EQ Pro

Overview

EQ Pro is a transparent, surgical equalizer with up to 24 freely typed bands over an interactive curve, a real-time spectrum analyzer, per-band dynamics, Mid/Side and Left/Right processing, and selectable phase behaviour. No analog colouring: it does exactly what the curve shows.

The drawn curve and the processed audio share the exact same filter maths, so what you see is what you hear. Every band is an individually host-automatable parameter, so a full automation lane is available for each.

Installation

macOS

Run the macOS installer (a notarized .pkg). It adds two formats:

• VST3 to /Library/Audio/Plug-Ins/VST3
• Audio Unit (AU) to /Library/Audio/Plug-Ins/Components

Windows

On Windows, EQ Pro ships as a VST3 inside a zip (Audio Unit is macOS-only). After downloading, unzip it and copy the folder Jeesonic EQ Pro.vst3 into your system VST3 folder:

• C:\Program Files\Common Files\VST3\

The zip brings two ways to get there, so you do not have to hunt for that path:

• Double-click Open VST3 folder.cmd. It opens the folder in Explorer and does nothing else. It copies no files and changes no settings.
• Or press Windows+R, paste %CommonProgramFiles%\VST3 and press Enter. Same folder, no file to run.

Then drag the .vst3 folder into the window that opens. Writing there needs administrator rights, so Windows asks you to confirm. The plug-in is not code-signed, but Windows does not block VST3 plug-ins, so no security prompt appears; your host simply loads it. README.txt in the zip repeats these steps.

After installing on either platform, rescan plug-ins or restart your host so it picks up the new version. If an instance is already loaded, remove and re-insert it (or reopen the project).

EQ Pro is free to use, privately and commercially, with no registration and no time limit. Please download it from jeesonic.de rather than from a copy elsewhere, so you always get the current build. See the terms of use.

The interface

The window has four areas: the header along the top, the meter margins left and right, the curve and analyzer in the centre, and the control strip along the bottom, laid out like a piece of hardware on one axis from Input to Output.

1. Preset browser. Factory starting points and your own presets; the arrows step through them. The undo and redo arrows sit at the top right, beside the tooltips and settings buttons.
2. A/B compare. Holds two versions of your settings so you can flip between them; the arrow copies one side to the other.
3. Tooltips. The speech bubble turns the hover help on and off. It lights up while they are on.
4. Settings. Manual and website, window scale, Make Default, version.
5. Input meters. Stereo peak meters with a peak-hold value in dBFS.
6. Output meters. The same, after the EQ.
7. Curve and analyzer. The grid, the live spectrum, the summed response and one thin coloured line per band.
8. Analyzer settings and view buttons. Along the top of the curve: Show, Slope and Decay for the analyzer in the middle, each with its own list, and at the right spectrum landmarks on or off and the piano keyboard on or off.
9. Band handle. Drag to set frequency and gain, scroll to set Q or slope, right-click for type, channel and delete.
10. Inline band panel. The selected band's values and switches, with the dynamics controls when DYN is on.
11. Piano keyboard. Reads any spot on the curve as a musical note.
12. Input. Level going into the EQ.
13. Bypass. A true bypass Since 1.3: input, EQ and output all drop out, and the signal passes as it comes in.
14. Gain Scale. Scales every band's gain at once.
15. Selected band. Freq / Gain / Q, the ON and SOLO switches, and the arrows that step from band to band.
16. Mode, Sampling and Auto Gain. The switch row: phase mode (Digital, Standard, Natural or Linear), oversampling (Off / 2x / 4x) and Auto Gain, which compensates the EQ's own gain change.
17. Output. Level leaving the EQ.

The window is freely resizable: drag the corner and the whole UI scales smoothly at any size between 75 % and 200 %. The size is remembered with the project. The settings menu still offers the fixed scale steps as quick presets. (In the Audio Unit the window uses the fixed steps only, because the main AU host has trouble with continuous resizing.)

