Frieve EffeTune
Documentation

Spatial Audio Plugins

A collection of plugins that enhance how your music sounds in your headphones or speakers by adjusting the stereo (left and right) balance. These effects can make your music sound more spacious and natural, especially when listening with headphones.

Plugin List

  • Crossfeed Filter - Headphone crossfeed filter for natural stereo imaging
  • MS Matrix - Converts stereo to Mid/Side and back for advanced stereo adjustment chains
  • Multiband Balance - 5-band frequency-dependent stereo balance control
  • Phase Select EQ - Boosts or cuts frequency components selected by L/R phase difference
  • Stereo Blend - Controls stereo width from polarity-swapped stereo through mono to enhanced stereo

Crossfeed Filter

A headphone crossfeed filter that simulates the natural acoustic crosstalk that occurs when listening through speakers. This effect helps reduce the exaggerated stereo separation often experienced with headphones, creating a more natural and comfortable listening experience that mimics the way sound reaches our ears in a real acoustic environment.

Key Features

  • Simulates natural acoustic crosstalk for headphone listening
  • Adjustable crossfeed level and timing
  • Low-pass filtering to mimic frequency-dependent crosstalk
  • Stereo-only processing (automatically bypassed for mono or other non-stereo signals)

Parameters

  • Level (-60 dB to 0 dB): Controls the amount of crossfeed signal
    • Lower values (-20 dB to -6 dB): Subtle, natural crossfeed
    • Higher values (-6 dB to 0 dB): More pronounced effect
  • Delay (0 ms to 1 ms): Simulates the time difference of acoustic crosstalk
    • Lower values (0.1-0.3 ms): Tighter, more focused image
    • Higher values (0.3-1.0 ms): More spacious, speaker-like presentation
  • LPF Freq (100 Hz to 20000 Hz): Controls the frequency response of crossfeed
    • Lower values (500-1000 Hz): More natural, frequency-dependent crosstalk
    • Higher values (1000-20000 Hz): Broader frequency response
  1. Natural Headphone Listening
    • Level: -12 dB
    • Delay: 0.3 ms
    • LPF Freq: 700 Hz
    • Effect: Subtle crossfeed for comfortable long-term listening
  2. Speaker Simulation
    • Level: -6 dB
    • Delay: 0.5 ms
    • LPF Freq: 1000 Hz
    • Effect: More pronounced speaker-like presentation
  3. Subtle Enhancement
    • Level: -20 dB
    • Delay: 0.2 ms
    • LPF Freq: 500 Hz
    • Effect: Very gentle crossfeed for sensitive listeners

Application Guide

  1. Headphone Optimization
    • Start with conservative settings (-15 dB level, 0.3 ms delay)
    • Adjust level for comfort and naturalness
    • Fine-tune delay for spatial perception
    • Use LPF to control frequency response
  2. Music Style Considerations
    • Classical/Jazz: Lower levels (-15 to -10 dB) for natural presentation
    • Rock/Pop: Moderate levels (-12 to -8 dB) can soften hard-panned guitars or vocals while keeping the music lively
    • Electronic or very wide mixes: Use lower to moderate levels (-18 to -10 dB) to keep width, or higher levels only when you want to tame excessive left-right separation
  3. Listening Environment
    • Quiet environments: Lower levels for subtle effect
    • Noisy environments: Higher levels for better focus
    • Long listening sessions: Conservative settings to reduce fatigue

Quick Start Guide

  1. Initial Setup
    • Set Level to -12 dB
    • Set Delay to 0.3 ms
    • Set LPF Freq to 700 Hz
  2. Fine-tuning
    • Adjust Level for desired crossfeed amount
    • Modify Delay for spatial perception
    • Tune LPF Freq for frequency response
  3. Optimization
    • Listen for natural, comfortable presentation
    • Avoid excessive settings that sound artificial
    • Test with various music styles

Remember: The Crossfeed Filter is designed to make headphone listening more natural and comfortable. Start with conservative settings and adjust gradually to find the optimal balance for your listening preferences and music material.

MS Matrix

MS Matrix converts normal stereo audio to Mid/Side format, or converts Mid/Side audio back to normal stereo. Use it when you want to adjust center and side information separately inside an effect chain, such as encoding to M/S, changing the Mid or Side level, then decoding back to stereo. For simple stereo width adjustment on normal music, Stereo Blend is the more direct tool.

