DecayCore User Manual

This manual is the practical end-user guide for DecayCore. It explains what the program does, which files it expects, how to choose the main settings, what gets exported, and how to deploy the result to a convolution-capable playback system.

DecayCore generates room-correction FIR filters from built-in sweep measurements, compatible external measurement imports, and WAV/IR captures. The typical workflow is:

1. Measure the left and right channels with the built-in measurement tool, or import existing compatible external measurements.
2. Load the measurement files into DecayCore.
3. Choose a target curve and operating mode.
4. Generate filters.
5. Export and deploy the output to CamillaDSP, Roon, Equalizer APO, or another FIR-capable DSP.

1. What is DecayCore?

DecayCore is a room-correction FIR filter generator for loudspeaker and listening-room optimization.

It is designed to:

• read built-in measurement results, compatible REW-style imports, and WAV/IR sources
• compare the measured response against a target curve
• create left and right FIR filters
• export ready-to-use files for convolution playback systems
• keep correction behavior safer and more repeatable through built-in guard rails

Its default philosophy is simple: use cuts and bounded shaping as the main correction tools, and keep boost limited to cases where the measurement clearly supports it.

DecayCore can work in several styles:

• fully automatic with preset search
• guided manual operation with safety clamps
• advanced manual tuning with more direct control

2. Requirements

Before you start, you need:

• a measurement source: either the built-in DecayCore measurement tool or compatible external measurements, including REW-style exports
• a calibrated measurement microphone
• separate left and right channel measurements or equivalent generated IR sources
• a playback system that supports FIR convolution

Note on built-in measurement: Measurement has been verified to work on Windows. Linux has been verified to work at least on Ubuntu 22.04. macOS could not be tested due to unavailable test hardware. Subwoofer measurement on Windows requires the playback device to be configured for 5.1 or 7.1 multichannel output in Windows Sound settings. Users on platforms without measurement support can use compatible external measurements.

Common deployment targets:

• CamillaDSP
• Roon convolution
• Equalizer APO
• other DSP or player software that accepts FIR WAV impulse files

Recommended preparation:

• use the same microphone position and measurement method for both channels
• keep the sample rate consistent through your measurement and playback chain
• if importing REW text files, verify that the export includes phase data

3. Workflow Overview

The normal workflow inside DecayCore is:

1. Files tab Load left and right measurement files.
2. Target tab Select a built-in target curve or load a custom target.
3. Basic tab Choose the operating mode, filter type, sample rate, taps, and the main safety settings.
4. Advanced / Window / XO tabs Refine advanced correction, timing, windowing, and crossover behavior when needed.
5. Run tab Start the generation process and review the produced output.

For most systems, start simple:

• load measurements
• choose DecayCore automatic mode (recommended) or Basic
• choose Asymmetric or Mixed Phase
• generate filters
• listen and re-measure before making more aggressive changes

Practical rule:

• do not treat Max Boost as the main tuning lever
• let cuts and conservative band-limited correction do most of the work
• avoid chasing deep nulls or a perfectly flat-looking low end with boost

4. Input Files

DecayCore accepts measurements from the built-in tool and common import formats.

4.1 Built-in measurement tool

The recommended path. Measure directly inside DecayCore and save the resulting IR WAV files. Load those files from the Files tab when the session is complete.

4.2 REW text export (.txt)

Import frequency-response data exported from REW.

Expected content:

• frequency in Hz
• magnitude in dB
• phase in degrees

Important notes:

• the left and right channels must be loaded separately
• phase data is required if you want full phase-aware correction behavior
• headers are acceptable as long as the export is a normal REW text export

4.3 WAV impulse export (.wav)

DecayCore can also import impulse-response WAV files and convert them internally for processing.

Use this when:

• you saved IR files from the built-in measurement tool
• you prefer an IR-based workflow from REW
• you want DecayCore to derive the response using its own windowing path

Practical guidance:

• use mono impulse files for each channel
• keep the export settings consistent between left and right
• match the sample rate to the rate you expect to use in playback when practical

5. Operating Modes

DecayCore has three main operating modes. The DSP engine is the same, but the workflow policy changes.