Hover help Since 1.2

Rest the pointer on any knob, button or value and a short explanation appears, including the controls in the inline band panel. Turn it on or off with the speech bubble at the top right; it lights up while they are on, and the choice is remembered with the project.

Presets Since 1.2

The preset browser sits in the centre of the header.

• Factory templates give you a starting point rather than a finished mixing decision: High Pass, Low Pass, Tilt, Dynamic EQ, plus a flat Default.
• Your own presets: Save as stores the current setup, Delete removes one, Reveal preset folder opens it on disk.
• The arrows step through the whole list. The display shows the current preset name, with a * once you edit away from it.

Make Default Since 1.2

Make Default in the settings menu saves the current setup (all bands plus the analyzer and UI options) as the state every new instance opens with. Once you have set one, the entry reads Update Default, and a Factory Default entry appears to return new instances to the built-in default. A project you reopen always restores its own saved state; only fresh instances start from your default.

Undo and Redo

The two curved arrows at the top right, beside the tooltips and settings buttons, take back the last edit, and put it back again. They are lit while there is something to do and dim when there is not.

A step is one action, not one value: adding or deleting a band, a handle you dragged and let go, a type or channel you picked, a value you typed, a knob you turned, a switch you flipped, a preset you loaded, an A/B switch. Dragging a handle across the screen is a single step, not one per pixel.

The plug-in keeps the last 50 steps. They belong to the instance and are not saved with the project: a session you reopen starts with nothing to undo, because the history would otherwise lead into a state you never saw.

Undo covers what you did to the sound. It leaves your view alone: the analyzer settings, the window size, the tooltips, the span and the keyboard stay as you set them.

A/B Since 1.2

The A and B buttons in the header hold two versions of your settings so you can flip between them and hear the difference instantly. Click A or B to switch. The arrow between the letters copies the current version to the other (it points at the destination and flashes it), so you can branch an alternative from where you are. Both versions are remembered with the project.

Working with bands and the curve

The canvas maps frequency across its width (log scale, 10 Hz to 20 kHz) and gain over its height (up to +/-24 dB shown). Each band is a coloured dot sitting on its own response curve.

Every band also draws its individual response Since 1.2 as a thin coloured line behind the summed curve, so you can always see which feature in the result belongs to which band without selecting it first. The active band draws brighter. A band's handle always sits on its own per-band curve, so marker and curve line up. (For a dynamic band the handle stays at the static gain and the ring around it sets the far end of its travel; the summed curve shows the live movement.)

Creating, selecting and removing bands

• Add a band: double-click an empty spot on the curve. A band dropped near the far left or right edge defaults to a low cut or high cut. New gain bands start at 0 dB, so the handle lands on the existing curve; the cursor then follows the new marker so you can drag it straight away.
• Select a band: click its handle. The bottom Freq / Gain / Q knobs and the inline panel follow the selection. The arrow steppers next to the knobs walk through the bands in frequency order.
• Delete a band: double-click its handle, or use the x button in the inline panel, or right-click the handle and choose Delete.

Shaping with the mouse

• Drag a handle to set frequency (horizontal) and gain (vertical) at once. Dragging is relative to where you grab: a band that overlaps others moves smoothly from the grab point, with no jump.
• Scroll over a handle to set Q (bells, shelves, notch) or the slope (cut bands, 6 to 96 dB/oct).
• Hold a modifier while you drag: Shift for fine steps, Cmd (Ctrl on Windows) to lock the drag to one axis, Alt to set Q with the vertical move instead of the gain. The axis lock follows the direction you actually took, so you do not have to decide before you start.
• Right-click a handle for a menu of type, slope, channel and delete. Right-click empty space for an add menu.

Filter types

Right-click a handle (or use the shape button in the inline panel) to pick the band type:

Bells and both shelves are symmetric (constant-Q): a cut is the exact mirror of the boost of the same Q. Cut types are only offered when no other band sits further out on that side, so a cut never swallows bands beyond it.

