Mic Comparison – a Tutorial

Thursday, June 25th, 2009

Mics are fun. They are a great gear fetish item, because they’re collectible, a bit esoteric but still familiar, come in a wide range of types and sizes, and most of them have a bit of a phallic quality (grin). Even better, when I read about microphones on the internet or in recording magazines it seems that each mic has a dramatically distinct personality, and a big part of the job of a recordist is choosing the optimal mic for any given source and style.

Sometimes when I’ve listened to mic samples I thought I heard these dramatic differences, but after a bit I realized that I was listening to different performances, not different mics. Sure the mics had been changed, but the player was hitting the strings differently and playing different riffs at a different volume – so how could I tell what part of the difference was the mic, and what part the player?

Since then I’ve tried to do some mic tests of my own, and I’ve tried to educate myself on audio testing. At this point I’m beginning to think that the differences in microphones are a lot more subtle than I had been led to believe, which makes a careful test even more important. As I’ve mentioned before, very small differences in volume are registered by our ear/brain combination as differences in quality rather than loudness. I’d like to demonstrate the steps I now take to try to make my mic comparisons, and preamp and a/d comparisons, meaningful.

Mic Setup

The mics need to be close together, but not interfere with each other. I try to determine the location of the diaphragm, the part of the microphone that gets hit by the sound waves, on each mic, and align them along that position. This is pretty easy with large diaphragm mics, often a bit tricky with small diaphragm units. All the mics should be on axis to the source or all should be equally off axis. Check pattern switches, rolloff settings, pads, any feature of the mic than changes its response. I’ve missed this step a few times.

I also arrange the mics so they don’t interfere with each other. For instance, it’s not a good idea to tie a bunch of small diaphragm mics into a bundle, because the ports behind the capsule contribute toi the frequency response and pattern of the mic. If those ports are blocked the mic is not performing normally.

There are three mics being compared in this example. The CAD M179 is a low cost continuously variable mic in an unusual looking housing. One salesperson began a drumbeat for these mics and they are now widely recommended in internet recording forums. The Rode NT2a is one I’ve used before. I think it does a fine job of capturing audio with low noise and no noticeable distortion, but many forum posts are negative toward Rode in general and the NT2a in particular. The Audio-Technica AT3035 has recently been discontinued, replaced by the AT2035. In the past I’ve read a wide range of comments about this mic, with some calling it a secret gem and others decrying its overwhelmingly bright character.

Here’s a picture of a mic array arranged for testing. A cheater clamp that fastens to the mic stand main tube can help fit an extra mic into the array. Adapters to attach mics at an angle can be very handy as well.

Three large diaphragm mics in an array for comparison

Three large diaphragm mics in an array for comparison

I often hear this arrangement, with all the mics equidistant from the source, criticized because different mics work best in different positions. I strongly suggest that if you wish to evaluate different positions you try all the mics in all the positions. It’s a little more trouble, but it’s a great learning opportunity, and omitting this step means no valid comparison can be made. We’re right back to asking what part of the difference is the mic, what part is the location with no way to answer the question.

Of course, my aim here is different from trying mics and positions to get a good recorded sound. I’m after data, not art. When the aim is art, the ears rule!

Equipment wise, you can do a useful comparison with as few as two recording inputs. In fact, comparisons that are done two by two are probably the most revealing and useful. Still its fun to line up three or four mics for a single session – in which case it’s helpful to have four identical channels, especially if the comparison will be made public. In my experience, more posters will criticize a change in preamp than will mention a change in performance, amazingly enough.

Here’s a video that illustrates the setup process and takes you through gain calibration, discussed below:

Microphone Comparison - A Tutorial - part 1 of 2 from Fran Guidry on Vimeo.

