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Review: BT PHOBOS Soft Synth by Spitfire Audio

BT PHOBOS Soft Synth Review

Wow! Spitfire Audio teamed up with BT. That’s something that makes you listen. And on top of that, they are building a synth. Now that really had me wondering, not really what I expected from my favorite orchestral library supplier.

And now, after over 2 years of development, Phobos software synthesizer is finally here, let’s have a look at it!

Different than expected…

“Phobos” does a lot of things different, both, compared to what we are used to from Spitfire, and compared to most other synths.

First of all, it is a standalone VST. It doesn’t run within Kontakt or Kontakt Player.

Second, it is a Polyconvolution-Synth. Now what that means is, instead of using convolution for a reverb, BT and Spitfire Audio managed to take a rhythmic element – a convolution – and make it respond tonally. I don’t know about you, but that instantly makes the sound design juices flow in my brain.

BT PHOBOS Synthesizer

And while you might expect something mostly rhythmic and subtle, “Phobos” is actually very versatile and comes with over 600 Presets, containing everything from rhythmic to Pads, from Atonal to Textures, and even the raw sound sources are really cool. And given all the possibilities for sound manipulation, it is unlikely that you will ever run out of things to try out.

Interface and more…

Let’s look at the basic concept behind “Phobos” since I think that helps both, understanding what it does, and how the interface works. You might think, that while Spitfire usually has these wonderfully simple and elegant interfaces, they went for something more complex this time, but this is actually equally simple as soon as you know what you are looking at.

Spitfire Audio Phobos Controls

So, the basic parts of “Phobos” are these:

There are 4 Sound sources, in which you can load sound from a huge variety of materials. The sound sources are numbered 1,2,3 and 4 and are at the top of the interface. They also contain an envelope, filter, and some more sound-shaping tools.

In the middle, you can see a triangle with four smaller numbered triangles in it, we’ll come back to that in a second. The big triangle is surrounded by three other fields. One on each side and one beneath it. They are marked W, X, and Y.

These are the three convolution engines. Each of them shows a waveform of the convolution if one is loaded. They also all contain an envelope, a pitch module, and a high pass filter
Now here is the part that took me a few minutes to figure out.

Remember the smaller triangles? Each of them represents one of the sound sources. So, if you move triangle “1” in the top left corner it will get responses from the convolution engine “W”, if you move it to the top right, from the convolution engine “X” and so on. You can adjust how much of the convolution response and how much of the dry signal you want in your final mix by adjusting the “WET” and “DRY” knobs in the sound sources.

I know it all sounds a bit confusing, but it really is easy once you get the hang of it. I would suggest you play around with just one sound source until it makes sense to you.

Another really cool feature is also the key assignment system they build in. You see it on the bottom of the interface. Basically, each line represents either a sound source or a convolution. By dragging the nodes on each end of the line you can change which key area triggers which module.

Phobos synthesizer review

This is great for many reasons, but it particularly strikes me as something very useful for building performance patches. So that is “Phobos” in a (very small) nutshell. There is lots more to explore though. You will find the full preset list on the official webpage (link below).


“Phobos” is obviously something that will have a special appeal to all the sound design nerds out there, like me. But it really is very versatile and the approach is quite unique, so it will definitely add something very recognizable to your sound. I wish the sound sources would be available as .wave somewhere in the folders and I wish I could add my own sound sources into “Phobos”.

Nevertheless, I think “Phobos” is a very useful and fun tool, for both media composers as well as musicians. I would not recommend it if you are completely new to synthesis, but otherwise, get your synth nerd shirt out and go get it. It is wonderfully weird and playful and will surely cost me many hours of sleep, which I will happily invest.


  • Price: 309,- € inc. VAT
  • 2381 Samples
  • 22.9 GB Uncompressed WAV
  • 22.9 GB disk space required
  • 45.8 GB disk space required during install
  • Revolutionary polyconvolution synthesizer, across 3 separate convolvers
  • Contains more than 2000 unique sounds, created by BT, that can be used both as a source or as an impulse response
  • Over 650 presets showcasing the possibilities of Phobos
  • A plugin that loads directly into any DAW that supports VST / VST3 / AU / AAX.
  • IRs in Convolvers are polyphonic, track pitch played and render in real-time
  • Loops as sound source / or as IR track host tempo
  • MPE Compatible (for use with multidimensional controllers such as ROLI Rise or Roger Linn Linnstrument)
  • Dedicated Gate Stages and Filters on each sounds source/convolver unit
  • All controllers are mappable to the controller and/or multiple LFOs

Find out more about this great software synthesizer by visiting the official website.

More Details: BT Phobos

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