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Is my new C414 B-ULS close enough to form a matched pair??

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Is my new C414 B-ULS close enough to form a matched pair??

Postby Guitarking » Fri May 17, 2019 6:35 pm

Hi everyone,

I acquired a second AKG C414 B-ULS today to form a pair with a C414 B-ULS I already owned.

I recorded my acoustic guitar with both mics simultaneously and a couple of things occured to me.

It seems the mics don't sound EXACTLY the same. My first AKG seems a bit brighter/more open than the one I got today. Is this normal? Or does it have to do with the fact that the capsules can never be at exactly the same place because the mic is quite big?
I also recorded my guitar with both mics on top of each other and next to each other. I both cases my first mic seems a bit more open like I said. Also, the latest mic seems to have a bit less gain. In fig8 the new mics has a bit more gain and in omni has quite a lot less gain than the first mic in omni (both mics are softer in omni compared to card, is that normal?).

-Is this the good way to test whether the can form a matched pair?
-Are these results saying my latest mic is bad/broken (it doesn't sound broken, just a bit darker? It has the say vibe as my first mic)
-Are these results good enough to do XY and blumlein?
-Even though SDC's are better suited for recording a choir etc... would this be good enough to give recording a choir a go?

Thanks for helping out again!
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Re: Is my new C414 B-ULS close enough to form a matched pair??

Postby MOF » Fri May 17, 2019 7:15 pm

There’s a good possibility that one mic’ has had a bit more abuse than the other over the years.
I think you’ll be OK using them in the ways you mentioned though, try mid-side recording if you like, it’s more forgiving of mismatched pairs.
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Re: Is my new C414 B-ULS close enough to form a matched pair??

Postby Hugh Robjohns » Sat May 18, 2019 10:45 am

Guitarking wrote:It seems the mics don't sound EXACTLY the same. My first AKG seems a bit brighter/more open than the one I got today. Is this normal?

Tolerances are normal... but the tolerances should be extremely tight in a high-end mic like the C414 and for you applications as a stereo pair, they need to sound more or less identical. If there is an obvious difference -- one being obviously brighter than the other -- they aren't a good match.

Or does it have to do with the fact that the capsules can never be at exactly the same place because the mic is quite big?

Placement will be a significant factor if you're close-miking because an inch either way will sound noticeably different on something like an acoustic guitar. So place the two mics one above the other (the top one upside down to keep the capsules as close as possible), and at least three feet away from the source, and then compare the outputs.

Also, the latest mic seems to have a bit less gain.

Sensitivity in a microphone, not gain! ;-) But this is much less of a problem since you can tweak the gain of the preamp to compensate.

What's important in a stereo pair is matched frequency responses both on-axis and off-axis (matching polar patterns at all frequencies).

...both mics are softer in omni compared to card, is that normal?

The sensitivity will vary with different polar patterns and is highly dependent on the capsule biasing voltages. In some (more modern) mics, the biasing voltages are generated by internal DC-DC converters and are reliably stable, but in many older mics it is very reliant on the received phantom voltage which can vary with the length of mic cable and the source voltage...

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Re: Is my new C414 B-ULS close enough to form a matched pair??

Postby MOF » Sat May 18, 2019 2:10 pm

I don’t disagree with Hugh but it seems to me that buying a matched pair of 414s is not possible for you at the moment.
If you think about it most studio mic’ collections will have been bought over time and are unlikely to be matched pairs and engineers will grab two 414s out of the cupboard and use them.
So I say you should just give it a go and maybe have to subtly eq one mic’ to match.
No doubt there will be some people with golden ears that can tell you they’re not matched but I think you just have to try them and judge for yourself. Experiment with M&S as I said in my original reply.
My caveat would be, if it’s a paying client expecting high end studio results, then hire in a matched pair, but it doesn’t sound like this is the case.
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Re: Is my new C414 B-ULS close enough to form a matched pair??

Postby Hugh Robjohns » Sat May 18, 2019 2:23 pm

You're right -- matched pairs didn't used to be a thing and we would just grab two same-model mics from the cupboard to use in a stereo array.