Gain Calibration

Once we’ve arranged the mics to capture a single performance we need to minimize the volume difference in the our samples. I like to start with a test tone played into all the mics from a speaker only a foot or so away. A 1000 Hz tone is not very challenging, so even a low cost computer speaker can be used as the source. A test tone is easy to come by and it doesn’t need to be calibrated for volume since we’re interested in relative rather than absolute levels.

I’m using Reaper to conduct this test, and a little inquiry on the Reaper user forum and learned about MDA Test Tone, a plugin that provides the beep.

In Reaper I created a project with MDA Test Tone on one track, and three tracks for recording the three mics. I also adjusted the range of the Reaper console meters. With these connections in place I hit record and adjusted the preamp gain for each mic so they all were very close to -18 DbFS.

Next I discarded these recordings and captured three more tracks to store a consistent level for each mic. These 1000 Hz tones are used to fine tune the track levels later.

Recording

In the next video we actually do a little recording. After all the setup and calibration work, the recording process is anticlimactic. Move the calibration speaker, tune up the guitar, hit Record in Reaper, play a few bars, and we have our clips in the can. Be sure to record the clips on the same tracks as the reference tones we created in the last step. That way when we adjust the reference tones we adjust the clips at the same time.

For straight mic comparisons, I like to position the guitar about 32″ from the mics. This avoids proximity effect and hopefully presents a fully developed guitar sound to the mics, instead of one mic picking up the neck of the guitar while another picks up the bridge.

Here’s the video demonstration of recording simultaneous tracks and fine tuning the gain:

Microphone Comparison - A Tutorial - part 2 of 2 from Fran Guidry on Vimeo.

Volume Fine Tuning and Rendering

As the video illustrates, working with that 1000 Hz test tone can be pretty annoying, but we need to delve into it one more time. Actually, this time we can turn the volume down, because we’re adjusting levels “in the box” – that is, internally in the computer.

The helpful folks at the Reaper Forum pointed me to the Sonalksis FreeG plugin. This tool adds high resolution metering and gain adjustment we can use to tweak the levels of our clips that last little bit.

Simply place the Reaper track cursor so the recorded test tone will be played, reset the FreeG meter, and play a bit of the clip (the space bar starts and starts playback). Note the RMS level, and repeat for each track. Then, to be fair, apply a gain adjustment to each track so they all show the same RMS level. In the video I’m fiddling with the Gain knob using the mouse, but after I recorded the session I realized that you can simply type the desired gain change into the value box, making it very easy to get the level just right.

Finally, click and drag the cursor to make a time selection of the recorded clips, then render each track separately as illustrated in the video. It’s a good idea to render to 44.1/16 format if you plan to make the clips public, because everyone can play this CD standard format.

Blind Comparison

I have had the experience many times of listening to mic comparison clips and clearly hearing the difference between them when I knew their identities, then finding that I could not hear a difference at all when I hid the identification in some way. Even getting momentarily confused about the source of the clips has been enough to change what I “hear”. Our brains are at least as important as our ears in defining what we hear, and our brains like new stuff, shiny stuff, expensive stuff. So when we know a clip was made with our shiny new expensive mic, we’re going to “hear” how wonderful it sounds.

For a test to be meaningful, we need to hide the identity of the clips somehow. This is pretty hard to do when working by ourselves. The foobar2000 audio player offers one solution, with the ABX testing utility built-in, as described in this blog post. This is a powerful tool, because it not only offers a way to test clips double blind, it helps us determine if we can hear any difference at all before we try to determine a preference.

Mic comparisons are useful for our own recording knowledge, but it’s even better to share. There are lots of folks hanging out at recording forums on the internet who are looking for information about mics and other recording gear. I like to contribute when I can by posting comparison clips, but I think it’s important to make the original post without identifying the devices used. It’s more informative, and more fun too.

