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Version: v2

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.
  • Three collapsible sections underneath: AutoEQ, Audio player, and Device PEQ.

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.

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.

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.

Device PEQ — push EQ to hardware​

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 Device PEQ section lets modernGraphTool talk directly to those devices over WebUSB / WebSerial / WebHID / WebBluetooth and push your filter list into the device's own EQ memory. Unplug your computer and the EQ stays loaded.

Supported devices, connection instructions, and troubleshooting all live in Device PEQ. In brief:

  • Chrome and Edge have the best support for the Web APIs this feature uses.
  • Firefox works for some device classes but not others.
  • Safari doesn't support WebUSB at all, so Device PEQ doesn't work there.

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.

Next: Sharing and exporting.