Creative Ways to Use Room Mics — Not Just for Drums!

Using room microphones during a recording can add a sense of space and natural acoustics, which are crucial to making a recording sound real. But room mics can also be used to create some incredible, otherworldly effects! Simply put, I think that room mics set the overall vibe for your recording. A singer/songwriter baring their soul into very personal lyrics may sound better in a small room because of the intimacy of a small space. On the other hand, a rock band going for a larger-than-life sound may opt for cranking amps to 11 in Clearwell Castle, a famous English studio where bands like Black Sabbath, Led Zeppelin, Deep Purple, and Bad Company recorded! Regardless of what room you record in, here are some ideas to ponder when using room mics.

PhaseBoundary EffectRe-ampingThe Tony Visconti Gated Room TrickSteve Albini & Boundary EffectRe-amping MadnessGeneral Processing Tips & TricksRoom Mic ConfigurationsStereo Mic ConfigurationsBlumleinDecca TreeSurround Mic ConfigurationsSurround ArraysHamasaki SquareImmersive Audio 

Phase

Phase and polarity are big considerations — and entire articles are written about those topics alone. I’ve included links to a few resources below, so I’ll greatly oversimplify here. Phase isn’t an issue when using a single microphone, but as soon as you use two (or more) mics to capture a sound, phase becomes a factor. This is due to the time difference between when a sound arrives at the first microphone versus the second microphone. Sounds that are in phase will reinforce each other. The waves will reach all the microphones at complimentary points in their wave cycles, reinforcing each other, and the combined sound will be big, bold, and beautiful.

Polarity – Does It Really Matter?

A Guitarist’s Guide to In and Out of Phase

However, sounds that are out of phase will result in “phase cancellation,” which is succinctly demonstrated in the entertaining Instagram video listed below. Phase cancellation can cause volume dips or even complete silence at certain frequencies depending on the difference in arrival time. For example, the wavelength of a 1kHz sine wave is 13.5 inches, so if the capsules of two microphones are spaced 6.75 inches apart (1/2 wave), then the 1kHz signals will be 180 degrees out of phase with each other. If you combine the two signals, then you wouldn’t hear anything! To listen to an excellent demonstration of phase cancellation using sine waves, visit this phase tutorial from Taylor & Francis and follow along with the instructions. Sine waves easily demonstrate how in-phase sounds can reinforce each other and how phase cancellation can be destructive to your recordings.

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You’re probably not recording sine waves, though. You’re probably recording a voice, an instrument, or another sound with many different frequencies all put together. So, your out-of-phase sounds won’t get silenced entirely, but they’ll sound weaker and not as full as they would have been if their components were in phase. Think of a 10,000-piece jigsaw puzzle with 2,500 of the pieces removed. You’ll still probably be able to tell what the image is supposed to be, but it would look better if all the puzzle pieces were there. This is the effect that phase cancellation can have on your recordings. 

Boundary Effect

Sound reflecting off a hard surface increases the perceived volume of that sound depending on where you are in the room. This is particularly noticeable at low frequencies, and it’s why acousticians recommend placing your monitors at least three feet away from the wall (and never in a corner!) so that your bass doesn’t sound louder than it actually is. If you must place your monitors closer to the wall than this, then you should use small, front-ported speakers, such as the Neumann KH 80 DSP 4-inch powered studio monitor, for more accurate bass representation. And, of course, a nice set of open-back headphones is always welcome, as is a plug-in to simulate speaker crosstalk, like the Blue Cat Audio Re-Head head response.  

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Re-amping

Re-amping is where a recorded clean DI signal from a source — usually a guitar, but not always (like from a Moog Minimoog Model D analog synthesizer) — is amplified through a cabinet or amplifier, and the amplified sound is then recorded. Re-amping is a popular technique used in conjunction with room mics because it enables you to capture a processed signal in a different space from where it was initially recorded. At my alma mater, the recording studios were next door to the university’s ballroom, and students had a lot of fun re-amping and capturing sounds in that huge reverberant space! There are also many creative ways to “prepare” the speaker/amp and microphone(s) for re-amping — we’ll touch on these later.  

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When using room mics, these basic concepts — phase, boundary effect, and re-amping — are essential because once you understand these rules, you’ll know how to break them (or at least use them to your advantage). Using room mics creatively comes down to (1) recording in exciting spaces and (2) using — and abusing — these concepts to create interesting effects. Above all, remember to experiment and have fun! Here are some ideas to get you started.

