynamic can offer is long‑term consistency: the knowledge that if you buy an M 88 or an M 160 today, it’ll sound exactly like the one you used in 1978. “You can buy a cheap microphone from a large retailer and it can sound great,” he cautions. “But then you buy what is advertised as the exact same microphone two years later and it might be completely different!”

Making Headphones

There are two main strands to beyerdynamic’s business: headphones and microphones. In terms of volume, headphone production is by far the larger of the two, and the factory is capable of turning out several thousand drivers for a particular model in a single shift. For this reason, a certain amount of automation is involved. Nevertheless, there is still a surprising amount of skilled work done by hand, especially on models such as the DT 990 PRO.

The M Peoplebeyerdynamic’s commitment to German manufacturing is wholehearted and actually extends to the complex machinery used in “system production”, much of which was developed in‑house. The first stage in producing a headphone driver, for example, requires a precise number of turns of wire to be wound around a polished steel former and glued together to form a voice coil. Varying the gauge of the wire and the number of turns changes the impedance of the resulting headphone driver, and the machines can be set up to produce a number of different versions. Hardest to manufacture is the 600Ω driver, which uses wire thinner than a human hair.

Other custom machines cut and form the diaphragms from different types of plastic foil, and ‘cook’ them to achieve the desired level of rigidity. But on models such as the DT 990 PRO, it’s down to human beings to slide the voice coils onto the diaphragms and glue them in place, with the impossibly fine wires extending at exactly the right angles. The glue is applied using a paintbrush; amazingly, says Thorsten Bender, tests have shown that Beyer’s assembly workers are able to do this with a precision and consistency that can’t be bettered by automation.

Voice coils for dynamic mics and headphone drivers are wound on custom machines using impossibly fine copper wire.Voice coils for dynamic mics and headphone drivers are wound on custom machines using impossibly fine copper wire.

Once the diaphragm and voice coil are mated with a magnet assembly, the first of several stages of testing can begin. Each driver is tested for various qualities such as frequency, amplitude and phase response, and once assembled, each pair of headphones is also tested. The idea is to minimise waste by ensuring that defective parts are weeded out before they can reach the later stages of production, so if there’s something wrong with an individual driver, it won’t lead to a complete pair of headphones having to be thrown away or broken up. Also, faults that do occur are often down to imperfections in the acoustic material used to form baffles within the headphones, so it’s often the case that a driver that tests faulty can be rescued by replacing the baffle.

The whole system is highly data‑driven. Major elements such as driver assemblies and PCBs have their own individual QR codes, with test results being entered automatically into a database. This process has helped bring down rejection rates from 10 percent to below 3 percent. That’s no mean feat when you consider that tolerances are set so low that there’s no need for pair matching between the left and right drivers in a set of headphones.