Friday, November 25, 2011

Engineering Drums Part Six: The Snare Drum

There are so many variables in the recorded sound of a snare drum – so many woods and metals and synthetic materials shells are made from, types of strainer and snare assemblies, diameter and depth, types of rims, heads, tuning, muffling, and then selection of microphone, placement, etc...  Nevertheless, effectively miking a snare drum can can be done with a consistent, and rather simple approach.

Regarding snare drum selection and preparation, here are the bullet points:

  • wood shells are darker and drier sounding than metal shells
  • metal shells provide greater overtones or 'ring' and are brighter than wood shells
  • smaller diameters yield a higher pitch and similarly tensioned larger diameters
  • deeper drums have more body or tone than shallow drums
  • the more strands of snares on the drum (i.e. 42-strand vs. 20 strand), the greater the 'snare' content of the sound
  • tuning the top head of a snare drum below its midrange yields a very deep tone (which can be emphasized by bringing the mics in closer)
  • tuning above the midrange brightens the tone and shortens the decay, with higher tensions beginning to choke the response from the drum.

If you need more info on tuning, please refer back to my tuning entry for some essential guidance and a few tips.

Now let's briefly cover microphone selection. THE most relied upon microphone for snare drums these days (and for the last couple of decades now) is Shure's SM57 dynamic. This mic, used in every studio and live venue across the planet, has a frequency curve featuring a rising response through the midrange peaking in the 'attack' range at around 6kHz and rolling off above 10kHz. Also, the LF response rolls off below 200Hz and is several dB down at 100Hz, making it an excellent choice for the midrange nature and articulation of a snare drum.

There are other mics on the market that work well for snare drum. I have had fantastic results with the Audio-Technica ATM23HE, Audix D2 and i5, Sennheiser MD421, BeyerDynamic M201, and others. But for the sake of this article, I am going to suggest you stick with the SM57. Chances are you will get superb results with 57's, and if you don't, then something else is almost certainly wrong. Using a 57 will remove the mic from the list of factors when troubleshooting a poor sound.

Snare drums are typically miked with two mics: one on top to capture the overall tone and body, and one underneath to capture the response of the snares. The SM57 is a great choice for both positions.

So... the drum sounds great, and you got a couple of SM57's. Let's begin.

Critical question: What is it that we, as engineers, are ultimately trying to capture? The sound or the performance? 

Answer: the performance (with the best possible sound).

Next question: Should we hinder the performers in the quest for the perfect sound? 

Obvious answer: absolutely not.

I'll just say ithindering the very thing you've been hired to capture well is just dumb.  You've not been hired to make it challenging for performers to perform.  You've been hired to capture their performance.  Buckle up, dear readers;  here comes another rant.

I am convinced that as audio engineers it is our responsibility to capture the greatest possible performance with the greatest possible soundin that order.  To this end we must take great care to make players comfortable, so they can play their best.  Sometimes drummers arrange their kits in a way that makes placement of microphones tricky. If an engineer's default approach is to tell a drummer to raise his hi-hat to get it away from the snare, or to move a tom or raise his cymbals, etc, then they're essentially asking him to be uncomfortable when playing for the sake of sound (“... but by all means, don't play like you're uncomfortable..”). 

If this describes you, you need to wise up, or you should be fired.
Nobody has ever hired you for the purpose of making it harder for players to perform, and when they figure out that's what you're doing you likely won't get a second gig.  The performance you've been hired to capture is key – it's number one. If your approach to capturing it actually weakens the performance itself by forcing performers into a state of discomfort, then how is your effort doing anything other than damaging that which is most important? 

Wise up!  Do you seriously contend that the small improvement in sound you may achieve by making a player uncomfortable on his instrument outweighs the negative effect to the performance? 

Or put another way, "do you want to be hired again?" 

Performance comes first. Your sounds come second. Period.

Become a beloved engineer by ensuring the performers are comfortable with their instruments, and what they're hearing. If they aren't, they'll focus their energy on trying to overcome the obstacles thrown in their way rather than just playing, which is what they're really supposed to do.

