mic placement on guitar cab

[fire.is.real]

hi,

i'm using an sm57 to mic a guitar cab. the perceived sound coming out of the cab has a very smooth sound with a fairly scooped-out mid section. when it comes through the board it seems like the 56 "creates" the same tone with all the mid back in and then some. i've heard 57's are mid heavy but this is rediculous.
where on the speaker should i point the mic and how far away should it be? i tried various orientations - some were better than others, but i was just wondering if there is a concensus on this.

thanks,
nick

 

[Tom Hicks]

Its the SM58 that has a mid boost.The 57 is pretty flat.I'm sure you know its the gold standard for miking guitar cabs.
Listen to the individual speakers as they will vary.Pick the sweetest one.
The following is a starting point and not a rule.Position the mike about halfway between the cone and the surround,about an inch from the paper at 45 degrees off axis.
I would suspect the mike preamp in the board more than the mike for coloring your tone.Keep playing with different position as it really does make a big difference.

Tom

 

[bvaleria]

Sorry Tom, that's not correct -

The SM57 has a sloped presence boost between 2K and 10K with a peak of about 7db at 5k. See published spec at http://www.shure.com/pdf/userguides/guides_wiredmics/sm57_en.pdf

The SM58 is virtually identical to the 57 except for a dip in the presence boost between 7K and 8K (mostly due to the foam windscreen). You can see this at http://www.shure.com/pdf/userguides/guides_wiredmics/sm58.pdf

This presence peak in the mid to upper-mid range has a lot to do with it being the classic close-mic'ing mic.

You're right about your placement suggestions though!

Bruce
Blue Bear Sound

 

[greddin]

I've noticed that very small changes in distance from the amp produce big changes in frequency response due to the proximity effect. I've gotten a real mid-rangey sound by placing the mic at about 10 - 12 inches from the amp. If that's what you're doing move it up to 1 or 2 inches from the amp, or touching the speaker grille.

 

[Tom Hicks]

Thanks Bruce for the correction.My info is all seat-of-the-pants and very unschooled.My perception of the 57 as a more flat mike than the 58 comes from its habitual use as an instrument mike,where presumably the more accurate response is desireable.The 58s popularity as a vocal mike may have as much to do with its physical robustness as the conventional wisdom of its helping singers with an upper mid boost.All the other vocalists in my band use SM58s but I have always used 57s on my voice and my guitar cab.

Tom

 

[Tapehead]

You're experience what's known as the "proximity effect" of cardiod dynamic mics. Here's more information about it:

http://arts.ucsc.edu/EMS/Music/tech_background/TE-20/Proximity_Effect.html

The essence is that anytime you place such a mic close to a source (usually within an inch or so) you get a significant lower mid boost that needs to be corrected either by mic placement or eq, preferably in that order.