Recording Bass and Guitar with the Earthworks SR71 Cardioid Condenser Microphone

Best known for its high-quality omnidirectional microphones, Earthworks refers to the SR71 as a rugged live sound cardioid mic that can be equally at home in certain studio applications.

If used a few feet away from the sound source like a conventional cardioid microphone, the lack of low frequency output could be disappointing. With a little understanding of how this mic works, however, it could become a useful tool - placement being the keyword here.

No proximity effect

Proximity effect, which is inherent in directional microphones, increases low frequencies as the mic gets closer to the sound source. In fact, many cardioids have high-pass filters to compensate for this phenomenon. But like all filters there is phase shift that accompanies these low-end rolloffs. The SR71, on the other hand, really shines when it is close to the source using proximity to actually flatten the low-end response.

This can be advantageous in situations where more isolation is desired. In the studio, when unwanted sound from other instruments leaks into a microphone you do one of two things: move the mic closer to the source or get better acoustic isolation. You can either use gobos or, if you really can't control the leakage, put the instrument being leaked upon in a separate room.

On a recent recording project I used two SR71s in situations where EQ or some low-end rolloff would ordinarily be necessary. I prefer going to the trouble of changing a microphone to reaching for the EQ.

Acoustic bass almost always poses a problem when recorded in the same room as other instruments, such as drums or horns, because of its relatively low acoustic output. Using an omnidirectional microphone is my usual choice if isolation is not a problem, which it usually is.

Most bass players today use a pickup on the bridge, which lets them use an amplifier on live gigs to compete, loudnesswise, with other instruments on stage. For recording, however, pickups don't make it in my opinion because they do not sound like the bass does, acoustically. Consequently, I always use a microphone. Now I'm going to show my age again and say, before pickups came on the scene, bass players had their bridges set up higher, pulled the strings harder and created much more output. This made the bass much easier to record and also sounded better.

Clean close miking

When using a cardioid to close mic a bass, proximity can make for a boomy low end and here is where the SR71 shines. The photo shows placement above the bridge at the lower end of the fingerboard. With no EQ, the sound of the bass was full and fat without getting boomy - very smooth with just enough finger sound to add to the articulation. Pitch definition was as good as with some of the best omni mics. I highly recommend the SR71 for this purpose.

Since I had two mics, I used the other one on a guitar amp in the same session. Here again, proximity can be a problem with conventional cardioids if you get too close. This was not a problem with the SR71. The sound was very smooth with the SR71 only a few inches from the amp's speaker cone. Most dynamic mics commonly used for this purpose do not have the smooth midrange and top end. Another plus for this application is the ability to handle extreme SPL - how about 145 dB - without a pad. Earthworks specs the noise at 22 dB (A-weighted), which is not a great number but, because this mic is used close to the source, it presents no problem.

One of the perfect applications for the SR71 is home studio recording, where close miking is almost a must due to the extraneous noises, such as refrigerators, washers and dryers found in most home environments.

At a retail price of $450, the Earthworks SR71 is a good addition to almost anyone's microphone collection.

Contact Earthworks at 603-654-6427

Tom Jung, founder of DMP Records, is Pro Audio Review's technical consultant and a regular contributor.