Key Features

  • Separate Mid and Side gain (–18 dB to +18 dB)
  • Mode switch: Encode (Stereo→M/S) or Decode (M/S→Stereo)
  • Optional Left/Right swap before encoding or after decoding

Parameters

  • Mode (Encode/Decode): Encode turns left/right stereo into Mid on the left channel and Side on the right channel. Decode treats the left channel as Mid and the right channel as Side, then rebuilds normal stereo.
  • Mid Gain (–18 dB to +18 dB): Adjusts the Mid level during the selected conversion.
  • Side Gain (–18 dB to +18 dB): Adjusts the Side level during the selected conversion.
  • Swap L/R (Off/On): Swaps left and right channels before encoding or after decoding
  1. Subtle Widening for Normal Stereo
    • First MS Matrix: Mode: Encode, Mid Gain: 0 dB, Side Gain: +3 dB, Swap: Off
    • Second MS Matrix after it: Mode: Decode, Mid Gain: 0 dB, Side Gain: 0 dB, Swap: Off
    • Effect: Slightly strengthens the Side component, then returns the result to normal stereo
  2. Center Focus for Normal Stereo
    • First MS Matrix: Mode: Encode, Mid Gain: +3 dB, Side Gain: -3 dB, Swap: Off
    • Second MS Matrix after it: Mode: Decode, Mid Gain: 0 dB, Side Gain: 0 dB, Swap: Off
    • Effect: Brings vocals and centered sounds forward while reducing side ambience
  3. Decode Existing M/S Audio
    • Mode: Decode
    • Mid Gain: 0 dB
    • Side Gain: 0 dB
    • Swap: Off
    • Use only when the incoming signal is already Mid/Side format
  4. Creative Flip
    • Mode: Encode
    • Mid Gain: 0 dB
    • Side Gain: 0 dB
    • Swap: On

Quick Start Guide

  1. Decide whether you need a single conversion or a full Encode -> adjust -> Decode chain.
  2. For normal stereo listening, place one MS Matrix in Encode mode and a second one later in Decode mode.
  3. Adjust Mid Gain and Side Gain on the Encode stage.
  4. Enable Swap L/R only for channel correction or creative inversion.
  5. Bypass to compare and make sure the stereo image still feels natural.

Multiband Balance

A frequency-dependent balance processor that divides the audio into five bands and lets you shift each band slightly left or right. Use it when bass, vocals, cymbals, or other frequency ranges feel pulled to one side and you want to rebalance only that part of the sound without moving the whole track.

Key Features

  • 5-band frequency-dependent stereo balance control
  • High-quality Linkwitz-Riley crossover filters
  • Linear balance control for precise stereo adjustment
  • Independent processing of left and right channels
  • Automatic fade handling when crossover filters are reset

Parameters

Crossover Frequencies

  • Freq 1 (20-500 Hz): Separates low and low-mid bands
  • Freq 2 (100-2000 Hz): Separates low-mid and mid bands
  • Freq 3 (500-8000 Hz): Separates mid and high-mid bands
  • Freq 4 (1000-20000 Hz): Separates high-mid and high bands

Band Controls

Each band has independent balance control:

  • Band 1 Bal. (-100% to +100%): Controls stereo balance of low frequencies
  • Band 2 Bal. (-100% to +100%): Controls stereo balance of low-mid frequencies
  • Band 3 Bal. (-100% to +100%): Controls stereo balance of mid frequencies
  • Band 4 Bal. (-100% to +100%): Controls stereo balance of high-mid frequencies
  • Band 5 Bal. (-100% to +100%): Controls stereo balance of high frequencies
  1. Correct a Treble Pull to the Right
    • Low Band (20-100 Hz): 0% (centered)
    • Low-Mid (100-500 Hz): 0%
    • Mid (500-2000 Hz): 0%
    • High-Mid (2000-8000 Hz): -10% to -25%
    • High (8000+ Hz): -10% to -30%
    • Effect: Moves bright content slightly left while keeping bass and vocals stable
  2. Correct a Low-Mid Pull to the Left
    • Low Band: 0%
    • Low-Mid: +10% to +25%
    • Mid: +5% to +15%
    • High-Mid: 0%
    • High: 0%
    • Effect: Moves warm body and lower vocals slightly right without changing the whole stereo image
  3. Keep Bass Centered While Adjusting Air
    • Low Band: 0%
    • Low-Mid: 0%
    • Mid: 0%
    • High-Mid: +5% to +15%
    • High: +10% to +20%
    • Effect: Gently moves upper ambience to the right while the low end stays centered

