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Stereo Imaging:
Beyond Mid Side Processing


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In my opinion, stereo imaging is one of the benchmarks of a superb final master.

And as powerful as mid side mastering can be as a tool, it’s very elementary. At it’s most basic, I use it to restore any sense of space and depth that may be lost with any necessary processing. At it’s most advanced, it can be a restoration tool saving a client remixing, time, and money.

Stereo Imagine with Ozone 5's Imaging Module

In my opinion, stereo imaging is one of the benchmarks of a superb final master.

Stereo Imagine with Ozone 5's Imaging Module

And as powerful as mid side mastering can be as a tool, it’s very elementary. At it’s most basic, I use it to restore any sense of space and depth that may be lost with any necessary processing. At it’s most advanced, it can be a restoration tool saving a client remixing, time, and money.

More advanced processes beyond mid side primarily involve delays, along with leveling, phase manipulation and filtering to enhance the stereo soundstage. Many times, it's a complex combination of the above. For the most part, I make no attempt to re-create these on my own. Instead I rely entirely on what each plugin can achieve.

It goes without saying that a light touch is required when mastering a song.

What’s interesting to me with a process like this, the less it's deliberately necessary (maybe needed 5-10% of the time) the greater number of options it has!

So here’s...

A List of Stereo Imaging Tools....

....I have at my disposal when I work on my clients’ projects:

Har-Bal 3.0's Air Function


Like I said, how these processes actually work is not my concern, other than it gives some great results. However, in the interest of information, Paavo Jumppanen (designer and programmer) explains this process best in his own words:

It is a "Haas zone ambiance process.

  • "...(The Air tool) is realized as a log normal random deviate applied to a unity gain all pass response with the variance of the deviate tapering at higher frequencies to add warmth. Without the taper it would sound too bright."

And further in a forum post:

  • "Har-Bal Air is realized in the frequency domain using random deviates giving an entirely predictable effect on the frequency domain (that is not the case with K-stereo) and a much more random and complex looking response as far as the impulse response of the process."

So there!!

NUGEN Audio's Stereoizer

...works in two ways: by amplifying intensity (level) differences, and by amplifying timing (delay) differences, between the left and right channels.


In addition there are options to filter the frequency regions to process. I can choose either process to work alone, or both at the same time. Finally, a basic linear mid-side expander is added to the works as well.

iZotope's Ozone 5 Advanced Imager Module

...adds a stereo-izing delay function to its features.


This however only comes in to play if some linear width expansion is applied first.

Bob Katz' K-Stereo Processor by UAD

...works on existing ambient cues enhancing side to side width and front to back depth.


In all the stereo imaging processes I've listed so far, applying them pulls the mid channel out into the side field. This is not always a good thing for some mixes. With K-Stereo that side effect can be eliminated by disengaging the WIDE button. All in all, the K-Stereo is the most naturally subtle of the lot.

Next and sometimes forgotten is...

PSP's Stereo Enhancer Module


This can be slightly heavy handed if one isn't careful with it. But like the K-Stereo it has the option of not "pulling the mids out into the sides". I can choose to enhance the full stereo signal, just the mid channel, or just the sides.

So there are many, many options on my end for something that - in the end - should be subtle and felt rather than in your face.

But it doesn't end there!

Although this page will...

To find out more techniques I use for stereo imaging click here.


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