Three Stereo Mic Arrays Compared

Friday, April 7th, 2017

The video forums and sites I visit go in a lot of different directions, but one of the most consistent points they make is the importance of audio in video. Those of us shooting “look at me play guitar” videos actually have it easy compared to folks doing documentaries or dramatic films, because we usually don’t mind having the microphone(s) visible in the shot, but since we’re showing off our music we really need the audio to shine. For acoustic players like me that means using microphones. The natural sound of the acoustic guitar just doesn’t come across with any pickup system I’ve found yet, so learning to position mics for a compelling recording is a big part of making a satisfactory video.

When I visit discussion forums about recording guitar the most common topic is the choice of mics. I know when I started this journey I was constantly looking for that magic microphone that would make my recordings great, but the recommendations were so many and so various and contrary that the process made me dizzy. Microphones are fascinating, advice was numerous and my resistance was low so I’ve spent way too much time and money on the pursuit of that magic mic. By the time I started to get good results in my recordings, though, I’d learned a few important things. First, there are many mics that will do a great job of capturing the sound of an acoustic guitar. Second, the mic hears the guitar in the room, so the sound of the room is a big part of the recording. Third, the placement of the mic can make or break the recording quality. Which brings us to the subject of this article – stereo mic arrays.

Mic the Guitar

The default mic configuration I see suggested for acoustic guitar seems a bit odd to me – a large diaphragm condenser mic at the bridge and a small diaphragm mic at the 12th fret or so. This is usually accompanied by a discussion of the “warm” quality of the LDC and the “bright” characteristic of the SDC. But in reality there is no certainty that a large diaphragm mic will be warm, that is, emphasize the low mids. Many of these mics are quite bright, in fact. And the opposite is true of small diaphragm mics – some are bright, some are warm, some are as linear as possible. And capturing stereo using mics with different frequency response characteristics is a recipe for a wandering stereo image, with the sound jumping around as the guitar produces different frequencies.

Mic the Space

My preference is to use a pair of matched mics in a stereo array, just as a recordist would approach a classical music recording, with the aim of capturing the sound at a point in space. Various stereo mic arrays have been used for symphony, small group, and solo recordings for many years, and I share their goal of capturing the feeling of being in the room with the performance. So the question then becomes, which mic array should we choose. Since I have all these mics hanging around I decided to set up three different proven mic arrays and record a single performance through all three at the same time.

Three Stereo Arrays

XY is a coincident technique, that is, the two mic capsules are placed as close together as physically possible. Directional mics, usually cardioid, are used for XY. This approach gives optimal mono compatibility but sacrifices image width. For this demo I used the XY mic module of my Zoom H6 recorder.

ORTF is a spaced mic array developed by the French national broadcasting organization, Radio France. The Schoeps cardioid mic has been the definitive ORTF microphone since that format was developed. When I was breaking the bank in my search for the magic microphone various Schoeps configurations were recommended by many sources and I was unable to resist. In this example I’m using a pair of CMC64 cardioids.

AB is the term used for a spaced pair of (usually) omnidiretional mics. While directional mics seem to be the most common choice for us home recordists, many professionals prefer to use omni mics when possible. These have a different quality of bass response due to the tricks used to make directional mics, so they’re especially favored for sources like pipe organs and grand pianos where the bass register is an important part of the sound. An acoustic guitar has a much more limited bass output, but I still enjoy the sound of my Shure KSM141 mics in omni mode and used them for this demo.

Here’s a video of the session. With the different mics in use there will definitely be tonal differences between these examples, but hopefully you can hear the spatial difference as well:

And here are uncompressed WAV files for each array:

XY
ORTF
AB

Since these files are uncompressed they may not stream well so I recommend downloading them to your local device for comparison.



This entry was posted on Friday, April 7th, 2017 at 4:59 pm and is filed under Comparisons, Recording. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.

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    About the Blog

      Howdy, my name is Fran Guidry and this is my Homebrewed Music blog.

      I play Hawaiian slack key guitar and recorded my solo acoustic CD at home. Most of the recording information I find on the internet seems focused on bands, drums, multitracking, and so on but my main focus is recording solo acoustic guitar. Lately I’ve been enjoying video recording along with audio, so that shows up in the blog as well.

      I’m also a guitar nut. I love big ones and little ones, handmades and factory guitars, cheap ones and expensive ones. So I’ll be sharing the fun of exploring guitars as well, along with the challenges of amplifying acoustic guitars for live performance.

      Welcome!

    Philosophy

      My recording philosophy is pragmatic, skeptical, not super critical. After all, the performance is by far the most important component of a track, and every aspect of any recording is a matter of taste.

      But I do like to know “about stuff.” Back in hifi days I learned about double blind testing. I learned that we humans can easily hear differences that don’t really exist. The more I’ve learned about our human auditory system, the more I’m skeptical of what people say they hear, especially if they claim that a particular microphone or preamp or cable has some magical property.

      I’ve only been recording since 2001, and when I started I found the usual places on the internet. I sought advice and accepted it, thought I would improve my recordings by using more expensive equipment. It didn’t work.

      Two things that did seem to lead to better recordings were experience and room treatment. Getting an appealing sound is the combination of many small details, and learning those details only comes from experience. Amd the sound of the recording space is obviously a big factor.

      I’ve only recorded seriously using digital technology, but I remember trying to record rehearsals and gigs back in analog days. I don’t have any nostalgia for analog recording and playback systems at all. I think even low end digital systems can capture marvelous recordings. So when I look at gear, I look for good specs: low noise, broad flat frequency response, wide dynamic range, low distortion. I’m not interested in colorful components, mics and preamps with a sound, I want the sound to be the sound of my guitar.

      But the last word is that I’m just learning and I hope you find something useful in my posts.