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Shure KSM137/Sl Stereo Mic Pair

January 16, 2008


The KSM137 is set to a fixed, highly consistent cardioid polar pattern; a 3-position pad switch chooses 0, –15, and –25dB. With this pad, the KSM137 can handle extremely high SPLs (Sound Pressure Levels) up to 152dB. (Remember, 135dB is the human threshold of pain, and 140dB is the sound of a jet taking off.) The frequency response covers 20 to 20,000Hz and includes two low frequency filters which, when activated, roll off the mic’s low end starting at either 80 or 115Hz. The KSM137/SL (stereo pair kit) includes two foam windscreens and a solid carrying case.


I’ve been working recently for Levi Riggs, a contemporary Christian artist, and the acoustic tracks are crucial to his music. For one song, we used a beautiful Marin acoustic guitar for the main rhythm track; it needed a full, wide, and warm sound as the song was very pure, without much production or instrumentation.

We started out by listening to the 137s in an X/Y miking configuration. With a standard coincident X/Y miking position, it’s typical to have the two mics on top of each other forming an X. The angle of the two mics can range from 80–130 degrees, depending on the size of the source you’re recording and the tone you want. I positioned the two mics around 6" in front of the sound hole in an X fashion at around a 100-degree angle. One mic faced toward the edge of the sound hole next to the fretboard, while the other pointed to where Levi’s fingers were picking the strings.

One advantage of this particular X/Y pattern is that it minimizes phase cancellation issues. As the two KSM137 mics are virtually identical and the capsules are positioned closely together, the sound travels through the air to them for almost the same distance, so the two recorded waveforms will be very similar.

I engaged the 115Hz rolloff switch on both mics, plugged them into two pres of our DDA console, then ran the signal straight to Pro Tools. The sound was phenomenal: It was wide, and the mics seemed to roll off just enough of the low end “thumps” that I usually need to filter with EQ when I use other mics in the same situation. After EQing down about 2dB at 8kHz on the finger mic and 12kHz on the other mic, we had the sound we wanted.

Next up: piano. My studio houses a 4'7" Ridgewood baby grand, and it’s always a challenge to achieve a wide stereo spread with such a physically small piano. The piano sounds best when jammed in a corner nook, with the lid all the way open so that the sound can project across the room. I remove the top of the piano (which holds the music stand) and use a pencil mic (e.g., AKG 451 or Shure SM81) on the high end, around 6" from the dampers; a tube mic set to a cardioid pattern on the low end around 8" off the bass strings gives some beef and warmth, and then I’ll often use a room mic (centered in front of the open lid, about 12' back and 5' off the ground) to add a natural gloss.

I compared the KSM137, an AKG 451, and a Shure SM81 on the piano’s high end to determine which would provide the best mix with my beefy low end. The vintage AKG 451 sounded good, but could be just a little harsh (also, a few strings really seemed to “chime”). The Shure SM81 (which I normally use) had a nice, accurate tone, and the mic’s cardioid pattern picked up just the right amount of piano. The Shure KSM137 and the SM81 both sounded somewhat similar; the 137 had just a bit more high end around 10–12kHz and a noticeable difference in the low end, almost as if there is a very fine natural rolloff.


Shure has definitely kept up with the standards set by its predecessors. I’m very impressed with the KSM137 for piano and acoustic instruments in general, and the stereo pair will become the “go-to” choice in my studio for these types of applications. For the money, the KSM137 is a great buy.

Product type: End-address condenser mic with cardioid polar pattern.
Target market: Recording studios.
Strengths: Serious value. Sounds great. Suitable for many applications.
Limitations: Nothing significant.
List price: $575 each, $1,150 for stereo pair

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