Plexus Spectral Dynamics — User Manual

User manual · v0.4.19 · September 2026 · Kaizen Audio

Contents

1. Introduction
2. System requirements and installation
3. Signal flow
4. Quick start
5. The interface
6. Selecting and editing channels
7. Channel filters
8. The spectral ducker
9. The sidechain
10. The true-peak limiter
11. Bass management
12. Output, mute, solo and listen
13. Meters and spectral displays
14. Ambisonic operation
15. Settings and session recall
16. DAW routing and automation
17. Troubleshooting
18. Specifications

1. Introduction

Plexus Spectral Dynamics is a multichannel dynamics processor for stems and buses. It keeps the input and output format unchanged while giving you one working surface for four jobs that often require several plug-ins:

• per-channel high-pass and low-pass filtering;
• sidechain-driven spectral ducking;
• bass management;
• true-peak limiting with per-channel peak history.

Plexus Spectral Dynamics accepts speaker layouts from mono to 9.1.6 and first-, second- and third-order Ambisonics. Every speaker channel has its own filter, ducking, gain and monitoring controls. You can work on one channel, a hand-picked selection or a complete role group without leaving the main window.

The intended use

Plexus Spectral Dynamics is designed as the last dynamics stage between a stem mix and the print bus. A typical example is a music stem that must make room for dialogue while remaining protected at the output:

1. insert Plexus Spectral Dynamics on the music stem;
2. feed the dialogue bus to Plexus Spectral Dynamics’s sidechain;
3. select the channels that should move out of the way;
4. set the sidechain range, ducking depth and timing;
5. set the limiter ceiling for the print.

It can also be used only as a multichannel limiter, only as a spectral ducker, or as a channel-by-channel filter and gain stage.

Plexus Spectral Dynamics changes the source intentionally. It is not an upmixer, a downmixer or a fold-safe matrix processor. Main input and output always use the same layout.

2. System requirements and installation

2.1 Version

This manual describes Plexus Spectral Dynamics v0.4.19.

2.2 System requirements

There is no customer-facing standalone application. AudioSuite and AAX DSP are not part of the current build.

2.3 Installation

The macOS installer offers the three plug-in formats independently and places them in their standard locations:

Quit and reopen the DAW after installing. In Pro Tools, use Cmd+Q rather than only closing the session so that AAX is scanned again on launch.

2.4 Licence activation

Plexus is licensed through your Kaizen Audio account, powered by Moonbase. A perpetual licence includes two activation seats. Open the plug-in and follow the activation overlay, or click the Plexus logo to open License Management. You can activate and deactivate online or load an offline licence file; no iLok is required.

When a valid paid or trial licence is active, processing is continuous. Without a valid licence, Plexus alternates 3 seconds of processed audio with 3 seconds of silence. This cadence is intentional and is not a DSP fault.

3. Signal flow

Plexus Spectral Dynamics processes each main channel in this order:

Input → HPF → LPF → Bass management → Spectral ducking → Channel gain → True-peak limiter → Output

Mute, Solo and Listen operate as monitoring and output utilities around the end of that chain. The sidechain is analysed separately: it never replaces or mixes directly into the main signal.

Three practical consequences follow from this order:

• filtering the main channel changes what reaches the ducker and limiter;
• channel gain can push the signal further into the limiter;
• the limiter is the final protection stage and keeps the same reported latency whether it is enabled or bypassed.

When bass management is active, its crossover becomes the relevant band edge for that channel. Plexus Spectral Dynamics does not apply a second high-pass or low-pass at the same edge.

4. Quick start

4.1 Dialogue-controlled music ducking

1. Insert Plexus Spectral Dynamics on the music stem. The plug-in’s input and output must use the same format as the track or bus.
2. Route the dialogue bus to Plexus Spectral Dynamics’s sidechain input in your DAW.
3. Click the SIDECHAIN row. Set SC HPF and SC LPF so that the key follows the useful part of the dialogue rather than rumble or excessive sibilance. The defaults are 200 Hz and 6 kHz.
4. Use KEY GAIN if the send is too quiet or too hot.
5. Select the channels you want to duck. Start with FRONTS, or use ALL and remove the LFE with −LFE when appropriate.
6. Click the vertical DUCK strip to enable the module for the selected channels.
7. Start with SENS 33%, REDUCTION 6 dB, ATTACK 5 ms and RELEASE 150 ms.
8. Play dialogue over music. Raise SENS if the key is not engaging enough; raise REDUCTION only after the response is reliable.
9. Set the limiter THRESHOLD and choose PAIRS or ALL when image stability matters.
10. Click TP RESET, play the loudest section and inspect the per-channel TP and GR readings.