5.1 DecayCore automatic mode (recommended)

Use this when you want the program to search for a technically strong preset automatically.

What it does:

• evaluates multiple preset combinations
• scores candidates
• picks the best candidate before final export
• keeps the workflow guarded compared with unrestricted expert tuning
• can use harmonic curves and IACC-aware ranking to avoid overly aggressive or overly symmetric winners
• prefers solutions that solve more with cuts and containment than with risky boost demand

Target selection strategy

In AUTO mode, the target curve can be determined three ways (selectable from the Basic tab):

• Auto: search best built-in (default) — evaluates multiple built-in target curves in parallel and picks the best-ranked result. Most robust choice, especially with external measurements.
• Adaptive: derive target from room acoustics — synthesizes a Harman6-based target from the measured room’s bass buildup, tilt, and RT60 characteristics. Faster than the search path. See section 6 for full details and RT60 requirements.
• Use selected target curve from Target page — uses the target curve you manually selected in the Target tab.

Best for:

• first-pass results
• users who want a strong starting point quickly
• rooms where you do not want to hand-tune every parameter

5.2 Basic

Use this when you want manual control but still want guard rails.

What it does:

• applies conservative defaults
• keeps important safety clamps active
• reduces the chance of extreme or unstable correction
• makes it clear in day-to-day use that boost is secondary to safer attenuation-based correction

Best for:

• most home systems
• users learning the software
• repeatable day-to-day filter generation

5.3 Advanced (expert)

Use this when you already understand the tradeoffs and want broader control.

What it does:

• exposes more direct tuning freedom
• relaxes mode-based safety constraints
• makes you responsible for the result

Best for:

• experienced users
• deliberate A/B testing
• expert tuning of difficult systems

6. Target Curves

DecayCore includes a large set of built-in target curves, including:

• Harman variants
• Not Dr. Toole
• B&K variants
• Flat
• cinema and speech-oriented targets
• nearfield and studio-style tilts

You can also load a custom target file.

General guidance:

• a mild house curve is often more natural than perfectly flat in-room playback
• bass-heavy targets can sound impressive, but they increase headroom demand
• if a target demands a lot of boost, it is usually a sign to back off rather than push harder
• if you are unsure, start with a moderate built-in target and listen before pushing bass harder

In automatic mode, DecayCore can also determine the target automatically. Three strategies are available (see section 5.1).

Adaptive target

The Adaptive: derive target from room acoustics strategy synthesizes a custom Harman6-based target instead of searching through built-in curves.

How it works:

1. Starts with a Harman6-style reference shape as a base.
2. Estimates the room’s natural bass buildup and tilt from the measurement.
3. Adjusts bass and tilt compensation fractions based on those estimates.
4. When RT60 data is available, further refines the compensation using measured decay times across bass, mid, and treble bands (bounded to ±2 dB).

RT60 requirement: adaptive target achieves its full room-specific behavior only when RT60 data is present in the measurement. RT60 is captured automatically by DecayCore’s built-in measurement tool. With external REW exports or WAV impulse files, RT60 data is typically absent — in that case the RT60-based compensation step is skipped and the target is derived from bass buildup and tilt only.

If you are using external measurements without RT60 data, Auto: search best built-in is the safer choice. It evaluates how well different built-in curves match the measured room without requiring RT60 data.

7. Filter Types

DecayCore supports four main filter types.

