Quick fix: Open Sound → More sound settings (legacy mmsys.cpl), right-click the output device, choose Properties, and uncheck Enable audio enhancements on the Enhancements tab. The new Settings app exposes the global toggle, but per-device control lives only in the legacy dialog.

Windows 11 ships with audio enhancements turned on for every endpoint — bass boost, virtual surround, loudness equalization, automatic gain. These help with cheap built-in speakers but distort serious headphones and ruin clean monitor outputs for music production. The frustrating part is that the new Settings UI only has one toggle, which kills enhancements for every device. If you want speakers enhanced but headphones flat, you need per-device control.

Symptom: You want to disable audio enhancements for one output device but keep them on for another (or vice versa).
Affects: Windows 11 with multiple audio outputs.
Fix time: 3 minutes per device.

Why per-device control matters

Each audio endpoint — speakers, headphones, HDMI, USB DAC — has its own enhancement chain. The chain runs after the source app and before the driver output. For built-in laptop speakers, bass boost compensates for tiny drivers. For studio monitors, the same processing is distortion. For Bluetooth headphones, loudness equalization fights with the codec’s own dynamic processing. The right answer depends on the device.

The legacy mmsys.cpl dialog has held the per-device controls since Windows 7. The new Settings app doesn’t expose them yet, even in 24H2 — you have to use the legacy path or set the registry directly.

Method 1: Disable enhancements per device via the legacy dialog

Right-click the speaker icon in the taskbar and choose Sound settings.
Scroll down and click More sound settings. The legacy mmsys.cpl opens.
On the Playback tab, right-click the device you want to flatten and choose Properties.
Click the Enhancements tab. Check Disable all enhancements (or Disable all sound effects on some drivers).
If the tab has individual effect checkboxes (bass boost, virtual surround, room correction, loudness equalization), uncheck specific ones instead of disabling all.
Click Apply, then OK.
Repeat for any other device. Leave devices you want enhanced unchanged.

Test by playing a stereo reference track — bass should be tight, treble shouldn’t roll off artificially. Compare to a device that still has enhancements on — the difference is obvious.

Method 2: Disable Apo Effects via registry for per-device control

Some Realtek and Conexant drivers re-enable enhancements after every reboot or driver update, overriding the dialog. The fix is to disable the audio effects (APO) at the registry level.

Open the legacy dialog as in Method 1 and click Properties on your device.
On the General tab, note the Controller Information — you need the device hardware ID.
Run regedit as Administrator and navigate to HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\MMDevices\Audio\Render.
Each subkey is a GUID for an audio endpoint. Look inside each one’s Properties subkey for {a45c254e-df1c-4efd-8020-67d146a850e0},2 (the friendly name) to identify your device.
Inside the device’s FxProperties subkey, find {d04e05a6-594b-4fb6-a80d-01af5eed7d1d},0 (Stream Effects). Set its REG_BINARY value to 00 00 00 00.
Do the same for {e0a941a1-9bba-4d3c-9e3f-d6dcdb3c7f0c},0 (Mode Effects) and {b725f130-47ef-101a-a5f1-02608c9eebac},0 (Endpoint Effects) if present.
Reboot. The driver loads with effects disabled and the dialog reflects that on the next open.

This is the only path that survives driver updates from some vendors. Keep a registry backup before editing.

Method 3: Use a third-party driver-side tool for advanced control

Realtek, Nahimic, Dolby Access, and Sonic Suite all install their own per-device controllers. If you have one of these, the in-app toggle is more reliable than the Windows dialog.

Open the Windows Search and type the brand name (e.g., Realtek Audio Console).
Inside the app, locate the per-device or per-output settings.
Disable any audio effect or boost for the device you want flat.
Some apps have a “Music” or “Reference” preset that disables enhancements while keeping basic equalization — choose that if available.
Confirm with playback. The vendor app overrides Windows enhancements on most modern hardware.

If you don’t want any vendor processing at all, uninstall the vendor audio app entirely. Windows’ generic UAA driver gives you a flat output by default.

How to verify the fix worked

Play a reference stereo track (e.g., a piano recording) and switch outputs. The flattened device sounds neutral; the enhanced one has visible bass boost or stereo widening.
Open the device Properties on the flattened device. The Enhancements tab shows Disable all enhancements checked.
Reboot and recheck. The setting persists.

If none of these work

If the Enhancements tab doesn’t appear at all, the driver doesn’t expose APO effects — that’s common with generic Bluetooth audio drivers and some USB DACs. The output is already flat in that case; there’s nothing to disable. If enhancements re-enable themselves on every reboot despite registry changes, a vendor service is restoring them — disable the vendor service via services.msc (typically named after the brand, e.g., Realtek Audio Service) or set it to Manual start.

Bottom line: Per-device enhancement control isn’t in the new Settings app, but it’s still available in mmsys.cpl. For drivers that fight your changes, the registry path under MMDevices is the durable fix. Vendor apps trump both.