The Tony Visconti Gated Room Trick

One famous room mic technique can be heard on David Bowie’s song, “Heroes,” from his album Low, produced by Tony Visconti and Brian Eno. Visconti had one close mic on Bowie’s voice and two room mics set up at different distances. One room mic was 15 to 20 feet away from Bowie in the middle of the room, and the other was set even farther away in the room — approximately 50 feet. Visconti then put gates on both room mics (but not on Bowie’s close mic) and set the thresholds so that they would only open when Bowie sang loudly. If you listen to the first verse, then you won’t hear any room sound — but by the fourth verse, when Bowie is starting to let it rip, you can hear the gates on the two room mics open, adding the room’s natural reverberation to the vocal sound.

Steve Albini & Boundary Effect

Putting omnidirectional mics on the floor manipulates boundary effect; this technique is perhaps best known as used by the great recording engineer Steve Albini. By putting the mic capsules next to the floor, you turn your omnis into semicircle (or half-omni) microphones that capture the room while eliminating the reflections from the floor. Pressure Zone Microphones (PZM) utilize this technique and are a great way to use the floor or walls to capture great room sounds. Another room mic technique involves pointing a microphone directly at a wall or in a corner precisely to utilize boundary effect to your advantage. You can naturally boost your signal’s low-end content by capturing those reflections from the wall or corner.

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Re-amping Madness

Re-amping into a new space with actual microphones is a lot of fun. While the quick and easy route is to audition amplifier plug-ins on your DI track, re-amping into your space through your cabs and capturing your sounds with your mics will result in a sound that is genuinely yours! No amp simulator or reverb plug-in can match that. Plus, much like John Cage and his infamous piano, you can get even more creative by “preparing” your speakers or mics in interesting ways. Try taping a snare drum over a speaker (à la record producer Matt Wallace) through which you’re re-amping, and see how it sounds. Tape a funnel over the speaker, and then attach a long hose to it. Tape the other end of the hose around your microphone and hear what happens. Build your own Cooper Time Cube mechanical delay device à la record producer Sylvia Massy. The possibilities with re-amping are truly endless.

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General Processing Tips & Tricks

Compressing room mics is a trick frequently used on drums to tame wayward cymbals, but it can have similar positive effects on instruments with a lot of high-frequency content, such as distorted guitars or lead synths. It tends to make the room sound larger and enlarges the instrument as a whole once blended in with the direct mics.

Delaying the room mics is another simple trick for creating a room that sounds larger than it is. Try putting a short delay of 20ms on your room mic(s) via a delay plug-in. This delay should give the listener the impression that the sound is bouncing back later, so naturally, the space will seem larger.

Another delay trick is using a stereo delay on a mono signal to create a “fake stereo” effect. Insert a stereo delay onto your mono room mic track, and then adjust their delay times independently. Offset the delay times by a few milliseconds (e.g., put your left channel’s delay time at 16ms and your right channel’s delay time at 21ms). Try playing with the delay times and the dry/wet mix control to blend in the effect. You can also try putting a compressor ahead of the delay in your insert chain to give the room mic more presence per the previous tip, and then this delay effect will be even more pronounced.

Room Mic Configurations

Let’s wrap up by looking at some room mic configurations. Sweetwater already has a great stereo miking article you can read, which is listed below, and I’ll also provide some mic recommendations that I’ve successfully used. Since immersive audio is all the rage, we can’t discuss room mics without touching on surround and immersive audio. After all, what are the most significant enhancements that these formats bring to recordings? The sense of space and localization. In other words, the room! So, if you want to get creative with room mics, then it only makes sense to consider using some of those configurations.

7 Stereo Mic Techniques You Should Try

Stereo Mic Configurations

Blumlein

Blumlein is one of my favorite configurations for room mics because it captures a significant amount of the overall room ambience and is easy to set up (especially with this excellent Grace Design SB-BL Spacebar Blumlein microphone mounting kit). You’ll want bidirectional (also called “figure-8”) mics for Blumlein, and I like to use ribbon mics. I’ve achieved excellent results with the Royer R-121 studio ribbon microphone and the sE Electronics Voodoo VR1 passive ribbon microphone. Also, many engineers prefer using a matched stereo pair of microphones when working with stereo mic configurations.

Blumlein configuration.