But in those days all the mics came from high-end manufacturers and they always had sufficiently close tolerances to work in stereo arrays as required. Importantly, they sounded the same (as near as dammit)...

If a mic sounded obviously different from its sibling models -- because of age, or abuse, or whatever -- we marked it and didn't use it in stereo arrays.

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Re: Is my new C414 B-ULS close enough to form a matched pair??

Postby Guitarking » Sat May 18, 2019 4:40 pm

I don’t disagree with Hugh but it seems to me that buying a matched pair of 414s is not possible for you at the moment.

No, halas. I was happy to acquire this second mic for a good price.

Placement will be a significant factor if you're close-miking because an inch either way will sound noticeably different on something like an acoustic guitar. So place the two mics one above the other (the top one upside down to keep the capsules as close as possible), and at least three feet away from the source, and then compare the outputs.

Ah I was already wondering... because the guitar is not exactly 'symmetrical'. And I put the two mics quite close to the guitar, about 15 cm. I'm gonna try with at least 3 feet away (is that about 90 cm??). I will report back with the results.

Sensitivity in a microphone, not gain! ;-)

Of course!!I still have a lot to learn ;)

but in many older mics it is very reliant on the received phantom voltage which can vary with the length of mic cable and the source voltage...

Mmm One had a longer cable than the other. I'll try to use the same kind of cables.

Would it be wise to send both mics to a mic-tech so he can have a look and maybe replace aged components like capacitors etc... so they match better? Or would that take away the character and personality of the old mics and turn them into a C414 XLS with a more modern sound?

Also, I'm thinking, I could benefit from (possible) slight differences in sound, like having 2 personalities and being able to pick. But than again, I really like to use them in XY and, finally, try some Blumlein...
For background, I do have a matched pair of NT55's but they obviously sound different than the 414's and don't do Blumlein. I really like LDC on my upright piano for instance, that's one other reason I bought a second C414 B-ULS.
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Re: Is my new C414 B-ULS close enough to form a matched pair??

Postby MOF » Sat May 18, 2019 8:49 pm

but in many older mics it is very reliant on the received phantom voltage which can vary with the length of mic cable and the source voltage...

Mmm One had a longer cable than the other. I'll try to use the same kind of cables.

I'm fairly sure Hugh meant over very long distances, a few feet difference won't be discernible.



Would it be wise to send both mics to a mic-tech so he can have a look and maybe replace aged components like capacitors etc... so they match better? Or would that take away the character and personality of the old mics and turn them into a C414 XLS with a more modern sound?


I don't think a mic' technician would do more than try to get them back to factory condition, so definitely worth a try.
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Re: Is my new C414 B-ULS close enough to form a matched pair??

Postby Guitarking » Sun May 19, 2019 6:32 pm

Just did the test Hugh suggested: 1 meter away from guitar and mics on top of each other. Still my first mic seems to have more highs.
If the mics should be identical, would they cancel each other out complete when I flip phase on one mic? I've tried this but at the most cancelation I still hear quite a few highs.
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Re: Is my new C414 B-ULS close enough to form a matched pair??

Postby Hugh Robjohns » Sun May 19, 2019 6:36 pm

Guitarking wrote:If the mics should be identical, would they cancel each other out complete when I flip phase on one mic?

They'll never cancel perfectly, and the remnants will tend to be at the high end, but you should get a null of around 30dB or better on-axis, and a bit less as you move around the sides and back.
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Re: Is my new C414 B-ULS close enough to form a matched pair??

Postby Guitarking » Sun May 19, 2019 6:56 pm

Do you mean that with max cancellation the total is 30dB less?
I've just checked, it's 17 dB less.

So... these mics sound different then :(

Is this a problem? I'd really like to do blumlein and xy with them.
What to do? Sell? Repair? Already mailed a mic tech, he said changing caps etc will not alter the sound a lot. He can clean the capsules. He suspects one of the mics has been serviced and maybe another capsule (there are 2 nylon versions apparently) has been installed.

So maybe no choir recording with these (I have my mp NT55's), but still hoping to be able to do blumlein, xy, mic my upright with it or use it as overheads/roommics.
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Re: Is my new C414 B-ULS close enough to form a matched pair??

