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best way to match mics?

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Anonymous
December 13, 2004 11:12:03 AM

Archived from groups: rec.audio.pro (More info?)

GC is out of matched MK012's and I can't afford sound room. So how do you
all suggest I go about "matching" a pair in the store?

I guess this also raises the question, does it really matter if they are
matched or should I just find a couple good sounding mics? Thanks!

--

Jonny Durango

"Patrick was a saint. I ain't."

http://www.jdurango.com

More about : match mics

Anonymous
December 13, 2004 11:37:03 AM

Archived from groups: rec.audio.pro (More info?)

"Jonny Durango" <jonnybush_from_officedurango1@comcast.net> wrote:

>GC is out of matched MK012's and I can't afford sound room. So how do you
>all suggest I go about "matching" a pair in the store?
>
>I guess this also raises the question, does it really matter if they are
>matched or should I just find a couple good sounding mics? Thanks!


Interesting challenge - how to test mics in a store without test gear of any
kind. Here's a thread I did at homerecording.com that may help:
-------------------------------------------------------------------------

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.

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.

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 full, and 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.

______________________________________________________________

Quote:
Originally Posted by
mixmkr
"this does sound like a great post....but...what store is going to pull out a
dozen $150 mics and let you do these tests on? This doesn't sound like it will
take a couple of minutes. The stores in Nashville that I have frequented, don't
either stock these budget mics, or are on the other end of the spectrum and the
salesman doesn't know how to hook up 12 mics at once. To quote "assuming you
have become friends with the salesman", would be a major requirement, I would
think, and you would probably also need to drop some decent change on a regular
basis with this salesman to "prove" your friendship.But, anyway...PLEASE
continue, as this is just good information in general.Harvey...don't bother to
waste your time to answer this post."

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.
__________________________________________________________

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.
______________________________________________________________

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.
_______________________________________________________________


Quote:
Originally Posted by charger
"Any suggestions for those annoying Guitar Center employess whi insist that you
can only test the sample mic, because of "state health regulations?"

Yeah, tell them:

1. You want to buy a pair of them so just listening to one of their sample mics
ain't gonna cut it.

2. Tell them you wanna buy a windscreen that you will use on each mic you test,
so that will not cause any "state health regulation" problems, since the
windscreen will block any germs.

(It's the same principle as buying new socks to try on different pairs of shoes,
or compare it to using a condom, if you get a blank look from the salesman about
the socks.)


Quote:
Originally Posted by
alanhyatt
"Harvey has made some excellent suggestions. My only concern is will this piss
off a salesman, or will he want to do this so he can learn.Another not so
extensive method would be to use a portable DAT recorder if you have one, or
bring in you're own DAT Tape, and ask the salesman to let you record a 30 second
vocal or passage on each mic using one of their DAT's. Write down each of the
mics serial number so you have you're key code if you decide to buy after 24
hours or so.This will give you an opportunity to go home, listen to them again
and again while giving you lots of time to refresh you're ears. If it?s a vocal
mic, sing into it, if it?s a mic for guitar, bring yours. This way, when you go
home and take the time to listen you can hear what you're voice or guitar sounds
like.Either way, this is not an easy task in a busy store, and you always run
the risk of the mic you want being sold if you take too much time to decide. The
only thing I can caution you about is ear fatigue. Doing all those tests as
Harvey suggests is fine and a good thing, but with all the other noises around,
you're ears may trick you.All of this is better than having to just go in and
buy one the saleman gets from the back room, but in store testing is not easy.
So keep in mind if the mic you are thinking about buying has a bad reputation
for quality control, you will either have to find a way to do it in the store,
or buy a brand that you know has a solid reputation for it's consistency of
build and sound."

Alan Hyatt PMI Audio Group


Good points, Alan.

My main focus on this was trying to find a "pair" of decent Oktava MC012s at
Guitar Center, for example. I don't even think they have serial numbers, do
they? The same tests would probably be important if I were buying a pair of NT1s
or BPMs or any of the "really cheap stuff.

It is very important that you don't try to bug the salesman when the store is
packed, or even moderately busy.

We know the GC Oktava deals ain't gonna go away any time soon, so this just
gives the buyer a little more ammo in making the best of a bad situation to
begin with.

With your mics, and the Marshalls (above the 2001 level), I would have no
problem about walking into any store, plunking down the money, and taking
whatever unit the guy hands me.

Harvey Gerst
Indian Trail Recording Studio
http://www.ITRstudio.com/
Anonymous
December 13, 2004 1:00:05 PM

Archived from groups: rec.audio.pro (More info?)

