Ambience

Changelog

v1.1.0

Bug Fixes:

• PreDelay fix: Fixed PreDelay parameter not being applied to DSP. Now correctly feeds both ER and FDN paths.
• Metallic comb-filter artifact fix: Addressed metallic ringing at long DecayTime values with four countermeasures: DC blocker in FDN loop, decay-dependent micro-saturation blend, modulation depth scaling, and dynamic nested allpass modulation.
• Preset PRO Mode fix: Fixed PRO Mode state being incorrectly restored on preset load. Now always resets to Normal mode.

Sound Quality Improvements:

• Chorus-style pitch modulation: Added sine-wave LFO (ChorusLFO) per FDN channel with golden-ratio phase/rate distribution, layered on top of the existing noise LFO for richer, more organic tail texture.
• 3-stage serial allpass chain: Expanded nested allpass from 1 stage to 3 serial stages per FDN channel with varied delay times and modulation depths, greatly increasing late-field echo density.
• ER→Late reverb transition smoothing: Early reflection output is now fed into the FDN input at 15% blend, simulating the natural transition from early reflections to late reverberation.
• Frequency-dependent modulation: Modulation depth now scales per FDN channel (1.5× for short-delay/HF channels, 0.5× for long-delay/LF channels), matching the physical behavior of air turbulence.
• Soft-knee RMS compression in FDN loop: Added per-channel RMS envelope follower with soft-knee compression (threshold 0.35), providing transparent level control without harmonic distortion.
• Thiran allpass fractional delay interpolation: Replaced linear interpolation with 1st-order Thiran allpass for FDN main delay lines, achieving flat magnitude response (|H(ω)|=1) and preserving high-frequency clarity in the feedback loop.

CPU Optimizations:

• Replaced std::sin() in chorus LFO with parabolic sine approximation (5-10× faster, <0.1% error).
• Moved std::sqrt() in soft-knee compression inside threshold branch (only computed when compression is active).
• Precomputed all loop-invariant values: frequency-dependent modulation scales, input diffuser delays, allpass base delays (16ch × 3 stages), ER tap gains, and allpass gain stage.
• Cached sample rate as float to eliminate repeated double→float casts in the hot path.

Overview

Ambience is a high-quality, open-source algorithmic reverb VST3 plugin built on a 16-channel Feedback Delay Network (FDN) architecture. Designed with professional audio standards in mind, it delivers rich, natural-sounding reverberation ranging from intimate studio rooms to vast concert halls and beyond — with the precision and stability demanded by real-world production environments.

Ambience ships with 21 factory presets modeled after some of the world's most iconic acoustic spaces, including Abbey Road Studio 1 & 2, Vienna Musikverein, Amsterdam Concertgebouw, Boston Symphony Hall, Carnegie Hall, and more. Whether you need a tight drum room, a lush orchestral hall, a vintage plate, or an infinite ambient space, Ambience covers it all.

👉 Watch the Demo Video (動作デモ動画はこちら！)

Key Features

🏛️ 16-Channel FDN Reverb Engine

A research-grade Feedback Delay Network forms the acoustic core of Ambience:

• 16-channel FWHT Feedback Matrix: Fast Walsh-Hadamard Transform ensures dense, colorless diffusion with optimal mode distribution.
• Nearest-Prime Delay Allocation: Delay lines are tuned to unique prime numbers distributed on a logarithmic scale, guaranteeing mutual coprimality across all 16 channels and eliminating comb-filter artifacts at any room size.
• 7 Reverb Algorithms: ROOM1 / ROOM2 / HALL1 / HALL2 / PLATE / SPRING / GOLDFOIL — each with distinct topological routing, Allpass gain, and ER patterns.

