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Author Topic: Actual frequency response of high end mics: how useful?  (Read 13713 times)

Timtape

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Hi,
I've been recently told that the frequency response graphs published by microphone manufacturers have been "smoothed" such that they do not reveal the whole picture with the mic with respect to narrow band peaks and troughs in the mic's response.

Is this so? Or is it possible that the resultant plot is perhaps a valid averaging of a number of "snapshots" of the mic's response perhaps to a calibrated  but necessarily "bouncy" pink noise source in the anechoic chamber?

Thanks for any help or leads in understanding this.

Regards,

Tim Gillett
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Jim Williams

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Re: Actual frequency response of high end mics
« Reply #1 on: May 23, 2013, 12:03:56 pm »

I have a "compute smooth" function in my Audio Precision analyzer. It does as you suggest, smooth out bumps in the response. One pass, not too much. Run enough passes and any curve can get converted to a straight line. It's sort of like stretching a loose hose straight.

Measuring high frequency response on a mic is not easy to do. The source stimulus may have bumps. The measuring mic may have bumps. The room creates bumps. The DUT also has it's own bumps, the ones you are attempting to isolate. All of those errors add up and adds stuff to the measurments.

Whether the curves are accurate or "wishfull thinking" I leave up to the consumers to decide.
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klaus

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Re: Actual frequency response of high end mics
« Reply #2 on: May 23, 2013, 01:28:34 pm »

I have come to the conclusion that looking at a manufacturer's response graphs of microphones is a fool's errand:

* There are no universally agreed-upon standards of measurements which all manufacturers would submit to, so that a consumer could compare mic graphs from different manufacturers.

* The allowed tolerances of frequency deviation are usually represented in the graph by two lines (for example, look at Neumann's owner's manuals): the response can then vary between these two extremes, at any point of the frequency response. With a ± 2dB range, for example, you can theoretically have a spread of 4dB between any two points on the curve-this could be quite an audible jolt.

* Smoothing the curve of the actual frequency response of an individual mic can be a reasonable marketing strategy, particularly when the buying public equates smoothness with quality (which, again, is partially the manufacturers' fault): If you were to base your purchase solely on the jagged lines of an ELA M 251's frequency response curve, you would look elsewhere.

Which brings up my main objection to publishing response curves, smoothened or not: They do not predict the quality of a microphone for musical recording purposes. As a mic is nothing better than a poor simulator of our quite sophisticated hearing, euphemistic aberrations in the response curve can, and in good mics will, make up for the technical deficiency of the device. A bit of a boost at the exact spots, a bit of a cut at some other precise frequency points add up to us liking the music better, or rejecting the mic altogether as "unmusical". You need look no further than a B&K industrial measurement mic with its ruler-flat response to prove that point.
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Klaus Heyne
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Timtape

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Re: Actual frequency response of high end mics
« Reply #3 on: May 24, 2013, 12:31:27 am »

Thanks for your responses Jim and Klaus. Klaus, not sure what you are saying about B & K industrial measurement mics. Are you saying that effectively they are "ruler flat" compared to other recording studio mics or that even they have audible narrow band peaks and troughs?

The question relates to what is possibly a modern practice where engineers try a collection of high quality vocal mics on the one vocalist, before settling on one which, just to their ear complements that vocalist the best. Not so much because of broad differences in emphasis such as a mic with a broad presence peak re one that doesnt have one, but to hit on a mic whose narrow band peaks and troughs work better on that vocalist.

I have some reservations about the practice, especially when it then expands to people recommending certain mics fror certain genres of music such as jazz, pop, crooning, rap etc. Frankly I dont see the connection between a mic and a music style. Obviously a valid exception might be the use of a D type EV mic designed to minimise proximity effect when close micing but that would seem to be a special case.

I've seen this approach in recording magazines aimed at the home recordist who may not necessarily have such finely honed listening skills to be able to hear such anomolies between top quality mics., but still be tempted to buy a closet full of top quality mics in the hope that he might just hit on the "magic mic" for a particular vocalist. I certainly doubt that I could reliably pick  differences between mics and mic samples  which may be quite small and subtle, and I think I have pretty good listening skills.

