Extron Audio Design and Technology Patents

Extron Audio Technology Patent

Class D Amplifier Ripple Suppression

Three patents form the basis for Extron's CDRS™ - Class D Ripple Suppression technology found in the MPA and XTRA Series amplifiers. The primary end user benefit is the reduction in electromagnetic interference.

The output waveforms of a conventional Class D amplifier typically consist of an audio frequency waveform with a high frequency carrier superimposed on it. This high frequency carrier wave has often caused problems in installations due to the radiated emissions on long speaker wires, which act as an antenna. Ripple steering is a way to nearly eliminate the high frequency carrier so it will not cause interference in a system. The resulting waveform is a more accurate reproduction of the audio input signal.

Extron Audio Technology Patent

Class D Amplifier Soft Switching

Extron's soft switching design works with Class D Ripple Suppression technology to reduce switching losses, i.e., dissipated power. The end user benefit is higher efficiency under typical operating conditions.

Soft switching reduces idle losses in a Class D converter. It typically occurs in a very narrow range around the zero crossing of a Class D amplifier. The range at which soft switching occurs can be broadened to include a much greater part of the typical audio signal if high switching ripple is used, but this would typically cause emissions problems. By using ripple steering, this patented technology eliminates the emissions problem while keeping the efficiency improvement of the soft switching for much of the audio signal.

Extron Audio Technology Patent

Class D Amplifier Power Convertor

Power converters in Extron Class D amplifiers use synchronous rectifiers to facilitate energy transfer between positive and negative output rails. The end user benefit is more precise performance at clipping while using less capacitors (the dominant lifetime-limiting components).

Class D amplifiers notoriously pump energy back into the power supply rails, which causes the rail voltages to vary with the audio signal. The resulting audio content on the power supply creates an envelope on the clipped signal of both channels, leading to non-harmonically related frequency components at clipping. The typical way of dealing with this involves using more capacitors to partially mitigate the effect. This patented technology allows bidirectional energy flow, which makes the power supply rails look more like ideal DC voltage sources. This also allows for the use of fewer capacitors, contributing to longer lifetime.

Extron Audio Technology Patent

Low Noise Triangular Waveform Generator

The end user benefit is lower audio noise floor.

A triangle generator is the heart of a Class D amplifier. Triangle generators have audio band noise content, which can be reduced to equal that of a low noise op amp by use of a closed loop feedback system.

Extron Audio Technology Patent

Class D Circuit Bandwidth Extension

This Extron technology advances the technology of the CDRS™ - Class D Ripple Suppression amplifier design. The end user benefit is lower THD at high audio frequencies.

Class D amplifier bandwidth is limited by the switching frequency; bandwidth equal to a Class B amplifier is not practical, as the efficiency would be greatly reduced. Error correction techniques with a bandwidth exceeding the switching frequency are not practical in a typical Class D amplifier since the ripple content is high, leading to an impractically large error correction amplifier. With ripple steering, the linear error correction amplifier can be an order of magnitude smaller, making it practical to implement.

Extron Audio Technology Patent

SpeedMount Speaker Mounting System

Extron’s exclusive SpeedMount® speaker mounting system is designed to accommodate installations requiring division of labor. The low-voltage contractor can begin during rough-in by pulling speaker cables and installing the mounting system or ceiling speaker enclosure. Later, an AV system contractor completes the installation by securing the speaker onto the wall mount or into the ceiling tile enclosure.

Conventional speaker system installations typically involve a multi-step procedure with a variety of parts. The patented two-piece design of the SpeedMount ceiling speakers and the SpeedMount surface mount speakers helps to streamline sound system integration by reducing parts and labor. The user benefit is significant time and cost savings, as well as simplified speaker installation. This can speed up project schedules, reduce parts counts, and reduce costs dramatically, especially in large projects.

Extron Audio Technology Patent

Flat Field Technology

Extron's exclusive Flat Field® Technology used in the FF 120, FF 120T, and FF 220T ceiling tile speakers reduce concentrated, on-axis areas of mid and high frequency energy found in the coverage patterns of conventional speakers. The user benefit is uniform delivery of audio content from ceiling speakers to all participants in a listening environment.

Conventional speaker design poses limits and challenges to overcome in order to provide uniform sound pressure levels - SPLs for every listener. At the listening plane, listeners sitting 60 degrees off-axis are subject to as much as a 12 dB reduction in sound pressure level versus those listeners who are sitting on-axis. Tradeoff solutions involve an increased number of speakers of this design, or increased levels to maintain adequate sound pressure level to all listeners, resulting in over-specification of speakers and costs, or undesirable on-axis SPL, respectively. Flat Field Technology uses a combination of a hyperbolic ground plane with an optimized grille, to compensate for off-axis losses and provide a constant SPL to all listeners within its coverage area.

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