Here's something Harvey posted a while back that you all may find as helpful as I have.
Matching microphones by Harvey Gerst
How to 'audition' a microphone before buying
In another post a user was lamenting the poor QC measures used in Russia (Oktava) and China (everyone else it seems). But he noted that you could paw through the inventory and find a 'good one'.
Okay.
How?
How do you objectively evaluate a mic at a store to determine whether or not the factory f'd it up or did it right? Is this talent and experience or is it something (hope hope) more objective.
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Actually, there are some tricks you can do that will get you close to finding the best mics out of a batch, but it would require going into the store when you and the store both have some free time. Asking to test mics in a busy store on a Saturday is NOT a good idea, for example.
Give me a few days to come up with some simple tests using headphones, keys, store noises, mixer meters, etc. It will help you find the "best" of the bunch, match a pair of mics (which may not be the best but they'll match), find the loudest, or the most quiet of the bunch.
Interesting challenge - how to test mics in a store without test gear of any kind.
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I have a band coming in in a little while, so I'm gonna hafta do this in sections.
Stuff you'll need to bring with you
One small Post-It Pad (the really small one)
One key ring, with at least 5 to 15 assorted keys on it.
Chromatic tuner with built-in speaker.
A decent set of headphones.
Small note pad.
Culling the herd
Assuming you've become friends with the mic salesman, he's dragged out every unit he has in stock of the same model, including the one on display. You'll need to get the use of a mixer that has phantom power, some kind of metering on it, and a headphone output jack. Let's say you have 12 mics to test. Take the post-it pad and number each mic, 1 thru 12.
Plug the first mic in, and turn on the mixer. Adjust the preamp gain to maximum, and bring up the channel slider till the store's background noise lights up the first 3 or 4 segments of the channel meter (or any meter on the mixer). Note the number of segments showing on the meter and put that number right on the mic's post-it paper. (It will be a number between, let's say 2 and 6.)
Go thru all the mics (without changing any settings) and write down the number of segments that show for each mic on the mic's post-it. As you do this testing, listen to each mic and listen for anything strange (lots of noise, hum, hiss, crackle, weird honking tone, etc.), and note that on your notepad. If you run across any obviously bad mics, remove the post-it paper from that mic and take that mic out of the tests.
As you test them, try to roughly pair up mics (mics that have the same segment readings and sound similar to you), and put those mics together. You should wind up with about 4 piles of mics; those with high segment readings, those with medium segment readings, those with low segment readings, and a pile of defective mics that hum, buzz, crackle, honk, or don't work at all.
Ok, congratulations. You've just completed test one. You've tested all the mics for defects, and measured the mics sensitivity. You've also done some preliminary rough matching.
I'll try to get to the next step (the dreaded "jangling keys" test) a little later today. Hang in there.
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It's not a waste of my time, and you brought up some interesting points. Mainly, this thread is about buying budget mics (that are well known for varying degrees of quality control), but it might also help you spot the best of 3 "high dollar" mics in a more upscale store.
It's actually helps the store that sells these cheap mics, since you're going to be doing extra quality control on their behalf. And when you're finished, they'll have some mics they can sell as matched pairs, and some that need to go in for repair (rather than wait for a pissed off customer to return it).
If the salesman is interested enough, you'll actually teach him some things that will help him sell more mics. But you hafta catch them at a really slow point in the day. So the salesman knows that you're gonna be buying at least two mics from him, so he doesn't have anything to lose by playing along.
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Okay, Part Two - Now where the hell were we?
Oh yeah. So we have our three good piles of mics and one "to dump" pile. Too bad we don't have more time or we could try switching out capsules to see if that fixes any of them, or testing the weird pile by swapping their capsules with some known good ones (to find any good capsules and/or bodies in the bad pile), but we'll just work with what we have - the 3 "good" piles, sorted by output levels.
The Dreaded "Key Jangle" Test
What's so scary about this? Think of a tamborine at point blank range. Those little keys put out a ton of high frequency energy, enough to overload most mics if you get right up on the mic. And that's what we're gonna do, jangle the keys and listen for any severe distortion in the mic.
Make sure you're not clipping anything in the mixer and leave at least 6 to 10dB of headroom, so you're sure it's coming from just the mic. Start with the keys up close, and jangle.