The band frequency runs from 10 Hz (for subsonic high-pass work) up to 20 kHz, the right edge of the display, so the Freq knob and the marker stop at the same place. A band loaded from an older session above 20 kHz is clamped to 20 kHz.

A cut band parked at the edge is off: a Low Cut at 10 Hz or a High Cut at 20 kHz does nothing to the sound or the curve, and its marker dims. This is for hardware controllers such as the SSL UC1, which have no on/off button for the cuts and only a frequency knob. Move the band a little away from the edge and it works again.

The modifier keys

The same three keys mean the same thing everywhere in the window, on the curve and on every knob, slider and value:

Double-click a knob to return it to its default. Double-clicking its number still opens it for typing, and double-clicking a band handle still deletes the band.

Hardware controllers

For controllers that map the plug-in's parameters (the SSL UC1 through SSL 360, for example), every band has an extra on/off parameter named Band N Shelf in the host's parameter list. It is not shown in the plug-in window. Switched on, it turns a Bell into a shelf (Low Shelf below 1 kHz, High Shelf above); switched off, it turns the shelf back into a Bell. It follows the type you pick in the plug-in, so a BELL/SHELF button on the controller always shows the band's real state. Other band types ignore it.

Spectrum landmarks Since 1.2

Spectrum landmarks (the button at the top right of the curve) mark where something keeps going on in your spectrum. The plug-in listens to the energy of the incoming signal over a few seconds and marks the narrow peaks that stand out of their surroundings, rather than just the loud regions. A peak that stays in one place is emphasised the longer it holds, while ones that drift around stay faint or drop away, so what is structural separates from passing spectral movement.

The colour tells the two cases apart: a red marker is a frequency that holds its place over time, a green one wanders. A steady red marker is the typical room mode, ringing note or resonance; green is more often musical movement that only passes through.

A landmark is a place to look, not a verdict. Whether the note, room mode or resonance it points at is a problem or the character of the instrument is your call: the marker only tells you something is consistently there. Listen first, then decide what the EQ should do about it, if anything.

• Small markers stand on the frequency axis at the bottom of the curve, each with a faint guide line rising through the spectrum to line a band up on.
• Hover a marker to see its exact frequency, its nearest note, and how far it stands out.
• Press and hold a marker to hear it on its own for as long as you hold it (a momentary, narrow audition). Drag up onto the curve to sweep the audition continuously across any frequency, snapping back to the markers in the bottom strip. Releasing goes straight back to normal.

Nothing is judged, created or changed, it is purely a listen. Click the icon to switch it on or off; the state is remembered with the project. It is otherwise display only.

The inline band panel

Selecting a band shows a panel floating at its handle. Everything for that band lives here, so the bottom strip never reflows.

The panel keeps itself clear of the curve as you work, sliding to the other side of the marker when the band would otherwise be hidden. Its frame and the short leader line to the handle carry the band's own colour, so it is always clear which band the panel is editing.

Top row

• Power: switch the band on or off without deleting it.
• Solo (headphone): audition just this band as a band-pass, to find the exact spot. It is a listen tool, not a mute, so it does not change the mix. On a dynamic band the dynamics stay active in solo, so you hear exactly what the band is doing. The button lights up and the curve carries a SOLO banner while it runs.
• Delete: remove the band.
• Shape button: open the filter-type popup.
• Channel button: set the stereo placement (see Mid/Side and Left/Right). It shows the stereo mark for Stereo, and M, S, L or R otherwise.
• DYN / AUTO / EXT: the dynamics toggles (see Dynamic EQ).

Editable readout

The Hz / dB / Q (or slope / tilt) values are editable both ways: drag a value up or down to nudge it (hold Shift for fine steps), or double-click it to type a number. Enter k for kHz. The four compressor values (Ratio / Knee / Attack / Release) are typed by double-click, on top of dragging their sliders; for Ratio you can type Inf for brickwall limiting.

Dynamic EQ

Any bell or shelf can be made dynamic: its gain engages only when the signal inside that exact band crosses a threshold. The detector listens to precisely the band you drew, at its own frequency and Q and on its own channel (Stereo, Mid, Side, Left or Right), so it reacts only to what that band covers, nothing else.