So here are the three clips I recorded in the video, with no EQ, no compression, no reverb, no processing of any kind except to match volume levels and trim ends. To recap, the three mics being compared are the CAD M179, Rode NT2a, and Audio-Technica AT3035. Naturally the clips are not in the order listed.

download 20090625-J.wav
download 20090625-K.wav
download 20090625-L.wav

I’ll post the key to the clip identities in a future blog entry. Or if you post your opinion and preference in a comment here or on one of the forums I visit I’ll email or PM the information to you.



This entry was posted on Thursday, June 25th, 2009 at 1:56 pm and is filed under Audio, Comparisons, Tutorials. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.

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    53 Responses to ' Mic Comparison – a Tutorial '

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    1. David Wright said in post # 1,

      on October 31st, 2009 at 6:44 pm

      Now, if you could devise a test between democrat and republican, that would be something.

      Ok, what about a vocal shoot out? Maybe your source is too mid range to test the higher ends or maybe lower ends. I note that your guitar sounds excellent, doesn’t have the high brittle treble sounds that many smaller guitars have.

      Anyway, can you send me the key? Thanx.

    2. on June 16th, 2010 at 3:02 pm

      [...] think the NT4 sounded darned good? I’ve gone into some detail on the procedure needed for a meaningful mic test, and I’ve done some other comparisons. But a recent flurry of “what is the best [...]

    3. Johan D said in post # 3,

      on September 12th, 2010 at 5:05 pm

      I really like your scientific approach to audio – very refreshing in a field flooded by myths and spoken “truths”.

      Anyway, I’m very interested in the key for this blindtest – especially because I’m close to buy a Rode NT-2.

      My ranking for the soundclips are (best to worst): K – J – L

      Best regards/ Johan

    4. Fran Guidry said in post # 4,

      on September 13th, 2010 at 3:24 pm

      Pardon my scattered brain, I have too many irons and not enough fire.

      I’ll email you the key.

      Fran

    5. Angler said in post # 5,

      on September 30th, 2010 at 6:10 pm

      Sound so similar. In order of preference…J, k, l. k has a very slight notch at 500 to 1k,
      nothing eq couldn’t fix, L has too much zing, the string slides are evident, again, nothing eq couldn’t fix. J is fine. I’d just buy the cheapest mic frankly. What I’d like to hear, is these mics on plectrum strummed chords, I don’t find individual notes really challenge a mic. Anyways, thanks for the great tests, I appreciate them.

    6. Fran Guidry said in post # 6,

      on October 4th, 2010 at 8:53 pm

      Thanks a lot for commenting. I’ve been on the road for a bit but I’ll email you the key.

      Fran

    7. fabio said in post # 7,

      on October 8th, 2010 at 2:55 pm

      My choice is, best to worse, K J L.
      I own a couple of nt2-a and I’m looking forward to have the key e-mailed.
      Thank you

    8. Riverborn said in post # 8,

      on November 29th, 2010 at 5:17 pm

      Your tests and the explanation of your procedure are excellent. Thanks for the enjoyable write up. For my purposes any one of these mics would do fine – we’re just splitting hairs. Please send me the key.

    9. Eric said in post # 9,

      on March 13th, 2011 at 9:00 am

      Thanks a ton for the shootout, I’m in the market for a large diaphragm condenser so this post, and the one after this are very helpful. I just need the key for both of them.

    10. Alessandro said in post # 10,

      on March 30th, 2011 at 6:39 am

      My guess,

      J – AT 3035
      K – RODE NT2A
      L – CAD M179

      I’m planning to buy a cad m179 and this test came in handy
      Thanks again

    11. Fran Guidry said in post # 11,

      on March 30th, 2011 at 9:06 am

      Thanks for stopping by and commenting. I’ve sent the key via email.

      Now that you’ve heard the clips, are you still interested in the CAD M179?

      Fran

    12. Martin said in post # 12,

      on April 3rd, 2011 at 1:38 pm

      um, i think…

      J AT3035
      K M179
      L NT2A

      I think J sounds pretty open, K sounds a little rough/hard/harsh, and L sounds smooth & bright.
      wonder if I’m anywhere close…

    13. Fran Guidry said in post # 13,

      on April 3rd, 2011 at 2:27 pm

      Martin, I just sent you the key.

