Article Courtesy of Bobby Owsinski https://bobbyowsinskiblog.com/2019/03/06/guitar-amp-miking/
“There are about as many ways to mike an electric guitar amp cabinet as there are opinions on which music is the best, but there’s one that’s always been my favorite. The reason is that it provides a lot of versatility in sounds, something that we’re always looking for especially when guitars tracks are stacked.
I’m not sure who taught me this technique but it was something that I saw used a lot when I first came to Los Angeles. It’s pretty easy, but it does depend on specific mics, at least in its original form. Here’s what to do:
1. Place the Shure SM57 slightly off the voice coil (see photo) and then add a Sennheiser MD 421 at the same position to the right of the 57, at a 45-degree angle pointing toward the voice coil.
2. A surprising variety of sounds can be achieved from this setup by using one mic or the other, summing them both at different levels, or by flipping the phase on one of them.
3. Many engineers today prefer to use a Royer R-121 instead of the 421, but they usually place it straight into the cone or on a different speaker instead of at a 45-degree angle to the 57. While that will work well and provide the additional warmth that comes with using a ribbon mic, it doesn’t quite get you the same versatility. Try using the angle and see what I mean.
4. Some engineers add a 3rd mic about 6 feet back from the cabinet to add some room and to capture some of the low frequencies that develop away from the speaker. Usually this is a large diaphragm condenser. If the room doesn’t sound particularly good or is too reflective this might not work well though.
Obviously there are dozens of techniques, but that little 45-degree angle from a second mic can add more than you think from the variety of just a couple of mics.”
Bobby Owsinski is a producer/engineer, author and coach.