Your thoughts?

Tim

 
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klaus

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Re: Actual frequency response of high end mics
« Reply #4 on: May 24, 2013, 01:51:37 am »

Tim,
I agree with you assessment: to pigeonhole a mic for a whole genre of music strikes me as superficial.

As to your question about B&K measurement mics: these types of mics are made to be as frequency linear as humanly possible, to detect non-linearities in acoustic events they are measure. Yet all that finagling to reign in tolerances and flatten the response  makes for lousy music recording, I find (and the lack of acceptance in the professional recording community seems to confirm my observation).
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Klaus Heyne
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Nob Turner

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Re: Actual frequency response of high end mics
« Reply #5 on: May 24, 2013, 03:27:56 am »

I believe one can make some generalizations about certain microphones vis a vis certain music styles... and they'll just be generalizations. E.g., female pop ballads tend to have airy, breathy vocals, and while the singers may strive for that sound, certain microphones also accentuate it. Doesn't mean that a C12 or C800 will be ideal for any particular singer, but that knowledge should help one find a starting point, or at least to discourage trying a Coles 4038.

This is a part of what makes an experienced engineer: knowledge of their tools and the genres of music they are recording.

And yes, the typical home recordist will be foolish to spend large amounts of money in pursuit of the "perfect" mic for their needs. That won't stop manufacturers, salespeople and magazine ad executives from encouraging the practice.

Yet I would argue against Tim's assumption that "...the home recordist... may not necessarily have such finely honed listening skills to be able to hear such anomolies between top quality mics." Given a decent listening environment, the differences are not necessarily that subtle. While a frequency response graph is not likely to be meaningfully informative about mic choice, a brief listening test will be.

And in the end, it is mostly about taste.

Jim Williams

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Re: Actual frequency response of high end mics
« Reply #6 on: May 24, 2013, 12:48:13 pm »

B+K, (now under the DPA name) also makes music recording mics. The 4003, 4006 and the newer 4011 unidirectional are well recieved mics in the industry.

MA Recordings (Todd Garfunkle) uses a matched set of 4006 mics. Others that have used them include George Massenberg and many more.

Those are not flat mics, they have a 3 db peak at 16k hz, I find that annoying. They also have a slight metallic overtone due to the metal diaphrams.

There is far more to consider than simple response curves when selecting a mic. Noise, THD, IMD, linearity, bandwidth, slew rate are all factors, many involve the electronics past the capsule. A microphone is a system, not just a capsule.

Others also make measurement mics like APEX in No. Cal. Most are 1/2 or 1/4" diameter capsules, omnidirectional. That alone limits their use in a recording situation. Follow one with a great EQ and you can create the curves you like instead of the microphone designer.
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Timtape

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Re: Actual frequency response of high end mics
« Reply #7 on: May 25, 2013, 09:02:41 pm »

Thanks for your replies. The question as to whether high end mics have the audible narrow band non linearities was because this was given to me as the reason why such mics apparently sound different on different vocalists, and that engineers test out various top mics, which otherwise might be expected to sound very similar, on a particular vocalist before settling on one as subjectively sounding better. Sorry for the longish sentence!

What interests me is whether this subjectively superior sounding mic and vocalist combination  could be verified by say 10  engineers all listening independently to the same combinations of mic, and vocalists and independently coming to the same conclusion, that is, the same mic for that vocalist. I wonder if it has ever been properly tested, or whether it has just been assumed that it has been established beyond doubt. Something  about the subjective and the objective I guess.

Cheers Tim

   
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klaus

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Re: Actual frequency response of high end mics
« Reply #8 on: May 25, 2013, 10:20:58 pm »

Why make it so complicated? If the producer/engineer chooses the right mic for the right artist, the results will be so stunning that you and I and a million other listeners will hear the difference, even while driving in our cars listening to the shitty car stereo, and we all will be drawn into the voice and many of us will then go out and buy the record.

