Too Many Microphones? Part I

We’ve all been there.  Somewhere closer to the beginning of the journey of learning our new recording skills than the end.  We’ve watched tutorial videos, seen photos of famous sessions from the past, and maybe even *gasp* cracked open a book or two on the subject of instrument mic placement.  “Man,” we think, “my stuff just doesn’t sound as good as the stuff in these videos/photos/books.  WHAT’S THEIR SECRET?”  Then it clicks:  They’re using three microphones on that kick drum!  There are two on that snare!  They’ve got 2 microphones on the guitar cabinet, and neither one of them is an SM57!  I HEARD THAT EVERYTHING ON MICHAEL JACKSON’S “THRILLER” WAS RECORDED IN STEREO!!!

“THAT’S the ticket,” we think!  They must be getting all that (insert nebulous descriptive term – punch, edge, etc. – here) from the multiple microphones!

And thus begins a journey down a potentially slippery slope.  But what makes it so slippery, and how can we avoid taking a bad first step into this brave new world?

Learning “The Rules”

There’s an often-quoted phrase:  “You have to learn the rules before you can break them.”

Man I hated that phrase.  “SCREW THE RULES,” I wanted to shout every time I heard it, “I’m doing what I want.  I’m breaking new ground here!  And it’s going to be WAY cooler than your boring-assed rule-following method!”

You know what?  I was wrong.  That awesome inner-monologue was – in my case – wanting to skip learning the stuff everybody knows, so I could introduce the world to my obvious next-level genius.  There were just a few small problems with that plan:

1.) Clients (it turns out) had certain expectations of my skill set when they hired me.  Much to my chagrin, those expectations most often involved understanding the meat-and-potatoes basics of recording.  Or if you’re working on your own material you can translate this as, “You want the best possible result in the shortest amount of time in order to stay creative.”

2.) I (it turns out) had certain expectations of how much food, shelter, and clothing I needed in order to continue…you know…living.  How much of those things I could afford was intrinsically tied to meeting my clients’ needs.  That’s true no matter whose material you’re working on!

3.) My “next-level genius” ideas (it turns out) were often neither.  Most of the time they were interesting experiments that didn’t work out.  Or worst of all they weren’t actually new ideas.  Just new to me.  No matter, because my clients didn’t have time, budget money, or patience for any of it.

Suddenly I found myself running smack into the, “You have to learn the rules before you can break them,” wall.  Which nearly all of us do.  It’s all a part of the process.

The First Phase

The basic problem in any multiple microphone situation is this:  phase cancellation.

I could spend many pages worth of time writing about what phase cancellation is, what causes it, why it can be a bad, or a good thing in regards to audio.  But many very smart people have already committed their fine minds to that cause.  Here’s a solidly written article from Sound On Sound magazine to get you started:


I highly recommend putting the time, and effort into learning about the subject.  It’s a little knowledge that will feel like free money when you apply it.  But if you want to cut a corner for now here’s the TL;DR version:

If you record an instrument with two microphones that are receiving acoustic information at different times, when combined those two signals will cancel out frequency ranges in one another.  And unless you learn to recognize it, you’ll spend endless amounts of time chasing your tail trying to fix it later on.

Story Time I

Some years ago while engineering an album for a successful producer, he asked if I could do him a favor.  He’d been hired to mix a single for an independent artist.  They had a tight deadline, and the producer wanted me to take a quick break from working on the album to prep the indie single for mixing.  He was going to do that on our usual day off.  Our album artist was in town from overseas, and the producer was up to his neck in work.  So I happily agreed.

I don’t remember very much about the song, or the quality of the recording.  Here’s what I DO remember in vivid detail:  48 tracks of the same rhythm guitar part.  12 passes, 4 microphones on the amplifier for every pass.

My very next (and private) thought?  What a phenomenal waste of time.  I had a fair amount of experience mixing professionally at this point, and I knew the tendencies of the producer I was working for.  The fate of at least 44 of those tracks was going to be the mute button.

A few days later I pulled up the mixed Pro Tools session.  Of the original 48 rhythm guitar tracks, 45 had been muted.  Of the three that remained (each from a different pass), every one was recorded with the same microphone.

Stereo Vs. Mono Sources

The first step on our road to understanding is the difference between using multiple microphones on mono vs. stereo sources.

Now I might be getting a little simplistic for some of you.  Please know that I understand we’re about to dive into basic recording 101 here.  But we can all use a little refresher every now and then, right?

Most things we record in the studio can at their simplest level be described as mono (or point) sound sources.  Individual drums, guitar amplifiers, bass amplifiers, acoustic guitars, and many mechanical keyboards.  Some synthesizers have only a single mono output.  Many stereo synthesizers have patches that are mono as well, even if they have stereo outputs (exactly the same information is being sent to both left and right outputs).  These instruments can be captured, and faithfully represented by a single microphone (or DI box) on a single track.  Under certain circumstances an engineer may choose to capture them with multiple microphones for creative reasons, but it isn’t a necessity.

A few things are inherently stereo audio sources, which means they require two microphones (or DI boxes) on two tracks (or in DAW world a stereo audio track) to be correctly represented.  Drum overheads, room microphones, stereo keyboard.  Though again, the engineer may choose to record these things in mono under some circumstances.

Then there are a few things that over time have come to be accepted when recorded either as mono, or stereo.  Acoustic piano is a great example.  Rhodes electric piano, and Leslie speakers (with B3 organ or guitar as their source) are others.

It’s important to understand what category the sound source you’re recording falls into.

Back To Basics

The first guideline you should keep in mind before trying to throw three microphones on something that really only requires one is:  Can you make it sound great with just one microphone?  If the answer to that question is no, then you’ve got a whole host of options at your disposal before adding a mic.

Let’s look at the idea of a mic-ing a guitar amp.  As mentioned above it is nearly always a mono sound source.  Play the guitar in the room with the amp.  Does it sound good in the room?  Does it sound good at the spot where you’ve placed the microphone?  (Yes get right down on the floor and listen close up…with flat-filtering earplugs in if the amp is cranked.  ALWAYS PROTECT YOUR HEARING!)  If it doesn’t, try adjusting the settings on the guitar, the amp, or both.

If that doesn’t get you where you need to be then you can try a different guitar.  A different amp.  If you’ve got a session guitar player, and don’t have a tight deadline you can even try another guitarist!

Once you’re happy with the sound in the live room, go back and listen in the control room.  If it’s not working there, the work you’ve already put in allows you to be certain your problem isn’t the guitar tone.  It’s in the recording chain.  So move the microphone, try a different microphone, or a different pre-amp.  Chances are you’ll have it sounding great long before you’ve exhausted all of those options.  And every time you do this exercise, you’ll learn something new about a certain guitar, amp, microphone, gear setting, etc.  Each one of those things is another tool you’ve added to your belt that will make you better/faster next time.  And the same concepts apply to any instrument you’re recording.

Adding microphones without understanding why you’re adding them, and how to place them correctly is likely to create more problems than it will solve.  And in a worst-case scenario, you could end up delivering 3 bad sounding microphones worth of information to your client/mixing engineer, instead of one good one.  Which isn’t the end result anybody is after!

Great!  So When SHOULD I Think About More Microphones?

That, my friends, will be the topic of my next post!

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