Time To Widen Your Image
The use of stereo imagers tends to draw mixed reactions from producers – some people love them, and some never touch them. Imagers are usually applied at the mastering stage, where the overall mix needs to be tightened up a bit at the bottom and spread out more at the top…
Wider Than A Mix Can Be
The soundstage of a recording needs to be considered from the very beginning of the creative process, which is songwriting and arrangement. A well-structured song features carefully selected elements that sit in their own space, not only across the audible frequency spectrum, but also across the stereo spread from left speaker to right speaker.
However, at the mastering stage the engineer may decide that she wants to spread the recording even further, or narrow down some marauding bass sounds. A stereo imager can help in this regard.
Keeping The Bass Under Control
Human hearing isn’t very good at deriving directional information from bass signals; this is why you can put the subwoofer from your home theatre sound system pretty much anywhere in the room.
The bass frequencies also are the most powerful; a big bass sound will take up a lot of headroom in a recording, and place a lot of demand on your speakers. Because of this, it is advisable to keep as much of the bass signal as possible in the centre of the stereo field – the workload is then divided evenly between the two speakers.
There are other reasons for keeping the bass in the centre, which may not be relevant to all forms of music. For example, if you’re recording a bass-heavy track that will be played on vinyl in clubs, you need to keep the bass in the centre so that the needle won’t skip every time the bass notes hit. Also, if you have the bass on only one side, then half the club probably won’t be able to hear it properly.
Using Your Imager
Bearing in mind the points above, a common use of a stero imager is to tighten up the bass so that it’s more focused towards the centre. This can be used in conjunction with a widening of the higher frequencies to create an additional sense of space.
The key to good imager settings is in determining the crossover frequency. In a dual band imager, there will be separate controls for the high frequency channel and the low frequency channel, and the crossover sets the point at which the controls move from one to the other.
Generally speaking, you want to set the crossover frequency just above the dominant bass sounds of the recording. The exact point will vary for each track, so you’ll need to listen carefully to get it right. On Reason’s stereo imager, for example, you can solo the ‘lo’ and ‘hi’ bands to home in on the ideal setting.
Once you have your crossover, you can reduce the width of the bass and increase the width of the treble. How much you change the signal will depend on your taste, but the lower your crossover frequency, the narrower your bass band should be – perhaps even completely ‘mono’.
Widening of the high frequencies is usually achieved by manipulating the mid and side signals. The mid signal, as its name suggests, is in the centre of the mix and consists of the common elements of the left and right signals. The side is the difference between the two channels. For more info on stereo imaging, have a look at this article from the ever-informative Sound On Sound.
You can also download a free Mid/Side plugin from the Brainworx site, which works in AU, VST and RTAS hosts.