Gain, Range and Threshold

A dynamic bell or shelf rests at 0 dB, and its handle sits where the band can reach: at the far end of the Range, the distance the dynamics may move it. Drag the handle up or down, or turn the Gain knob, to set the Range.

Switching DYN on turns the band's gain into the Range, and switching it off turns the Range back into the gain. The handle stays where it is either way: a bell boosted by 6 dB keeps its handle at +6 dB, rests at 0 dB while it is dynamic and lifts by up to 6 dB as its region gets loud.

A minus sign moves the band down, a plus sign up; a small Range is a gentle move, a large one is firmer.

The Threshold is separate and absolute (in dBFS): the band starts to act as the in-band level rises above it and reaches the full Range as the level climbs further.

The shaded area between the 0 dB line and the handle is the ground the band can cover. The wheel over the handle sets the band's Q.

Press and hold a band's handle for a moment to make it dynamic on the spot, and keep the button down to drag the Range, with no trip to the band panel. Press and hold the handle of a dynamic band to make it static again. If you drag after all, it stays dynamic and the drag sets the Range.

In AUTO the band uses automatic, program-adaptive ballistics, and the ratio follows the Range: you set the Range with the handle and the Threshold on the meter.

Drag the marker on the meter to set the Threshold. The number beside it reads the same.

Switching AUTO off hands you ratio, knee, attack and release. The ratio starts at 4:1 unless you have already set it by hand.

How the band reacts to the threshold

A dynamic band reacts to content above the threshold: it adds the Range as the region gets loud. With a Range that lifts it pushes loud content further up, with a Range that cuts it holds loud content down (the classic de-esser).

The dynamics meter

Whenever a band is dynamic, the panel shows a per-band dynamics meter, the standard view:

• The level bar is the level in the band's frequency range, for setting the threshold. It has its own fixed meter fall and does not follow the band's attack and release. The part that sits above the threshold (what actually drives the move) is drawn in amber.
• The threshold marker (a small triangle in the band's colour) sits on the level track. Drag it to set the threshold; the T readout shows its dBFS value.
• GR shows the live move the band is applying right now: GR (coral) for a cut band and GA (green) for a boost band, so the meter fills whichever way the band works.

Toggles

• DYN turns the dynamics on for the band.
• AUTO lets the band set itself up: automatic, program-adaptive ballistics, and the ratio follows the Range. Switching it off puts ratio, knee, attack and release in your hands, below the meter as two rows of sliders: Ratio and Knee, then Attack and Release.
• EXT drives the detector from the external sidechain bus instead of the band's own signal. An amber dot warns if EXT is on but no sidechain signal is arriving (the band then falls back to internal detection).

Automatic or by hand

With AUTO on, the band uses automatic, program-adaptive ballistics and shaping, a good starting point.

An automatic band now levels gently Since 1.2 rather than limiting: the strength of the grab follows the Range you set, so a small range (say -3 dB) eases its region down softly (about 1.5:1) and a large range grabs firmly (5:1 at -24 dB). This is the Musical default. By hand you still get the exact ratio you set, including brickwall.

Dynamics in the settings menu picks how the dynamics behave. It is stored with the project, and a project always loads on the setting it was mixed with:

• Adaptive Since 1.3 is what a new project starts on: the ratio comes from the Range and the threshold stays yours, and with AUTO off the release is adaptive (see The full compressor below).
• Fixed threshold: the ratio comes from the Range, but the threshold and the knee stay yours.
• Classic is the original: only the timing is automatic, and the band limits at the threshold.

Switching AUTO off no longer jumps the Ratio to brickwall: on a musical automatic band it starts at the value the automatic reduction was already using, so the sound stays continuous while you take over. The moment you set the Ratio by hand it is kept from then on; a band you never touch follows the automatic value.

