Voxengo SPAN

Overview

Voxengo SPAN is a free FFT spectrum analyzer plugin for music and professional audio work. It suits producers and engineers who want frequency, level, and stereo checks inside a compatible plugin host. Its range of analysis tools is unusually broad for a zero-cost option, though spectrum import and export are reserved for SPAN Plus.

Key features

SPAN covers mono, stereo, mid-side, and surround analysis, including 5.1 and 7.1. It can display spectra from two channels or channel groups at once, making it useful for examining multichannel routing rather than only a single signal. FFT block size, overlap, visual slope, smoothing, and a secondary spectrum display let users tailor the view; these controls are valuable when a default display does not make a particular frequency relationship clear.

Metering includes EBU R128 and K-system options, RMS and true-peak measurement, clipping detection, and stereo correlation. That combination gives engineers several complementary checks in one plugin, but it does not replace dedicated spectrum exchange for comparing tracks: importing and exporting spectra is a SPAN Plus feature. Voxengo says a method using the free plugin works only in some hosts, such as Ableton Live.

Channel routing and grouping, output power statistics, preset management, undo and redo, A/B comparisons, and a resizable interface support repeat analysis and session work. Compatibility includes VST, VST3, AudioUnit, and AAX, although the offered downloads vary by operating system. Listed hosts include Ableton Live, Cubase, Logic Pro, REAPER, Pro Tools, FL Studio, Studio One, OBS, Bitwig Studio, Nuendo, and Adobe Audition.

Pricing

Voxengo SPAN — free. The free plan includes the real-time analyzer and its spectrum, loudness, level, RMS, true-peak, clipping, correlation, and mid-side views. There is no paid tier described for this product entry, and there is no free trial because SPAN itself is free. The meaningful trade-off is workflow rather than a quota: spectrum import and export for easy track comparisons requires SPAN Plus. Choose SPAN when its in-host analysis is enough; look elsewhere or consider Plus if direct spectrum transfer is central to your process.

Platforms

SPAN is offered for macOS and Windows. Voxengo specifies Windows XP, Vista, 7, 8, 10 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. Mac downloads include AU, AAX, and VST3; Windows downloads include VST, VST3, and AAX. Check that your host supports one of those formats before choosing it.

Who it's for

SPAN is a strong fit for audio producers, mixing and mastering engineers, and other users who need spectrum and metering views within a plugin workflow, particularly when working with stereo or multichannel material. It is less suitable for anyone who needs the free plugin itself to import and export spectra across tracks, or who cannot use a compatible desktop host.

Pros and cons

• Broad analysis at no cost: frequency views span mono through surround, while metering adds loudness standards, RMS, true peak, clipping, and correlation.
• Useful multichannel visibility: simultaneous display of two channels or groups helps inspect relationships in routed sessions.
• Flexible presentation: FFT, overlap, slope, smoothing, and secondary-display controls let users adapt the analysis view.
• Comparison workflow has a boundary: importing and exporting spectra is a SPAN Plus feature, and the free-plugin workaround is host-dependent.
• Host and format compatibility matters: users must match the available OS-specific formats to their plugin host.

Alternatives

Audio Mastering Software and Audio Analysis Software are useful category starting points if you want to compare options beyond a single analyzer plugin.

IK Multimedia ReSing is a freemium macOS and Windows option with a free tier limited to 2 voices, 2 instruments, and 1 RVC import, with no model generation; choose it when that voice-and-instrument workflow matters more than SPAN's metering focus. Its paid plan is $129.99, paid once.

Matchering is free open-source software under GPLv3 for Linux, macOS, Windows, web, and self-hosted use. It is the alternative to consider when open-source mastering across those deployment choices matters more than a host-based analyzer.

Tunr is a free macOS and Windows option with a machine-counted key process and a free tier that allows 3 masters before a licence key, with 16-bit and 24-bit output. Consider it when that mastering workflow and output choice better fit your needs.

StudioZIO Mastering Suite is a free macOS suite for macOS 11 and later, offered as AU, VST3, AAX, and standalone without a licence key or account; choose it if those platform and installation terms fit better.

TDR Limiter 6 GE is a paid Linux, macOS, and Windows option at €60, paid once, with free updates, one user, and up to five computers. It may suit readers seeking a limiter rather than SPAN's analysis plugin.

DSP-Quattro is a freemium Mac option with a free trial; consider it if you want to assess that software on macOS before buying.

Acustica Audio Erin Studio is a paid macOS and Windows alternative.

FabFilter Pro-L 2 is a paid option with a free trial for iOS, macOS, and Windows.

Verdict

Choose Voxengo SPAN if you want a free, format-flexible analyzer that combines spectrum views with substantial metering inside your audio host. Its multichannel analysis and adjustable display make it a capable choice for production and engineering work. Look elsewhere if importing and exporting spectra is essential, since that comparison workflow is not part of the free plugin.