Application Guide

  1. Listening Balance Correction
    • Keep low frequencies (below 100 Hz) centered for stable bass
    • Shift only the frequency range that feels off-center
    • Use small signed values first (about 5-20%)
    • Check mono playback for tonal or level changes
  2. Problem Solving
    • Rebalance frequency ranges that feel too far left or right
    • Tighten unfocused bass by centering low frequencies
    • Reduce harsh stereo artifacts in high frequencies
    • Improve recordings where different parts of the sound lean to different sides
  3. Creative Listening Effects
    • Create unusual frequency-dependent placement
    • Make high frequencies lean one way while low frequencies stay centered
    • Build a wider-feeling ambience by making small balance shifts in upper bands
  4. Stereo Field Adjustment
    • Fine-tune stereo balance per frequency band
    • Correct uneven stereo distribution
    • Avoid treating this as a stereo width control; use Stereo Blend when you want to widen or narrow the whole image
    • Maintain mono compatibility

Quick Start Guide

  1. Initial Setup
    • Start with all bands centered (0%)
    • Set crossover frequencies to standard points:
      • Freq 1: 100 Hz
      • Freq 2: 500 Hz
      • Freq 3: 2000 Hz
      • Freq 4: 8000 Hz
  2. Basic Enhancement
    • Keep Band 1 (low) centered
    • Make small adjustments to higher bands
    • Listen for changes in spatial image
    • Check mono compatibility
  3. Fine-tuning
    • Adjust crossover points to match your material
    • Make gradual changes to band positions
    • Listen for unwanted artifacts
    • Compare with bypass for perspective

Remember: The Multiband Balance is a powerful tool that requires careful adjustment. Start with subtle settings and increase complexity as needed. Always check your adjustments in both stereo and mono to ensure compatibility.

Phase Select EQ

Phase Select EQ boosts or cuts stereo frequency components according to the absolute phase difference between the left and right channels. It applies the same positive gain to both channel spectra, so it does not rotate, correct, or create a phase difference. Use it when a sound occupies a particular frequency and stereo-phase region that an ordinary frequency-only EQ cannot isolate.

Five independent Bands are always available. Each Band has an inner Core, where its Gain is applied fully, and an outer Transition, where the multiplier fades smoothly toward 100%. Overlapping Bands multiply their gains; for example, overlapping 150% and 50% Cores produce 75%. Several boosts can therefore raise the signal above 0 dBFS, so leave enough headroom and compare with bypass.

Phase Select EQ reports processing latency equal to its FFT size plus its hop size. At 48 kHz, this is 4,096 + 1,024 = 5,120 samples, or about 106.7 ms (about 116.1 ms at 44.1 kHz). Check the complete chain in the app’s Total Delay display. This latency can affect real-time monitoring and audio/video synchronization.

Reading the Phase Map

  • The vertical axis is logarithmic frequency: low frequencies are at the bottom and high frequencies are at the top.
  • The horizontal axis shows signed L/R phase difference for display: 0° in the center means in phase, while -180° and +180° at the edges are the same opposite-phase point.
  • Each dot represents a recently measured input component. Brighter or larger dots are stronger; older dots fade away.
  • White dots show the measured components. Only enabled Band frames are drawn; the Band being edited is bright green and the other enabled Bands are light green. The number in the upper-left corner of each Core identifies its Band.
  • Selection uses the absolute phase difference. A single logical region is therefore mirrored across 0° and processes +60° and -60° identically. Swapping L/R mirrors the dots but does not change which components are processed.
  • The solid inner frame is the Core and the dashed outer frame is the Transition. A Band touching 0° joins at the center; a Band reaching 180° continues across both map edges.

Listening Enhancement Guide

  1. Reduce wide high-frequency glare
    • Set a Band around 4-12 kHz and 90-180°.
    • Start with 70-90% Gain and broad transitions.
    • Effect: Softens strongly out-of-phase upper-frequency content while leaving more centered detail largely unchanged.
  2. Add presence to centered vocals
    • Set a Band around 1-4 kHz and 0-30°.
    • Start with 110-125% Gain.
    • Effect: Emphasizes near-in-phase midrange components without applying the same boost to widely spread ambience.
  3. Control diffuse low-mid ambience
    • Set a Band around 150-600 Hz and 60-150°.
    • Start with 80-90% Gain and widen the frequency transitions until the change is smooth.
    • Effect: Reduces broad stereo low-mid energy while retaining near-center fundamentals.