The full compressor (AUTO off)

With AUTO off, the band is a complete compressor on its own frequency region. Together with the Threshold (on the meter) and the Range, the controls are:

• Ratio sets how much of the level over the threshold is removed, from 1:1 (nothing) up to Inf (brickwall). The Range still caps the maximum move.
• Knee is the soft-knee width (0 to 24 dB) around the threshold, so the onset can be a gradual ease-in (wider) or a hard switch (0 dB). The default is 6 dB.
• Attack and Release set how fast the band reacts and recovers.

With Dynamics set to Adaptive in the settings menu Since 1.3, the band recovers in two stages. A short gap between notes opens the band less, and after a long loud passage the band lets go more slowly. The Release control then shows a step from 1 (fast) to 10 (slow) instead of milliseconds, here and in your host's automation. With Fixed threshold or Classic, the band recovers at the Release time. The Spectral band always recovers at its Release time.

Mid/Side and Left/Right

Each band can act on a chosen part of the stereo field. Click the channel button in the panel, or use the Channel submenu at the top of a band's right-click menu, and pick:

The right-click Channel submenu and the panel's channel button stay in sync. When non-stereo bands are present, the curve splits into colour-coded component lanes (Mid and Side, or Left and Right) so you can see each placement's own response. A band's handle rides its own lane.

Spectrum analyzer

A time-smoothed FFT analyzer sits behind the curve, on a log-frequency display with an interpolated low end (no staircase). Its three settings stand along the top of the curve, above the preset display. Each one shows its value; clicking one drops its list open underneath. Show picks the mode:

• Off: no analyzer.
• Post: the processed (output) spectrum, filled.
• Pre + Post: the input spectrum as a faint line behind the filled output, so you can see what the EQ did.

Decay and display slope Since 1.2

The other two stand beside it, both display only and both remembered with the project:

• Decay sets how quickly the spectrum falls back after a peak, from Fast (a snappy trace that follows the signal down) to Very slow (a steady, heavily damped display where peaks linger), with Medium the default.
• Slope tilts the spectrum by 3, 4.5 or 6 dB/oct (pivoting at 1 kHz) so the top octaves are easier to read and a typical mix sits flatter, or leave it Flat for the raw spectrum. It affects only the display, not the audio.

While a state banner is running, the three step aside: the middle of that row carries it instead.

Piano keyboard Since 1.2

A piano keyboard along the frequency axis lets any spot on the curve read as a musical note. The selected band's key lights up in the band colour, and its note is written in a small field at the right end of the keyboard, where the keys are above 15 kHz and no longer say anything. The keyboard is switched on and off by the note button at the top right of the curve.

Use the analyzer to find problem frequencies, but trust your ears for the final move.

Phase modes and oversampling

The mode sits as a switch in the bottom strip under the MODE legend. Digital, Standard and Natural Phase are all zero or near-zero latency; only Linear Phase adds real delay.

Dynamic bands work in all four modes (see Dynamic EQ). Oversampling sits next to MODE as the SAMPLING switch (Off / 2x / 4x): left-click cycles it, right-click picks directly, and its LED is dark at Off and lights when engaged (green at 2x, blue at 4x). It runs the filters at a higher internal rate for cleaner behaviour near Nyquist on steep or high-frequency moves, applies to the IIR paths (Digital, Standard and Natural Phase), and uses a low-latency design.

On CPU. Digital and Standard are the lightest and cost the same, so choose between them by ear, not by load. Natural Phase and Linear Phase cost a bit more (a correction filter and an FFT, respectively); the practical difference between them is latency, not CPU. Oversampling roughly doubles the load per step (2x, 4x). The heaviest combination is many dynamic bands in Natural Phase, since each moving band re-fits its correction filter; even then a single instance stays well within real time on a modern machine.

Gain Scale and Auto Gain

Gain Scale

The Scale dial (0 to 200 %) scales every band's gain at once: 100 % is as drawn, 50 % is half the moves, 0 % is flat, 200 % is double. The whole curve, the handles, the on-curve readouts and the Gain knob follow the Scale, while the stored per-band values stay untouched. Use it to dial the whole EQ in or out, or to A/B a gentler version of your curve. Cut and notch bands have no gain, so they are unaffected.