7.1 Linear Phase

• strongest timing accuracy
• can produce the highest latency
• can introduce audible pre-ringing in some situations

Latency estimate:

• latency is approximately taps / (2 * sample_rate)
• at 44.1 kHz and 65,536 taps, linear-phase latency is about 743 ms

Best for:

• offline listening
• systems where latency is not important
• users prioritizing timing accuracy

7.2 Minimum Phase

• very low latency behavior
• magnitude-focused correction
• avoids linear-phase pre-ringing behavior

Best for:

• low-latency systems
• conservative playback chains
• cases where phase correction is not the main goal

7.3 Mixed Phase

• linear-style behavior in bass
• minimum-phase style behavior at higher frequencies
• good balance between correction quality and practical use

Best for:

• general home listening
• users who want strong bass correction without full linear-phase behavior everywhere

7.4 Asymmetric

• near-linear low-frequency control with earlier impulse placement
• lower perceived delay than full linear phase
• often the most practical all-round choice

Best for:

• mixed music, movie, and desktop use
• users who want strong correction with more practical timing behavior

For many systems, Asymmetric is the most sensible first choice.

8. Key Settings

These settings have the biggest effect on the result.

8.1 Taps

Taps define FIR length.

• more taps improve low-frequency resolution
• more taps also increase latency and CPU load
• short filters are faster, but they can lose low-frequency precision

8.2 Sample Rate

Choose a sample rate that fits your playback chain.

• match the playback system when possible
• avoid unnecessary sample-rate conversion if you do not need it
• use Generate All Rates when you want one export package for multiple playback rates

8.3 Correction Range

The correction band defines the range where DecayCore is allowed to work.

Typical use:

• lower limit protects against unnecessary infra-bass correction
• upper limit helps avoid over-correcting poorly measured high frequencies

If the result sounds unnatural, narrowing the correction range is often safer than increasing algorithmic aggressiveness.

8.4 Maximum Boost and Cut

These settings limit how strongly the filter can move the response.

• high boost increases headroom risk
• strong cuts can sound overdamped if overused
• safer values are usually better for first runs

8.5 Level Matching

Level matching aligns the measured response to the target before correction is generated.

DecayCore supports:

• smart automatic scan
• manual window selection

If the target sounds consistently too lean or too heavy, check the leveling window before changing multiple other settings.

8.6 HPF and Low-Bass Protection

Low-frequency protection matters for real loudspeakers.

Relevant controls include:

• HPF
• Low-bass boost lock
• Excursion Protection

These are especially important for:

• small woofers
• bass-reflex systems
• ambitious house curves

9. Advanced Features

9.1 Temporal Decay Control (TDC)

TDC is designed to reduce excessive ringing and slow modal decay, especially in bass.

In practice it can:

• tighten bass decay
• reduce boom
• improve bass articulation

Use it carefully:

• stronger settings can sound drier
• if bass becomes too lean or over-damped, reduce TDC strength first

9.2 Adaptive Frequency-Domain Windowing (A-FDW)

A-FDW changes how finely different frequencies are corrected based on measurement confidence.

In practice:

• high-confidence regions can follow the target more closely
• low-confidence regions are smoothed more conservatively

This helps avoid over-correction in uncertain data.

9.3 Bass-first AI

Bass-first AI tells the system to treat low-frequency room modes as meaningful correction targets instead of smoothing them away too aggressively.

Use it when:

• room modes dominate the bass
• you want stronger intentional low-frequency cleanup

Be more conservative if:

• measurements are noisy
• the speakers have limited bass capability

9.4 Excursion Protection

Excursion Protection is a dynamic safety feature.

It helps prevent dangerous low-frequency boost by reacting to the measurement and target relationship.

Use it when:

• you are using bass-heavy targets
• your speakers have limited low-frequency headroom
• you want safer automatic bass behavior

9.5 Stereo Link

Stereo Link helps preserve left/right balance and phantom center stability.

Keep it enabled unless you have a specific reason to let each channel behave more independently.

9.6 IR Windowing

Additional controls affect timing and final impulse behavior:

• IR window style and shape
• asymmetric window placement controls

These matter most when you are refining latency behavior, channel alignment, or export impulse shape.

9.7 Hybrid IIR (FIR + IIR bass preconditioning)

Hybrid IIR is an optional bass mode that adds a small set of narrow IIR Peaking EQ biquad cuts targeting confirmed room modes, before the FIR filter is synthesized.

