What are some good sources for testing a KM-84 style mic on?

[joulupukki]

I’ve got a few varieties of KM-84 clone microphones that I’d like to put through some different scenarios so I can tell which mics sound/perform the best. Are there any particular sources that would be great for testing KM-84 style mics? So far, I’ve tried:

• Acoustic Guitar
  • I can hear some subtle differences between my mics
• Mandolin
  • Can’t really hear much difference between the mics
• Banjo
  • The mics sound about the same
• Speaking
  • I can hear some differences between them
• Electric guitar (about 1 ft away from my combo tube amp)
  • Cannot hear any difference between the mics

The mics I’m comparing are:

• Neumann KM-184
• Microphone Parts SDC-84
• @jp8’s KM84+ (built in a Takstar CM-60 w/ 3U capsule and 3U transformer)
• @jp8’s KM84++ (built in a Takstar CM-63 w/ 3U capsule and 3U transformer). This one is a little more versatile because it has both a high pass filter switch and a pad switch … and runs at a higher polarization voltage.
• My Graeme Woller PCB KM84 clone built into a CM-60 w/ 3U capsule and 3U transformer

 

[Barry Hufker]

So far, your sources are limited in their tonal range and power output. Try piano (a good quality grand), pipe organ if you can, a good choir singing “in parts” and real drums. A variety of singers (soprano, alto, tenor, bass) one at a time is good.

None of this may be practical for you but that is my thought anyway…

 

[gyraf]

imo, KM84 is all about the off-axis response, not so much about on-axis

 

[RuudNL]

When I worked for a radiostation, my supervisor said that any microphone was good enough for spoken word.
I never agreed with him. Human speech consist of such a wide spectrum, that you easily can hear differences in microphone quality.
Often musical instruments seem to sound the same on different microphones, but on spoken word the differences will become obvious!

 

[jp8]

When I worked for a radiostation, my supervisor said that any microphone was good enough for spoken word.
I never agreed with him. Human speech consist of such a wide spectrum, that you easily can hear differences in microphone quality.
Often musical instruments seem to sound the same on different microphones, but on spoken word the differences will become obvious!

@joulupukki recorded a voiceover and shared with me. The microphones are all so close, that I could not hear a difference. But that could be just my ears. Only the silent period at the end revealed a slight difference between background noise of the mics. The clear winners were the KM184 and my KM84++.

I'd also liked to see them compared on very loud sources, where transformer saturation kicks in. The KM84++ should be able to handle up to 140 dBSPL with the pad engaged. Expect the original KM84 to distort on snares, wouldn't it?

Jan

 

[Icantthinkofaname]

When I worked for a radiostation, my supervisor said that any microphone was good enough for spoken word.
I never agreed with him. Human speech consist of such a wide spectrum, that you easily can hear differences in microphone quality.
Often musical instruments seem to sound the same on different microphones, but on spoken word the differences will become obvious!

I feel like that can also be voice dependent. But I've definitely heard some voices I'm familiar with sound very different on different mics, including stuff that should be voiced similarly. A lot of the time mine sounds the same, but most of my mics are flat, except my LDC utility mics (not counting my C414 B-ULS) which are all kinds bright-neutral if that makes sense. They're CAD M179s and AT4050s, which at the same level I feel perform similarly (both on my voice and other voices I've heard).

Acoustic guitar is another one that should be simple to recreate, and I've heard a lot of people say that shouldn't be used for comparison, but I find different mics sound pretty different there. The more flat mics sound like they pick up a lot more of the body resonance and sustain of the strings, and I find brighter mics seem to pick up a lot more of the string sound (both strumming noise and the notes without as much body resonance).

Not at all scientific but I call the former dark and rich and the latter bright and twangy.

Dark and rich is what I expected from a Schoeps, a flatter Sennheiser, an Oktava, or a Neumann.

