1st Place - Innovative Product Development: Front Bass project

Project details

Development engineer Rainer Albus likes music a lot. From pop to classical, all are fine as far as he’s concerned. But it was his job in the automotive sector rather than his passion for music that provided the initial spark for the “Front Bass System” project. Albus unpacks an array of sub-woofers on the table, a collection of 35 bass loudspeakers that would be fit to grace any store specializing in automobile sound systems. Some of the impressive examples would fill an entire spare wheel well or take up all the space on the shelf behind the rear seats. Others are so deep that you wonder how they can fit into a side door. Also included are the mid-sized and rather “delicate” variants for rear side pockets. All of these speakers have one thing in common: each can be found in one or the other of the various Mercedes-Benz series. However, the engineers from the Front Bass team, led by Norbert Niemczyk, wouldn’t swear that this selection covers the entire range of sub-woofers for Mercedes-Benz vehicles.

Laureates: Rainer Albus, Norbert Niemczyk

 

“In terms of production,” says Albus, “this diversity is extremely complex and causes high costs.” The drive to achieve “grand unification” is therefore the main force behind the Front Bass system. Primarily, the idea was to find a constructive solution for Mercedes-Benz audio systems that would be suitable not only for all body variants of a vehicle family — in other words, everything from a convertible to a station wagon — but also for all series on a long-term basis.

A second disadvantage was the enormous amount of space required due to the nature of the large sub-woofers, particularly in areas of the vehicle which could be put to far better use. The third and final factor is that the engineers are so highly motivated to achieve top-quality sound, says Mario Fresner, an acoustics specialist on the team whose nickname is “the golden ear.” “Sure, one of our aims was to improve listening pleasure in the vehicle,” he says.

Three parameters play a key role when it comes to achieving top quality bass sound in an automobile interior: pulse stability, even at high volume levels; a low-resonance, crisp sound; and minimal vibration in the door. The last feature is particularly important to heavy metal enthusiast Jochen Linkohr, who says, “It’s okay to feel the bass, but I don’t want it to give me a full body massage.”

With these objectives in mind, the team set about searching for suitable placement areas. Of course, they immediately thought about the body shell. Attached to the stable steel sections, even the super heavyweights among the sub-woofers would produce a low-resonance sound with a stable pulse. It should also be possible to find a free installation space behind the sections, which if used as a metal box surrounding the unit, could provide extra sound volume.

The search rapidly focused on the front and side sections of the body. The reason was simple enough. Within a vehicle family, these areas are subject to relatively minor design adjustments. In comparison, the rear of the body of a convertible differs significantly from the its counterpart in a station wagon. Having measured the irritating structure-borne noise, the team ultimately focused on the front third of the body, because it offers the most advantages.

However, the next major challenge was just around the corner. The design of the support structures at the front is vital to the vehicle’s safety in the event of a crash. The team was well aware that requests to change these painstakingly optimized structures wouldn’t go down well with colleagues from the vehicle body workshop. Team leader Niemczyk can recall the initial discussions only too clearly: “This was a key issue. Our colleagues would have refused to make even the slightest compromise when it came to crash safety.” So there was little alternative for the team but to stick to its task. Eventually they found a position low down in the bulkhead where it is connected to the body’s other support structures to the right and left.

At this point, the bulkhead profiles can be opened slightly on both the driver and passenger sides, a gap wide enough to accommodate the bass loudspeakers. Just as important, the space behind the loudspeakers can be used as a bass box and sealed, creating an optimum resonating cavity for the sub-woofer.

The team also discovered that the selection of materials and design will immediately make it possible to use the Front Bass system in a planned series production vehicle. The new audio system will be used in series production in this vehicle model for the first time. Further research revealed it will not be possible to use the assembly area in other series without adjusting the design of the support profiles. “That’s why our colleagues from the body shop are currently working on the necessary changes,” explains Niemczyk.

The test vehicle that was used by the team to test the Front Bass system in a car for the first time greatly boosted motivation, recalls Linkohr. The unit was also used to implement the highly complicated sound configuration with a specialized supplier. “If the skeptics weren’t already completely convinced, the quality of the sound did the rest,” says the engineer, smiling mischievously. “And that made things a lot easier.”

However, several obstacles still had to be overcome. Countless tests were necessary. What kind of temperatures are prevalent in the new speaker space, which is located directly between the potentially bitterly cold outside world and the hot engine compartment? Can the loudspeakers hold up under the conditions? Does more noise from the engine compartment penetrate into the vehicle’s interior due to the two openings for the loudspeaker units? Are vibrations transferred as a result? Is the loudspeaker compartment sealed effectively enough against moisture, or even water in extreme cases? The team’s tests included simulation of a four-wheel-drive vehicle plowing through a dip filled with water to the level of the hood for 72 hours.

Even the electromagnetic compatibility of the loudspeaker with other components in the vehicle had to be tested. After all, the loudspeaker chassis, which is located on the driver’s side and contains a large driver magnet, is in direct proximity to the pedals. And that’s important, given that the gas pedal sensors use a magnetic variable to detect the pressure applied. However, many months and several folders of test print-outs later it was confirmed that all conceivable objections regarding the Front Bass system were unfounded. In other words, nothing stands in the way of the realization of this audio concept.

On the contrary, the Front Bass system has many advantages. First and foremost, there is the sound quality. Acousticians can measure this variable in figures and evaluate it in diagrams. However, a layperson simply needs to listen for a few moments to realize just how good the sound quality is. And the location of the sub-woofer isn’t the only reason for the improvement. The space freed up in the front doors also makes it possible to shift the mid-range speakers and tweeters to a higher level. As every stereo enthusiast knows, moving these two sound transducer types closer to ear level improves sound quality.

The Front Bass system is a big hit in terms of the main motivation behind the project. Three unit variants — from the basic version to a premium line and a high-end set for sound enthusiasts — could soon replace the nearly three dozen sub-woofer types currently in use. There would be room for all of them in the different production series and body variants. The only requirement for customized mounting to the bulkhead would be a very inexpensive plastic adapter.

The extra space gained in the interior or trunk thanks to Front Bass is not only useful for extra storage. Linkohr remembers the enthusiastic response when the Front Bass system was presented to development colleagues who focus on door safety during side impacts. “Previously, our door design engineers had to build crash structures around the large sub-woofer units. This made things significantly more complex and added extra weight. Thanks to Front Bass, they can now design the reinforcement structures with less material, reduce manufacturing complexity, and still guarantee optimum side impact protection.”

And says Norbert Niemczyk, there’s another benefit: “In comparison to the previous solutions, placing the Front Bass loudspeaker in the bulkhead means we can achieve significantly higher volume using the same amplifier power.” In practice, this means the Front Bass system requires considerably less electricity. It may sound crazy, but improved sound even helps to save fuel.