Review of the Shure SM81 Microphone by TweakHeadz Lab
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sm81

 

Review of the Shure SM81LC

Great Mic for Acoustic Guitar

by Tweak

It has taken years for the SM81 to rise to the top of my GAL (Gear Acquisition List) but it finally did a few weeks ago.  The package has arrived and the acoustic guitars are dusted and polished.  Expectations high.  Plug it in to the Focusrite Voicemaster Pro, turning off all the enhancers and mashers and position the mic 5 inches off the last few frets angled at the sound hole of a now Vintage Romance Classical Guitar. Placement is critical.  I know a difference of even one inch can make a dramatic difference when recording guitar.

Ordering Info

Shure SM81LC Cardioid Condenser Microphone

tweaks pick

The Shure Model SM81 is a high-quality, unidirectional condenser microphone designed for studio recording, broadcasting, and sound reinforcement. Its wide frequency response, low noise characteristics, and low RF susceptibility have made it a standard for applications involving acoustic instruments, especially guitar, piano, and cymbals. Tweak: For those serious about acoustic, wooden music or anything that needs a full 20Hz-20kHz response.   Check out the SM81 User Guide  Usenet:  Best Mic for recording acoustic guitar  Read questions and answers about the SM81 in Shure's KnowledgeBase

Sigh. I had been waiting for this moment a long time, having wasted much of my teen and college years recording on $8 plastic mics held up with bent coat hangers.  I then lapsed into remembrances of all mics past I used on guitar, from the radio shack $17 electrets, the $30 stereo condenser, the $50 PZM and finally not long ago, the $125 Octava M012.  But today was the day, I have finally graduated into the league of the respectables with a brand new SM81.

The first moment of perception in the first strum tells all.  I know that, so I slowly grab the pick, gently slide the guitar on my lap to make sure the first sound it reproduces is not a clumsy clunk of a guitar hitting the stand.  I tap lightly on the guitar to set the preamp.  Then put the cans on. 

Pause.  (I know you are wonder how it sounds, I'll get to that...)

First Impressions: 

For those of you who don't know mics, The SM81 falls into the small condenser category.  Among condenser mics, these are sometimes loosely called "instrument" mics as opposed to "vocal" (large condenser) mics.  The mic is ideal for acoustic guitars, acoustic piano, cymbals. I think it would do well on acoustic bass, cellos, violins, mallets and hand drums.  I would not hesitate to try it on other things.  It's really not a vocal mic, but with a sock (windscreen ) over it it might get by in a pinch.  Shure says the mic is flat and has 20hz to 20kHz response.  I don't doubt that it goers low.  Heh, I am ready to play the first strum and go "What is that subsonic rumble!"  Take off the cans and sure enough, the AC just turned on and is blowing air in the room. Not to worry.  The SM81 has a 3-position low frequency filter (off, rolloff of 6db an octave @ 100Hz and 18db an octave below 80Hz.  These are quite gentle on the sound and help you keep the good part of the bass response. There is also a -10 pad for time when you need to record really loud things.  You won't need that for acoustic guitar, but its nice to have.

Newb: "So, How did it Sound, Tweak?!!"

Patience, my friend, patience.  You know, that reminds me.  Why should one get a mic like the the SM81 when you already have a perfectly useable SM57?  Its really a matter of ear here.  If you have your SM57 working well on acoustic guitar and can't hear the difference, why bother?  Is the difference that great?   Shure writes this at their site:

Sound is a very personal thing. Only you can decide if you think that one microphone is worth the extra expense when compared to another microphone. Whether you will hear any difference between the microphones will be dependent on the quality of the rest of the system as well as how good your ears are.

Newb: "So is there a BIG difference?..TWEAK!".

OK, I hear you, but first, do you know when the SM81 was introduced?  Can you guess?

"Oh come on now Tweak stop frickin' toying with me!"  Sigh.  Alright...er 1995.

"Nope, older"

"OK! 1985!"

Nope again.  Way off.  The SM81 was introduced in 1978 as "the first truly reliable studio quality microphone." Amazing that it is still the Mic of Choice for acoustic guitar and many other things.  Go check out the bluegrass forums and read the ever fierce mic debates at rec.audio.pro.  And it makes total sense.  The acoustic guitar was very big in 79, 80, 81.  In fact that's around when you start hearing the classic SM81 sound.

"So ARE you going to tell us about the SOUND?"

Yes. Right now.  If you have an ear for recordings, you will recognize the sound of the SM81.  It's been on tons of records.  When I hit the first strum on this old classical guitar, I immediately shouted "Yes!".  The strings are clearly articulated, and the bass regions come through with definition.  In fact if you get too close to the soundhole there is too much bass.  With some mics its a problem getting such bass out of them,  not here.  You can control it easily by moving the mic so it's in front of the fret board and slightly angling it towards the picking hand, away from the sound hole.  Slightly turning the mic away from the hole is like having your hand on a bass control knob.  It's an altogether wonderful sound capturing subtle nuance when playing lightly and capturing the pick ripping through the strings when playing hard.  Try to EQ it.  It's hard to find a better setting than none.

"So did you test it against anything?   sm81+octava m012

You bet I did.  One of first experiments was to try stereo miking with an SM81 close in and a Neumann TLM 103 back about a foot.  I really liked that sound a lot as it gave good depth, but there was some minor phasing going on so I know i have to experiment more with that.  Then  i tried the typical X-Y approach with my Octava M012 at 90 degrees.  (see pic).  The result was good, but not as rich as the previous experiment.  When I soloed the Octava then soloed the SM81 I could figure out why.  The Octava was much more a mid-rangy sound, not as deep, lush, or articulate as the SM81.  By the way, Shure does not sell matched pairs of SM81s but they say on their site that the customer can be assured that the quality of the sm81 is such that two mics bought at separate times will match well.  Guess we'll have to take their word on that for now.  Interestingly, at least to me, is that this mic sound excellent in mono.  I liked the mono recordings better than stereo.  (of course, in a mix you may need to eq for the sake of making room for other instruments).  Oh yeah, acoustic guitar through the SM81 blows the doors off an SM57.  It's a dramtic difference having the crystalline high frequencies come through.  Even with near-dead strings the sm81 will sound good. 

So by my take the sm81 is a mic that sounds best without EQ and without stereo processing.  That should tell you something.  I am very pleased with the purchase, and i have no problem bestowing the Tweak's Pick award for this product. 

 

Strummin',

Tweak

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