HoRNet SpectraDuck — User Manual

Introduction

SpectraDuck is a side-chain ducker that "sees frequencies". A normal ducker cuts everything; SpectraDuck cuts only where it matters — one frequency at a time, based on what the sidechain is doing right now. It's built for anyone who wants musical ducking without configuring six bands of compressors.

What it is, in plain terms

SpectraDuck sits on the channel you want to duck (say, the bass bus, the drum bus, or a music bed). You tell it where to "listen" (the sidechain — usually the kick or a vocal), and it lowers the volume of your channel in the frequencies where the sidechain is loudest. The rest of the signal passes through untouched.

One line summary: surgical, musical ducking — no crossovers, no fixed bands, no phase issues between bands.

Who it's for

Mix engineers doing musical sidechain on buses (kick ↔ bass, vocal ↔ BGM, drum bus, master glue).
Producers who want surgical de-essing or de-masking without configuring six multiband compressors.
Podcasters, voiceover artists, video post: background music that ducks only in the frequencies where the voice lives.
Anyone who wants a "smart" ducker without huge plug-ins and without a 100-page manual.

The idea, in plain words

Why "spectral"?

A traditional ducker looks at the signal and says: "it's loud, I'll pull everything down". SpectraDuck looks at the spectrum and says: "it's loud around 200 Hz, I'll pull down only there". If your sidechain is a kick hitting at 60 Hz, the ducking only touches the low end of your bus — the rest stays exactly as it was.

The result is ducking that follows the natural masking of the signal: where there's conflict, SpectraDuck cuts. Where there isn't, it leaves things alone.

Three knobs do most of the work

Amount — how hard the ducker pushes, as a percentage. 0 % = inactive, 100 % = full strength.
Range — the maximum number of decibels it can cut at any moment. Think of it as the ducker's ceiling.
Sharpness — how surgical the cut is. High = follows the sidechain's spectrum exactly; low = spreads the cut over neighbouring frequencies, more "musical".

Three knobs, and the rest is garnish. With those three and a good starting preset, you cover 90 % of use cases.

What you see in real time

The signal's spectrum is drawn in cyan. The post-ducking spectrum in dashed yellow. The gain-reduction curve — how much SpectraDuck is cutting at each frequency — is drawn in magenta: the higher it gets at a point, the more it's cutting there.

On top of that you get classic L/R meters and a dedicated gain-reduction meter. That's everything you need to see what's going on.

Installation

What you get

VST3 — Windows and macOS (all modern DAWs)
AU — macOS (Logic Pro, GarageBand, Reaper)
AAX — Pro Tools, macOS and Windows
Standalone — for testing and reference

On macOS, the bundles go into the matching Audio/Plug-Ins folders. On Windows, into the system's VST3 and AAX folders. No installer — copy, paste, and your DAW picks it up next time it scans.

Wiring up the sidechain

In your DAW, open the channel that hosts SpectraDuck and route the sidechain from the trigger you want (kick, vocal, anything). In Ableton Live, Logic, Cubase, Reaper, Studio One, and Bitwig it's a single click: the SC indicator in the top right of the SpectraDuck interface lights up when the sidechain is active. If it stays off, SpectraDuck runs in passthrough — nothing breaks, it's just not ducking.

Quick Start

Up and running in 5 steps

Drop SpectraDuck on the channel you want to duck

On the bass bus, the drum bus, or the music master. Not on the trigger channel.

Turn on the sidechain in your DAW

Route the kick (or vocal, or whatever) as SpectraDuck's sidechain. Make sure the SC indicator is lit.

Pick a preset close to your use case

The factory presets are already dialed in. For kick ↔ bass, start with Classic Kick-Bass. For ducking under a vocal, Vocal Duck on BGM. For EDM, EDM Wide Sidechain.

Tune the detector's frequencies

The HP Detector and LP Detector controls tell SpectraDuck which frequencies to listen to in the sidechain. For a kick: 35 Hz to 220 Hz. For a voice: 180 Hz to 5.5 kHz. Tighter ranges mean more focused ducking.

Amount, then Range, then Mix

With Mix at 100 %, raise Amount until the ducking feels musical. If you want more "depth" without losing the bottom of the signal, raise Range. Finally, if you'd rather a softer, blended duck, lower Mix.