4.2 Limiter-only operation

1. Leave DUCK and BASS MGMT off.
2. Leave channel filters at 20 Hz / 20 kHz, or turn the FILTER module off.
3. Turn LIMITER on and set the ceiling with THRESHOLD.
4. Choose UNLINK for maximum channel independence, PAIRS for stereo-pair stability, or ALL to preserve the balance of all non-LFE speakers.

The plug-in still reports its fixed latency when LIMITER is off, so bypass automation does not ask the host to renegotiate delay compensation.

5. The interface

Plexus Spectral Dynamics uses one fixed-size window divided into three zones.

5.1 Top zone — global stages

5.2 Middle zone — meters and channel rows

The left bank shows input level, output level and gain reduction for every channel. Its bars are centred between the dB scale and the limiter-threshold readout. TP RESET clears the held true-peak values.

To the right, every analyser uses the same left and right edges. The dark SIDECHAIN row starts with vertical FILTER and ATTACK shortcuts and sits above one row for each channel in the active layout. A channel row combines:

• its full channel name;
• held TP and current GR values;
• full-height vertical DUCK and FILTER module switches at the far left;
• horizontal S, M and L buttons;
• a spectral lane with filter edges, bass-management crossover and ducking activity.

5.3 Bottom zone — selected-channel controls

The bottom panel edits the current selection. For normal channels it contains:

• FILTER — HPF, LPF and their slopes;
• DUCK — sensitivity and maximum reduction;
• OUT — channel gain.

When the sidechain row is selected, the same panel changes to:

• RANGE — sidechain HPF and LPF;
• TIMES — ducking attack and release;
• GAIN — sidechain key gain.

The vertical FILTER and DUCK name strips are also on/off switches. Their colour shows whether the module is active for the first channel in the current selection.

The SELECT GROUPS block is aligned with the selected-channel controls. The Kaizen flower and wordmark sit immediately below it.

5.4 Footer

The footer shows the main layout and sidechain format on the left, this plug-in instance’s real-time audio-block CPU use in the centre, and the installed Plexus version on the right. The CPU figure is not the computer’s total CPU percentage; it shows how much of the time available for each audio block Plexus is consuming.

6. Selecting and editing channels

Plexus Spectral Dynamics separates which channels you are editing from the limiter’s LINK mode.

• Channel selection gangs control changes in the editor.
• LINK decides which channels share limiter gain reduction.

They are independent.

6.1 Direct selection

• Click a channel’s name/header area to select only that channel.
• Shift-click or Command-click a channel header to add or remove it from the selection.
• Click the SIDECHAIN row to edit the key filters, gain and times.

The selected row is outlined, and the bottom header shows the selected channel names. A selection of more than six channels is summarized as a channel count.

Clicking inside a spectral lane edits the nearest HPF or LPF edge. Use the channel header when you only want to change the selection.

6.2 Selection groups

The active group button lights only when the current selection exactly matches that group.

6.3 What a grouped edit changes

Knobs and the vertical FILTER/DUCK switches apply to every selected channel. The value shown in the panel comes from the first selected channel; moving it writes the new value to the whole selection.

The vertical DUCK and FILTER tabs and the horizontal S, M and L controls in an individual row act on that row only. This makes it possible to set up a group, then make a quick exception without rebuilding the selection.

The current selection is saved with the session and survives closing and reopening the plug-in window. On a new instance, FRONTS is the default selection.

7. Channel filters

Every channel has a high-pass filter and a low-pass filter.

Click a slope button to cycle 6 → 12 → 24 dB/oct.

Editing in the lane

Click or drag in a channel’s spectral lane. Plexus Spectral Dynamics chooses the nearest edge: the left side controls HPF and the right side controls LPF. If the row belongs to the current selection, the drag edits every selected channel. If it is not selected, only that row changes.