Jonny Durango <jonnybush_from_officedurango1@comcast.net> wrote:
>GC is out of matched MK012's and I can't afford sound room. So how do you
>all suggest I go about "matching" a pair in the store?

GC never had matched pairs, no matter what they say.

You could probably put two mikes into a console, set one channel to invert,
and select a pair that has the best cancellation. IF the sales guys at GC
will let you do that.

>I guess this also raises the question, does it really matter if they are
>matched or should I just find a couple good sounding mics? Thanks!

Well, do you need accurate stereo imaging? If you are doing real stereo
miking, they need to be well-matched. If not, they don't.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Related resources
December 13, 2004 1:00:06 PM

Archived from groups: rec.audio.pro (More info?)

How about using a lap top with a real time (spectrum) analyzer.

You also need a high frequency acoustical hiss generator like an
aerosol can of air that hisses when you push the button. (Don't direct
the air AT the mic obviously)

You can get a pretty good idea of the high frequency resonse this way.
Doesn't work too well for the bass and mid-range.

Anybody have any ideas for a good portable acoustical white noise
generator or maybe an impulse generator. If you can generate good
acoustical white noise or impulses, you could do a pretty good mic test
with a lap top ( and mic pre.)


Mark
Anonymous
December 14, 2004 10:26:42 AM

Archived from groups: rec.audio.pro (More info?)

On Mon, 13 Dec 2004 03:12:03 -0500, Jonny Durango wrote
(in article <n9cvd.649769$mD.41943@attbi_s02>):

> GC is out of matched MK012's and I can't afford sound room. So how do you
> all suggest I go about "matching" a pair in the store?
>
> I guess this also raises the question, does it really matter if they are
> matched or should I just find a couple good sounding mics? Thanks!
>
> --
>
> Jonny Durango


Um, for what?

Ty


-- Ty Ford's equipment reviews, audio samples, rates and other audiocentric
stuff are at www.tyford.com
Anonymous
December 14, 2004 1:43:06 PM

Archived from groups: rec.audio.pro (More info?)

Jonny Durango <jonnybush_from_officedurango1@comcast.net> wrote:

>GC is out of matched MK012's and I can't afford sound room. So how do
>you
>all suggest I go about "matching" a pair in the store?
>
>I guess this also raises the question, does it really matter if they
>are
>matched or should I just find a couple good sounding mics? Thanks!

Get a simple 1 KHz mic test tone generator. They typically come
in 94 and 104 dB versions. The old GenRad calibrator had both. You can
often find the GenRad for under $75 on eBay.

Hook the mics to a decent recorder. Record 'em. Take the recording
home to your DAW (or bring your PDAudio system with you) and compare the
levels.

This is far from being a full matching test, but it's doable in the
store.

--
Len Moskowitz PDAudio, Binaural Mics, Cables, DPA, M-Audio
Core Sound http://www.stealthmicrophones.com
Teaneck, New Jersey USA http://www.core-sound.com
moskowit@core-sound.com Tel: 201-801-0812, FAX: 201-801-0912
Anonymous
December 14, 2004 2:07:42 PM

Archived from groups: rec.audio.pro (More info?)

Len Moskowitz <moskowit@panix.com> wrote:
>
>Jonny Durango <jonnybush_from_officedurango1@comcast.net> wrote:
>
>>GC is out of matched MK012's and I can't afford sound room. So how do
>>you
>>all suggest I go about "matching" a pair in the store?
>>
>>I guess this also raises the question, does it really matter if they
>>are
>>matched or should I just find a couple good sounding mics? Thanks!
>
>Get a simple 1 KHz mic test tone generator. They typically come
>in 94 and 104 dB versions. The old GenRad calibrator had both. You can
>often find the GenRad for under $75 on eBay.
>
>Hook the mics to a decent recorder. Record 'em. Take the recording
>home to your DAW (or bring your PDAudio system with you) and compare the
>levels.
>
>This is far from being a full matching test, but it's doable in the
>store.

Unfortunately this will only tell you that the levels match at 1 KC. So
the fact that the frequency response on these microphones varies a lot from
unit to unit (mostly because the diaphragm tension is different from unit
to unit) won't show up. Level matching at 1 KC will mostly wind up selecting
a pair whose front end FETs have the same gain rather than two whose capsules
match. (and the gain on the FETs is also all over the place on older ones,
but they are getting better in that regard).
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."
!