These phase ranges describe typical tendencies, not fixed sound-source locations. Watch where the dots actually appear in the recording, make small changes, and confirm the result on both headphones and speakers.

Parameters

  • Band 1-5 / checkbox (Off/On): Selects a Band for editing and enables or disables it without changing its settings.
  • Gain (0% to 200%): Sets the level multiplier inside the Core. 100% leaves the level unchanged, 0% removes the selected component, and 200% doubles its amplitude.
  • Core Low Frequency / Core High Frequency (20 Hz to 40 kHz, limited by the current sample rate): Set the fully processed frequency range.
  • Core Low Phase / Core High Phase (0° to 180°): Set the fully processed absolute L/R phase-difference range.
  • Low Frequency Transition / High Frequency Transition: Set how far below and above the frequency Core the gain fades between 0% and 100%.
  • Low Phase Transition / High Phase Transition: Set how far toward 0° and 180° the gain fades between 0% and 100%. The map handles edit the same values as the sliders and numeric inputs: drag anywhere inside the selected Band’s outer frame to move the whole Band, drag Core edges or corners to resize it, and drag the outer edge handles to change one transition at a time. A low-phase handle stops at the center instead of crossing it: Core Low Phase stops at 0°, and Low Phase Transition stops at its maximum width. When Core Low Phase is exactly 0°, the center handle can initially move either left or right; after the pointer moves to one side, it stays locked to that side for the rest of the drag.

Stereo Blend

An effect that helps achieve a more natural sound field by adjusting the stereo width of your music. It’s particularly useful for headphone listening, where it can reduce the exaggerated stereo separation that often occurs with headphones, making the listening experience more natural and less fatiguing. It can also enhance the stereo image for speaker listening when needed.

Listening Enhancement Guide

  • Headphone Optimization:
    • Reduce stereo width (60-90%) for more natural, speaker-like presentation
    • Minimize listening fatigue from excessive stereo separation
    • Create a more realistic front-focused soundstage
  • Speaker Enhancement:
    • Maintain original stereo image (100%) for accurate reproduction
    • Subtle enhancement (110-130%) for wider soundstage when needed
    • Careful adjustment to maintain natural sound field
  • Sound Field Control:
    • Focus on natural, realistic presentation
    • Avoid excessive width that could sound artificial
    • Use negative width only for corrective or creative side-polarity inversion
    • Optimize for your specific listening environment

Parameters

  • Stereo - Controls the stereo width (-200% to 200%)
    • Negative values: Invert the polarity of the stereo side (L-R) component before reconstruction
    • -200%: Maximum width with inverted side polarity; use only for correction or special cases
    • -100%: Original stereo width with the left/right image swapped
    • 0%: Full mono (left and right channels summed)
    • 100%: Original stereo image
    • 200%: Maximum width enhancement; keeps the center component while strongly boosting the stereo side difference
  1. Headphone Listening (Natural)
    • Stereo: 60-90%
    • Effect: Reduced stereo separation
    • Perfect for: Long listening sessions, reducing fatigue
  2. Speaker Listening (Reference)
    • Stereo: 100%
    • Effect: Original stereo image
    • Perfect for: Accurate reproduction
  3. Speaker Enhancement
    • Stereo: 110-130%
    • Effect: Subtle width enhancement
    • Perfect for: Rooms with close speaker placement

Music Style Optimization Guide

  • Classical Music
    • Headphones: 70-80%
    • Speakers: 100%
    • Benefit: Natural concert hall perspective
  • Jazz & Acoustic
    • Headphones: 80-90%
    • Speakers: 100-110%
    • Benefit: Intimate, realistic ensemble sound
  • Rock & Pop
    • Headphones: 85-95%
    • Speakers: 100-120%
    • Benefit: Balanced impact without artificial width
  • Electronic Music
    • Headphones: 90-100%
    • Speakers: 100-130%
    • Benefit: Controlled spaciousness while maintaining focus

Quick Start Guide

  1. Choose Your Listening Setup
    • Identify whether you’re using headphones or speakers
    • This determines your starting point for adjustment
  2. Start with Conservative Settings
    • Headphones: Begin at 80%
    • Speakers: Begin at 100%
    • Listen for natural sound placement
  3. Fine-tune for Your Music
    • Make small adjustments (5-10% at a time)
    • Focus on achieving natural sound field
    • Pay attention to listening comfort

Remember: The goal is to achieve a natural, comfortable listening experience that reduces fatigue and maintains the intended musical presentation. Avoid extreme settings that might sound impressive at first but become fatiguing over time.