      Fran

    14. Mitch said in post # 14,

      on June 23rd, 2011 at 8:05 pm

      Very cool testing process here. I have to say, I think L is my favorite (although by a slim margin), but I don’t think I could identify which clips are from which mics. Could you send me the key? Thanks.

    15. Fran Guidry said in post # 15,

      on June 24th, 2011 at 1:17 pm

      Hi, Mitch,

      I’m sending you the key via a PM on Acoustic Guitar Forum. I hope that’s the right guy .

      Fran

    16. Paulo Barone said in post # 16,

      on July 3rd, 2011 at 10:57 pm

      Hi. Great test, congratulations. Could you please send me the key? Thanks, inadvance.

    17. Sti said in post # 17,

      on July 4th, 2011 at 6:33 am

      Hi Fran
      My ranking from best to worst is test J,L,K.
      It’s close for me between J and L.
      K stands out to me as the harshest and too resonant.
      Lookin’ forward to your reply.

    18. Martijn said in post # 18,

      on July 28th, 2011 at 3:18 am

      Hi Fran – great site. Thanks for making all this available. Really helpful. My ranking is J, L, K. L sounds too bright to me, K too compressed. But they’re remarkably close!
      I would appreciate receiving the key.

    19. Marc said in post # 19,

      on September 14th, 2011 at 2:47 am

      Hey nice site I think J=Cad m179 K=AT and L= Rode send me the key also thanks

    20. Fran Guidry said in post # 20,

      on September 14th, 2011 at 6:49 am

      Thanks, Marc,

      Just sent the key for these mics.

      Fran

    21. orcny said in post # 21,

      on November 29th, 2011 at 6:01 pm

      J = M179
      K= Rode
      L=AT3035

      ?

    22. Fran Guidry said in post # 22,

      on November 29th, 2011 at 7:06 pm

      Thanks for your comment. I’ll send you the key via email.

      Fran

    23. JD in LA said in post # 23,

      on January 8th, 2012 at 5:12 pm

      This will very helpful as I’m contemplating purchase of the NT2A.
      My guess:
      J=AT3035
      K=NT2A
      L=M179

      Please send key. Thanks!

    24. Fran Guidry said in post # 24,

      on January 8th, 2012 at 9:50 pm

      Howdy, JD, thanks for stopping by. I emailed the key to you.

      I’m curious, though, did you try a double blind comparison to confirm that the difference in the mics is audible to you?

      Fran

    25. Miki said in post # 25,

      on January 21st, 2012 at 4:25 am

      I think…
      J – AT 3035
      K – RODE NT2A
      L – CAD M179
      I`m very interested in buying AT3035.
      Please, send key. Thank you

    26. Fran Guidry said in post # 26,

      on January 22nd, 2012 at 9:38 am

      Thanks for visiting and commenting. I’ve emailed you the key.

      Fran

    27. Mike said in post # 27,

      on March 14th, 2012 at 8:30 am

      Hey very nice test indeed. im between J and L.. K stands out but not in a good way.
      please send the key, thanks!

    28. Fran Guidry said in post # 28,

      on March 14th, 2012 at 9:30 am

      I’ve emailed you the key, Mike.

      Fran

    29. Peter said in post # 29,

      on May 13th, 2012 at 9:48 pm

      Hi Fran,

      I *just* purchased a NT2a, but looking for a second mic to record in figure eight config (thanks for your youtube video which helped so much!).

      My preference in order of mics is K, J, L.

      I’m looking forward to seeing the key. Again, thanks so much!

      -Peter

    30. Fran Guidry said in post # 30,

      on May 17th, 2012 at 1:56 pm

      Hi, Peter,

      I just emailed you the key.