Bright and twangy is what I expect from a Rode (except an NTG3/8 or 4th gen NT1), a brighter Sennheiser (ME64, E914), Behringer, or pretty much any Chinese SDC (iSK, Alctron, etc.).

I'm mostly commenting on SDCs here though.

 

[joulupukki]

Really good points here. Thanks so far for giving me some additional ideas.

I know that some people like to use KM-84 mics as drum kit overheads or on the snare. In those situations, what’s the difference between leaving the preamp turned really low (because of the loud source), or turning up the preamp but using the preamp’s pad switch? Is one method preferred over another?

Additionally, is there a practical difference between using a microphone’s built-in pad switch vs one you might find on your preamp?

The reason I’m asking is that I do have a drum kit here though it’s not in a studio room. It’s my son’s and he’s off to college but I can put down a basic beat just to do some mic evaluations and I’m wondering what’d be “best” for testing between these four mics. Suggestions?

 

[Barry Hufker]

The microphone's pad is to keep the capsule from overloading the mic's internal electronics. The preamp's pad is to keep the mic's output from overloading the preamp electronics. The preamp's gain control is to keep from overloading whatever follows it (computer, recorder, etc.) The drums can acoustically overload both the mic capsule and the room they are in, so a reasonable sound pressure level is a good start.

 

[joulupukki]

The microphone's pad is to keep the capsule from overloading the mic's internal electronics. The preamp's pad is to keep the mic's output from overloading the preamp electronics. The preamp's gain control is to keep from overloading whatever follows it (computer, recorder, etc.) The drums can acoustically overload both the mic capsule and the room they are in, so a reasonable sound pressure level is a good start.

I’m having a big “duh” moment reading this. I think I try to overcomplicate things in my head and your explanation makes a ton of sense. I think I need to now train my ears to be able to hear when a mic circuit is overloaded when actually using it (as opposed to when seeing it while dialing in the JFET bias with an oscilloscope).

Earlier this morning I tried to make a recording using these mics as overheads on a drum kit and I think that’s probably what ended up happening. The initial hit on the cymbals causes a drop in volume a little bit (subtle) even though the preamp shows they weren’t clipping. I wonder if that’s what was going on (overloaded the mic circuit)?

 

[Barry Hufker]

Others may know more/better, but it could be the momentary drop out was caused by the mic diaphragm touching the backplate due to excessive sound pressure level, which the mic couldn't handle (not an overload of the electronics from the diaphragm).

 

[joulupukki]

Short of having an actual KM-84, I'm trying to determine which of these mics might perform/sound "closest" to a KM-84 only based on what others have described a KM-84. Right now I have a KM-184 for testing and so I'm using that as a comparison/baseline/reference. My goal, in the end, is to determine how closely in sound and performance are these clone microphones coming to the original(s). So I'm simultaneously trying to learn about the originals and compare the clones in real-world situations.

What I've heard others say when describing the 184 vs the 84 is that the 184 is hyped between 5-10k vs the more flat 84. I've also heard that the 84 has more low end. I know these are probably generalities, but that's what I've got to work with.

So, I discovered this interesting post yesterday where the poster did some extensive comparison recordings of a KM-84 and KM-184 that he had:

https://gearspace.com/board/gear-sh...ore-mic-madness-chapter-4-whats-up-km84s.html

Finally, at least something I could test out my ears on. Commenters on the post say that you can definitely hear differences if you're listening on good quality equipment in a treated room. Perfect, I thought. Yes, after downloading the original WAV files, I can hear some subtle differences between the two microphones.

But, I don't yet trust my ears. What if I were to use an EQ match to get a visual on the actual differences rather than my perceived differences? Since I only have a KM-184 here to compare with, I figured I would use the 184 as the "reference" in these WAV files. So I opened up these files and used FabFilter Pro-Q3 and did an EQ Match with the 184 as the reference. So, these EQ curves are applied to the KM-84. In other words, what EQ changes would I need to make to the 84 in order for it to sound like the 184?