The two edges cannot cross. Plexus Spectral Dynamics preserves a small separation between them.

Filters and bass management

When bass management is enabled for a main channel, the global XOVER becomes that channel’s effective high-pass edge. The LFE lane shows the complementary low-pass edge of the redirected feed. This is intentional: the signal is split once at the bass-management crossover rather than filtered twice. The line in the LFE lane describes the feed arriving from the main channels, not a new filter on the LFE channel’s original input.

8. The spectral ducker

The ducker uses the sidechain to reduce only the parts of a main channel that compete with the key. A dialogue signal can therefore create space in a music stem without lowering the whole stem by the same amount at every frequency.

The sidechain analysis is global. SENS and REDUCTION are per channel, so the same dialogue key can move the center, fronts, surrounds and heights by different amounts.

Plexus separates the timing of the audible duck from the movement of its spectral shape. The broadband detector decides when the duck opens and closes directly from ATTACK and RELEASE. An overlapping spectral mask decides where the additional reduction belongs. The mask establishes quickly on a new onset, but moves more deliberately while the key remains active so a sung note or moving formant broadens the occupied region instead of sweeping a narrow notch through the music.

The response is intentionally frequency dependent. Low-frequency conflicts receive the fastest and deepest adaptive action. Low mids and mids move more gradually, while upper-mid and high-frequency activity is spread over a wider area and prevented from reaching the same depth as the lows. This voicing is internal; no additional setup is required.

A practical way to set it

1. Set REDUCTION to the most attenuation you would accept at the loudest moment.
2. Raise SENS until the orange reduction shape follows useful key material reliably.
3. Use ATTACK to decide how firmly consonants and transients open the space.
4. Use RELEASE to decide whether the bed breathes tightly around speech or returns more slowly.

Very fast attack settings can put the opening transition underneath an incoming consonant or transient. Slower settings make the onset more rounded. Spoken-word work normally benefits from a release long enough to avoid obvious pumping.

Per-channel strategy

A useful starting point for an immersive music bed is:

• more reduction in Center and the front stage;
• moderate reduction in side and rear surrounds;
• less reduction in heights;
• no ducking on LFE unless the programme calls for it.

Plexus Spectral Dynamics does not impose that profile automatically in the current interface. Use the selection groups to build it quickly and keep the decisions visible.

9. The sidechain

Plexus Spectral Dynamics accepts an optional sidechain bus and analyses it as one mono key. A multichannel key in VST3 or AU is folded to mono before analysis; Pro Tools supplies the conventional mono key input.

Click the SIDECHAIN row to open its controls.

Range handles

The two gold handles in the sidechain lane set the key’s HPF and LPF. Drag a handle to change its edge. Double-click the sidechain lane to restore the default 200 Hz–6 kHz range.

The displayed filter curve is the filter that actually drives the ducker. Frequencies outside the selected range contribute less according to the chosen slopes.

Reading the 32 bars

The off-white bars show which analysed bands are currently leading the ducker. They are not gain reduction meters: reduction happens in the orange overlays on the main channel lanes.

If the bars remain inactive:

• verify the DAW send and sidechain assignment;
• check that KEY GAIN is not too low;
• widen the SC HPF/LPF range temporarily;
• confirm that DUCK is enabled on at least one main channel.

10. The true-peak limiter

The limiter is Plexus Spectral Dynamics’s final audio stage. It is enabled by default with a ceiling of −1 dB.

LINK modes

The LFE remains independent in every mode. It uses its own low-frequency-aware response and never pulls the full speaker bed down with it.

Use UNLINK when level independence matters most. Use PAIRS when a stereo pair must not shift sideways under limiting. Use ALL when preserving the balance of the complete non-LFE field is more important than obtaining the least reduction on each speaker.

Fixed latency

Plexus Spectral Dynamics reports a fixed latency for the active sample rate. At 48 kHz it is 159 samples. The exact value is shown in Settings and is compensated by the host.

Turning LIMITER off makes it transparent but does not remove the delay. This keeps timing stable when the limiter is automated or bypassed inside the plug-in.

TP MAX and GR

Each channel row shows:

• TP — the highest reconstructed output peak observed while the editor is open, held since the last reset;
• GR — current limiter gain reduction when active.

