Thirty one bands spectrum analysis and auto eq

HoRNet ThirtyOne auto eqThirty one is a single package that includes a spectrum analyzer and a graphic equalizer, both has the standard 31 one third octave bands.

This pair of tools is very common in every rack of any live mixer as the final tool in the master bus, for this reason we decided to recreate the behaviour and specific time response of a very common Italian analog spectrum analyzer.

The equalizer is also inspired by analog units allowing ThirtyOne to recreate that master chain feeling that you are used to.

We put a great care in recreating the smooth lighting of LEDs driven by a smoothly increasing current flow, each column of twelve LEDs comes after a 20dB/octave filter (like the original hardware unit) and it’s response speed is selectable between 0.25, 1 or 4 seconds allowing you to see both fast peaks and average frequency level.

Each of the LED of the bar can have a value of 1, 2 or 3 dBs (like in the original hardware unit) and we also added 6dB/LED option, when changing the resolution the scale on the left of the LED display updates accordingly.

We also added a maximum peak hold LED for each frequency band that can be enabled or disabled that the original unit did not have.

Hovering the mouse on each of the analyzer band will let you know the band frequency and the maximum peak recorded for the specific band.

Right below the spectrum analyzer we have put the 31 sliders that will let you shape the output and fix any particular resonance. Each of the sliders drives a standard 1/3 octave second order filter and can be adjusted from -15 to +15 dB, you can also change the value for each band typing in the box below each slider.

The equalizer has a very special feature called the “Auto EQ”, when enabled (both in static and continuous mode) the output of the spectrum analyzer is used to tune the gain for each of the EQ band allowing the equalizer to automatic set itself so that the maximum harmonic balance is achieved, removing frequency masking and improving mix clarity.

Internally the “Auto EQ” algorithm compares the average peak level of the frequency bands with each of the bands and computes the necessary gain to apply to the EQ to bring the level of that specific band to match with the one of a carefully designed ideal response. This sounds complicated but it’s actually very effective in automatically balancing the frequency content of the mix.

You can choose between two different modes for the “Auto EQ”, the static and the continuous one.

The first takes in consideration only the maximum peak of each band so that you have an EQ curve valid from the beginning to the end of the mix, this mode is very useful in mastering a single track as it gives a “static” EQ correction curve.

The second algorithm is more complex and continuously look at the level of each frequency band and consequently updates the equalizer to reduce masking and keep the track balanced in ever single moment. If you use the plugin with this mode inside a broadcasting chain you can always guarantee a constant frequency optimized output even if the content of your audio changes a lot.

“Auto EQ” is linked to the frequency analyzer output so changing the analysis speed affects the algorithm, using the 0.25s changes the equalization very fast and allows you to track also the fast frequency spikes, while using the 4s setting works more on the average frequency content.


  • 31, one third octave, spectrum analyzer bands.
  • Spectrum analyzer carefully crafted to give you the feeling of analog hardware units.
  • three different integration times for the analyzer.
  • four scale ranges for the analyzer.
  • peak hold display.
  • display both the L+R (mid) component or the L-R(side) component of the audio spectrum.
  • 31, one third octave, equalizer.
  • each band gain adjustable from -15 to +15 dBs.
  • “Auto EQ” automatically balances frequency content.
  • Two different algorithms for AutoEQ
  • Each of the two modules can be disabled to save CPU.
  • AutoEQ amount knob to scale the effect impact
  • Custom compensation EQ profile for the AutoEQ algorithm
  • Bypass button for the eqalizer.
  • 2x internal oversampling to allow analog sounding filters up to 20kHz.
  • Mac OS X (>=10.7) and Windows (Vista an later) support.
  • 32 and 64-bit compatibility both on Mac and Windows.
  • Audio Units VST2.4, VST3 and AAX format.

Copy protection

The HoRNet ThirtyOne has no copy protection, I don’t believe in copy protection, they are always cracked and they are annoying for the users, we all know you are not going to give away the plugin on the internet…

So simply download the plugin and enjoy your recordings!

21 thoughts on “HoRNet ThirtyOne

Jeroen Simons (Drummer JS) says:

This is another great plugin from HorNet!!! I tried it today and I was very surprised by its very useful function… The automatic eq function you can set and then turn it off and set your eq to taste further…But…HorNet did it again: Making outstanding plugins for an outstanding low price…Thanks a lot HorNet!! Cheers from The Netherlands, Jeroen Simons, Independent/ ex- Epica.