What it does:

• detects narrow modal peaks in the bass using confidence and group delay excess criteria
• designs conservative Peaking EQ cuts (no boosts) for confirmed peaks
• subtracts the IIR biquad contribution from the FIR magnitude gain curve — the FIR then handles only what remains after the IIR stage

The result is a combined correction: IIR biquads handle the narrowest peaks precisely, and the FIR handles the broader response.

When to use it:

• one or two narrow room modes in the bass remain clearly audible despite FIR correction
• measurements show high-confidence, high-Q peaks with strong group delay excess
• you are deploying to CamillaDSP and can run an IIR biquad filter stage alongside the FIR convolver

When not to use it:

• measurements are noisy or uncertain
• the room bass does not show clear narrow modal peaks
• your deployment target cannot run IIR biquads

CamillaDSP deployment note: when hybrid IIR produces biquads, they are included in the exported CamillaDSP YAML alongside the FIR convolver. Both stages must be active in the pipeline. Loading only the FIR WAV file without the IIR biquads will result in incomplete bass correction, because the FIR was designed with the IIR contribution already subtracted from its target.

Controls are available in the Advanced tab under a collapsible hybrid IIR tuning section. Default state is disabled.

9.8 XO Phase Model (Crossover Phase Correction)

The XO tab models the phase shift introduced by your speaker’s passive or active crossover filters. When configured correctly, DecayCore accounts for this phase contribution during FIR generation, ensuring the correction cooperates with the speaker design instead of fighting it.

What it does:

• defines the frequency and slope of each crossover network in the speaker
• tells DecayCore to include theoretical phase data for those crossovers in its FIR synthesis
• avoids over-correcting or partially opposing the speaker’s intended crossover behavior

Availability:

The XO tab is only active when the filter type is Asymmetric or Linear Phase. It is disabled for Mixed Phase and Minimum Phase modes, which do not use a theoretical crossover phase model.

How to use it:

1. Identify the speaker’s crossovers — look for passive dividing networks (crossover frequencies and slopes) or active HPF/LPF filters built into the speaker or amplifier.
2. Fill in up to five XO slots:
   • Frequency (Hz) — the crossover point, e.g., 2500 for a tweeter crossover
   • Slope (dB/oct) — the filter slope, e.g., 12 dB/octave. Options are 6, 12, 18, 24, 36, or 48 dB/oct
   • Leave unused slots empty
3. HPF/subsonic filter — the high-pass filter (e.g., a subwoofer’s 20 Hz 24 dB/oct HPF) is configured in the Basic tab but feeds the same theoretical model

Practical examples:

• 2-way speaker, 2.5 kHz tweeter crossover at 12 dB/oct: enter 2500 Hz, 12 dB/oct
• 3-way speaker with woofer/midrange crossover at 500 Hz (18 dB/oct) and midrange/tweeter at 4 kHz (12 dB/oct): fill XO 1 with 500 / 18 and XO 2 with 4000 / 12
• Active subwoofer with 80 Hz low-pass (24 dB/oct): enter 80 Hz, 24 dB/oct
• Full-range driver with no crossover: leave all XO slots empty

Only describe filters that already exist in your system. Do not invent crossovers.

Understanding the results:

After a run, the results section shows:

• XO Phase Model — the list of configured crossovers and slopes (e.g., “2500 Hz / 12 dB/oct”)
• XO delta GD badge — a coloured indicator (LOW / MED / HIGH) describing how much phase complexity the crossover introduces:
  • LOW (green) — “Small crossover effect”
  • MED (orange) — “Moderate effect - correction helps”
  • HIGH (red) — “Large effect - correction needed)”
• Phase and group-delay metrics — detailed values showing the phase deviation and group-delay excess at and around the crossover frequency

If left empty:

DecayCore assumes a flat theoretical phase response (no crossovers). This is correct for full-range drivers or coaxial designs but leaves the crossover region uncorrected on multi-driver speakers. If your speaker has multiple drivers with a crossover, specifying the XO parameters usually improves the overall phase coherence of the room-correction result.

