vox ac15 universal bass response amp mic position royer

A look at optimal mic placement for recording amps

Last night, I was working on a session with a well-known guitarist who’s been making records for 30-plus years. Even after all that time standing in front of blasting Marshall cabinets, he’s still got ears. With the small change of a mic position at his suggestion, the sound we were searching for came through the studio monitors. It got me thinking about how important a nudge here and there can be.

The example I speak of above was being recorded with a single SM57 through a Universal Audio preamp. It was a small Vox AC15 being slightly overdriven with a beatup Telecaster and no pedals. Interestingly, since the amp was so small, we dialed up the sound while sitting in the control room. When I took the amp out to the live room to mic it up, I put the 57 slightly off axis about an inch from the grill cloth.

After we got some level, he mentioned that it wasn’t the sound he’d heard in the control room. So I went out there and we placed the Vox on the floor, directly on the wood. That didn’t do it. Then he asked if the mic was right up on the grill. An assistant went out there and pushed it in as he was playing— pretty amazing how you could hear the bass response and midrange change in real time, with just an inch of movement. That was the sound he “heard” in his mind, the one he wanted to capture.

Driving home later on, that small episode really stuck with me. I’ve recorded countless guitar players and sessions along the way, and this was a cool little lesson learned. It made me realize that for one thing, you’re never sure what the player that you’re recording hears through the speakers. You can only go out there and place a mic, (or two or three) in positions you feel will achieve a great tone. Once the setup is complete, you may think it sounds great, while they’re still not pleased, or vice versa.

Micing up an amp is really not a secret or a science project; it can be a lot of trial and error. You select the mics that relate to the character—clean, distorted, bassy, bright, etc. The 57 we chose for the Vox was in character with the sound presented. I also placed a Royer 121 a few feet back to catch some ambience if needed. To fit the track, the guitar needed to have some midrange punch and a touch of grit to cut through. So his suggestion to push the mic right into the cone provided that deep response that having it even an inch back didn’t deliver.

While it sounds fundamental, it couldn’t be any truer: don’t settle for placing that mic on the amp and just recording. Mess around with various positions and angles. Straight on the speaker (on axis) will present the most direct signal to the microphone. The sound will change by angling the mic slightly off axis, especially with cardioid dynamics like the SM57.

Of course, if you’re using a ribbon mic like the Royer, the polar pattern is a figure 8. That means that sound will be captured from both the front of the mic and the rear. It’s the perfect thing to include some room ambience and direct sound with the same mic.

Experiment with placing your mics back from the speaker an inch, two inches or even more. For that extra punch we found on last night’s session, try jamming it right on the speaker. With open back cabinets, you can even see what it sounds like putting it behind. If you can, try to get someone to put on a pair of headphones and move it for you, while you’re talking to them. This way, you’ll be able to monitor the sound in the control room and hear the subtle changes take place with each movement.

Also, don’t forget to alter your position on the actual speaker itself. The sound in the middle of the cone will be different from that just off to the side. You just never know what will sound right until you try it.

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