When doing Sound design or mixdowns, it’s important to know which part of the spectrum is being used by a channel. Working with a analyzer makes it easier to group audio into one channel and control your mix better, without losing an overview. It allows you to work with subtractive EQing on a much more accurate level and keep an eye on your db scale across the spectrum if you have a good analyzer. Lucky for us there is a big choice in the freeware department, among commercial and open source developers alike. A round up, in no particular order:

Roger Nichols Inspector

Mac OS X 10.5Universal BinaryWindows XP or VistaWindows x64 (64 bits)VSTRTASAudio UnitDirectX

Roger Nichols unfortunately has health issues (cancer). The company he started is now defunct and the plugins are hosted on freeware sites like Gersic.  You can visit his website to pay respect and donate to his costly treatments. The plugin itself has a small, 90’s looking UI. There are two speeds and two types; Peak and average.  All the parameters have a threshold and left right settings. The UI is very small yet it contains information (and alarms) about all the important things: headroom, Channel balance, Number of times audio waveform is clipped, Number of consecutive samples clipped, Total number of clipped samples, Peak meters.

Conclusion: I can see this being of great use for a mastering engineer. However when you want to keep a fast workflow, and your also working on a creative piece; the small UI and limited visual feedback are not ideal.


Voxengo SPAN

Universal BinaryMac OS X 10.5Windows XP or VistaVSTWindows x64 (64 bits)Audio Unit

I mainly know Voxengo from their convolution and IR reverbs and room simulation modelers. The first thing I noticed about SPAN is the much bigger layout compared to Roger Nichols ‘Inspector’. One of the biggest i’ve come across.  However the anti phase interface is a lot smaller then in for instance the WAVES PAZ analyzer which has a more graphical 2-d representation. Voxengo has chosen for a single meter called the correlation meter. It has easy to understand ratio’s (-1/1.0) and it’s telling you all you need to know at a glance.  You can find RMS info (you need to add the “RMS” and “Max Crest Factor” values together to obtain a peakRMS value) in the statistics pane.  Also there is a dropdown with 8 different signal metering types.

The “Metering” selector allows you to choose the meter biasing mode. The “dBFS”mode applies no biasing. The “dBFS+3” mode adds 3 dB to level meter indicatorsand RMS value (peak level indication on the level meter is unchanged in comparisonto the “dBFS” mode). The “K-20”, “K-14” and “K-12” modes offer various K-systemVoxengo SPAN User GuideCopyright © 2004-2010 Aleksey Vaneev 5biasing modes originally offered by Bob Katz. The “K-20 C”, “K-14 C” and “K-12 C”implement level calibration modes. In these “K” modes level meter’s RMSintegration and release time constants are fixed to 600 ms as per K-systemspecification.

Conclusion: One of the better free plugin around. It’s easy to keep an eye on phasing, has a lovely big FFT spectrum analyzer screen where dark curves represent the secondary spectrum and the zoom option is really nice. intuitive overall UI. Good for both mastering and single channel analyzing.


Blue Cat’s FreqAnalyst

Mac OS X 10.5Universal BinaryWindows XP or VistaWindows x64 (64 bits)VSTRTASAudio UnitDirectX

A nice looking plugin from Blue Cat. It’s big and has a simple UI. Everything you need is there. Good zoom very fast spectrum representation and very easy to work with. You can really notice a lot of thought has gone in to making this a tailor fit solution for engineers that work with a analyzer on every channel. Studio usage. They have skins on the website and you can download new ones as they are uploaded by Blue cat and their users. I can see some big advantages there. In sound design, music and post, specific freq ranges are more common then others. The need to have a visual aid of those sweet spots in the spectrum is increased by the number of different settings you work in at any given time.

However compared to Voxengos’ SPAN, FreqAnalyst has one downside. It’s ‘ just’ a freq analyzer. Nothing more. While that’s perfectly fine, it does make it less versatile. Another minor bug was that setting the opacity of the plugin, not only effected the plugin, but FL studio too. (It worked fine in Ableton and Nuendo)

Conclusion: Blue Cat’s FreqAnalyst is a nifty plugin with a great UI. Ideal when you just want to meter your freq spectrum on a single channel.



Besides the obvious spectrum analyzers there is a plethora of smart little tools to help you battle inter sample peaks or metering your M-S channels.

Robin Schmidt Track Meter

Track Meter is a plugin to display the current level of a stereo input signal separately for the left, right, mid and side channels and also to display the cross-correlation between the two channels. Download


X-ISM is a state of the art VST/AU plug-in which can interpret inter-sample peaks, allowing engineers to make informed judgements about the resultant sound quality of the mix. Download

TT Dynamic Range Meter

Measurement and display of the Dynamic Range – as well as splitting the dynamics into wholenumber values for reference via a Offline meter (standalone). Download

Classic Style

Sometimes you might just want the classic metering on a single channel. I prefer this on my drum channels. Here are some nice ones:

Seven Pahses Spectrum analyzer

PSP Vintage Meter

Robert Schmidt Signal Analyzer

SmartElectronix Freakoscope (thanks martin)

That wraps up this overview of the free analyzers I’ve tried. Did I miss anything?