      Fran

    31. Brian said in post # 31,

      on September 1st, 2012 at 11:44 pm

      My preference. J,L, K. I own a CAD M177 and if I had to hazard a guess, I’d say L is the 179. But I have no experience with the others besides trying out at the store. Can you send the key? Thnx

    32. Fran Guidry said in post # 32,

      on September 4th, 2012 at 3:46 pm

      Brian, sorry for the delay. I just sent you the key.

      Fran

    33. gabe said in post # 33,

      on October 6th, 2012 at 3:41 am

      Nice test. Can you please send the key? I think j is the smoothest, l is a bit harsh, and k is a bit nasaly.

      (Hoping…)
      J – cad
      K – rode
      L – AT

    34. Fran Guidry said in post # 34,

      on October 6th, 2012 at 7:40 am

      Thanks for commenting, Gabe. I just sent you the key via email.

      Fran

    35. giorgos said in post # 35,

      on October 15th, 2012 at 7:05 am

      great test fran, i’m planning to buy a large diaphragm condenser and this blind test really helps. i like better warm vintage sound so J seems too bright for me. i like better K & L which are quite similar with K having some more mids. may i have the key e-mailed? thanks.

    36. Fran Guidry said in post # 36,

      on October 15th, 2012 at 10:00 am

      I’ve sent the key via email. Thanks a lot for stopping by and commenting.

      Fran

    37. Lee Fawkes said in post # 37,

      on November 27th, 2012 at 10:11 pm

      Fran, thanks for these great scientific comparisons!

      On this shootout I really struggled to tell the mics apart, though I am listening through an ancient and noisy Mackie mixer right now since my nice Presonus interface is loaned out.

      I’d give a very slight edge to J, though I’m struggling to put my finger on exactly why. It seems like it had a little more “warmth” on the bassline, and a little more detail overall. I can’t really put it an any more objective terms than that. I’d also give L a tiny edge over K, but that might just be my imagination.

      So my rank J, L, K. Really J is the only clear preference, and that’s only by a hair.

    38. Fran Guidry said in post # 38,

      on November 27th, 2012 at 10:35 pm

      Lee, I’ve sent the key by email. Thanks for visiting and commenting.

      As you say, any of these mics would seem to be doing a fine job. I
      once believed that mics must be wildly different, certainly they’re
      described that way in many internet discussions. But in my comparisons
      the differences seem quite small _if_ they’re the same pickup pattern
      and _if_ the comparisons are same source and level matched.

      Fran

    39. Chris said in post # 39,

      on February 3rd, 2013 at 8:36 am

      All sound fine for budget mics! My order of favorites (best to “less best”): K, J, L,…
      The differences are not that remarkable though and could be smoothed out by EQing…

      Would you send me the key in order to see which recording corresponds to individual mics?

      Great test, thanks….

    40. Fran Guidry said in post # 40,

      on February 3rd, 2013 at 9:00 am

      Thanks for your comment. I’ve sent the key by email.

      Fran

    41. Mike Smith said in post # 41,

      on March 18th, 2013 at 6:50 am

      Fran,
      Thanks for the well planned comparative test. Am looking for my first LDC mic now so your tests are most helpful. I like k, j, and l. Now I’m off to check some of your other comparasions!

      Best Regards,
      Mike Smith
      Suwanee, GA

    42. Todd Belden said in post # 42,

      on April 14th, 2013 at 6:47 am

      I think the results will be: J = RodeNT2A, K = AT3035, L = CadM179. I like J best, with K next. L is a little bright. Thanks, Fran.

    43. Fran Guidry said in post # 43,

      on April 19th, 2013 at 9:34 am

      Thanks so much for commenting, sorry for the delay but I’m sending you the key via email.

      Fran

    44. marv said in post # 44,

      on August 5th, 2013 at 1:36 am

      Hello. Nice test. Very very helpful. Ive been thinking of buying a cad m179 to use with my H4n… Could you please send me the key? Thank you agaun very much

    45. Fran Guidry said in post # 45,

      on August 7th, 2013 at 6:31 pm

      I just emailed you the key.