Use TP RESET before a measurement pass. The built-in TP reading is intended for operating Plexus Spectral Dynamics; use the compliance meter required by the delivery specification for formal loudness or broadcast sign-off.

11. Bass management

Plexus Spectral Dynamics’s bass-management stage redirects low-frequency content between the main speakers and LFE around one global crossover.

What it does

• Below XOVER, content from enabled main channels is redirected to LFE.
• Each enabled main channel retains the complementary high-frequency side of the crossover.
• The LFE channel’s own incoming signal remains in place; the redirected low-frequency feed is added to it.

The channel lane marks the active crossover with BM. On a main channel it appears as a high-pass edge; on LFE it shows the low-pass shape of the feed arriving from the main channels.

Bass management requires a speaker layout with an LFE channel and front Left/Right channels. It has no effect on layouts without LFE and is disabled in Ambisonic mode.

Bass management changes routing and level relationships. Check the result on calibrated monitoring and verify the LFE path before printing.

12. Output, mute, solo and listen

12.1 Channel gain

Channel gain sits after filtering, bass management and ducking, and before the limiter. Positive gain can therefore create more limiter reduction.

12.2 Row buttons

L is a diagnostic tool. It lets you hear broadly what filtering, bass management, ducking and gain have removed or changed. It is not a conventional pre-fader listen bus and should be switched off before printing.

The row buttons act on the clicked channel only, even when several channels are selected.

13. Meters and spectral displays

13.1 Meter bank

The left meter bank shows, per channel:

• input peak in a subdued colour;
• output peak in the main Plexus Spectral Dynamics colour;
• limiter gain reduction in a narrow strip;
• the active limiter threshold as a horizontal line.

The bank follows the current display order. Meter ballistics are intentionally calmer than raw sample-peak flicker so a wide layout remains readable.

13.2 Channel lanes

Each main channel lane can show:

• the post-processing spectrum;
• HPF and LPF curves and frequencies;
• the bass-management edge;
• the orange spectral shape being removed by the ducker;
• TP MAX and current limiter GR in the row header;
• optional compact lane level and GR strips.

The displays are for operating the plug-in. They do not alter the audio and run only while the editor is open where possible.

13.3 Sidechain lane

The dark sidechain lane shows:

• the key spectrum and waterfall history;
• the real sidechain filter curve;
• draggable HPF and LPF handles;
• 32 off-white activity bars for the analysed ducking bands;
• KEY GAIN at the right edge.

13.4 TP RESET

TP values are held until TP RESET is clicked or the processor is reinitialized. Reset immediately before the passage you want to measure.

14. Ambisonic operation

Plexus Spectral Dynamics supports first-, second- and third-order Ambisonic B-format in ACN/SN3D channel order:

Ambisonic channels are encoded components rather than speaker feeds. Processing them differently can deform the decoded soundfield, so Plexus Spectral Dynamics changes its behaviour automatically:

• limiter LINK is forced to ALL;
• every component follows channel 1 / ACN 0’s processing controls;
• bass management is disabled;
• the selection header reads AMBISONIC — LINKED.

For clear editing, select ALL before changing filters, ducking or gain. Do not use speaker-role groups such as FRONTS or HEIGHTS for an Ambisonic bus.

The LFE exception described in section 10 does not apply because an Ambisonic bus has no LFE speaker channel.

15. Settings and session recall

Right-click or Control-click the Plexus logo to open Settings. A normal click opens License Management directly.

Film channel order is display-only

Film order places the center-family channels near L/R, followed by wides, side surrounds, rear surrounds, heights and LFE. It does not remap, copy or reorder the audio supplied by the host.

What is recalled

The DAW session stores:

• every processing parameter;
• the selected channels or sidechain page;
• film channel order;
• lane-meter visibility;
• RTA floor.

Changing the main bus to a narrower layout may make part of a saved selection unavailable. If no saved channel remains valid, Plexus Spectral Dynamics returns to the default FRONTS selection.

16. DAW routing and automation

16.1 Main bus

Plexus Spectral Dynamics requires matching main input and output layouts. Insert it directly on the stem or bus you want to process. It does not create, remove or fold channels.

