ArrayProcessing is an optional feature within the d&b ArrayCalc simulation software V8, available to download from dbaudio.com. Using this function, the advanced Digital Signal Processing within the D80 and D20 mobile amplifiers as well as the 10D and 30D install amplifiers can enhance the performance of the d&b J Series, V-Series and Y-Series line array systems.
Example for unprocessed (top) and processed (bottom) frequency responses over distance. ArrayProcessing calculates and designs the holistic behavior of a line array, creating individual sets of FIR and IIR filters for every single cabinet of the array, each of which are powered by a dedicated amplifier channel. These filters shape the sound generated by the array to precisely match a user-defined level distribution and obtain a uniform frequency response over a given audience geometry. ArrayProcessing adds 5.9 msec of latency; this is in addition to the 0.3 msec of the d&b amplifiers, arriving at a total of only 6.2 msec.
MOTIVATION AND BENEFITS
Typically, a line array setup for a given situation is planned in a way that optimizes the level distribution over distance in the high-mid frequency range (2 kHz to 4 kHz). This requires a specific vertical aiming for the individual cabinets that is defined by the splay angles between them. However, the array dispersion at lower frequencies (100 Hz to 1,000 Hz, depending on the array length) is a direct result of the total array curvature created by the splay settings (and not the individual aiming of a cabinet). This often creates a different level over distance distribution compared to the high-mid range.
The result is an uneven spatial balance and spectral response from the front of a venue to the back—a rich and (too) warm sound close to the array, which may become thin and almost aggressive in remote areas. The effect is well-known and has often been a cause for criticism against line array technology.
Another example is the difference in spectral response when covering steep seating areas with a strongly curved array, as it is often used in out-fill and 270-degree applications for tiers or balconies. In the highest seats, it sounds very thin, while in the seats around the middle, there is a strong and annoying midrange beam, which disappears again when approaching the stage. In these situations, it can often be perceived that the lower midrange dispersion does not follow the array shape.
ArrayProcessing can eliminate these issues by providing a consistent frequency response throughout all listening positions. The optimization means each area within a listening area has the same spectral consistency, so the sound at the FOH position applies to each member of the audience. The mix is valid for everyone.
COMPENSATING AIR ABSORPTION EFFECTS
ArrayProcessing includes air absorption effects in its calculations and provides a precise and seamless correction for all relevant cabinets. This provides a more consistent sound balance over distance, and in many applications where the system has sufficient headroom, its throw can be extended and the need for delay systems greatly reduced.
The level distribution in the audience area can be modified and tailored to reduce the level towards the front of the audience area and modify the level drop over distance over the audience area. Different ArrayProcessing settings for the array can be compared at a mouse click.
In many applications, achieving a more accurate directivity control causes less stimulus to the reverberant field and leads to improved intelligibility.
HOW DOES IT WORK?
When ArrayProcessing is enabled, target points are distributed along the listening area profile with a 20 cm spacing (along the intersection of the array profile with all matching listening planes). ArrayProcessing calculates the contribution of each individual source of the array to each listening position using a high spectral resolution of 24 frequencies per octave, making a total of 240 individual frequencies per target point over the entire 10-octave audio band. The resulting data is stored in a matrix and serves as a basis for all further calculations.
The ArrayProcessing algorithm also considers and corrects refraction effects produced by neighboring cabinets. The ArrayProcessing optimization routine will then create a unified/standardized frequency response at all of these points. This target frequency response is exactly the reference response that is initially defined when tuning and voicing the controller setups for the d&b line arrays in conventional (unprocessed) setups. This response is identical for all systems above approximately 140 Hz; below that frequency, each system has its own individual LF extension, depending on the specific cabinet design.
The target response created by the ArrayProcessing algorithm is independent of array length, splay settings and system type. Any optimized line array will provide the same sonic characteristics, regardless of Series. Any combination using multiple columns of optimized line arrays (rear fills, out-fills, delays) does not require individual tuning and maintains this uniform sonic footprint.
Any further adjustment to the system response, like master equalization for example, is valid for all line arrays in the system. As all loudspeaker columns have the same response, these adjustments will be identical for the entire system for all listening areas.
The user can specify a desired level distribution along the listening profile. This is done in a simple way by specifying the level drop (in dB per doubling of distance) for up to three different sections of the listening area profile (Front/Central/Rear). Additionally, a level offset can be applied to specific listening planes.
Furthermore, there is another powerful parameter: The Power/Glory fader, which defines the processing emphasis. Special focus on either maximum SPL and system headroom (Power) or on a best match of the target level distribution and frequency responses (Glory) can be selected. The center position usually provides a good balance between those parameters.
Up to 10 different combinations of user-parameter settings can be prepared and stored in the ‘ArrayProcessing slots’ of the amplifiers. These can be selected using the R1 Remote control software V2. Switching between different slots is performed in near to real time.
After processing, ArrayCalc displays the optimized results for the frequency response and level distribution for each configuration (slot). The listening experience is as striking as the plots suggest.
Frank Bothe is head of Research and Development at d&b audiotechnik.