Open-Back Headphone Passive Filter for Leakage Frequency Compensation
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Solution Overview
Problem
Conventional open-back headphones suffer from leakage-induced loss of low and high frequency response, necessitating costly active circuits or impractical high displacement speakers, which are not cost-effective or suitable for prolonged use in studio environments.
Innovation Solution
A passive filter circuit integrated into open-back headphones, comprising three paths: a controlled low pass filter, a controlled high pass filter, and a sub-filter to normalize impedance, using resistors, capacitors, and inductors, which compensates for frequency losses without external power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If open-back headphones are used, then natural and clear sound is produced, but low and high frequency extension is compromised due to leakage
Solution Approach 1:
The patent converts the harmful leakage effect into a beneficial one by using the leaked sound waves to excite a passive filter circuit. The filter circuit, positioned to receive leaked sound, processes these waves and redirects them to compensate for the frequency losses, transforming the leakage problem into a frequency compensation solution.
Solution Approach 2:
The passive filter circuit acts as an intermediary between the leaked sound waves and the driver. It receives the leaked sound, processes it through RC and RL circuits to generate compensatory frequency components, and feeds these back to the driver to restore the lost low and high frequency responses.
2Reliability
If active digital circuits are used to compensate for leakage, then frequency response is improved, but cost and power requirements increase
Solution Approach 1:
The patent replaces the electronic/digital active circuit system with a passive acoustic-electric hybrid system. Instead of using powered microphones, digital signal processors, and amplifiers, the invention uses passive RC and RL circuits that operate solely on the acoustic energy from leaked sound waves, eliminating the need for external power and complex digital electronics.
Solution Approach 2:
The passive filter circuit is self-powered by the acoustic energy of the leaked sound waves themselves. The circuit requires no external power source, drawing all necessary energy from the sound pressure variations in the leaked waves to drive the compensatory frequency components back to the driver.
3Reliability
If high displacement speaker units are used, then leakage compensation is achieved, but size and cost increase and resonance modes are introduced
Solution Approach 1:
The patent segments the frequency compensation function into separate passive RC and RL circuit paths. Instead of using a single large high-displacement speaker unit, the invention divides the compensation into low-frequency compensation (via RC circuits) and high-frequency compensation (via RL circuits), each handled by appropriately sized passive components that fit within the headphone structure.
Solution Approach 2:
The patent changes the approach from mechanical displacement (large speaker diaphragms) to electrical parameter manipulation (RC and RL circuit time constants). By adjusting resistor and capacitor values, the system achieves frequency compensation without requiring large mechanical displacements, thus avoiding resonance issues and size constraints.
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
Enhances clarity in high and low frequencies, maintaining consistent sound quality across varying impedance conditions, thus improving audio performance without additional power requirements.
Implementation Method 1
The filter is a circuit board having three main paths. A first path comprises a parallel resistor and capacitor in series with the speaker, with a capacitor range between 0.1 and 5 uF, coupled to a resistor above 5 Ohms of impedance. A second path comprises a series capacitor and resistor in parallel with the speaker, with a capacitor in the range between 90 uF and 1000 uF, coupled to a resistor between 1 and 30 Ohms.
Implementation Method 2
A first path comprises a parallel resistor and capacitor in series with the speaker, with a capacitor range between 0.1 and 5 uF
Implementation Method 3
The third path has a series inductor and capacitor in parallel with the speaker
Data Source
AI summary
A headphone set includes a novel passive filter for processing an audio signal. The filter circuit uses three major sections. A parallel resistor and capacitor in series with the speaker, a series capacitor and resistor in parallel with the speaker, and a series inductor and capacitor in parallel with the speaker, with values changing relative to the combined impedance of the first two sections. The first section serves as a controlled high pass filter and the second section serves as a controlled low pass filter. The third section reduces overall impedance in order to reduce differences between the lowest and highest impedance on the spectrum established by the first two sections in order to maintain a consistent response across amplifiers which would otherwise have a more drastic effect on the filter values due to highly variable impedance being affected by an amplifiers output load.