Open Audio Analyzer vs Voxengo SPAN

Open Audio Analyzer is free, open-source software for measuring loudness and spectrum in live audio and audio files. Its fourteen meter types include loudness, true peak, VU, spectrum, spectrogram, oscilloscope, phase scope and histogram. Loudness measurements follow EBU R 128 and ITU-R BS.1770-4, with momentary, short-term and integrated LUFS, loudness range and oversampled true peak. Users can arrange meters across tabs, save presets, choose delivery targets for streaming or broadcast, and create their own targets. A command-line tool analyzes individual files or album folders and can produce reports or CSV output. VST3 and Audio Unit plugins send measurements and DAW transport position to the app. An AAX plugin is in the plugin archive but is not signed for a released Pro Tools version. A tablet on the same network can display the app's published measurements over Wi-Fi. The maker says measurements stay on-device and audio is neither stored nor transmitted. The remote display link has no encryption or authentication. The app runs on Android, iOS, Linux, macOS and Windows.

Voxengo SPAN is a free real-time FFT spectrum analyzer plugin for audio and music production applications. It analyzes stereo, mono, mid-side, and surround signals, including 5.1 and 7.1, and can display spectra from two channels or channel groups at once. Metering includes EBU R128 and K-system readings, RMS and true-peak measurements, clipping detection, and stereo correlation. Users can adjust FFT block size, window overlap, visual slope, smoothing, and a secondary spectrum display. Other functions include output power statistics, channel routing and grouping, presets, undo and redo, and A/B comparisons. SPAN is available for Windows and macOS in VST, VST3, and AAX formats, with AudioUnit also listed for Mac. The maker lists Windows XP and later and macOS 10.12 and later, with a 2.5 GHz dual-core or faster processor and at least 4 GB of RAM. Spectrum import and export for track comparisons is a SPAN Plus feature; the free plugin workaround works only in some hosts.