Galileo 616Loudspeaker Management System

Galileo and Compass

Galileo 616: Processing

Processing Functions

Providing up to two seconds of delay for each input and output represents just the beginning of Galileo 616’s power; it is the unit’s filtering that truly sets it apart in the realm of DSP-based loudspeaker management systems. Each input and output includes a careful digital implementation of Meyer Sound’s famous CP-10 complementary phase parametric equalization (five bands on inputs, ten bands on outputs), coupled with our new TruShaping program filters. This unique combination gives users the ability to treat acoustical problems appropriately and accommodate subjective needs without creating excessive phase shift that can degrade intelligibility and signal clarity.

Galileo 616 supplies a powerful signal processing arsenal incorporating delay and many forms of filtering. Shown above is the Compass screen that configures Galileo 616’s Composite EQ, available on each input and output.

Also supplied in Galileo 616 are digital implementations of the subwoofer crossover, air absorption compensation, and M Series array compensation filters first realized in the LD-3 compensating line driver.

Galileo 616’s all-digital design also enables Meyer Sound to give users entirely new capabilities, like low frequency coverage shaping for widening low-frequency dispersion patterns. A library of coverage-shaping presets is provided for large-scale M Series products, such as the MILO high-power curvilinear array loudspeaker and M3D line array loudspeaker.

Composite EQ Filter Architecture

Proper sound system design, implementation and alignment can avoid a host of problems in system response, and this should always be the first line of pursuit in sound reinforcement. When all possible measures in these areas have been taken, however, there are usually some problems that remain. Equalization is a primary tool for dealing with such problems.

Tuning a modern sound system with equalization is a complex task breaking down to a few basic needs: subjective shaping of the system frequency response, compensating for air attenuation and correcting for some anomalies resulting from interactions between loudspeakers or between loudspeakers and the acoustical environment. (This last category would include low-frequency buildup, for example.) But there are fundamental differences in character between some of these needs, which define a requirement for different tools to do the jobs appropriately. Failing to account for these distinctions can result in severe degradation of system phase response, with corresponding reductions in intelligibility and clarity of the sound.

Galileo 616’s Composite EQ filter architecture is intended to address this issue and provide the most potent equalization system available in any current digital loudspeaker management system, while keeping phase shift to the lowest amount practically attainable.

Let’s take a closer look at the problem and how Composite EQ solves it.

Interaction-based effects are, classically, second-order phenomena that produce ripple in the measured frequency response of a system. Using Meyer Sound’s SIM 3 audio analyzer, these artifacts can be clearly seen. In practice, there are many interactions for which equalization is not the most effective approach, but for those that do yield to equalization, the best tool for attacking them is a fully parametric equalizer producing both amplitude and phase responses complementary (that is, equal and inverse) to the characteristics of the interaction artifact being treated. Meyer Sound’s CP-10 complementary phase parametric equalizer’s second-order filters were created for this purpose, and Galileo 616 incorporates a careful digital implementation of a CP-10 filter set on each input and output. When such an equalizer is properly configured, the effect of treatable interactions can be essentially removed from the system response, leaving both amplitude and phase responses quite flat.

Subjective shaping and interaction effects like low-frequency buildup, on the other hand, tend to be much broader in shape. High-order filters are ill suited to this sort of gentle amplitude response shaping and, as well, generate considerably greater phase shift than low-order filters.

Compass Software: White line indicates phase

Galileo 616’s Composite EQ provides the right tool for these jobs, too: the TruShaping equalizer. The TruShaping equalizer (patent pending) is a digital implementation of Meyer Sound’s acclaimed VX-1 program equalizer, extended to contain four first-order interactive filters in an innovative configuration. Since the TruShaping EQ’s filters are low-order, they keep phase shift to a minimum, preserving the integrity of the signal. In fact, the unique cascading topology used to create the TruShaping equalizer allows the bands to overlap, which results in slopes as low as 3 dB per octave and response curves so smooth they could not be obtained any other way. Even with extreme settings, the TruShaping equalizer will rarely result in even so much as 45 degrees of phase shift. No other device currently on the market offers this approach.

This technique is so successful for system frequency response shaping applications that the Array Compensation filters in Meyer Sound’s Galileo 616 are based on the TruShaping filter topology.

As Meyer Sound self-powered systems are optimized to produce flat frequency and phase response when they ship from the factory, the TruShaping equalizer provides a powerful tool for adding “warmth,” “presence” or other subjective qualities.

Composite EQ, by providing both CP-10 complementary phase parametric and TruShaping low-order shaping equalization, gives the user the right tools to deal with both acoustical anomalies and subjective needs. Best of all, the Composite EQ user interface in the Galileo system’s Compass control software presents a clear picture of the resulting equalization by overlaying the CP-10 and TruShaping responses being applied, both amplitude and phase, in a single editable graphical display. EQ parameters can be edited directly by simply dragging in the display, or edited numerically for greater precision.

Air Absorption Compensation

As sound waves travel long distances through air, high frequencies are absorbed, a fact important to consider when setting up high-powered loudspeakers for a long-throw application. But the effect of air absorption on sound is complex to describe, as it depends on a number of factors, including distance, temperature, humidity and altitude. The equations shown here are used to calculate the sizable tables upon which Galileo 616 draws to provide its atmospheric compensation filtering.

Method for calculating frequency dependant air absorption from ANSI S1.26-1995.


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