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The Case for Matched Pair Microphones

Decca Tree

Used originally to capture orchestral recordings for Decca Records, the Decca Tree configuration may be perfect for your next death-metal album! Sweetwater sells Decca Tree mounting kits that make it easy to use this great-sounding stereo mic configuration. Omnidirectional mics are what you want for a Decca Tree, and one that I’ve used before and loved is the Earthworks TC20mp small-diaphragm condenser microphone. Many engineers like using a different mic for the “front” (center) mic. If you can get your hands on one, then try using a Neumann M 150 tube small-diaphragm condenser microphone in that position. As you can see from the first photo below, the original Decca Tree was a large configuration meant for orchestral concert halls, with its microphones spaced quite far apart.

Note: For all of the following photos, please remember that the suggested distances are meant to be the spacings between the microphone capsules, not the microphone bodies.

However, you can scale it back for smaller rooms and still get a nice stereo spread.

Original Decca Tree configuration

Suggested measurements for a smaller Decca Tree configuration

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Surround Mic Configurations

Surround Arrays

From the Decca Tree, it makes sense to transition into a surround array (a configuration made much easier by another great tool from Grace Design — the SB-SUR-HD Spacebar Surround Tree). Generally speaking, there are three basic surround arrays that are based on different mic polar patterns; these are cardioid-based, wide-cardioid-based, and omni-based surround arrays.

Different microphones and different microphone spacings are used for each. But each technique uses five microphones: three forward-facing and two rear-facing. I suggest starting with an omni-based array, as it’s the most forgiving of the three. Set your three front microphones up like a Decca Tree, and then place the two rear microphones where they’re not too far away from the front mics to minimize the delay. Preferably, the mics will all be the same, though that’s not a hard and fast rule.

An omni-based surround array

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Hamasaki Square

For capturing pure room ambience with no mics directly on the source, I’ve used a Hamasaki Square, named after audio engineer Kimio Hamasaki. For this configuration, you need four bidirectional microphones. I’ve used the AKG C414 XLII/ST large-diaphragm condenser microphone or the sE Electronics sE4400 large-diaphragm condenser microphone. Each mic should be spaced between 80 and 200 inches apart, forming a perfect square. The bidirectional mics should be pointed toward the sides, with the sound source in the null, so that all you capture is pure room ambience. When used with one of the surround arrays mentioned above, you’ll get an incredibly huge soundscape to play with.

Hamasaki Square configuration

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Immersive Audio

Immersive audio is the most exciting technological advance to happen in recording in quite some time. Companies across the industry are pushing development to deliver suitable immersive solutions for home/project studio setups. It is the perfect time to experiment with the use of it in your recordings. The forerunner in immersive audio is Dolby Atmos, which is a platform that combines traditional channel-based audio with steerable object-based audio. Several DAWs are capable of working in Dolby Atmos, including Avid Pro Tools Ultimate, Steinberg Nuendo 12, Steinberg Cubase Pro 12, and Universal Audio’s LUNA (along with the Dolby Atmos Music Panner plug-in).

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If you don’t have the space or budget for a full 7.1.4 Dolby Atmos system, then the simplest way to begin using Dolby Atmos in your DAW is by using headphones and a head tracker. I’m most familiar with Steinberg Nuendo, and it offers native head tracking for monitoring in immersive audio (as does Cubase Pro 12). Dolby’s Atmos Renderer also allows for a downmixed output in stereo and binaural and stereo headphone monitoring.

The Sky’s the Limit

Here are two principal things I hope you take away from this article:

1) Whether using compression and delay to make your room seem bigger, re-amping through a snare drum, or using surround mic configurations, when it comes to getting creative with room mics, there are endless possibilities. 

2) Most of our Sweetwater Sales Engineers are also competent studio engineers. If you ever need great mic recommendations or a mic configuration suggestion for room mics, then don’t hesitate to call them at (800) 222-4700!

References

https://www.dpamicrophones.com/mic-university/stereo-recording-techniques-and-setups

https://www.dpamicrophones.com/mic-university/immersive-sound-object-based-audio-and-microphones

Huber, David Miles and Robert E. Runstein. Modern Recording Techniques 9th Edition. Routledge, 2018.

Massy, Sylvia and Chris Johnson. Recording Unhinged: Creative & Unconventional Music Recording Techniques. Hal Leonard Books, 2016.
The post Creative Ways to Use Room Mics — Not Just for Drums! appeared first on inSync.