Flux Bittersweet Review – A Free Transient Shaping Beast

Flux Bittersweet (Quicker Review)


Flux Bittersweet V3 is a free transient shaper by Flux. It’s a widely used tool in the music industry, and produces fantastic results.
User Interface
Ease of Use


Flux Bittersweet is one of the best free transient designers, with great functionality, simple UI, and produces snappy, punchy results. It can add real punch to drums, or soften unwanted transients at the same time.



✅ Multiband Mode

✅ Simple to Use

✅ Up to 8 Input / Output channels

✅ Output Gain

✅ Compatible with Mac OS and Windows

✅ Available in AAX, VST and AU plugin formats

Transient shaping can often be overlooked, when there are many other types of dynamic processing. Bittersweet V3 by Flux audio is one of the best transient shapers out there, and it’s free.

Let’s check out just how good the Bittersweet V3 is in this review.

What Is Bittersweet V3?

flux bittersweet transient shaping vst plugin

Bittersweet V3 by Flux Audio is essentially, a really good, free transient processing unit.

If you’ve no idea what that means, it’s a tool that allows you to dynamically adjust the transients of your audio signal. Transients are the first big spike in a sounds loudness, essentially it’s the attack of you sound.

Controlling your transients allows you to be in total control over the energy of your mix. More transients results in more energy, while less, produces smoother sounds.

Transient Shapers are pretty much compressors with a slight difference. They apply expansion and compression to your audio signal, based on the dynamic range, and are threshold independent.

Where a compressor would only be able to add compression, or expansion at one time, and would react to a static threshold level set by you, transient shaping does both at the same time and adjusts the threshold dynamically to your audio.

How Does It Sound?

In the world of Transient Designers, there’s a definite tendency towards boosting, rather than removing. This means that transient shapers usually tend to sound better when you’re adding, nor removing. Bittersweet thankfully, does not suffer from this.

Flux Audio have purposefully designed it, to sound great both ways, giving us a better and more useful plugin. There’s no question, why Flux Bittersweet is one of the best transient shapers around.

To give you a better idea of what Bittersweet does, we’ll take one drum loop, and process it with the different amounts and modes that Bittersweet offers.


Drum Loop
Bitter 50% – Mid
Bitter 100% – Stereo
Sweet 50% – Main

Bittersweet Features

Transient Shapers focus on only the very start of a sound. They’re very easy to control and understand and usually feature one-knob interfaces.

Bittersweet is no different. It’s centre point is the large knob in the middle, controlling the amount of transient processing. Let’s go over the features it provides

Features Quick List

  • Great Reductive processing
  • Mid/Side modes
  • Adjustable detection window
  • Output Gain +-12dB
  • Gain Link
  • 8 channels of I/O
  • Different Speed modes
  • Easy to Use
  • Low CPU usage
  • Available for Windows and MacOS
  • Available in AAX, VST and AU plugin formats.

The Big Knob (Stop That Dirty Mind)

Turning the knob towards “Bitter” will start to bring out any additional transients, and you’ll start to hear it working.

Turn it towards “Sweet”, and you’ll actually begin to remove some transient information, making your overall signal softer. This is great, when you’re trying to reduce the punchiness of drum sounds, or when dealing with harsh attacks.

Where some plugins of this sort, can be an all-or-nothing kind of deal, Bittersweet manages to offer pleasing results at both high and low processing amounts. In addition to this, you also have 3 modes for the speed of the transient shaper. You get the choice between slow, medium and fast processing, which all provide a different kind of timbre and tone.

The Cha Cha Sliders

flux bittersweet transient shaper plugin sliders

Underneath the big knob, you’ll find three sliders. The slider in the middle, controls the “period”, or the window of transient detection. This is great, when you want to focus the shaping to a certain part of your audio.

On the right side you have your Output Gain slider, which goes to +-12dB. As well as the gain link feature, which helps to achieve gain equilibrium.

To the left of this, you’ll see the multiband slider. This allows you to split the audio signal into mid and side parts. This is great when you want to shape the centre of your signal differently from the side or stereo information. We personally like increasing the transients in the centre of a drum bus, while softly pulling down some harshness in the stereo field of the synth bus.

Lastly, you also get an output gain control. Just like a compressor, adjusting the dynamics of an audio signal, affects your gain structure. Adjusting for any unwanted gain is necessary for getting proper levels.

flux bittersweet pro transient shaping plugin

If you want more functionality however, Flux Audio also offers Bittersweet Pro, which they call the “Ultimate Frequency Dependent Transient Designer”. Bittersweet Pro offers an improved algorithm over the Free version, with the added ability to process a certain part of the frequency spectrum. This adds an almost Dynamic EQ-like functionality.

Bittersweet Pro is available on the flux.audio website, for 129$. a 50% student discount is also available.

User Interface

flux bittersweet free transient shaper UI

The User Interface of Bittersweet is a simple and easy-to-use GUI that looks pretty beautiful. It’s pretty limited and the sliders are sometimes annoying, but who needs an advanced transient shaper? You want it to do a job, and quickly.

It’s also necessary to mention that Bittersweet is not re-sizable, but does offer 3 different FPS modes, to make the interface look better.


Flux Bittersweet


User Interface
Ease of Use


Flux Bittersweet is one of the best FREE transient designers, with great functionality and amazing sound.


Flux Bittersweet holds up to a lot of the big-boy transient designers, while offering easy to use and really useful features, that others tend to miss.

Whether you want to make your audio bitter, sweet, or shape the transients of your stereo signal, the Flux Bittersweet transient processor is a no-brainer

And if you don’t like it’s simplicity, Bittersweet pro is a really amazing update to this useful plugin.