So... back to miking a snare drum – starting with the top mic, position it with its tip about one inch inside the edge of the top rim, about two inches off the drum, pointed at the center of the head. This is a good place to start as it generally produces a useful balance between attack and tone.

Audition the sound with this placement and decide what changes are needed.

If the sound is to long/ringy, add a bit of moon gel or drum gum (or a loop of duct tape) to dampen the ring and shorten the decay of the drum. If the drum is dead, it probably has too much muffling and needs to lose some to liven the sound up, or perhaps the head is too slack and needs to be brought up a bit.

If you want a bit more body in the sound, then either move the mic a little closer to the drum, or point the mic somewhere between the middle of the head and the rim nearest the mic. As the mic gets closer, the proximity effect will exaggerate the low mids a bit more. Use this effect sparingly, as in most mixes the higher frequency information of the snare can get lost in the blend of other instruments, leaving it darker sounding than you thought when first tracking it.

As you point the mic more toward the edge you will get more harmonic in the sound, and the decay may appear to lengthen.

Leakage from the hi-hat is always a concern when miking the snare drum. Because the hi-hat and snare are usually close together, it isn't practical to expect to get complete isolation, but careful placement can certainly minimize the leakage to manageable levels. Since the SM57 (or most any mic you'd choose for miking a snare) has a cardioid pattern, point it, as much as possible, away from the hi-hat. Generally the top mic will be between the hi-hat and the first rack tom mounted directly on/above the kick drum. If the drummer's hi-hat is particularly high, you might have success placing the mic below the hi-hat, pointed at the snare toward the floor toms. This position usually isn't possible, but can be helpful if there's room.

Remember to work with the drummer on placement. It's fine to ask it he would be comfortable moving something – many times it'll be no big deal. But don't demand he comply. If you need to lower the angle of the top mic to keep it out of his way, then do it. Use your ears and find the best possible sound with just mic placement while keeping the drummer comfortable.

If the placement leaves something to be desired in the sound, see if you can tweak the drum itself to compensate. For example, if you find that to keep the drummer comfortable you have the mic farther away than normal, you may be lacking a little body. See if you can drop the tuning a tad to compensate, or switch to either a deeper drum or a drum with a thicker shell, and, therefore, a stronger fundamental tone.

Or if you're forced to place the mic really close, see if you can switch to a brighter sounding snare drum to compensate for the increased proximity effect.

With regard to the bottom mic, placement is usually easy as it is out of the drummer's way.  With the bottom mic you're trying to capture the articulation of the snares. Start by placing the mic near the center of the drum, 2 to 4 inches off the bottom, pointed directly at the snares. When you listen to this mic it will sound very snarey and flat, with very little tone. The snare response should be clear and defined, not smeared. If the snares have a strong metallic character, try backing the mic off a bit more until you have a clear, almost delicate 'snap' from the snares with a minimum of rattle.

Now audition both mics together and blend the amounts of each to create the complete snare sound. If you hear odd interaction between the mics, alternate muting each one to see which mic has the sound you're hearing and tweak the placement of that mic in an effort to eliminate or minimize it the problems you're hearing.

When miking a drum from both the top and bottom the sound is literally going away from one mic while simultaneously moving toward the other mic. For this reason you will experience significant signal cancellation (particularly at lower frequencies) when the two signals of these out-of-phase mics combine. To solve this, reverse the polarity on one of the mics (often the lower mic). Doing so will put both mics 'in phase' together, preserving all the tone and articulation from both mics.

Even when reversing polarity of one of the mics, it can also be useful to further tweak the distance of the bottom mic to bring the pair more completely into complimentary phase. Simply flipping one mic 180 degrees out of phase doesn't ensure the best result. The layout of a drum kit often limits the amount of room you have to make adjustments to the placement of the top mic, so it is simpler to adjust the bottom mic, where you have more room.

As always, use your ears and take your time. A little time spent at this stage will reduce the amount of processing needed later (which we will get to in future posts) and will absolutely make your final product better.

Thanks for reading.


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