Keep moving the keys away from the mic till any distortion is gone, and mark down how far away the keys were when the distortion disappeared. That number when converted (we'll talk about that later) tells you the Maximum SPL level for each mic you test. Pretty cool, huh?
Name That Tone
Now it's time to do some serious listening for tonal balance and smoothness in response. We'll use
the chromatic tuner you brought with to set all the mics to the same level. Set the tuner to put out A440. If your tuner will play a range of notes, that's even better. Bb (one octave above A440) is around 1,000Hz - a good point to set the levels to.
Put the mic right on the speaker in the tuner and adjust the channel level slider till the signal reads 0 on the meter. Make a note of the dB number (along side the channel slider) on the post-it sheet for that mic, or in your notepad. The whole point here is to match levels as close as possible, so that you're hearing just tonal differences between mics, not volume differences.
Use The Force, Luke
Take a little break and give your ears a rest. I'm gonna take a break right now and I'll be back with the final wrap-up section.
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Ok, now we're actually gonna listen to stuff. Remember in the last section, I told you to make a note of the dB number (along side the channel slider) on the post-it sheet for each mic, or in your notepad? Well, here's where we use that number.
Plug in the first mic, and set the channel fader to that number. Adjust the headphone level or the mixer's master level to a comfortable volume and listen to the sound. Listen? Listen to what?
First of all, point the mic into the room, and listen to the room noises in the store, people talking in the distance, the sounds of fans or air conditioning, the ambient room noise. Does it sound different to you than listening without the headphones? What's different about it?
Notice any hollow sounds, like you're in a tunnel? Those sounds are mid range peaks. Any rumbling? You know what that is. Anything sound overly bright and "VERY detailed"? Those are probably high frequency peaks.
Turn the mic around and talk into it from around 12" away, holding it at eye level. Again listen for the same strangeness mentioned above. As you talk bring it in closer to your eyes till it's about 3" away. Did it bring up the bass in your voice nicely or is it kinda boomy? Make notes of your impressions, and go on to the next mic. Remeber to set the channel slider to the appropriate number for each mic, to keep the levels all the same.
After you've done the same tests for each mic, you should wind up with a few mics that sounded very neutral, or pleasing to your ear.
If the dB numbers on the mics are the same on the mics that you like, you have a matched set. If the dB numbers are different, but they sound the same, it's still a matched set, but with different sensitivities - no big deal.
If there are several sets of mics, buy the two with the lowest dB markings, if possible. The lower numbers mean you had to turn those down the most because they were the most sensitive mics.
After you've sorted them into pairs, check the distance number you wrote down for the key jangle test. Chances are that on mics with the same sensitivity, the distances will be about the same. If the written distortion distance of one mic is 1/2 or 2X the written distance of the other mic, that's cool. It means the MAX SPL distortion levels are within 3dB of each other.
If the mixer has a phase reversal switch on each channel (it's a polarity switch really), plug the two mics you like into the mixer and flip the polarity switch on one of the mics. Put the mics side by side and point them at the same spot. With the gain trim control cranked all the way on each channel, turn up one slider till you hear the background noise really loud.
Now bring up the slider on the second channel. As the second slider approaches the same level as the first slider, the sound will start to disappear. If the mics are really matched well, the sound will almost completely disappear at one point. What's left is the slight frequency response differences between the two mics.
As a final check, listen to your choices against the best similar mic in the store and see how close they sound to each other. If you're testing Oktava MC012s, try your chosen set against a Neumann KM184. Listen to the differences. If the Neumann sounds more like one of the sets you passed up buying, you might wanna reconsider your choice. Remeber, you're looking for a mic pair for guitar and misc. stuff, not just voice.
So now, you've matched the mics into mic pairs, and measured them all for sensitivity, frequency response, distortion, and noise - all without any fancy test equipment, or complicated procedures. And you've got the best two of those mics for yourself.
That's about it. Was that easy enough? After a while, you can put on a pair of headphones and just listen to ambient noise and tell a lot about a mic's characteristics, but it takes a bit of practice. Try testing the mics you already own this way and see if your test conclusions match your own personal experience using these mics. The key is to try and avoid any personal biases while testing; keep an open mind and try to listen objectively.
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Thanks Harvey