Auto Gain

The Auto switch level-matches the output so bypassing the EQ compares at an even loudness. It is deterministic: the trim is computed purely from the filter response (the average level the curve adds or removes), never from a level measurement. That means it has no detector of its own and never acts like a compressor, which is exactly what you want from an EQ. A broadband boost gives a downward trim, a broadband cut gives an upward trim, and a balanced curve leaves the level essentially unchanged.

Its LED turns amber while Auto Gain is on and a band it cannot fully level-match is present, so an incomplete level match is never invisible.

Auto Gain follows the dynamics

Auto Gain also folds in what the dynamic bands are doing right now. It reads each dynamic band's live gain (which the band's own dynamics already determine) and keeps the broadband loudness steady as the band moves. The result is a dynamic EQ that changes the spectrum without changing the level: the notch or peak still acts, but the track does not get quieter or louder as it does.

This is still not a second compressor: the only thing that moves over time is the band's own dynamic gain, and the compensation is feed-forward (the detector listens before it), so it cannot pump or run away. It holds the perceived (equal-energy-per-octave) loudness, so it tracks real program material closely.

Input, output and metering

• Input knob (left margin): gain applied before the EQ. The input meters follow it.
• Output knob (right margin): trim applied after the EQ.
• Stereo meters flank the curve: a pair on the left for input, a pair on the right for output. The outer bar of each pair carries the dB scale.
• Bypass (bottom left): a true bypass Since 1.3. Input, EQ and output all drop out, so the bypassed signal is exactly the signal coming in. It keeps any added latency (Linear Phase, for example), so playback does not pop or shift. The host's own bypass does the same.

For an honest bypass comparison, turn on Auto Gain so the levels match.

Settings

The button at the top right of the header, two small sliders, opens the settings menu:

• UI Scale: fixed steps (75 / 85 / 100 / 125 / 150 / 175 / 200 %) as quick presets; the window is also freely resizable by dragging its corner.
• Dynamics: how the dynamics behave, in three settings (see Dynamic EQ). A project always opens on the one it was mixed with, so switching it changes that mix.
• Make Default / Update Default / Factory Default: the state new instances open with (see Presets).

Under Help, at the bottom, are the manual, the website, Version with the format and build stamp, and:

• Check for updates: when on (the default), the plug-in looks for a newer version at most once per day, the first time you open its window that day. If one is available, the settings button tints green; opening the menu shows a link that opens jeesonic.de. Nothing is ever downloaded or installed automatically. It is a plain request for a small public version file, sends no personal data, and can be turned off here. See the privacy note.

All plug-in state (every band and setting) is saved with your host session.

Mouse and keyboard reference

Tips

• Find then fix: solo a bell and sweep to locate a resonance, then back the gain off to cut it. Or turn on spectrum landmarks and let them point you at the steady peaks first.
• Tame dynamically: for a frequency that is only a problem on loud notes (a harsh vocal S, a boomy kick), use a dynamic cut instead of a static one so it only acts when needed.
• De-ess in stereo or Side: a dynamic high-shelf or bell on the Side channel can tame sibilance or harsh cymbals without dulling the centre.
• Shape, don't squash: with AUTO off, dial a softer Ratio and a wider Knee for a gentle, musical move instead of hard limiting; the Range still caps how far it can go.
• Tone without loudness: keep Auto Gain on with your dynamic bands and the EQ changes the spectrum while holding the loudness steady, so you hear the tone change, not a level change.
• Match loudness: turn on Auto Gain before A/B-ing against bypass, so you judge tone and not level.
• Linear phase for masters: switch to Linear Phase on a mix bus or master where phase smear matters; use Digital or Standard while tracking to avoid delay.
• Scale to taste: build an aggressive curve, then pull Scale back to 60 to 80 % for a more natural version without redrawing every band.

Credits

The interface icons are from Lucide, used under the ISC License.