polaris sound effects Asbjoern Andersen

UK-based sound designer and recordist Mattia Cellotto has just released Polarity, a library that delivers a fascinating selection of recordings from science and electricity museums around the world.

There’s a lot of excitement about the library right now, and I’ve been really curious to hear how it was made. Here’s the story behind it – complete with some interesting recording examples:

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The trailer for Polarity

Mattia Cellotto, recording sounds for Polarity

Hi Mattia, please introduce yourself:

Hello, my name is Mattia Cellotto, I am a sound designer/recordist based in the UK. My passion for recording sounds started with music, while my passion with games probably first sparked when I watched the movie “The Wizard” as a kid.

Coming from a very small town in Italy back in 2000, to think playing games or recording/designing sounds would lead to stable career seemed madness to most parents, but thanks to a good sound design course, perseverance and a bit of luck, now I get to do both things I always loved.

How did you come up with the idea for Polarity? You’ve also captured some unique machines and devices for this library – can you highlight some of those?

I normally try and find myself something to do during holidays to flex the recordist muscles and get the dust off my Zaxcom recorder. Last year, back in November, I got in touch with an electricity museum in Italy, we arranged for me to visit it near the Christmas holidays, when it would have been closed to the public. We sorted out all concerns prior my visit, from AC to equipment list, so everything went down quite smoothly, but I couldn’t get as close as I wanted to the big machines like Jacob’s ladders and such.

After Christmas I decided to expand on the recorded material, I bought an insurance for my equipment and collected contacts to help me gather the best electrical sounds at the closest distance.

I must have heard the phrase “you can get closer, but it’s your equipment” about ten times within a week from different people

I must have heard the phrase “you can get closer, but it’s your equipment” about ten times within a week from different people, but when you focus on recording ultrasonic content proximity is too important, placing a Sanken CO-100K too far from the source means only using half of the mic. The collection of contacts turned into a month full of travelling during which I met some awesome professionals. I first drove to the Victorian Science Museum in North Yorkshire, a long trip but definitely worth it: the owner, Tony, is a truly inspiring person. Then I visited the UK’s largest high voltage test lab, a great electrician/youtuber’s lab and a science laboratory where my girlfriend works.

Some of the sounds included in Polarity:

Polarity delivers more than 950 sounds of electricity, science and technology. About 50% of the library is all about electricity, with various types of Jacob’s Ladders, Tesla Coils, Ruhmkorff lamp and all sorts of impactful bursts of energy. It also features welders, plasma spheres, 3D printers, old phones, telegraphs, dynamo wheels, rotary dials, whirling watchers, alarm, lab centrifuges, something scientists call a roller and a rocker, servo sounds, neon lights, a wimshurst machine and sparklers


What was your recording setup?

For this library I used a Zaxcom Maxx and a Sony D100 as recorders. While I always used the same set of 4 microphones with the Maxx (2 x MKH8040, the CO-100K and a KMR81i), I alternated the use of the D100’s built-in mics with an Elektrosluch electromagnetic “pickup” from LOM. While the Maxx would allow me to record endless top end, the Elektrosluch would pick up lower frequencies which were not audible with the other mics.
Welding Recording

You’ve got some pretty wild spark sounds in there – how did you capture those?

The wildest sounding material is a good blend of all of the mics mentioned above, where the truly unique ingredient is often added by the Elektrosluch. All these microphones are great but picked alone they do have weaknesses, here are some examples.
Here is the recording of what I describe as an “electric wand” where we only hear what the CO-100K captured:

You can hear how the CO-100K is a bit high frequency biased, it doesn’t have great sounding mids and the very deep low end is pretty quite weak.
Here is the same recording picked up by the pair of MKH8040, responsible for the stereo image of the file:

The 8040s behave in a similar manner, they add something to the low-mids but in a way that does not support the central image of the Sanken, so now our sound is still lacking some low mids richness and has lost its center focus.
To bring back the focus we add the MKR 81i’s perspective:

You can hear it right away, the KMR is nowhere near as harsh as the other mics and that’s why I bought it to record this library. In some form this mic seems to ignore the harshness the overwhelms both 8040s and the CO-1OOK to bring a sound that feels balanced and rich, but not quite powerful enough.
In reality this mic brings us the least reliable representation of the sound, which was truly as harsh as the CO-100K makes it.
One thing that we notice about all these recordings is the lack of proper proximity effect: because we are recording an electric arc we can only get so close before the equipment gets fried or suffers from too much interference.
Luckily the Elektrosluch 3+ is picking up exactly what we were missing:

Now we can really crank the harshness of the first two mics knowing that our signal will remain balanced as we have total control over mids and lows separately.
So the final asset is a mixture of all of these recordings where I made use of the best parts of the spectrum for each mic. Because all mics brought something different to the table, the result is a round yet aggressive sound:


Any surprises during the recording process? And what are some of your favorite sounds in the library?

I think the biggest surprise was when I first played back my recordings at 1/4 speed. Here is the same “electric wand” sound we just listened to played back at ¼ speed:

Most of the recordings, especially the Jacob’s ladders, preserved quality very well, but became something completely different.
You’d notice that up until ½ or 1/3 speed the classic 50Hz tonal element would simply shift lower and lower, but at ¼ speed it becomes subsonic, what is left is a very organic, transient-ful sound.

My favourite sounds in the library are the 1928s tram which has some nice, wellrounded pulley feel, and the “electric wand”, mostly because I got to control it myself while recording, amazing experience.


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A big thanks to Mattia Cellotto for the story behind the Polarity SFX library! You can get the full library below:

  • Sci-Fi Polarity Play Track 975 sounds included
    Rated 5.00 out of 5

    Polarity delivers more than 950 sounds of electricity, science and technology – captured in several locations around the world, from electricity museums to science labs. About 50% of the library is all about electricity, with various types of Jacob’s Ladders, Tesla Coils, Ruhmkorff lamp and all sorts of impactful bursts of energy.

    Then we go through welders, plasma spheres, 3D printers, starting to cover a more broad technology theme – like old phones, telegraphs, dynamo wheels, rotary dials, whirling watchers, alarm, lab centrifuges, something scientists call a roller and a rocker, servo sounds, neon lights, a wimshurst machine and sparklers.

    Many sounds in this section were captured from vintage equipment, from a 1928’s tram to old telephone switchboards, high voltage levers and control surfaces.

    All content was recorded at 192KHz with a Sanken CO100K, a couple of Sennheiser 8040 and a Neumann 81i, translating into final assets that have plenty of ultrasonic content, ready for the most extreme manipulation.

    Bonus: Two extra libraries included for free:
    This library also includes two additional releases from Mattia Cellotto - for free: Crunch Mode delivers 230 crunchy sounds made with a variety of vegetables, fresh bread, pizza crust and a selection of frozen goods. The Borax Experiment gets you 158 squishy, gory, slimy and gooey sounds.
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