Equalizing audio

The Equalizer panel lets you design a parametric EQ, preview it with real audio, and optionally send it to a compatible hardware device. This page is the user-guide-level introduction. The full feature reference lives at Equalizer, and hardware bridging is documented at Device PEQ.

What EQ is for, in one paragraph

A headphone measurement shows you exactly where a device is louder or quieter than you’d like. EQ lets you digitally counteract those differences before the audio reaches the headphone — turning down a peak at 5 kHz, boosting the sub-bass a little, softening sibilance on vocals. It’s the same principle as the bass/treble knobs on an old stereo, just more precise and more surgical.

modernGraphTool’s EQ panel works on measurements, not on arbitrary audio files. You pick a loaded device, add filters, and see both the modified measurement curve on the graph and — if you enable playback — hear the filters applied to a test audio sample in your browser.

The panel at a glance

Opening the Equalizer panel (third menu icon, or press 3 on desktop) shows you:

• A master enable switch at the top — flip it off to temporarily disable the whole EQ without losing your filters.
• A phone/target selector next to the switch — tells the EQ which loaded curve to modify.
• A filter list — the actual EQ bands, headed by a channel switch (L+R, L or R) that chooses which ear the list edits.
• Three collapsible sections underneath: AutoEQ, Audio player, and Hardware EQ.

Building an EQ by hand

In the filter list, click to add a filter. Each filter has:

• Type — Peaking (a bump or dip centered on a frequency), Low Shelf (everything below a corner), High Shelf (everything above a corner).
• Frequency — where on the X axis the filter is centered.
• Gain — positive values boost, negative values cut (in dB).
• Q — how wide or narrow the effect is. Higher Q = narrower.

As you adjust, the graph updates live — you’ll see a new curve appear showing the device-plus-EQ combination, so you can compare the corrected curve against your target in real time. Preamp gain is calculated automatically to prevent digital clipping when you add lots of boosts.

The minimum viable workflow is:

1. Pick a loaded phone in the phone selector.
2. Flip the enable switch on.
3. Add a filter, set it to Peaking, drag it to the frequency you want to fix, and set the gain.
4. Check the graph to see the corrected curve land on (or close to) the target.

Per-channel EQ (L / R)

No two drivers measure identically. Most of the time you want to leave that alone — the small left-to-right difference is part of how your unit sounds, and correcting the average is enough. But if one ear is noticeably quieter, or you want both ears to land on the target rather than merely their average, you need the two channels equalized separately.

That’s what the channel switch at the top of the filter list is for:

• L+R — bands that apply to both ears. This is the default and what every EQ did before this feature existed.
• L or R — bands for that ear only, applied on top of the shared ones.

Switching to L or R shows only that ear’s bands, with a note underneath telling you how many shared bands also reach it. If the graph was showing the averaged curve, it expands to draw L and R separately so you can see what you’re doing. To move an existing band between buckets, expand it and use Applies to.

Correcting channel imbalance

1. Load your headphone and select it in the Equalizer panel.
2. Pick a target in the AutoEQ section.
3. Switch the channel selector to L, run AutoEQ. Switch to R, run it again.

Each run only replaces its own bucket, so the two solutions coexist. Both ears now land on the target and the imbalance is gone.

To keep the imbalance and just fix the overall tuning, stay on L+R — AutoEQ there works from the average, which leaves the difference between the channels untouched.

Where per-channel EQ applies

The graph, the audio preview and the exported filter file all carry the full per-channel EQ. Device PEQ does not — hardware EQ slots have no channel concept, so a push sends the shared bands only and tells you how many left/right bands it skipped.

AutoEQ

If you don’t want to hand-design filters, open the AutoEQ accordion section. It walks through three steps:

1. Pick a target to match (any loaded target).
2. Click the AutoEQ button, which analyzes the difference between the device and the target and generates a set of filters that minimizes it.
3. Apply the filters to the filter list. Tweak further from there if you want.

AutoEQ can optionally include Low Shelf / High Shelf filters in its output as well as Peaking, which usually produces a flatter match with fewer bands. The two shelves count against the band total, so a ten-band run with shelves on is eight peaking filters plus the pair.

The fit mode picks between Exact match, the default, which fits the curve’s full shape up to 20 kHz the way the graph shows it, and Treble-safe, a careful approach that broadly adjusts the high-frequency range, minimizing errors caused by fit conditions and physical anatomy. See Fit mode for when to choose which.

After the first run the button reads Recalculate, and the Auto-apply switch beside it re-runs AutoEQ whenever the target or the options change — handy while tilting a target to taste. Editing the filters by hand switches it off. See Auto-apply.

With a graphic-EQ preset active, AutoEQ optimizes the gain of each fixed band — the frequency and Q inputs disappear, because the preset already sets them.

AutoEQ follows the channel switch: on L+R it works from the averaged curve, and scoped to one ear it works from that ear’s measurement and replaces only that ear’s bands.

Audio preview

Open the Audio player section to listen to the EQ applied to a test audio sample. Play/pause and a mute toggle give you a quick way to A/B the corrected vs uncorrected sound.

Browser autoplay

Most browsers block audio from starting automatically until you interact with the page. If the player seems dead when you hit play, click anywhere on the page first, then try again. This is a browser policy, not a tool bug.

The player uses the Web Audio API, so CPU usage goes up slightly while it’s running — particularly with many EQ bands.

Playback continues across panel switches — switching to the Graph or Device panel won’t stop the audio. Return to the Equalizer panel and use the player’s stop button when you’re done.

Hardware EQ — push EQ to a device

Some USB DACs, Bluetooth adapters, and even a few headphones have onboard parametric EQ slots that apply EQ in hardware instead of in software. The Hardware EQ section lets modernGraphTool talk directly to those devices — over USB, Bluetooth or your local network — and push your filter list into the device’s own EQ memory, or pull the device’s current EQ into the filter list. Unplug your computer and the EQ stays loaded.

Once connected, the device’s limits — band count, gain range and so on — become the EQ constraint: bands it can’t hold are marked, and before anything is written you see what the device will actually get.

It needs a Chromium-based browser — Chrome, Edge or Opera. Firefox and Safari lack the device APIs it relies on, so the section shows a compatibility notice there instead. Supported devices and connection types are in Hardware EQ.

Import and export

You can export your current filter set as a text file (compatible with common EQ formats) and import one back in later. Useful for:

• Sharing a specific EQ with someone else.
• Keeping a library of presets for different headphones.
• Moving an EQ between modernGraphTool and a system-wide EQ application.

The import/export controls live inside the filter list. See Equalizer for format details.

Per-channel bands survive the round trip. The exported file uses Equalizer APO’s Channel: syntax — a Channel: ALL section for the shared bands, then Channel: L and Channel: R — and import reads it back into the same buckets. An EQ with no per-channel bands exports without any Channel: lines at all, exactly as before, so existing presets and other tools are unaffected.

The Graphic EQ export is a single curve with no channel syntax, so when you have per-channel bands it writes two files instead of one — an L and an R, each combining the shared bands with that ear’s own.

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Next: Sharing and exporting.