What I expected is that surely the EQ curve would need a decrease in low end. I also expected to see that the EQ would need to be boosted in the 5-10k range. That's not what the analyzer/match resulted in exactly. In all 6 recordings of the acoustic guitar by this poster, the low end of the 84 needed to be boosted – but we're talking the very low end. Also, not all of the sound samples have a distinct need to adjust in the 5-10k range. Perhaps these differences are explainable by the placement in relation to the guitar? Maybe with the same exact recording situation and the mics were to swap placements, we'd see different results? But, we're probably only talking an inch or two difference in position. I'm not sure how close the mics were positioned to the guitars or which part of the guitar these mics were pointing at, but it does make me curious.

The thread poster on that site said he recorded the mics as close together as he could get them. Also of note, unless he changed the phase on his preamps, the two microphones are out of phase with each other (which doesn't seem to affect the EQ matching at all).

See the attached files. Is this what you would have expected? Am I doing this wrong?

AcGtr1:
http://www.mindseyeprod.com/wp_mic_clips/KM84vs184_Clips/AcGtr1-KM84.wav
http://www.mindseyeprod.com/wp_mic_clips/KM84vs184_Clips/AcGtr1-KM184.wav

AcGtr2:
http://www.mindseyeprod.com/wp_mic_clips/KM84vs184_Clips/AcGtr2-KM84.wav
http://www.mindseyeprod.com/wp_mic_clips/KM84vs184_Clips/AcGtr2-KM184.wav


AcGtr3:
http://www.mindseyeprod.com/wp_mic_clips/KM84vs184_Clips/AcGtr3-KM84.wav
http://www.mindseyeprod.com/wp_mic_clips/KM84vs184_Clips/AcGtr3-KM184.wav


AcGtr4:
http://www.mindseyeprod.com/wp_mic_clips/KM84vs184_Clips/AcGtr4-KM84.wav
http://www.mindseyeprod.com/wp_mic_clips/KM84vs184_Clips/AcGtr4-KM184.wav


AcGtr5
http://www.mindseyeprod.com/wp_mic_clips/KM84vs184_Clips/AcGtr5-KM84.wav
http://www.mindseyeprod.com/wp_mic_clips/KM84vs184_Clips/AcGtr5-KM184.wav


AcGtr6:
http://www.mindseyeprod.com/wp_mic_clips/KM84vs184_Clips/AcGtr6-KM84.wav
http://www.mindseyeprod.com/wp_mic_clips/KM84vs184_Clips/AcGtr6-KM184.wav

 

[Barry Hufker]

To my mind, the difference between the 184 and 84 is as you described. That difference was Neumann's design goal so it's not a "some people say" kind of thing, but the actual difference. I'm not sure I understand why you want to make an 84 sound like a 184, when I would think the opposite would be the goal. But I guess it's just two different approaches to the same end.

 

[joulupukki]

To my mind, the difference between the 184 and 84 is as you described. That difference was Neumann's design goal so it's not a "some people say" kind of thing, but the actual difference. I'm not sure I understand why you want to make an 84 sound like a 184, when I would think the opposite would be the goal. But I guess it's just two different approaches to the same end.

I actually don’t want to make an 84 sound like a 184. My end goal is to test and see how closely these 84 clones are to the 84 sound. So at first glance, my visuals might seem misleading. However, I’ve only got a 184 to compare with, so flying blind and using that as a comparison. Maybe it’d be better to find a local studio who might have an 84 or two and take these mics in and see if they’ll help me try them all out together?

 

[Barry Hufker]

It's better to deal with the real thing than an approximation. If you could find an 84 and send some noise (white?) through it to create a profile? Then possibly you could use that as a model of some sort? I know iZotope has a plugin called Match EQ (in Ozone 11) that might help model... I don't know. I'm just trying to think of useful things off the top of my head...