How to Mic a Guitar Cab

Whether feeding a live mix or laying it down in the studio, an important part of your guitar sound usually involves placing a mic or mics in front of your combo or stack. You may have your technique dialed in or, like most of us, are still searching for that signature sound. That tone is ringing in your head, but not coming out in the mix.

You have, at your finger tips, an almost infinite variety of amps, cabs and sounds but the one you hear from your rig, doesn’t sound anything like what you hear out front- frustrating. Well it’s time to adopt a method to avoid any potential madness.

A Matter of Focus
The biggest problem with many guitarists is that they really don’t know what they sound like at the front of the cabinet. Sure, you are standing “in front” of it, but your ears are usually way above the sweet spot at the front of the speakers. Unless you are doing a handstand and playing with your feet (I would pay good money for that show), you are listening to your rig off axis and the entire high end is being rolled off. This narrowing of focus is a function of the speaker diameter being longer than the wave of the frequency as it goes up. Also, the cause of many guitarists cranking up the high-mid and high frequencies, presenting an unpleasant tone to the mic placed “at the front’ of the cab.

Listen to your amp and guitar combination at microphone level and create your tone before you start placing a microphone in front. You may also try your rig leaned on a leg or on an angled stand pointed up toward you (Check our MA12 amp stand).This will change the bottom a little but it will get more of the higher frequencies that the speaker is producing to your ears. This is your first step toward avoiding frustration and sharing your signature sound with the rest of us.

Remember that this is a snowball that is rolling downhill. It all starts with controlling your tone and finishes at that end by smashing into someone’s ears. You control the way you play, the instrument you chose, the stack you carried in, the tone that is produced and where the mics are placed in front of your cabinet. Your sound is then handed off to the sound engineer who will do his or her best to make you sound better. Do your work up front and get dialed in. Give the sound engineer great sound right away and you will be acknowledged for being far ahead of most guitarists that he or she comes across.

Microphones Natural Selection
Now that you have found the settings that produce a tone that you are happy with, it is time to pick a mic or mics. The default microphone to start with would be a good dynamic microphone. They are robust, able to withstand high sound pressure levels, do not require phantom power and are affordable. There are good condenser microphones that sound great and will take the abuse, but if you have a tight budget, start with good dynamic mic.

Note: Mics have different “personalities” which are differences at frequencies within pick-up patterns of the same category (cardioid, hyper, etc.), sensitivities and loudness threshold limits. It never hurts to ask the journeyman player what he has had good luck with.

Live and studio will generally benefit from different mic patterns dictated by different goals. In a studio you may want more of “the room” in the sound and may opt for a ribbon mic, an omni or even a figure 8 condenser. In a live show, good sound with a lack of noise and feedback are the primary goals. Note: Particularly hot mics may need to be padded down and if your mic does not have an attenuation switch built-in or it isn’t enough, you will need to add an inline pad to your system.

You may find your mic right off the bat but as you develop and refine your setup method, some experimentation with different mics may just get you to that wonderful place that until previously only existed in your mind.

There are Lots of Places to Go
Once you have adjusted your tone so that you're happy with it, it is time to place the microphone. An instrument loudspeaker does not operate as a true piston through all frequencies. Placing the mic in the middle will not get you the most natural sound and a good place to start is off of center, about a third of the way out and 1 inch to 10 inches away.

Always remember – brighter toward the center, warmer to the edge and the bottom fades away
If you want more bottom and a warm sound, move the mic in closer and toward the edge. Less bottom and brighter, move away and toward the center. If you like a blend of warm and the top end clarity of the middle, use two mics, one toward the middle and one toward the edge and mix to your taste.

Note: Low end response for most mic patterns show low end proximity effect, an omni pattern will not.
It's also ok to mic the back of a cab in one of the speaker frame windows- you may have to flip the phase when combined with the front mic to preserve some bottom, but this blend can offer an interesting fullness to your tone.

Note: Do this for your A-rig and your fly-in B-rig.

When testing placement of the microphone on a 4x12 or 4x10 cab, try both the upper and lower speaker. Placing the mic on the lower speaker can pick up reflections off the floor. You may find that using the upper speaker yields a more true and cleaner response. Once you have found the “sweet” spot on your cabinet, use gaffer tape to create a square or triangle around that spot on the grill or grill cloth. You’ll then have no trouble finding that spot again.

In the studio, make sure your amp cabinet is in the “live” room and you listen to your tone in the control room. This is a good way to hear your mic’d tone for recording. Employ a helper to position the mic as you listen. If you use a head & speaker cab rig for recording, you can even use a long speaker cable and place the head in the control room so you can dial in your tone and hear it as it will appear on the recording.

Some experimentation and creativity can lead to some great sound.

Calling for Backup
There are times when things go wrong, a speaker loses a coil or the amp doesn’t work and it is always at the worst time. You have checked the fuses but didn’t pack backup tubes. Time to break out the direct box that is sitting in the bottom of your bag. Yes, this is not the subject we are covering, but it applies.

Once you have your method and sound dialed in, it is your job as a professional to make sure the show goes on.. If you haven’t worked hard to make sure that you can assimilate your sound through your direct box, you are making more work for you and the sound engineer.

Direct input to the mix will not have the natural compression of the speakers or the added EQ benefit of mic placement. The box is just an in-line transformer taking a low-level line signal of your guitar and making it a microphone-level signal that your mixer or interface can use.
You should spend a little time with a compressor and EQ to get close to your sound and be able to communicate these settings to a sound engineer. He will appreciate you getting him in the ball park and it looks “real professional” while saving time at sound check.

Love Your Work
When you have done the work and you “know” what works, write it down. Make notes, draw a diagram and take pictures on your phone of all your settings, placements and equipment. When you are road weary, having these makes everything repeatable and easy.

With your acquired knowledge of the different guitar and amplifier capabilities and new microphone techniques you will always be able to find the right guitar sound that fits for the part, the song, or the genre.

If you have more than one amp rig – one for small venues and another for large venues, it helps to have separate diagrams or “stage plots” ready as they are sometimes required by venues. County fair stages often ask for a stage plot diagram so they are prepared with enough microphones and channels for each band.

Remember it all starts with good playing, on the right amp and the right guitar. No engineer can make poor gear or poor playing sound wonderful. Play well, on the best gear you can afford, use good mic techniques and the audience will know why you love what you do.

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