🎛️ Professional DSP Modules

• Stage 2 GEQ Absorption (Välimäki-Liski): A 10-band biquad Graphic EQ cascade per FDN channel, solving a Weighted Least Squares system to achieve accurate, frequency-dependent RT60 targets across the full audible spectrum.
• ISM-Based Early Reflections: Image Source Method patterns tuned per algorithm, providing perceptually accurate pre-echo with full stereo imaging control.
• BandlimitedNoise LFO: Each of the 16 FDN channels is driven by an independent, mutually asynchronous low-frequency oscillator using a white noise source filtered by a 1st-order IIR — initialized via the Golden Ratio Weyl sequence to guarantee non-periodic modulation.
• ADAA Saturator (4 Modes): Anti-Derivative Anti-Aliasing saturation applied to the wet path. Modes: Warm (Vicanek x/√(1+x²)), Tape (Padé rational polynomial), Tube (asymmetric ADAA for even-order harmonics), Hard (hard clip + ADAA).
• Micro-Saturation (FDN Loop): An internal Padé saturator in the FDN feedback loop acts as a safety limiter, suppressing limit cycles without audible coloration.
• Output EQ: Linkwitz-Riley 12 dB/oct Lo Cut (20–500 Hz) and Hi Cut (1 kHz–20 kHz) applied exclusively to the wet path.
• Brick-Wall Output Limiter: -0.5 dBFS brick-wall limiter as the final stage, transparent under normal use.
• Ducking: Sidechain-style envelope follower with independent Threshold, Amount, Attack, and Release controls.

📊 Real-Time Visualizers

• RT60 Graph: Displays 10-band RT60 curves (31 Hz – 16 kHz) in logarithmic scale. The orange curve shows the actual effective RT60 (including HF Damping and LF Absorption), while the gray curve shows the raw preset reference. The Y-axis dynamically scales to the current decay time.
• Decay Curve Visualizer: A split time-axis display showing Early Reflections (0–200 ms, expanded 2×) and Late Reverb decay curve side-by-side, with color-coded ER tap markers and envelope fill.
• Acoustic Metrics: Live readout of D50 (%), C50 (dB), C80 (dB), and EDT (s) derived from real-time signal analysis.

🎚️ Pro Mode

Unlock deep per-band control:

• 10-Band RT60 Multiplier: Fine-tune the RT60 curve at each octave band (31 Hz – 16 kHz) independently.
• Tilt EQ × 3: Broad spectral tilt controls for Low / Mid / High regions.
• Saturation Type Selector: Choose from Warm / Tape / Tube / Hard within Pro Mode.
• Output EQ: Lo Cut and Hi Cut knobs available in both Normal and Pro Mode panels.

💾 Preset Management

• File-Based Preset System: Presets are saved as .ambpreset files — a standard binary XML format compatible with JUCE's state management system.
• 21 Factory Presets: Modeled after real-world acoustic spaces across all 7 reverb algorithm types.
• SAVE / LOAD / DELETE / PREV / NEXT: Full preset browser UI integrated directly into the main panel.
• Shareable: Simply share .ambpreset files directly with other users — no installation required.

⚡ Real-Time Safety & DAW Compatibility

Built to the strictest real-time audio standards, with specific hardening for Ableton Live:

• Zero Heap Allocation on Audio Thread: All buffers pre-allocated in prepareToPlay(). No new / malloc / std::vector::resize() calls in processBlock().
• Dirty-Flag Parameter Dispatch: setParams() is called only when DSP parameters change, preventing the expensive Stage 2 GEQ WLS matrix computation (16 ch × 10-band LDLT) from running unnecessarily every buffer.
• Ableton Live Sample-Rate Jitter Protection: A mismatch guard at the top of processBlock() detects asynchronous sample-rate changes (a known Ableton Live edge case) and triggers a safe internal reset.
• ScopedNoDenormals: Applied at the entry of every processBlock() call to suppress denormal CPU spikes.
• SmoothedValue Gain: Wet and Dry gain changes are interpolated sample-accurately to eliminate zipper noise under automation.
• Safe Editor Destruction: stopTimer() and setLookAndFeel(nullptr) are called explicitly in the Editor destructor to prevent Ableton Live cleanup-order crashes.