Ivan says:

well, I just try demo and bought plugin .. this is fantastic .. i use it as mastering eq tool , results are amazing, the price is so low, this plugin must to cost 150+$ .. i must to investigate other plugins from you ! congrats for this tool

Angel Ayala says:

Such a great plugin!!! This eq adds clarity to whatever source it's on. Clears out mud and makes mixes sound clear and punchy. Great job!!!

373rn17y says:

Overall, EXCELLENT! But, TWO requests for the AUTO EQ! 🙂

1 – Only seems to work in Stereo. If feeding a mono signal, Auto EQ goes crazy and drives into feedback! Alternatively, add option to process each channel individually ("Channel Separation" knob or slider). That way we can Auto EQ individual mics and use as channel tool as well as mastering tool.

2 – Please add "Wet/Dry" or "Effect Strength" knob or slider for AutoEQ that adds simple control to increase or decrease the total effect of the Auto EQ!

Dan Stanley says:

Wow Saverio, You did it again.
The solutions you provide are simple, effecient, easy to use and the price for this….. is great.
This plugin really seems to clean up the mix and make room in the mix.
Fantastic tool for your production.

Tibor Szabó says:

It's a good equalizer for mix and mastering …

DeeJay12 says:

Saverio, I have found Thirty One a great edition to my bus EQ plugins thankyou. After just watching your video on use of Custom curve I was wondering if a future version might enable a user to capture, save and apply of Custom curves from a reference track(s) perhaps?

Keith Ricker says:

Great plugin. Only feature it's missing is the ability to bypass certain bands. Otherwise, stellar work.

Dr. Werner "Mad Musicologist" Linden says:

This stable and easy to adjust plugin is the finest mixing and mastering eq I could find. It allows to shape the sound you are searcing for with great precision and reliability. Il will not go without it anymore.

Dominik Hüttermann says:

Great for the mixbus, but also great for overheads, room mics, drum busses, etc.

Francesco Donadel Campbell says:

Great mastering Eq that fixes things that can't be fixed or improved with other Eqs. I mainly use it for audio mastering of Tv and Cinema trailers and for animated series broadcasted on tv or released blu-ray .Great great tool! For the price it's a no brainer.Highly recommended!!!

3dZion says:

I liked it from the first minutes of testing. I already bought and used it in my work.
I missed some of my recordings through it on the master bus and after a short adjustment everything sounded with new colors.
As for me, he does his job very carefully and has not spoiled more than one track, plus there are different modes of auto-equalization and manual mode.
Of the minuses, only that on a weak laptop in the project was able to run only 3 plug-ins at the same time, due to the heavy load on the processor, and sometimes when opening the plug-in some menu items are not displayed. But I think this will be fixed in future versions.
Thank you for this wonderful product.

Jose Nilton says:

Very interesting I really liked this audio tool she is very useful

Dee T says:

All good things with this plugin. And yes , very affordable and so obviously useful,
Hmmm what's next on my list to download here?

Tom Goodson says:

This is a great plugin, I use it on almost every one of my tracks; however, after I bought it I soon realized that it would be really nice to have a solo button on each frequency band to listen to them individually. It would also be great to be able to have a "select all" button where ALL of the sliders could be selected moved simultaneously. I wrote to the developers about these potential improvements but did not receive a reply. Oh well…

Hank says:

This is my new favorite plugin! If I knew how powerful this plugin was prior to purchase I would have easily paid $100 for it! No hype, simply impressed with how easy it is to use and dial in audio to make it sound its best.

I am sure I will be able to trick people into thinking I'm on a microphone I can't afford. 🙂

TWD24 says:

This plug in is such a time saver and i know the track or bus i put it on comes out sounding good. Great U, ease of use. And, the price cant go wrong.

David Neal says:

phenomenal **************

Ján Čverčko says:

I´m blown away… seriously. I have done mastering milion times with many expensive plugins, but only now my jaw drops. I AM BLOWN AWAY!!!!

Albert May says:

I've been using it on the mix bus with continuous auto eq @ 40%. Really cleans up the sound. Espec bearing in mind I use high end mics, interface and plug ins.

AtmanActive says:

As a standalone equalizer – not so much, there are better sounding and better controllable EQs out there, but for auto-equalization of the overall spectrum – it's fantastic.

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