“When a mechanic hears that sound, his heart fills with joy,“ declares Manfred Kürbis. We are observing the fully automated production line for the evolution series of dynamic microphones, affectionately known as the Evo Line or Evo. The equipment fills an entire room at the Sennheiser headquarters in Wedemark near Hanover. It fills the space both physically and acoustically. The room is long and narrow, the production line almost fills the entire space. The key component of the system—the transducer production unit—strikes an imposing figure when visitors first enter the room. Here, the membranes are punched out from a plastic film and smoothly transferred to the rotary table. These membranes are then connected to the voice coils that are wound at the adjacent workstation. The rotary table rotates one notch allowing further assembly steps to take place. On reaching the end of the machine, the finished transducers are forwarded to automatic quality control. The transducers must pass an initial acoustic test before being further processed and continuing on to the assembly unit directly behind. Any transducers that fail the test will end up in the crusher.
Fully automated production systems are now available at various Sennheiser production locations, in Albuquerque, in Tullamore and of course at the headquarters in Wedemark. The Evo Line was the first of its kind in 1997.
In the 1990s, Sennheiser was faced with the question of how to deal with price pressure from Asia. Production in Germany is expensive; the greater the number of workers, the greater the outlay. The only way to keep production of the dynamic capsules in Germany was to switch from manual or semi-automatic assembly to fully automated production systems. That was a real technical challenge. There were no prototypes for a system like the one Sennheiser had in mind. The system had to be developed in-house. The Sennheiser engineering workforce had wildly different opinions on the matter. Some believed it was totally impossible, while others were up for the challenge. A team of motivated engineers set about implementing the idea of automating the production of dynamic microphones. It was a truly pioneering feat since there was nothing comparable and no points of reference to start from.
The engineers eventually found similar production techniques, the use of small components and high-precision systems, in a different industry altogether—the watch industry. In order to gather information from watch manufacturers, the engineers spent a lot of time traveling to southern Germany, and developed the system together with a manufacturer according to the process requirements. The work processes that were part of manual microphone production were transferred to automated systems. “Sennheiser already had a semi-automatic transducer production unit. This consisted of a rotary table that the employee could rotate using a foot pedal. The same concept was used to build the transducer production unit,” recalls Axel Bergmeier. The complex transducer production unit in the Evo Line therefore also follow the rotary table principle, which is why the footprint of the system is so large. “We found other solutions in more modern production facilities. But before we could do anything, we had to realize that fully automated production requires a rethinking of processes. We gained a lot of knowledge from this first system that would help us in the future, namely that the thinking behind automated production is very different to that of purely manual assembly”. And, of course, the Evo Line was simply the first step in the automation process. “From 2004 onwards, we erected fully automated systems for headphone transducer production in Ireland. It was a gradual process, but we now have five systems in operation similar to the Evo Line. The latest feat of engineering is the MDA line in the main plant which is used to produce dynamic miniature transducers for in-ear headphones. This is the latest generation of high-tech production technology, superior in quality and speed to the Evo Line.” Yet if we hadn’t dared to take that first step 22 years ago, who knows where Sennheiser would be today?”
If you ask different members of staff to describe the launch of the Evo Line as the first fully automated system, the responses will vary greatly. The first machines were built at the end of 1997. The system was designed to manufacture a completely new product, the evolution microphone. The product was new to the market but was already heavily advertised before the production system was complete. We couldn’t deliver for ages because the system wasn’t working properly,” some employees will tell you. While those who were working on site say: “Actually, we got the system up and running quickly. Things were a little bumpy to start with but then we reached 80% of our target production pretty quickly. With further reworking and fine adjustments, the Evo Line became even more effective. ” But was it just a case of setting up and switching on? It’s not that easy with a fully automated manufacturing system. Sennheiser has a strong focus on quality, therefore quality products should be supplied. When it comes to highly sensitive audio equipment, there are extremely narrow margins in the assembly processes. A fine tolerance that is imperceptible to the human eye can have a huge effect on the acoustics. The new Evo Line had to be calibrated first. Many different production steps had to be timed to the tenth of a second to ensure that everything ran smoothly. Calibrate, test, calibrate, test: Something like that takes time, because of course the engineers were only satisfied when the test results were perfect.
Since it was not known how popular the new microphones would be on the market, the Evo Line was built so that it was possible to switch between the production of microphone and headphone transducers on a day-to-day basis for economic reasons. Within a few years, the evolution microphones proved to be a bestseller and, with the commissioning of the first production line in Ireland, the Evo Line produced its last headphone transducer. “I distinctly remember it was the HDC 55 for Lufthansa,” recalls Michael Nickel, “since then we have only been building microphones here.” To date, the Evo has supplied 750,000 dynamic headphone transducers
The Evo Line produces around half a million transducers and microphones every year. The transducer production machine not only produces components for evolution, but also the basic modules of other dynamic Sennheiser microphones, such as the MMD 9235—also known as the Rockheiser. “The Evo Line is unique. It was built for Sennheiser and over the years the engineers have continued to optimize the processes, make changes, replace parts, and so, of course, the machine is very different to the one designed by the manufacturer in 1997. It is truly unique.” The Sennheiser mechanics are solely responsible for the care, maintenance and upkeep of the system; after all, they know the old girl best. During each shift there are two technicians to carry out maintenance tasks on the Evo Line. And believe me the lady is demanding! The technicians really have to rely on their dexterity to ensure that everything is fine-tuned perfectly. Everyone who works here knows the system inside out. “When you come in, you can immediately tell from the sound whether the machine is running smoothly or whether something is wrong. Even before the machine displays the first error message.”
Machines make noise, and the Evo Line also has a sound all of its own. “Everyone knows exactly what the system should sound like, and any irregularities are immediately noticeable. Noises that you wouldn’t expect to hear, or a rhythm that is slightly out.” Numerous video monitors are used to observe the system. “There are also visual signs that quickly tell us if everything is not running smoothly. We can then intervene before any damage occurs. You can’t just turn on a system like the Evo Line and leave it to its own devices; it needs constant care and attention,” explains Manfred Kürbis,“ and,” he adds with a smile, “sometimes it just needs a bit of tender loving care.”