Postby Hugh Robjohns » Sun May 19, 2019 7:14 pm

Guitarking wrote:Do you mean that with max cancellation the total is 30dB less?
I've just checked, it's 17 dB less.

Yes, the level should drop by around 30dB on axis if the mics are well matched (and precisely co-located). So your matching is not the best.

Is this a problem?

Strictly speaking, yes. ... But pragmatically speaking it depends what you want to achieve and how critical you are about the recordings you make.

I'd really like to do blumlein and xy with them.

Do it then...You'll get a stereo effect, a stereo image. But the perceived placement of individual source sounds will not be as precise or stable as they should be. Whether you notice that or not depends on what you're recording, and your monitoring...

What to do? Sell? Repair? Already mailed a mic tech, he said changing caps etc will not alter the sound a lot. He can clean the capsules. He suspects one of the mics has been serviced and maybe another capsule (there are 2 nylon versions apparently) has been installed.

Yes, that's a distinct possibility. The problem is that you don't know which is the 'right' sounding one! You'd have to buy a third mic and hope you can match two of them... Or flog them both and buy a genuine matched pair! :-)

The close matching of frequency response and polar pattern is a fundamental requirement to all coincident stereo arrays -- so XY, MS, Blumlein, etc. but it is far less critical for spaced arrays (AB, Decca) and not too critical for near-spaced arrays (ORTF, NOS, DIN, Faulkner) etc.

In your situation I'd suggest you try making some recordings and see what you think of the stereo you get. If you notice uneven imaging or instabilities then you'll know the reason for it. If you don't, happy days! :-)
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Re: Is my new C414 B-ULS close enough to form a matched pair??

Postby Ramirez » Sun May 19, 2019 7:46 pm

Hugh Robjohns wrote:...flog them both and buy a genuine matched pair! :-)

My thoughts exactly!
You might well get almost enough for two B-ULS' to buy a new matched pair of XLS.
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Re: Is my new C414 B-ULS close enough to form a matched pair??

Postby Guitarking » Mon May 20, 2019 2:18 pm

My thoughts exactly!
You might well get almost enough for two B-ULS' to buy a new matched pair of XLS.

Mmm i choose b-uls because it is said (and what Ive heard on comparisons) that they sound more neutral/less hyped than the newer line of C414s. But I cant confirm this by personal experience though.

Whether you notice that or not depends on what you're recording, and your monitoring...

Would recording drums or piano in blumlein be a situation where a precise stereo image would be less important but you choose blumlein for the sake of sound if you know what I mean.
Also, recording a guitar in xy and using the output in mono, would that also be a situation where a non matched pair isnt a problem or is the mismatching going to create strange shifts in my mono sound?
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Re: Is my new C414 B-ULS close enough to form a matched pair??

Postby Hugh Robjohns » Mon May 20, 2019 3:08 pm

Guitarking wrote:Mmm i choose b-uls because it is said (and what Ive heard on comparisons) that they sound more neutral/less hyped than the newer line of C414s. But I cant confirm this by personal experience though.

I've not tried any recent XLS models either, but I did try the first of the new XLS generation when they came out a while ago and thought they retained the neutral transparent character of the previous generation of B-ULS models, but with much better, quieter switching and lower overall noise.

When I wrote about the Beeb's 'In Tune' classical live music programme I noted they used a lot of XLS models there (and elsewhere in Radio 3), so they can't be that bad... ;)

Would recording drums or piano in blumlein be a situation where a precise stereo image would be less important but you choose blumlein for the sake of sound if you know what I mean.

I think this is just something you're going to have to try and judge for yourself. You've established that one mic is brighter than the other on axis, but we don't know how that affects the polar pattern overall. Nevertheless, the unmatched nature of the mics will inevitably mean that the high end harmonics of a central sound sources will appear to come more from a position to one side (the side of the bright mic), so the stereo image will be smeared in frequency to some extent... In other words, a narrow source will gain an unnatural width, and wide ranging note runs will move around slightly instead of being solidly central.

...but just how significant and noticeable that effect will be is down to your ears and your monitoring.

