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7/7/2007

Know your mic, part III

This is the third installment of our little mini-series on amplifying acoustic instruments. After switching from condenser mics to instrument pickups, we’ve switched back to condenser mics.

Our goal with amplification has been to get a sound that matches our acoustic sound, only louder. We want natural instrument and vocal sounds.

Our recent setup involved using Oktava MK-012 mics on the banjo and mandolin. The MK-012 is a good mic for this purpose. It’s an inexpensive and reasonably durable workhorse that can handle high sound pressure levels (SPLs). It can handle SPLs up to 130db, waaaaaaaaaaaaaay louder than what an acoustic instrument can put out. We’ve been getting solid tone from the Oktavas. They don’t seem to color the sound in any dramatic way, and don’t have the pronounced midrange proximity boost that dynamic mics like the SM57 have.

We’ve used the Oktavas for dozens of gigs in venues from small, noisy bars to large stages at outdoor festivals, and we’ve had pretty consistently good results. We ask the sound engineers to set them hot so that we have a good solo volume, and then we back off when we’re playing rhythm. This is infinitely better than having to hit a boost pedal or ride a volume pedal with an instrument pickup. One can focus on playing and not futzing with equipment. It also makes it mostly unnecessary for the engineer to ride the faders during the show, which makes life easier for everyone (engineers sometimes jack up the level on my mic when I step back for rhythm playing, but that’s another story for another day).

Cardiod pickup patternThe mistake we made was with capsule selection. Condenser mics, by their nature, pick up sound from a fairly large area, but the shape of the pickup pattern varies by capsule type. The Oktava MK-012s come with a cardioid capsule by default. If you have one with a hypercardioid capsule, you can buy hypercardioid or omnidirectional capsules as an add-on.

hypercardioid pickup patternThe cardioid capsule is a good all-purpose choice for recording, but it’s not always ideal for onstage use. The cardioid pickup pattern doesn’t cancel out sounds that come from the side as effectively as a hypercardioid pattern does. That makes it more likley to pick up sounds from stage monitors and create feedback problems. These problems can be mitigated somewhat by clever mic placement, but on small stages or in unusually noisy rooms, the mics are likely to pick up a lot of unwanted sounds.

Our guitarist Scott was the first one to try something a little different: the AKG c1000s. The C1000s is a small diaphragm condenser mic with a cardioid pickup pattern. But it comes with a little widget you can use to switch the pattern to hypercardioid. The guitar is one of the more difficult instruments for us to mic because its solo volume is much lower than that of the banjo or mandolin. We usually need to set the guitar mic extremely hot. The more focused pickup pattern of the c1000s has made it a much better choice for us–we can set it hotter without feedback problems.

I was so impressed with Scott’s mic and the tone he was getting from it that I picked one up for myself. I used it for the first time last weekend, and look forward to trying it out at some of the different venues we play. They can be had for around $150 on eBay.

Earlier posts:
Know your mic, part II
Know your mic, part I
Plugging in