The trick to knowing whether you're doing it right

Set Listen Mode to Delta. You'll hear only the part of the signal SpectraDuck is cutting right now. If it's exactly the masking you wanted to remove, you're set. If you hear attenuation where you didn't expect, tighten the detector range with HP/LP Detector. It's the fastest way to learn how to read SpectraDuck.

Interface

Fig. 1 — SpectraDuck's interface in light mode. Input spectrum (cyan) and output spectrum (magenta), per-bin gain-reduction curve overlaid on the spectrum, input/output and GR meters on the right (12.0 dB reduction, sidechain active).

The spectrum

The cyan curve is the incoming signal, the yellow one is what's coming out. The magenta curve shows how much SpectraDuck is cutting at each frequency — the higher it gets at a point, the more it's attenuating there.

When SpectraDuck is inactive (sidechain off or Amount at zero), the two curves overlap and the magenta one sits flat at zero. When it's working, you'll see the magenta rise exactly where the sidechain's spectrum "pushes" hardest.

Listen Mode — your tutor

Three options, three different uses:

Off — normal output. This is your working mode.
Sidechain — hear what the detector is "listening" to, filtered and aligned. Useful to verify that HP/LP Detector are set the way you think.
Delta — hear only what the ducker is cutting. The teaching mode par excellence: it shows you exactly where SpectraDuck is doing its thing.

The Controls

The full table

Control	Range	Default	What it's for
Amount	0–100 %	100	How hard the ducker pushes. 0 = inactive, 100 = full strength.
Range	0–24 dB	24	Maximum attenuation, in decibels. Amount decides "how much" of Range is used.
Sharpness	0–100 %	30	How surgical the cut is. 100 % = follows the sidechain spectrum exactly; 0 % = smooth, more "musical".
Mix	0–100 %	100	Blend between clean signal and ducked signal. 100 % = duck only, 0 % = bypass.
HP Detector	20–1000 Hz	20	The frequency above which the detector starts listening.
LP Detector	2k–20 kHz	20000	The frequency below which the detector stops listening.
Attack	0.5–200 ms	8	How fast the ducker "grabs" when the sidechain rises. With Auto Time, it sets itself.
Release	5–2000 ms	90	How fast the ducker "lets go" when the sidechain falls. Auto Time estimates it from the signal.
Auto Time	on / off	on	Automatically estimates Attack and Release from the sidechain content. Recommended: leave it on.
Lookahead	off / on	off	Helps the detector "see" incoming transients. Usually keep it on.
MS Mode	Linked / Mid / Side	Linked	Ducks both channels, only the centre, or only the stereo sides.
Listen Mode	off / SC / Delta	off	Diagnostic listening mode. See the previous section.
Output Gain	−12 / +12 dB	0	Final volume after all the ducking. Useful for level compensation.
Bypass	on / off	off	Switches off all processing. Handy for A/B checks.

The three knobs worth remembering

If you only remember three things, remember these:

Amount — how strong the ducking is. Start from the preset and adjust to taste.
Range — how many dB it can cut at most. High = aggressive pump; low = gentle duck.
HP/LP Detector — which frequencies the trigger is listening on. This is the knob that turns a generic duck into a surgical one.

Factory Presets

What's in the box

Preset	When to use it	What it does
Init	Neutral starting point.	Full-band detector, Amount at max, medium Sharpness.
Classic Kick-Bass	Classic rhythmic pump on the bass bus.	Detector 35–220 Hz, Lookahead on, decisive attack.
Sub Bass Tightening	Cleans up the 20–80 Hz sub under the kick.	Very narrow detector, highly surgical.
Vocal Duck on BGM	Music bed under a lead vocal.	180 Hz – 5.5 kHz, Mid channel only, soft range.
Podcast VO Clarity	Voice-over work.	250 Hz – 4 kHz, Mid Only, gentle ducking.
Dialog over Music	Dialog over music (film/TV).	200 Hz – 6 kHz, Mid Only, stronger ducking.
EDM Wide Sidechain	Pump on the stereo sides.	60 Hz – 8 kHz, Side Only, perfect for pads and tails.
Drum Bus from Kick	Drum bus ducked by the kick.	50–300 Hz, surgical ducking.
Acoustic vs Vocal	Acoustic guitar vs vocal.	200 Hz – 3.5 kHz, soft blend.
Instrument Bus Glue	Soft ducking on an instrument bus.	120 Hz – 5 kHz, Mid Only, reduced Amount.
Bus De-Mask	Surgical de-masking on a pre-processing bus.	300–8 kHz, very surgical, small cuts.

