Development Manager Markus Wolff cannot hold back a grin as he turns to the front door. “Staff only” is written on a big sign. Photos and mobile phones are prohibited from this point on. “Many people believe that loudspeaker development has gone as far as it can go. They think that everything about them has been known for decades,” says the system architect. “But that’s simply not true.” After he says that, he turns around and opens the door to a world in which no certainty is taken for granted. The tour through the studio monitor development department begins.
Preparing laser measurement of a prototype: Neumann engineers measure the precision of the behaviour of new driver diaphragms at thousands of measuring points. Do all parameters fit the simulation?
A wide corridor, office doors, computers, and many screens, beside which there are almost always loudspeaker components. “A loudspeaker is always a trade-off in every possible component,” explains Markus Wolff on the way to the electronics development. Taken on their own, typical characteristic values such as frequency response, power, inherent noise, and distortion thus say nothing about the quality of a loudspeaker. “It’s our job to find the best trade-off for each application and to weigh all these parameters appropriately.” That’s why the expertise of each colleague in every technical area is so important. In the end, the fine art that distinguishes Neumann monitors only emerges in the interaction of mechanics, electronics, and drivers. He smiles again and says, “In principle, as a system architect, I am the master of ceremonies for this interaction.” It takes some two to three years for a new system to be developed and made available in all parts as a prototype. On the way to this point, there is little room for compromise in the selection and design of the components: how the drivers are built, how the housing is made of which materials in which technology, how the electronics work: every detail is created from the team’s designs, nothing is off the shelf.
Electronics: “Thinking beyond the data sheet”
We arrive at the electronics lab. It quickly becomes clear that the team is quite proud of the extraordinary performance of the analog power amplifiers. The ultra-compact KH 80 DSP, a digital monitor, was recently added to the series range. But how do you achieve the same acoustic level with a digital power amplifier? It offers higher efficiency, but is far more difficult to handle in terms of distortion, intermodulation, inherent noise, and many other values. “Those are major problems to be overcome,” electrical engineer Johannes Storch muses. For the KH 80 DSP, he developed the complete power amplifier anew. It provides 115 watts for the woofer and 70 watts for the tweeter — and is only marginally bigger than a matchbox. At the same time, it provides safe energy for any transients that the drivers are to follow afterwards. To suppress the high-frequency switching voltages of the switching power supply unit, the high signal edges, and other interference — in order to keep them out of the audio path — that is where art comes in. Especially if the design is to be cost-efficient and the price of the device is to be kept out of the stratosphere. The solution: thinking outside the box. “In this case, think beyond the data sheet,” as Johannes Storch says with a smile. The developers therefore used some standard components differently than intended. And then there are details such as the heat sinks: Inside the speaker, the ribs act like tuning forks and are susceptible to vibrations. In the worst case scenario, they could cause audible ringing. To prevent such effects from adding up to a peak in the first place, each individual rib is cast in such a way that it has a frequency that cancels itself out inside the housing.
Tolerances? “You need to know them and take them into account.”
In general, every single component of the electronics remains in focus. A Monte Carlo simulation runs on a computer next to the electronics board. It calculates the effects of the tolerances of all components in the electronics and shows the sum of all parameters over which they have an influence. Markus Wolff points to a narrow range: More than 0.1 dB variation? “We accept whatever lies within this tolerance band but nothing outside of it.”