When it comes to audio, you have likely heard the terms mono and stereo. The question is: what are they? and how are they different? We’re going to give you the rundown on mono vs. stereo—from what they are, to how they work to how they differ.
Origins
To truly appreciate stereo, we need to understand the changes that accompanied it at the time. The last 60 years have seen several major shifts in recording technology. The 1950s saw the advent of multitrack recording and move towards stereo. By the late 1960s, these were the norm, we can attribute some of this to the likes of Les Paul and the Beatles. Tape recording peaked both technologically and creatively over the next 40 years.
Fast forward to the 1980s and we start seeing the first hints of digitization with sampling, and the DAT format. The first Digital Audio Workstations — DAWs — emerging at the start of the 1990s. Through all this we had stereo and it’s hard to imagine the music and movie industries would sound like without it.
Mono vs. stereo: defined
Monaural is single position audio that emanates from a single source. The original iteration of mono audio is a single-channel recording that is output through a single speaker. Recording meant gathering around a microphone in the middle of the studio room. The overall balance is determined by the proximity and dynamics of the performers. Stereo consists of two discrete channels routed to separate left and right output channels and speakers.
This was before the advent of tape, which meant everything was cut in real-time to a vinyl master. The recording boom of the 1920s recorded everything from solo singers, early blues, big bands and jazz. You are correct to conjure images of large groups of musicians huddled around a single microphone.
While microphone technology improved, this was largely the normal way of recording until multitrack recording and stereo mixing emerged and everything changed.
Sound stage
The mono stage is purely vertical and level driven where sounds are either higher or lower. There is no translation between left and right or forwards and backward. Stereo provides a new sound stage that allows sounds to be panned to the left and right. Giving a much greater sense and control over the foreground and background.
Stereo playback: consuming
Our listening habits started changing 60 years ago with the adoption of stereo in both studios and homes alike. Playback of existing recordings through stereo speakers becomes a dual-mono using the same signal for both channels.
We see a similar trend today with surround sound systems and passing a stereo signal through more than two speakers. Amplifiers will give you the option to playback in stereo or feed the stereo signal through the surround array. A word of caution, multi channel speaker configurations for the front left and right channels use different placement angles. It is common for engineers to use multiple A and B channels to mix against multiple speaker configurations. For a better understanding of speaker placement and orientation you can refer to our article on Monitoring Sound in Post.
Recording
Recording in mono is the norm for the majority of studio applications: dialogue, vocals, foley and instrument recording. These sounds are inherently nondirectional or are panned later in the mix. Dialogue almost always sits in the centre, effects are placed where they are needed and instrumental tracks are layered and panned to taste.
Stereo recording becomes a little trickier because we need to distinguish between the use of stereo microphone patterns or using two microphones on a single stereo track, we will cover both.
You should ask yourself how a stereo recording will benefit your project.
You should ask yourself how a stereo recording will benefit your project. Close-miking a source is best done in mono because there is not much room for a stereo image to form. However, it makes sense to use a stereo track when recording that same source at a distance, more on that below.
Disk space is a smaller concern today than it was 10 years ago, but we still risk artificially inflating project sizes by unnecessary use of stereo tracks.
Mono recording
We record voice and ADR tracks in mono using a single microphone because they typically sit in the centre and stereo offers few gains in this case.
Multi mic recordings of a single source in mono can make some amazing contributions to your stereo image, this is common practice when recording music and is comparable to using multiple cameras to capture the same scene.
We love doing this with guitars where a single take recorded with multiple microphones is blended and panned to create a richer sound. A single guitar gains so much more density! Microphones have their own characteristics and this is just one way to take advantage of them.
Why not have both?
Drum recordings are a good place to begin a transition from mono to stereo. Depending on the style of music you can pursue a more complex approach using 10 or more microphones recorded to mono tracks. Multi mic recording is common with Rock and its child genres. Particularly when seeking added definition and isolation. These multi-mic setups always incorporate overhead microphones and can just as easily be a spaced mono or XY stereo pair. The overhead and room channels pan out to the left and right and are a key part of the stereo image.
Room microphones are also commonplace in music recordings, we recommend using a pair during drum tracking sessions to capture how the kit sits in the room and make use of the space’s natural reflections. You can use a single omnidirectional microphone, spaced mono or stereo pair—pan out as necessary.
