Technical Report. Aero 12A-Design and Technology. Full-range System

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Joshua Mathews
7 years ago
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1 Aero 12A-Design and Technology The Aero 28 line array system manufactured by D.A.S. Audio has been in production for more than 7 years. During the preliminary discussions regarding a successor for this world-wide best seller, the design philosophy adopted by D.A.S. was to develop a completely new system that would take advantage of the latest audio technologies. The new system should offer a significant improvement in performance and not simply a replacement aimed at the same market segment. The result of this ambitious design and engineering challenge is the new Aero 12A. Full-range System The first design premise of the new system was that the Aero 12A had to be a real full-range system, capable of performing on its own in the many applications where bass reinforcement is not required. Where bass reinforcement was a requisite, the Aero 12A system would have to couple directly with the LX-218A double 18 powered subwoofer. To achieve this, D.A.S. engineers developed a new 12 cone transducer with neodymium magnet assembly, the 12LNC4, which extends the Aero 12A s lower frequency range to 60 Hz. This configuration of bass included in the tops, provides the low end with an array effect, offering coherent summing of the bass frequencies and an increased Q for improved bass presence and clarity which reaches the audience with greater impact. The 12LNC4 incorporates the Total Air Flow (TAF) heat evacuation scheme which efficiently vents voice-coil heat providing a high power handling capability and low power compression. Where low frequency reinforcement is required, the LX-218A is the recommended system. Set-up is simple, requiring basic time-alignment to achieve coherent summing between bass and sub bass frequencies. This configuration provides a 3-way system that is simple to implement and requires a minimal amount of equipment. D.A.S. Engineering Department 1

was to develop a completely new system that would take advantage of the latest audio technologies.

2 High Frequency Unit The second design objective was to maximize the high frequency extension and output of the drivers to be used. Put simply, in an array, each high frequency unit covers a certain area with minimal interaction between individual drivers. Due to this, the performance limit of an array is normally associated with the maximum SPL levels each driver is capable of generating. This motivated the design of a new compression driver and waveguide. The new M-75N compression driver uses a lighter, titanium diaphragm, an optimized phase plug and a neodymium magnet assembly. The motor group of the M-75N driver incorporates a copper shorting ring surrounding the pole piece which effectively reduces eddy current induced distortion with the added benefit of increasing the very high frequency output by reducing the inductive rise of the voice coil. The result is higher sensibility in the high frequencies providing the driver with exceptional acoustic coherence, crystal clear performance and definition. The graph above shows the frequency response of the M-10N (red), used in the CA-28A, in comparison to the M-75N 1 W/1 m, both attached to a 60º x 40º horn. The improved sensibility can be clearly seen as of 6 khz. Attached to the M-75N is the new BPS-9010 waveguide that extends array performance in the high frequencies with extremely low levels of distortion and resonance. The sound of the mid-range frequencies produced by the driver/waveguide assembly is natural and exempt of the characteristic horn sound of other waveguides. D.A.S. Engineering Department 2

Due to this, the performance limit of an array is normally associated with the maximum SPL levels each driver is capable of generating.

3 DSP Besides incorporating the latest in component design, the Aero 12A project counted on the implementation of the most advanced signal processing. A powerful 24 bit DSP was chosen providing unparalleled control over critical signal parameters. A complex software package allows the precise adjustment of gain, crossover points, EQ, alignment, indicators and level control-all with the precision and versatility of the digital domain. Exceptional sound quality is the result of this impressive processing power which provides adjustment levels beyond those of conventional analogue signal processors or less powerful DSP s. The signal processing includes a noise gate which silences the systems when no signal is present avoiding the typical background noise of powered systems that operate with the amplifier always open. D.A.S. Engineering Department 3

A complex software package allows the precise adjustment of gain, crossover points, EQ, alignment, indicators and level control-all with the precision and versatility of the digital domain.

4 FIR Filters Digital Finite Impulse Response (FIR) filters are used in the signal processing of the Aero 12A. Analogue filters and their digital reproductions introduce phase variations which translate to a temporal misalignment at different frequencies. The signal processing of the Aero 12A includes Finite Impulse Response (FIR) filters which operate directly in the digital domain and do not generate phase shifts as do analogue filters or their digital counterparts. The FIR filters achieve constant phase response which indicates perfect time alignment of all frequencies. The graph below shows the phase response of the Aero 12A, free of any phase shifts between 100 Hz and 12 khz. D.A.S. Engineering Department 4

The signal processing of the Aero 12A includes Finite Impulse Response (FIR) filters which operate directly in the digital domain and do not generate phase shifts as do analogue

5 Wavelet Analysis In the design of the Aero 12A, powerful Wavelet analysis was used to provide an accurate time-frequency representation. Using Wavelet analysis, a graph is generated displaying the behavior in terms frequency, arrival time and level. With the proper design of the appropriate FIR filters, the time alignment off-set can be corrected. Perfect alignment is achieved in the Aero 12A as shown in the graph below. The maximum levels at all frequencies are achieved at the same time. D.A.S. Engineering Department 5

With the proper design of the appropriate FIR filters, the time alignment off-set can be corrected.

6 Step Response Step response translates into improved dynamic response. The system s attack is quicker and more precise, achieving a clearer and more natural sound. Percussion sounds with more impact, cleaner and with greater definition. Shown in the graph above is the step response of the Aero 12A. The attack time is very fast, the response close to ideal, and the level is greater thanks to the perfect summing of the system s two ways. The latency of the processing is minimal. Limiters: Peak and RMS The fundamental objective of any D.A.S. design is reliability. With that in mind, the Aero 12A system is protected by two types of limiters-an instantaneous peak limiter to safeguard the systems against spikes and a sonically transparent RMS limiter that controls excessive overpowering and thermal damage to components. This combination provides comprehensive protection for both the speaker components and signal electronics without degrading the sound quality. D.A.S. Engineering Department 6

The attack time is very fast, the response close to ideal, and the level is greater thanks to the perfect summing of the system s two ways. The latency of the processing is minimal.

7 Amplification The state of the art amplifier electronics designed for the Aero 12A sets a new industry benchmark in audio performance, efficiency and power density. This is made possible by employing 3rd generation Class D technologies which have significantly improved three important parameters, audio performance, efficiency and weight. The 600 W amplifiers provide extended bandwidth, improved dynamic range and exceptionally low distortion. This makes the Aero 12A one of the best sounding systems on the market. The efficiency of the amplifier measures more than 90%. This ensures cool operation so that no fans or bulky heat sinks are needed. The low idle consumption also offers an easy way to reduce overall power use and in turn, care for our environment. The impressively small size and light weight of the new amplifiers makes the Aero 12A amp one of the worlds lightest. For portable systems, that is important. With a power density of over 20 W per cubic inch, the Aero 12A amplifier needs much less space, reducing the overall cabinet size and in turn, the total cabinet weight. Weight Reduction Being a touring system used in live events, where set-up times, logistics and personnel are crucial factors, reducing the weight and cabinet size without sacrificing performance was a another important objective. The use of neodymium components, 3 rd generation Class D amplification with SMPS and optimized rigging hardware have provided an extremely compact unit weighing in at only 27 kg (59.4 lb) D.A.S. Engineering Department 7

The 600 W amplifiers provide extended bandwidth, improved dynamic range and exceptionally low distortion. This makes the Aero 12A one of the best sounding systems on the market.

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