SDA Loudspeaker Aiming and HRTF Equalization for Wider Sweet Spots

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Solution Overview

Problem

Existing stereo loudspeaker systems, such as the Stereo/Dimensional Array (SDA) systems, face challenges in maintaining a stable sonic image and wide sweet spot, often resulting in phasiness and limited image stability due to inadequate crosstalk cancellation, especially at higher frequencies and when listeners move.

Innovation Solution

The improved SDA system employs a new signal processing method that includes controlling delay, aiming the crosstalk cancelling speaker's radiation, and using electronic equalization to generate an enhanced crosstalk cancelling signal effective across a broader frequency range, with tower-shaped enclosures featuring angled baffles to direct drivers more effectively and a crossover network that compensates for the head shadow effect.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional SDA systems use interaural crosstalk cancellation, then a stable sonic image can be achieved, but the effectiveness is limited at higher frequencies and the sweet spot is narrow

Engineering Contradiction:

Improvestability of sonic imageVSAvoidfrequency range effectiveness

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent applies parameter changes by modifying the electrical characteristics of the crosstalk cancellation signal through electronic equalization. Specifically, the system applies frequency-dependent gain adjustments to the cancellation signal to compensate for the head shadow effect, thereby extending the effective frequency range while maintaining image stability.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The system performs preliminary action by pre-compensating the crosstalk cancellation signal for the head shadow effect before it reaches the listener. The electronic equalization is applied in advance to account for the expected attenuation and phase shifts that will occur as sound waves interact with the listener's head and torso.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If electronic equalization is applied to compensate for head shadow, then crosstalk cancellation is improved at higher frequencies, but system complexity increases

Engineering Contradiction:

Improvecrosstalk cancellation effectivenessVSAvoidsignal processing complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent implements parameter changes through electronic equalization that adjusts the frequency response of the crosstalk cancellation signal. The system modifies specific parameters (gain, phase) of the electrical signal to compensate for acoustic effects, achieving improved cancellation without requiring physical structural changes.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If the listening position is moved from the sweet spot, then listener mobility is reduced, but phasiness and image stability are maintained

Engineering Contradiction:

Improveimage stabilityVSAvoidlistener position flexibility

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The system performs preliminary action by pre-compensating the crosstalk cancellation signal for the head shadow effect across a broader frequency range. This pre-compensation creates a more robust sonic image that maintains stability even when the listener moves from the optimal sweet spot position.

Inventive Principle:

Principle #10Preliminary action

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach results in a more natural spectral response, reduced phasiness, and a significantly expanded sweet spot, providing a more immersive and stable acoustic experience by effectively cancelling crosstalk across a broader frequency range.

Implementation Method 1

a left main speaker and a right main speaker disposed in a listener's space... an inverted right channel signal to a left sub-speaker and an inverted left channel signal to a right sub-speaker

Methodology Applied

Scientific EffectAcoustic wave propagation: Sound

Implementation Method 2

a crossover network that compensates for the head shadow effect

Methodology Applied

Scientific EffectElectrical signal filtering: Filter (electronic)

Data Source

PatentUS10327086B2Head related transfer function equalization and transducer aiming of stereo dimensional array (SDA) loudspeakers

Publication Date: 2019.06.18 POLK AUDIO LLC

AI summary

An enhanced Stereo Dimensional Array loudspeaker system 250 preferably including a mirror image pair of loudspeaker enclosures 280L, 280R configurable by a user or installer as a left-channel loudspeaker and a right channel loudspeaker each having a driver array aiming configuration with first and second angled baffle facets carrying main and effects drivers on separate facets and a Head Shadow filter signal processing system and method for driving the main and effects drivers to achieve a psycho-acoustically expanded image breadth by Head Shadow filter compensated inter-aural crosstalk cancellation.