Preset Guide

Factory Presets (21)

Ambience ships with 21 factory presets organized by reverb algorithm type:

Algorithm	Preset Name	Reference Space
ROOM1	Abbey Road Studio2	Abbey Road Studio 2, London
ROOM1	Drums in a Box	Small dead studio room
ROOM1	Tracking Room	Medium tracking room
ROOM2	Abbey Road Studio1	Abbey Road Studio 1 (large hall)
ROOM2	Capitol Studio A	Capitol Studios Studio A, Los Angeles
ROOM2	Skywalker Sound	Skywalker Sound, California
HALL1	Carnegie Hall	Carnegie Hall, New York
HALL1	Tokyo Opera City	Tokyo Opera City Concert Hall
HALL1	Berlin Konzerthaus	Konzerthaus Berlin
HALL2	Vienna Musikverein	Wiener Musikverein Goldener Saal
HALL2	Boston Symphony	Boston Symphony Hall
HALL2	Concertgebouw	Amsterdam Concertgebouw
PLATE	EMT140 Vocal	EMT 140 plate — vocal setting
PLATE	EMT140 Snare	EMT 140 plate — snare setting
PLATE	Dark Plate	Dark plate, enhanced low end
SPRING	Surf Guitar	Guitar amp spring tank
SPRING	Vintage Studio	Fender-style spring tank
SPRING	Deep Tank	AKG BX-20 style deep spring
GOLDFOIL	Gothic Cathedral	Cologne Cathedral reference
GOLDFOIL	Stone Chamber	Stone underground chamber
GOLDFOIL	Infinite Space	Synthetic infinite ambient space

Preset File Location

Factory presets and user presets are stored at:

Windows: C:\Users\<YourName>\Documents\Ambience\Presets\

Each preset is saved as a .ambpreset file (binary XML containing all plugin parameters).

Sharing Presets

To share presets with other users:

1. Navigate to Documents\Ambience\Presets\
2. Copy the desired .ambpreset file(s)
3. Send the file(s) to the recipient

Recipients simply place the .ambpreset files into their own Documents\Ambience\Presets\ folder. The presets will appear automatically in the Ambience preset browser on the next plugin load.

Tip: You can also ZIP the entire Presets folder to share your complete preset library at once.

Preset Compatibility

Presets use JUCE's standard state serialization. Future versions of Ambience will remain forward-compatible — unknown parameters in older presets are silently ignored, and missing parameters fall back to their default values.

Parameter Reference

Normal Mode

Parameter	Range	Default	Description
PRE-DELAY	0 – 500 ms	10 ms	Pre-delay before reverb onset
ROOM SIZE	0.3 – 2.0	1.0	Scales FDN delay times (room volume)
DECAY	0.1 – 20.0 s	1.5 s	Mid-band RT60 target
HF DAMP	0.0 – 1.0	0.0	High-frequency absorption (reduces high RT60)
LF ABSORB	0.0 – 1.0	0.0	Low-frequency absorption (reduces low RT60)
DIFFUSION	0.0 – 1.0	0.7	Controls Input Diffuser and Nested Allpass gain
MOD AMT	0.0 – 1.0	0.25	LFO modulation depth
MOD RATE	0.05 – 2.0 Hz	0.5 Hz	LFO base frequency
WIDTH	0.0 – 1.0	0.8	Stereo width (L/R decorrelation)
ER LEVEL	0.0 – 1.0	0.6	Early reflections level
SATURATE	0.0 – 1.0	0.0	Wet path saturation amount
WET	-60 – 0 dB	-4 dB	Wet signal level (-1 dB internal offset applied)
DRY	-60 – 0 dB	0 dB	Dry signal level (unprocessed)
LO CUT	20 – 500 Hz	20 Hz	Wet-path high-pass filter (bypass at 20 Hz)
HI CUT	1k – 20k Hz	20 kHz	Wet-path low-pass filter (bypass at 20 kHz)
AMOUNT	0 – 20 dB	0 dB	Ducking reduction amount
THRESH	-60 – 0 dB	-20 dB	Ducking threshold
ATTACK	0.5 – 100 ms	10 ms	Ducking envelope attack
RELEASE	10 – 2000 ms	200 ms	Ducking envelope release

Pro Mode (additional)

Parameter	Range	Default	Description
RT 31–16k Hz	0.5 – 2.0×	1.0×	Per-band RT60 multiplier (10 bands)
TILT LOW	0.5 – 2.0×	1.0×	RT60 multiplier for low bands (31–125 Hz)
TILT MID	0.5 – 2.0×	1.0×	RT60 multiplier for mid bands (250 Hz–2 kHz)
TILT HIGH	0.5 – 2.0×	1.0×	RT60 multiplier for high bands (4–16 kHz)
SAT TYPE	Warm/Tape/Tube/Hard	Warm	Saturation character