10. Running Filter Generation

When the main settings look correct:

1. verify that both channels are loaded
2. confirm target curve and mode
3. review sample rate, taps, correction range, and safety limits
4. start the run from the Start tab

During generation, DecayCore evaluates the measurements, builds the target relationship, applies safety logic, and exports the final result.

If you are using automatic mode, the program may take longer because it is comparing multiple candidates instead of generating only one direct configuration.

11. Output Files

After a successful run, DecayCore produces a result bundle. Common output files include:

• L_...wav and R_...wav Left and right FIR impulse-response files
• Summary_...txt Human-readable report with scoring, settings, and diagnostics
• camilladsp_...yml CamillaDSP-ready configuration file
• ZIP package Collected export bundle for convenient deployment

Depending on the workflow, the export package can also contain additional configuration files alongside the WAV filters.

When Hybrid IIR is enabled and biquads are produced, the CamillaDSP YAML will include both the FIR convolver block and the IIR Peaking EQ biquad blocks. Both must be deployed in the pipeline for the bass correction to function as designed. See section 9.7 for details.

12. Reading the Summary

Summary_...txt is the main report for understanding what DecayCore produced.

Useful sections include:

• acoustic score and target match
• confidence metrics
• core settings used for the run
• gain, headroom, and clamp behavior
• TDC, A-FDW, bass-first, and protection status
• alignment and stereo-related diagnostics

Use the summary to compare runs, especially when you change:

• target curve
• filter type
• correction range
• taps
• protection settings

When comparing runs, change one or two variables at a time. This makes the summary much more useful.

13. CamillaDSP Integration

CamillaDSP deployment is the most direct workflow.

Typical steps:

1. copy the exported FIR WAV files to your CamillaDSP coefficients folder
2. copy or adapt the generated camilladsp_...yml
3. point your CamillaDSP setup to the new filters
4. verify gain staging before normal listening levels

Practical notes:

• confirm that the sample rate matches your playback path
• if you hear clipping or overload, reduce master gain or convolution gain
• always test at moderate volume first

14. Roon and Equalizer APO Integration

DecayCore also works with other convolution-capable systems.

14.1 Roon

• load the exported FIR WAV files into Roon’s convolution engine
• make sure the sample-rate handling matches your playback chain
• leave enough headroom if the result includes bass lift

14.2 Equalizer APO

• use the generated FIR WAV files in the convolution block
• apply enough preamp reduction to avoid clipping
• re-check channel assignment and sample-rate behavior on Windows

15. Health Checks

DecayCore performs validation before and during a run.

Typical result classes:

• WARN Non-critical issues worth reviewing
• CRIT Critical issues that may block the run, especially in guarded workflows such as Basic or automatic mode

Warnings can indicate:

• risky boost/headroom conditions
• incomplete inputs
• setting combinations that are technically possible but not recommended

If a health check fails, fix the root cause instead of trying to bypass the warning blindly.

16. Troubleshooting

16.1 The run will not start

Check:

• both channels are loaded
• the files are valid and readable
• the sample-rate and mode settings are sensible
• any CRIT health checks have been resolved

16.2 The correction sounds too thin

Check:

• target curve choice
• leveling window
• correction upper range
• TDC strength
• low-bass protection settings

16.3 The correction sounds too bright or aggressive

Try:

• lowering the correction upper limit
• using a gentler target
• increasing smoothing or using safer defaults
• moving from Advanced to Basic settings for comparison

16.4 Bass is still boomy

Check:

• whether TDC is enabled
• whether Bass-first AI is appropriate for the room
• whether taps are long enough for bass resolution
• whether the measurements themselves are reliable

16.5 Bass disappears or becomes weak

Check:

• Low-bass boost lock
• Excursion Protection
• HPF frequency and slope
• overly aggressive TDC or conservative target selection

