ZL Audio has released ZL Spectrum Equalizer, a free and open-source dynamic spectrum equalizer plugin for Windows, macOS, and Linux.
I already expected something like this coming from ZL Audio at some point. The developer is behind the excellent ZL Equalizer 2 and ZL Compressor, both of which received some fantastic feedback from the BPB community.
I wrote earlier this year that free EQ plugins are getting close enough to paid tools that many producers may no longer need to buy a commercial EQ. ZL Equalizer 2 is one of my favorites, alongside TDR Nova and the excellent Jeesonic EQ Pro.
ZL Spectrum Equalizer is a new release, but it is not simply another version of ZL Equalizer 2. It applies broad filter curves based on wide-band audio triggers, while ZL Spectrum Equalizer works directly in the frequency domain using FFT processing. The audio is split into frequency bins, and each bin can be dynamically adjusted depending on the matching side-chain bin level.
The plugin supports up to 24 linear-phase frequency bands, with nine filter types, five stereo modes, and seven slope options. The filter types include Peak, Low Shelf, Low Pass, High Shelf, High Pass, Notch, Band Pass, Tilt Shelf, and Flat Tilt. Stereo modes include Stereo, Left, Right, Mid, and Side.
Each band can have dynamic behavior enabled, with controls for threshold, knee, attack, and release. You can also choose Absolute, Band, or Relative dynamic modes, depending on how you want the threshold to be calculated.
One of the main controls, and one that took me a bit to figure out, is Spectrum Resolution. Lower settings start around 12 ms of latency, while higher settings increase frequency precision at the cost of higher latency, going up to around 743 ms at the Extreme High setting.
There are also side-chain smoothing options, frequency-dependent attack and release skewing, a spectrum gate, external side-chain support, static gain compensation, and loudness-based output gain matching.
The interface follows the same ZL Audio direction we’ve already seen in the EQ plugin. It has an interactive spectrum graph, draggable filter nodes, pre/post/side analyzer views, optional collision detection, FFT freezing, custom colors, adjustable control behavior, and UI scaling options.
ZL Spectrum Equalizer is free and open-source under the AGPLv3 license. The current release is version 0.0.1, so ZL Audio notes that some bugs may still be expected and recommends testing the plugin in an empty DAW session first.
The download page includes Windows, macOS, and Linux builds, with separate packages for different CPU architectures. ZL Audio recommends using the AVX2 version if your CPU supports it. The developer also notes that AAX support is planned around version 0.1.0.
Download: ZL Audio ZL Spectrum Equalizer (FREE)
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Last Updated on August 2, 2026 by Tomislav Zlatic.