Special Controls

Control	Description
PRO	Toggle Pro Mode panel (RT60 bands + Tilt EQ)
ER SOLO	Solo the Early Reflections path (Late = silent)
Algorithm Buttons	Select reverb topology: ROOM1/2, HALL1/2, PLATE, SPRING, GOLDFOIL

Installation

1. Download the latest Ambience.vst3 from the Releases page.
2. Copy the .vst3 folder to your VST3 plugin directory:

   C:\Program Files\Common Files\VST3\
   

3. (Optional) Download the factory preset pack and extract to:

   C:\Users\<YourName>\Documents\Ambience\Presets\
   

4. Rescan your plugins in Ableton Live (or your DAW of choice).

📚 User Guide

A comprehensive manual covering detailed technical specifications and operational guidelines is included with this repository.

Requirements

• JUCE 8.0.x — place at C:/JUCE or update the path in CMakeLists.txt
• CMake 3.22 or higher
• Visual Studio 2022 (MSVC, C++20)
• AVX2-capable CPU (required for SIMD optimizations)

System Requirements

• OS: Windows 10 / Windows 11 (64-bit)
• Format: VST3 / Standalone
• CPU: AVX2 support required
• Tested Host: Ableton Live 11 / 12

⚠️ Compatibility Notice: This plugin is compiled and optimized exclusively for Windows with AVX2. Verified operation is confirmed in Ableton Live. Other DAWs (FL Studio, Bitwig, Studio One, Cubase, etc.) may work but are currently unverified. Use at your own risk outside of Ableton Live.

Technical Architecture

Input (Stereo L/R)
    │
    ├─► [Mid/Side Split]
    │
    ├─► [Input Diffuser × 4 stages] (Hall / Goldfoil)
    │
    ├─► [ISM Early Reflections] ──────────────────────────┐
    │                                                      │
    └─► [16-ch FDN]                                        │
         ├── FWHT + Sign Flip (feedback matrix)            │
         ├── BandlimitedNoise LFO (per channel)            │
         ├── Stage 2 GEQ Absorption (10-band, per channel) │
         ├── Micro-Saturation (Padé, loop safety)          │
         └── Nested Allpass (per channel)                  │
                    │                                      │
                    └──► [ER Mix + Late Mix] ◄─────────────┘
                                │
                         [ADAA Saturator]
                                │
                         [Output EQ: Lo/Hi Cut]
                                │
                         [Brick-Wall Limiter]
                                │
                         Wet Output × SmoothedWetGain
                                │
                    [Dry × SmoothedDryGain] ─────────────────┐
                                                             ▼
                                                      Final Output (Stereo)

Acoustic Metrics Reference

Metric	Description	Ideal Range
D50	Definition — ratio of early (0–50ms) to total energy	>0.5 for speech clarity
C50	Clarity (speech) — early-to-late energy ratio at 50ms	>0 dB for speech
C80	Clarity (music) — early-to-late energy ratio at 80ms	-2 to +4 dB for music
EDT	Early Decay Time — RT60 estimated from the first 10 dB of decay	≈ RT60 mid-band

Disclaimer

This software is provided "as-is", without any warranty of any kind. While extreme care has been taken to ensure real-time safety and audio stability through lock-free parameter dispatch, dirty-flag optimization, and Ableton Live-specific fail-safes, unexpected behavior may still occur in edge cases or unsupported hosts.

License

This project is licensed under the GNU Affero General Public License v3.0 (AGPLv3) - see the LICENSE file for details.

This software is built using the JUCE 8 framework. In accordance with JUCE 8's open-source licensing terms, this entire project is distributed under the AGPLv3.

Credits

Developer: @kijyoumusic (OTODESK)

Music Production Background: Electronic Music, Sound Design, DSP Engineering

Target DAW: Ableton Live 11 / 12

Framework: JUCE 8.0.x

DSP References:

• Välimäki & Liski — "Accurate Cascade Graphic Equalizer" (2017)
• Vicanek — "Matched Second Order Digital Filters" (2016)
• Schlecht & Habets — "On Lossless Feedback Delay Networks" (2017)
• Parker et al. — "Modelling plate and spring reverberation using DSP-informed DNN" (2019)

Support

• Social / Demo: @kijyoumusic
•