We will wrap up this section with a hybrid drum recording using an omnidirectional and stereo pair. Place the omni on the drummer’s side near the snare, hi-hat and kick. Move the mic around until you achieve a good balance between all the drums and cymbals, this is a good exercise in balancing lows, mids, and highs. We recommend a shock mount to reduce mechanical vibrations and offset any low-frequency sensitivity. A cardioid condenser mic makes for a suitable replacement if the omnidirectional mic does not balance. Feel free to experiment with the stereo pair as overheads or room mics from the audience’s perspective. This recording is a demonstration of the benefit of room mics on a drumset’s stereo image. They capture the drummer’s movement across the kit and give it some room to breathe.
Stereo recording
Orchestral recordings brought about the creation of some of the original stereo recording techniques, case and point the Decca Tree pattern. We should aim to capture essentially what is a self-governing mix and stay as true to the source material. The band, conductor and acoustics already provide the sound stage, levels and panning.
While the above mostly holds true, it is not uncommon to reinforce some sections with dedicated and overhead microphones. This gives you greater flexibility during mixdown to help maintain the overall balance, highlight sections or address any irregularities.
Location
Environmental recordings and stereo go hand in hand, that is why most field recorders come with a stereo microphone configuration out the box. The Zoom H1 would be nowhere as versatile if it recorded in mono using a single omnidirectional microphone. These recorders lend themselves well to recording direct sound, environmental and rehearsals. The latter categories are well served by stereo microphones that capture the focal points, reflections and movement within the space. Those cues tell our brains how to perceive a space we have never seen.
Newscast location footage makes fantastic use of stereo recordings because it captures the cues mentioned above. Dialogue is typically mono, recording location sound in stereo makes sense because the viewer is not limited to hearing sounds that are in frame, establishing shots for example.
Cinéma vérité
Cinéma véritié was born out of a desire to bring realism to cinematic formats and made possible by the miniaturization of the audio and video recording equipment required to record synchronized footage. The intention is to provide an added sense of reality through the intentional use of the camera to break the fourth wall and provoke a response.
Direct cinema
This is film style from the same period and similar to Cinéma vérité, where direct Direct Cinema diverges is its focus on and being a documentary genre. Growing portability allowed the genre to use handheld cameras in its pursuit of realism and truth. This produced a raw and unedited window into the world it captured.
Editing and mixdown
The last thing you want is a flat-sounding mix that lacks width and feels center heavy. You should always do a quick pass of leveling and panning during the editing phase before starting to layer in any processing. These are some of your most powerful tools to build a strong foundation for your mix.
We are going to leave surround sound mixing out of the equation in this article and continue our focus on stereo. Your mix will be a collection of mono and stereo tracks that are routed to a stereo output channel. Projects of growing size and complexity need to take into account phase, particularly at the master output stage. Phase issues can contribute to loss of clarity, muddyness, and sounds cancelling each other out.
The stereo tracks and pairs in your mix are like the walls of a room and the mono tracks are the furniture. They both work together to convey the space’s character and scale.
The hybrid drum recording from earlier demonstrates this, the omni or cardioid captures the kit and defines it as a feature, but the stereo pair defines it within the boundaries of the space.
Dialogue is panned to the center channel with the main exception being when reproducing dialogue movement across the screen. For example which direction does the on-screen dialogue come from? Panning the sound to the right cues someone entering or speaking outside of the shot.
Mono summing
Depending on your DAW, this will either be a function on your output bus, a plugin, or both. These features allow you to sum your mix to mono and help you audibly detect any phasing issues. Your mix will temporarily lose its stereo image, however, the overall balance and character should remain mostly the same. In Logic’s world, this can be done with the Direction Mixer plugin, we highly recommend that you use this in tandem with the Correlation Meter plugin to quantify what you are hearing into a graph.
Fake stereo
There are some common techniques available to get mono signals to sound wider or more spread out. We recommend plugins such as the Stereo Spreader in Logic, this converts a mono channel to stereo. It helps to push the sound further out to the left and right channels to produce a better balance. You can use stereo delay plugins to create a slight doubling that adds extra texture and also pushes the sound further out.
Mono vs stereo—stereo is still king
Having a reliable and accurate stereo setup is still a must in 2020 and is still the standard mixing format. Surround soundtracks downmix to stereo in the absence of a surround system. Instead of mono summing, surround tracks need to be checked in stereo during post.
A stereo field recorder is a must and a reliable way to capture rehearsals and location audio. Especially as reference material to use in working out the details before moving forward with production.
Start trying some of these techniques for yourself if you haven’t already done so. I hope you enjoy all the new found space in your mixes!
References
- Decca tree images
- Zoom H1
- How to monitor sound in post