Four Real-World Use Cases

Kick ↔ Bass

On the bass bus, with the kick as the sidechain. Open the Classic Kick-Bass preset and listen. If the pump is too strong, lower Amount; if you want more "cleanliness" in the low end, tighten the detector range to 35–220 Hz. Total setup time: 30 seconds.

Fig. 2 — Kick ↔ bass pump: the magenta gain-reduction curve acts only where the kick "covers" the bass.

Voice over Music

On the music master, with the vocal channel as the sidechain (routed via a send). Open the Vocal Duck on BGM preset. You'll hear the music "breathe" under the voice, but only in the frequencies where the voice actually lives — no "phone" effect, no loss of stereo width.

Compared to a multiband compressor: SpectraDuck ducks exactly the frequencies where the voice is present (typically 200 Hz – 4 kHz, with extra weight on formants at 800 Hz – 2.5 kHz), instead of attenuating fixed bands uniformly.

Bus de-masking

On a pre-processing bus (e.g. the bus that feeds the mastering chain), with the lead vocal bus as the sidechain. Open Bus De-Mask. Briefly switch Listen Mode to Delta: you'll hear a few surgical notches above 300 Hz, exactly where the voice was masking something else. Just a few dB, but they make a difference in the final master.

EDM "wide sidechain"

On the master or on a pad synth. Open EDM Wide Sidechain. Set MS Mode to Side Only: the centre (kick, vocal, lead) passes clean, while the stereo sides (reverbs, pads, tails) get ducked. You get a stereo "breathing" under transients without losing the punch of the centre.

Latency & Compatibility

How much delay does SpectraDuck add?

About 5 milliseconds. The plugin uses an FFT (a mathematical analysis of the signal), and that kind of processing needs a small buffer of samples. It's an extremely short delay that your DAW compensates for automatically — you won't hear it or see it, in any well-configured project.

If for some reason you want to reduce it (live contexts, monitoring), there's the Lookahead Off option: the delay stays the same, but the detector works slightly differently.

In your DAW

All modern DAWs compensate for plugin latency automatically. It's called Plugin Delay Compensation (PDC). It's on by default in Logic Pro, Live, Cubase, Studio One, Reaper and Pro Tools. You don't have to do anything: the plugin reports its delay and the DAW handles it.

Frequently Asked Questions

Can it replace a multiband compressor?

In many cases, yes. If you want musical ducking that follows the natural masking of the signal, SpectraDuck is more immediate. If you need surgical control — say, one band at 200–400 Hz with slow attack and fast release while the rest behaves differently — a traditional multiband is the right call.

Why do I need a sidechain?

SpectraDuck is a ducker: without a "trigger" signal telling it when to duck, it wouldn't make sense. If you connect only the main channel and no sidechain, the plugin passes the signal through clean. That's not a bug, it's the intended behaviour.

How do I know whether I'm cutting the right frequencies?

Set Listen Mode to Delta. You'll hear only the part the ducker is cutting: if it's exactly the masking you wanted to remove, you're set. If you hear attenuation where you didn't expect, tighten the HP/LP Detector range.

What's Auto Time?

It's the mode that automatically estimates Attack and Release based on the sidechain content. On a dry kick you'll get short times, on a sustained voice longer ones. It does it for you, in real time, without you having to think about milliseconds. We recommend leaving it on.

Can I automate the controls?

Yes, all of them. Amount, HP/LP Detector, Sharpness, MS Mode and Range are the most useful targets for automation.

Does it work on full stereo mixes?

Yes, especially with MS Mode set to Mid Only and HP Detector around 100–150 Hz. The ducking acts only on the mono part of the mix (kick, bass, lead vocal) leaving the stereo image untouched.

Can I use it for parallel processing?

Yes. Lower Mix below 100 % to blend the ducking with the clean signal. Mix at 50 % means "half ducking", useful when you want to attenuate without losing the original presence of the signal.

Does it add noise or colour to the signal?

No, not unless you want it to. With low Amount and a good preset, SpectraDuck is transparent on frequencies where there's no masking. The only risk of artefacts is when you crank Sharpness and Range to the max with a noisy sidechain.

HoRNet SpectraDuckUser Manual — English Edition