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Re: Is my new C414 B-ULS close enough to form a matched pair??

Postby Guitarking » Tue May 21, 2019 5:57 am

I do hear, like you say, that the brighter mic, of course, makes the higher freq's a bit louder on one side of the spectrum, so the xy recorded guitar is not exactly in the middle.
I've tried some eq (2dB shelf at 3K) and this seems to put it more in the middle.
If I pan both tracks to mono I don't really hear any strange things.

I was wondering, how did engineers do this in the old days of analog consoles? Say you had the perfectly matched mics but an analog console of which it is said the channels are never exactly the same. This would basically turn it into non matched signals, right? With the same problems I face now?

Is using eq for this done more often?

I must admit that the matched pair of NT55's when recording guitar in XY and panned hard left and right are not perfecly in centre either, maybe this is the nature of XY which picks up different parts of the guitar presented in stereo image? They were a foot from the source.
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Re: Is my new C414 B-ULS close enough to form a matched pair??

Postby Hugh Robjohns » Tue May 21, 2019 9:55 am

Guitarking wrote:I do hear, like you say, that the brighter mic, of course, makes the higher freq's a bit louder on one side of the spectrum, so the xy recorded guitar is not exactly in the middle.

A guitar is not really the best subject for this, as it naturally tends to produce more high frequencies at the neck side, and lower frequencies at the body side, and there is often also far more acoustic energy emanating from the body side... so a lopsided image is pretty much par for the course!

I was wondering, how did engineers do this in the old days of analog consoles? Say you had the perfectly matched mics but an analog console of which it is said the channels are never exactly the same. This would basically turn it into non matched signals, right?

Hmmm... I can't say I've ever had problems with unmatched console channels -- other than when there was an obvious fault, and that's using gear dating from the late 60s onwards.

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Re: Is my new C414 B-ULS close enough to form a matched pair??

Postby Watchmaker » Tue May 21, 2019 11:38 am

I'll defend the 414 XLS. Mine is gorgeous. I'd much rather have a new mic than used, for many reasons, but very, very few people are going to listen to a recording and say "by jove! they shouldn't have used the xls on that...the B-ULS is much better for that sort of thing"
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Re: Is my new C414 B-ULS close enough to form a matched pair??

Postby Hugh Robjohns » Tue May 21, 2019 11:40 am

Watchmaker wrote:I....very, very few people are going to listen to a recording and say "by jove! they shouldn't have used the xls on that...the B-ULS is much better for that sort of thing"

I bet they would over at 'the other place' ! :lol: :bouncy:
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Re: Is my new C414 B-ULS close enough to form a matched pair??

Postby John Willett » Tue May 21, 2019 12:13 pm

Guitarking wrote:I do hear, like you say, that the brighter mic, of course, makes the higher freq's a bit louder on one side of the spectrum, so the xy recorded guitar is not exactly in the middle.
I've tried some eq (2dB shelf at 3K) and this seems to put it more in the middle.
If I pan both tracks to mono I don't really hear any strange things.

I was wondering, how did engineers do this in the old days of analog consoles? Say you had the perfectly matched mics but an analog console of which it is said the channels are never exactly the same. This would basically turn it into non matched signals, right? With the same problems I face now?

Is using eq for this done more often?

I must admit that the matched pair of NT55's when recording guitar in XY and panned hard left and right are not perfecly in centre either, maybe this is the nature of XY which picks up different parts of the guitar presented in stereo image? They were a foot from the source.

If they are not perfectly matched - record with an MS array.

That's what Blumlein himself did.

You remove the problem completely of having mis-matched left and right channels. :thumbup:
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Re: Is my new C414 B-ULS close enough to form a matched pair??

Postby Hugh Robjohns » Tue May 21, 2019 12:29 pm

John Willett wrote:You remove the problem completely of having mis-matched left and right channels. :thumbup:

Technically, you don't remove the problem... you just translate the image distortion into a frequency-dependent width variation rather than a frequency-dependent position variation.

However, I certainly agree that this kind of image distortion is far less obvious or troublesome when using an MS array instead of XY, and so is much more easily overlooked or ignored.

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