16.6 Stereo image feels unstable

Check:

• left/right measurements were taken consistently
• Stereo Link is enabled
• Auto-Align L/R behavior is sensible
• one channel is not using a different file or rate accidentally

17. Best Practices

For the most reliable results:

• start with clean measurements
• use one target change at a time
• avoid extreme boost on first runs
• keep Basic mode as your reference workflow
• listen, then re-measure
• compare summaries instead of relying only on memory

The best correction is usually not the most aggressive one. A stable, repeatable, and well-protected filter is usually the better long-term result.

18. Recommended First Run

If you want a safe starting point, use this approach:

1. export left and right REW measurements
2. load them into DecayCore
3. choose Basic or DecayCore automatic mode (recommended)
4. choose a moderate built-in target
5. choose Asymmetric or Mixed Phase
6. keep boost conservative
7. generate the filters
8. deploy them at reduced volume first
9. re-measure with the filters active

That is the fastest path to a useful and defensible first result.

19. Built-in Measurement

DecayCore includes an integrated measurement tool that plays a sine sweep, records the response, and produces IR WAV files ready to import directly into the filter-generation workflow. It can replace a separate REW session when the hardware setup allows it.

19.1 What it produces

• Per-channel IR WAV files for Left, Right, Sub1, and Sub2
• Spatial averaging across multiple listening positions (magnitudes averaged; primary-position phase preserved)
• Repeat-based outlier rejection per channel

19.2 Configuration

Open the measurement dialog to set:

• Positions (1–12): number of listening positions in the room
• Repeats per channel (1–12): sweeps captured per channel per position; default is 5
• Primary position: which position supplies the reference phase and timing for spatial averaging
• Channel selection: checkboxes for Left, Right, Sub1, Sub2
• Outlier rejection: enable/disable and strictness level (safe / normal / strict)
• Per-channel settings: audio output and input device, channel index, sample rate, sweep frequency range and length, output gain, optional microphone calibration file

19.3 Measurement steps

1. Configure the session and start
2. For each position the tool captures all selected channels in sequence
3. After each position it pauses and prompts you to move the microphone to the next position
4. If Sub1 is selected it pauses before the first sub sweep so you can turn the subwoofer on
5. If Sub2 is also selected it pauses again after Sub1 completes so you can switch subwoofers
6. After all positions are captured it aggregates the results and saves the IR files
7. A summary shows how many takes were kept and rejected per channel

19.4 Subwoofer measurement — Windows requirement

Subwoofer measurement is only guaranteed to work on Windows.

The sweep is sent to the LFE channel (channel index 3 in a 5.1 or 7.1 layout). On Windows the output device must be configured for 5.1 or 7.1 multichannel playback in Windows Sound settings. Without multichannel mode active the LFE channel does not exist at the driver level and the subwoofer will not receive the sweep signal.

To enable multichannel output: open Sound settings → select the playback device → Properties → Advanced or Spatial sound → set the format to 5.1 or 7.1.

On other platforms subwoofer routing may work in some configurations but is not tested or supported.

19.5 Outlier rejection

Takes are assessed per channel after all repeats for a position are captured.

• Hard failures (clipping, excessive noise, severe peak-timing deviation) are always rejected regardless of strictness
• Strictness levels set the median-absolute-deviation threshold for softer outliers:
  • Safe: 3.5 σ — keeps most takes unless they are clearly wrong
  • Normal: 2.75 σ — balanced default
  • Strict: 2.0 σ — discards anything that deviates meaningfully from the group median
• The post-session summary reports how many takes were kept per channel

If many takes are rejected, check the signal level, cable connections, and microphone placement before tightening the strictness setting.

19.6 Using the results

• Load the saved IR WAV files via the WAV impulse export (.wav) path (section 4.3)
• Do not normalize individual IR files and do not move them to separate t=0 references — keep all files from the same session at the same gain so that relative timing and level are preserved