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Innovations: d&b audiotechnik KSL System

Matthias Christner, head of R&D Acoustics at d&b audiotechnik, takes us behind the scenes of the KSL System’s creation.

This article originally appeared in the July 2019 issue of Pro Sound News. Innovations is a monthly column in which different pro audio manufacturers are invited to discuss the thought process behind creating their products of note.

When d&b audiotechnik started the GSL project, we targeted applications that our large line array, the J-Series, would usually handle using a comprehensive system. The J-Series is used successfully in a wide range of applications, from medium to large clubs all the way up to stadiums. The GSL had to deliver even more than the J-Series. It had to sound great and establish a more efficient workflow for these larger applications.

Work began on KSL when the GSL electroacoustic properties had been finalized and most of the mechanical and hardware details had been clarified. This is typically the start of the “industrialization” phase in product development. It was around the time of the GSL preview events for customers that we discussed the possibilities of scaling down the GSL.

The idea of making the SL-Series feature set available in a smaller system package for a broader range of applications was clearly in place from the very start. Our experience of working with GSL and its prototypes set up the necessary development tools to design the system’s electroacoustic properties, so the knowledge about how we might deliver these same properties in a smaller format was already there. When we started to work with GSL in the real world, we fully understood the practical value of its features for a huge range of applications.

In our tests, we set up a GSL system in a large arena in a situation meant to replicate a shareholder meeting running lots of table microphones. The full range directivity of the system enables a much higher gain before feedback in the low-mids, and the difference in vocal quality and intelligibility was really obvious. It gave a very clear indication of where to proceed with features of the GSL in a smaller format.

Another example that demonstrated the need for a little brother for the GSL was outfill deployment: When there is a system in place that has well defined directivity across its entire range, the outfills need to work with that system, not against it. The KSL is great for outfills. It became obvious that we could add an accompanying system that offers a larger splay range in order to cover an arena’s side seating efficiently. If the main system intentionally keeps its LF energy well contained, the side system must also be full range and work autonomously without any LF support from other parts of the system.

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All the features that characterize the SL-Series have been transferred to the KSL, particularly the series’ directivity behavior that creates the “quiet stage” experience and the massively reduced environmental impact to the side and behind the arrays. We also wanted to keep the impressive dynamic linearity of GSL down to the lowest frequencies, which allows engineers to run lower LEQ levels while the audience still has the full perception of a highly energetic performance. The KSL offers a full-range performance, reducing the subs needed for many applications. And then there’s the transport and rigging system that, once experienced, nobody wants to give up.

The most striking difference is the perceived size of the KSL box from the audience perspective. With a width of 39.8 inches (versus 51 inches for GSL) and a height of 13 inches (vs. 15 inches), the front-facing area of a KSL is just about two-thirds of a GSL. There is only a small reduction in cabinet depth (24 inches versus 25). The physical loudspeaker arrangement is directly linked to directional behavior and coherence, so it couldn’t be reduced much; it’s key to the targeted bandwidth of the whole SL-Series.

In terms of weight, we could reach an attractive 127 pounds—even less than a J-TOP, at 132 pounds. When it comes to maximum acoustic output, KSL is around 3 to 4 dB below GSL in the frequency range above 150 Hz; hence exactly in the J-Series range and exactly what we wanted to achieve. The difference between KSL and GSL in the lower frequencies is largely due to the over-proportional reduction of cabinet volume, but KSL still clearly performs beyond a J-TOP—so every application achieved with a J can easily be done with KSL, plus you get the additional benefits of improved directivity, rigging efficiency, logistics and scale. These benefits are the keys that open up a wide application range for KSL, probably even wider than what we see today with the J-Series.

In addition to including all the features that characterize the SL-Series, the KSL also offers a wider splay range of 0° to 10°. For smaller applications that don’t need ArrayProcessing, two cabinets linked in parallel can be driven by one D80 amplifier channel pair.

Work on KSL started at the beginning of 2017, just after the basic design of GSL had been finished. It progressed in parallel with the GSL industrialization process and field tests. The advantage of that approach was that our experience with GSL—the purpose-built simulation tools and many of the basic feasibility studies made for GSL—could be transferred to KSL.

It’s trickier to design, test and build scaled-down speakers like the KSL, particularly if you have the aim of delivering the same driver excursion capability as a larger cabinet like the GSL; smaller drivers require more work on the suspension system to be made reliable. A scaled-down cabinet like this one is inevitably more tightly-packed with the components and structures that deliver the performance, so the manufacturing process can also be more challenging.

Another interesting factor is the rigging system. With the larger splay range, the geometry of the smaller box and the dual rigging modes, you quickly run out of space for holes in certain components. A lot of work had to be done on material selection and manufacturing methods of high-grade steel.

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Following the excellent experience of our test strategy for GSL, we chose a similar process; whenever possible, we used a venue or festival that had already been a GSL test site, which enabled data comparisons both on site and off site for noise “immission” monitoring. Feedback was entirely positive, both from engineers and rental houses that see the advantages the SL-Series would provide on a daily basis. Our partners clearly recognize the benefits of a smaller-brother system.

Matthias Christner is head of R&D Acoustics, d&b audiotechnik Corp.

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