Stereo Alignment Monitor

Overview

A comprehensive tool for analyzing the alignment and consistency between L/R channels.
It monitors L/R balance, frequency response match, center focus, and phase issues in real-time, providing both quantitative and visual evaluations. Extremely useful for verifying speaker setups and measuring channel imbalances in audio equipment.

What is Stereo Alignment?

In stereo playback, when the sound from the left and right speakers reaches the listener in a perfectly matched state, it is said to be in "alignment". Poor alignment typically causes the following issues:

Volume Balance Issues: The sound feels like it is pulling to one side.
Phase Issues: The sound arrival timing shifts, making the stereo image blurry or unnatural.
Phase Inversion: The left and right waveforms cancel each other out, making the sound thin.

This tool helps you visually monitor these discrepancies to verify the accuracy of your speaker setup and troubleshoot alignment problems.

Operation

Start and Stop Analysis

Start/Stop Button: Toggles the analysis on and off.

Parameter Settings

Show Physical Units (dB/r/°): When checked, displays detailed numerical values in physical units (dB, correlation coefficient r, degrees °, etc.) in addition to the analysis metrics (percentages and qualitative judgments like "Good/Poor"). This is useful when you need strict, exact data.
Smoothing: Adjusts the amount of temporal smoothing applied to the plots and analysis metrics. Higher values result in slower, more stable readings, making it easier to evaluate consistent trends.

Reading the Plots

L/R Difference FFT (Tone Color Shift)

Displays the spectra of both L and R channels and highlights the "difference" between them.

Green line: Left channel spectrum.
Yellow line: Right channel spectrum.
Shaded area: Indicates the level difference (tonal variance) between channels. When both channels match perfectly, the shaded area disappears.

Band-specific Phase Correlation

Displays the phase correlation coefficient (-1.0 to 1.0) across the frequency range.

1.0: Perfectly in-phase (monaural signal).
0: Uncorrelated (fully independent channels).
-1.0: Perfectly out-of-phase (phase inversion). Allows you to visually identify which frequency bands are experiencing phase alignment issues.

Analysis Metrics and Judgments

The panel on the right provides judgments based on four key metrics:

Metric	Description	Judgment Thresholds
L/R Balance	Displays the difference in total energy between L and R in dB.	< ±0.5dB: Excellent / < ±3.0dB: Good
Freq Match	Displays the correlation of frequency responses between L and R as a percentage.	> 95%: Professional / > 80%: Good
Center Focus	Displays the "center localization (M/S ratio)" of the overall signal.	> 85%: Mono / > 50%: Wide
Phase Issues	Displays the percentage of energy with negative correlation (out-of-phase components).	< 1%: Safe / < 10%: Minor

M/S Ratio Bar

A visual bar representing the ratio between center localization (Mid) and spatial components (Side).

Towards 100% Mid (Mono): The signal is concentrated in the center.
Towards 100% Side (Wide): The signal is spread widely across the stereo field.
Around Center: Indicates a natural stereo image.