If the host does not offer Plexus Spectral Dynamics on a track, confirm that the track uses one of the layouts in section 18 and that the insert is not asking for a different output width.

16.2 Sidechain routing

Assign the dialogue, voice or control bus to Plexus Spectral Dynamics’s sidechain/key input in the DAW. The exact command differs by host:

• Pro Tools: choose a key input in the plug-in header; the key is mono.
• VST3/AU hosts: enable or route the sidechain bus. Wide keys are accepted when the host exposes them and are folded to mono for analysis.

Plexus Spectral Dynamics does not need the sidechain for filtering, bass management, gain or limiting. With no sidechain signal, the spectral ducker simply has no key to follow.

16.3 Automation

Audio controls are exposed to the host for automation. In Pro Tools, Control+Command-click a mapped Plexus Spectral Dynamics control to open its automation lane.

For multi-selected channels, a movement writes the same value to each selected channel’s parameter. The host still sees those as separate per-channel parameters. The current UI selection and display settings are session state, not automation targets.

When automating fast changes:

• prefer level moves with CHANNEL GAIN rather than repeated Mute switching;
• remember that THRESHOLD and LIMITER are global editor controls but are stored per channel;
• use LINK for limiter image stability, not as a substitute for selecting channels to edit.

16.4 Pro Tools gain-reduction meter

The AAX build reports the deepest current limiter reduction to the Pro Tools insert meter. The detailed per-channel values remain visible in Plexus Spectral Dynamics’s own rows and meter bank.

17. Troubleshooting

The ducker does not move

1. Confirm that the DAW is feeding Plexus Spectral Dynamics’s sidechain.
2. Select SIDECHAIN and check that the spectrum or white band bars move.
3. Return SC HPF / SC LPF to 200 Hz / 6 kHz by double-clicking the lane.
4. Raise KEY GAIN temporarily.
5. Confirm that the channel’s D light or DUCK module is on.
6. Raise SENS and verify that REDUCTION is above 0 dB.

The whole image shifts when the limiter works

Use PAIRS for left/right pair stability or ALL for the entire non-LFE bed. UNLINK deliberately lets each channel reduce independently.

The LFE does not follow ALL

That is intentional. LFE always limits independently and uses different timing suited to low-frequency material.

FILTER controls do not match the line drawn in a channel lane

BASS MGMT may be active. Its crossover owns the relevant band edge and is labelled BM. Turn bass management off if you want the channel HPF/LPF to define that edge again.

Bass management has no audible effect

Check that the main layout contains LFE plus front Left and Right channels. Bass management is unavailable for Ambisonics and has no route to build in mono, stereo or other layouts without LFE.

A row changed when I meant to select it

Click the channel name/header to select. Clicking in the spectral lane edits the nearest filter edge.

The plug-in adds latency with LIMITER off

This is expected. Plexus Spectral Dynamics keeps a fixed processing delay so the DAW’s delay compensation does not change when LIMITER is switched or automated. Settings shows the exact value.

The spectrum is empty or too faint

Open Settings and raise the RTA floor from its default −80 dB. This changes the display only.

Audio alternates between sound and silence every three seconds

No valid licence or trial is active. Click the Plexus logo and activate online or load an offline licence file. If an activated machine still enters demo mode after restarting the DAW, contact support before deleting the licence file.

Pro Tools does not show Plexus Spectral Dynamics after installation

Quit Pro Tools completely with Cmd+Q, verify that Plexus Spectral Dynamics.aaxplugin is in the AAX path listed in section 2, then relaunch so Pro Tools rescans it.

A session from an older build reacts differently

The v0.4.13 state loader migrates the older pre-v0.4.9 attack/release mapping to preserve its audible timing. If an older session still needs adjustment, compare the real millisecond values and save it again in the current version.

For support, contact hello@kaizen.audio and include the Plexus Spectral Dynamics version, DAW, sample rate, channel layout and exact routing.

18. Specifications

18.1 Speaker layouts

Main input and output use the same layout.

Ambisonics: first order (4 channels), second order (9 channels) and third order (16 channels), ACN/SN3D.

18.2 Control summary

18.3 Technical summary

Kaizen Audio · Plexus Spectral Dynamics v0.4.19 user manual · hello@kaizen.audio