And if every engineer had the money, they all would pretty much end up with the same five mics. And 95% of all voices would be covered by the same five mics.

An example for how obvious the right mic on the right voice is, and how there would probably be very little deviation in opinion, at least among professional engineers, about that choice: 'Skyfall' sung by Adele.
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Klaus Heyne
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Timtape

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Re: Actual frequency response of high end mics
« Reply #9 on: May 26, 2013, 07:03:16 am »

Am I making it so complicated? Just the opposite, I'd suggest.

 I recently suggested to a group of people that one excellent vocal mic would be fine for any vocalist in the world, in the hands of an expert. I received howls of protests and was told I knew nothing.  Yet I suspect that for decades  one top vocal mic would have sufficed in top recording studios worldwide.

With your Adele example, I respectfully suggest it's untestable for we have no recording of that song using another mic. It's not obvious that other top mics could not have done just as well.

Regards
Tim
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soapfoot

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Re: Actual frequency response of high end mics
« Reply #10 on: May 26, 2013, 10:11:23 am »

If a manufacturer provides individual plots for each example of a microphone sold, with the measurements done under the same conditions, that may be of some marginal utility in verifying that a pair is matched well for stereophony.

Otherwise, I have little use for such documentation. The best tools for selecting a microphone to use on a particular source are ears and experience.
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Timtape

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Re: Actual frequency response of high end mics
« Reply #11 on: May 26, 2013, 11:17:59 am »

Sure. So if we had access to the same recording of Adele or anyone else, made with a similarly top vocal mic, we could put them side by side and use our ears and experience to judge how the alternative mic stacked up against the the mic which was used for the commercial release.

 Without that, we have no "ears and experience" basis for comparison and so, I'd suggest, we are acting on  faith.

Tim
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klaus

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Re: Actual frequency response of high end mics
« Reply #12 on: May 26, 2013, 12:39:28 pm »

Acting "on faith" is not necessary when it comes to good sounds. An experienced engineer or producer knows the palette.

As for someone less experienced: just listen, then decide whether you like what you hear. If you like it, investigate the components that created the recording. And among those, the mic always stands out as the most crucial, sound shaping link in the chain.

And in the case of Adele, it is quite obvious to me, and probably to most other people who are experienced with microphones,  that no other mic but an ELA M 251 would have been able to render her powerful passages as beautifully and harmonically rich as it did her intimate, soft passages in the same song.

Or put another way: If I did not know what mic was used in a seminal vocal recoding like that, I'd go investigate, find out, and save my pennies.  A mic like that will carry you through in 95% of all cases (hence the hefty price tag).
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Klaus Heyne
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Timtape

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Re: Actual frequency response of high end mics
« Reply #13 on: May 26, 2013, 08:33:37 pm »

The first link in the chain is not the microphone but the singer, the voice, the song, the performance. I read this comment about the 21 album:  " If the chain has Adele in it, its going to sound really really really good.  You'd need some seriously shoddy equipment to screw that one up."   An overstatement of course but I see the point nonetheless.

If you can use the one mic for 95% of vocals, is that because that mic is "shaping the sound" or because it is not shaping the sound, and is rather just rendering the performance faithfully to the audio recorder?

On  dynamics, sure the mic must capture those faithfully but from there it's a production choice as to how to render those dynamics in the final product. Significant compression - whether manual or automated or a combination - was used downstream on Adele's dynamics, as it often is on  dynamic vocals. Or was it upstream? Does Adele physically back off from the mic in louder passages? If so that is not the mic giving that effect. In an interview about the Adele sessions the producer also mentioned  tape emulation plugins, a plate reverb and perhaps other FX, although apparently he often passes on the stems to someone else to do the mix and then to another person for mastering.

How did you know the ELA M251 was  used on the Adele sessions? Did you work that out just from listening to the track or did you find out from other sources?

Tim

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klaus

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Re: Actual frequency response of high end mics
« Reply #14 on: May 26, 2013, 10:06:50 pm »

All good points to discuss. I will respond after the holidays.
Best,
KH
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Klaus Heyne
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