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Shure SM57 vs. Shure SM7a [EN]
the shure sm7 and the shure sm57 must be two of the worlds most popular microphones.
although the two were introduced over a decade apart, they use the same "unidyne III" capsule as a base component, and there are lots of opinions and rumors floating around the internet on whether the two sound alike or if they offer two completely different dimensions of sound.
i didn't know, and i had both microphones available, so it's obvious i wanted to find out...
the most common fact/myth that sm7/sm57 users seem to agree on, is that both microphones produce similar results, the sm7 having more bottom-end, the sm57 more high-end.
but can you believe "teh interwebz" and recording engineer's smalltalk? ... we'll find out in a second, but first a little history lesson and some basic info.
sm7's were first introduced in 1976, they're a secret weapon that makes just about all male "rock" vocals sound nice - even james hetfield of metallica, the guy who could have any microphone in the world - be it bought or custom tailored, used an sm7 to record his voice on metallica's controversial 2008 studio album "death magnetic", as the following video shows:
the sm57's history dates back even further, to 1965. sm57's are still used today as a standard microphone for guitar cabinet recordings, and are said to be still found in the U.S.-presidential speaker's desk.
for my comparison, i used a rather elderly sm7a and a brand-new, shiny sm57 that came straight out of the shop.
in three steps, i first recorded an acoustic guitar, then the cabinet of a (modern) distorted guitar, and finally some male rock vocals.
first, let's inspect the setup.
i aligned both the sm7's and the sm57's membranes, ignoring the presence of the sm7's "cage". this "cage" introduces a "forced minimum distance" to the source, which probably affects the way vocals and cabinets can be recorded with it.
the sm7 has two switches on its back, a low-cut and a treble-boost. for this test, i left both switches in the "flat" position.
short and shielded quality microphone cables were used, connecting the two mics straight to my tc electonic konnekt 8 audio interface.
i especially chose the konnekt 8 for its preamps, as it is widely known that the sm7/sm57 range need quite some amplification. the sm7b is said to have "more output", which probably deals with this problem.
the konnekt's preamps reach up to +62 dB of gain, which -when it comes to mic preamps in audio interfaces- is a lot! and, as the following picture shows, that was a pretty good choice. i had to turn the konnekt's preamp stages up really far to get decent level out of both microphones. (using no "pad" etc.)
the attached .mp3 files were encoded using the LAME encoder @ 44.1 kHz sample rate / true stereo / 256 kbps constant bit-rate, containing only the signal of one microphone.
the downloadable .wav files were rendered @ 44.1 kHz sample rate / true stereo / 16 bit PCM bit depth and contain the signals of both microphones, sm7 on the left channel and sm57 on the right.
please note that the recorded samples were only cut, but not processed otherwise. (so no dynamics, EQ, etc.)
now, let's have a listen.
first off - acoustic guitar.
this is actually not a really "good" one, it's a cort earth model. cheap wood, i know, but a sufficient prop for this test. in each clip, there are 3 takes: 1 - neck position / 2 - sound-hole / 3 - bridge.
acoustic guitar - sm7
acoustic guitar - sm57
[download .wav file] (approx. 7.6 MB)
the second possible application, and probably the most common, is recording guitars over an amped cabinet.
i dusted off my old '84 peavey vandenberg (modded with emg pickups) and plugged it into an engl powerball with the corresponding engl 4x12 box, home to 4 celestion vintage 30 speakers. to be honest, this was a quick test and it sounds like i didn't get the positioning right, too much low-end for my taste. but still, both mics aimed at the same spot on the speaker from the same (membrane) distance - so it might sound a little unprofessionally mic'd, but it's still a fair comparison.
peavey/engl - sm7
peavey/engl - sm57
[download .wav file] (approx. 7.3 MB)
the last and least modest field of use (covered in this comparison) is - vocal recording.
if the U.S. president holds his speeches over sm57's, and metal's president shouts into sm7's ... i think it's only fair to further investigate both mic's suitability for this specific application.
at this point, i want to thank michi l., the vocalist of my band exit dead end, for spontaneously shouting and growling at the two poor, helpless microphones i set-up for him, in order to round off this comparison with male "rock" vocal samples.
rock vocals - sm7
rock vocals - sm57
[download .wav file] (approx. 1.1 MB)
so, let's take a look.
i loaded up voxengo's span spectrum anlyzer plugin, panned the sm7 tracks hard left and the sm57 tracks hard right, and the following screenshots show the result.
the cyan/blue line represents the frequency spectrum of the sm7, the magenta/red line is the frequency spectrum of the sm57. feel free to download the .wav files (linked above) and to analyze them yourself.
finally, let's come to a conclusion.
the recorded samples and the frequency analysis all speak the same language as the common sm7/sm57 rumors on the net: there's hardly any difference between what the two microphones record, apart from the slightly stronger bottom-end of the sm7 and the slightly more brilliant high-end that the sm57 produces.
but let's not forget that the sm7 still has the low-cut and treble-boost switches on its back, and with those it could probably be modified to match the sm57's frequency response nearly 1:1.
so there you go.
"yes, it's true."