stereo width

Stereo width and audio mastering

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Using stereo widening plug-ins in audio mastering to try to expand your mix’s stereo width won’t sound natural and could cause major issues with your finished track.

We’ve said it before, and we’ll say it again: Having your album professionally mastered is one step you can take to make your audio mixes ready for radio and comparable to what you hear on major- and indie-label releases. Among other things, a mastering engineer can raise the overall volume of your mixes, correct minor EQ imbalances, bring consistency to an album, and clean-up the hiss and pops that may have snuck into your recording.

The team of engineers in The SoundLAB at Disc Makers masters over 2,000 albums and singles every year – you can bet that we’ve pretty much seen and heard it all.

One issue we hear frequently in The SoundLAB is a mastered recording that has had stereo width processing added to the final stereo mix down, or we’ll get requests to add this type of processing in an effort to make a mix sound wider, bigger, or “more stereo.” Unfortunately the mastering session is not the time to make dramatic changes to the stereo width of a recording!

Stereo width effects

Stereo width plug-ins generally work by discreetly adjusting some combination of the timing and/or EQ of the left and right channels. What these processes attempt to achieve is a widening of the stereo field on mixes where the individual elements were not properly panned to create a natural stereo sound. If most of the elements of the mix are panned to the center, the resulting master will sound narrow, with little discrete information coming from the left and right speakers. In other words it will not sound as big or wide as a properly mixed recording.

The problem with adding this type of processing effect to an entire mix is the effect can cause the center of your stereo image to sound weak and much less punchy. Instruments like kick drums, bass guitar, and vocals, which anchor a recording and are traditionally mixed in the center, can start to become less focused as the recording is spread further. In the most dramatic examples we hear in our mastering suites, the center of the stereo image has been severely hollowed out and the stereo spread is unnaturally wide.

Another issue that can arise from the overuse of these effects is a loss of mono compatibility, which is the ability to play a recording through a playback system that has only one speaker. This includes many cell phones, as well some phone docks/chargers/alarm clock combo units, and even some higher end speaker systems like certain models from Sonos.

When these systems combine the left and right stereo channels into a single mono channel, some of the elements that have been artificially widened, and are now partially or even completely out of phase, will start to cancel each other out and will sound much lower in the mix or even disappear completely. (Phase here refers to the time difference between a signal in the L/R channels.)

Most recording engineers will use a mono compatibility function in their software or on their mixing console to check for mono compatibility during a recording session, and many mastering engineers will use a similar function, or sometimes a single speaker, to double check that no elements in a recording are out of phase and cancelling out when played back in mono.

In addition to the problems we’ve already mentioned, you could also experience issues over certain streaming services, satellite radio, and even FM radio broadcasts. Though not likely now that Internet connections are generally pretty stable and fast, sometimes the stream from services such as YouTube and Spotify might temporarily drop in bitrate and/or switch from stereo to mono in order to prevent the stream from being interrupted. If your mixes are not mono compatible, some phase cancelation issues may occur. Similarly, satellite radio stations have a very limited amount of bandwidth to share, and some smaller stations may be allocated a lower bitrate and broadcast in mono.

The takeaway? Don’t wait until the end of the mixing process and apply a Band-Aid, across-the-mix widening effect. There’s no substitute for taking the time to pan instruments to different locations in the stereo field, adding reverb to select instruments and vocals to fill them out, and double tracking instruments like guitars and panning the tracks to separate sides of the stereo field. Not only will this lead to a more open and natural sounding mix, it will go a long way towards preventing the unnatural sound and potential phase issues created by overusing or misusing a stereo widening effect.

Brian Lipski is the manager of The SoundLAB at Disc Makers, and has been a mastering engineer there for over 20 years. He has personally mastered thousands of releases in his time at The SoundLAB.

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2 thoughts on “Stereo width and audio mastering

  1. Good advice Brian. The time to build a wide stereo soundfeild is during the recording. Spread out the acoustic piano, get a full spread on the drum overheads and use full left and full right to get guitars and percussion noticed.
    Checking for mono compatibility is essential. I remember on a Paul Simon mix years ago we checked for mono while cutting a ref disk for Paul and one of the acoustic guitars disappeared ! It turned out that when the guitar was stereo miked at the original session, one of the mike cables was wired out of phase !

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