      Thanks for visiting.

      Fran

    46. John K said in post # 46,

      on August 24th, 2013 at 5:32 pm

      Hi there! You tested 2 mics that I’m strongly considering using in a recorderman setup. Currently, I am torn between the at2035 and the m179. Both seem to have their strong points, but I am wondering which one will pick up the entirety of the frequencies of a drum kit better (most importantly the kick!). I would really appreciate any clarification you have to offer regarding this test and my specific situation. Thank you very much!

      -John

    47. Fran Guidry said in post # 47,

      on August 24th, 2013 at 7:43 pm

      Hi, John,

      Thanks for stopping by and commenting. I’ll email you the key so you can evaluate the mics in this comparison.

      I’m sorry to say that I’ve never had occasion to mic a drum or drum kit so I have no insight or opinion on that subject.

      The big advantage of the M179 is the variable pattern. It’s one of the few mics available with a continuously variable pattern selection from omni to bidirectional. Changing the pattern will change the quantity and character of off-axis and will also alter the low frequency response due to changes in proximity. If I were experimenting with any kind of recording I would be inclined to choose the M179.

      Fran

    48. james said in post # 48,

      on September 24th, 2013 at 11:07 pm

      best to worst in my opinion is l, j, k.

    49. james said in post # 49,

      on September 24th, 2013 at 11:08 pm

      i forgot to ask for the key

    50. Jan Hofmann said in post # 50,

      on October 13th, 2013 at 12:48 pm

      Hi Fran,

      Great comparison, specially for me as I’m looking for an affordable condensor mic with switchable or variable pattern. My favourite is J, followed by L and K. Could you please send me the key? Thanx a lot!

      Jan

    51. Felipe said in post # 51,

      on January 16th, 2014 at 2:50 pm

      J = CAD M-179
      K = RODE NT2A
      L = AT3035

      Right or wrong?!

    52. Fran Guidry said in post # 52,

      on January 16th, 2014 at 10:15 pm

      Thanks for posting. I’ve sent you the key via email.

      Fran

    53. Chris said in post # 53,

      on January 24th, 2014 at 1:21 am

      I think…
      J: CAD
      K: AT
      L: RODE
      Could I get the key please? Thanks very much for doing the test.

    Leave a reply






    About the Blog

      Howdy, my name is Fran Guidry and this is my Homebrewed Music blog.

      I play Hawaiian slack key guitar and recorded my solo acoustic CD at home. Most of the recording information I find on the internet seems focused on bands, drums, multitracking, and so on but my main focus is recording solo acoustic guitar. Lately I’ve been enjoying video recording along with audio, so that shows up in the blog as well.

      I’m also a guitar nut. I love big ones and little ones, handmades and factory guitars, cheap ones and expensive ones. So I’ll be sharing the fun of exploring guitars as well, along with the challenges of amplifying acoustic guitars for live performance.

      Welcome!

    Philosophy

      My recording philosophy is pragmatic, skeptical, not super critical. After all, the performance is by far the most important component of a track, and every aspect of any recording is a matter of taste.

      But I do like to know “about stuff.” Back in hifi days I learned about double blind testing. I learned that we humans can easily hear differences that don’t really exist. The more I’ve learned about our human auditory system, the more I’m skeptical of what people say they hear, especially if they claim that a particular microphone or preamp or cable has some magical property.

      I’ve only been recording since 2001, and when I started I found the usual places on the internet. I sought advice and accepted it, thought I would improve my recordings by using more expensive equipment. It didn’t work.

      Two things that did seem to lead to better recordings were experience and room treatment. Getting an appealing sound is the combination of many small details, and learning those details only comes from experience. Amd the sound of the recording space is obviously a big factor.

      I’ve only recorded seriously using digital technology, but I remember trying to record rehearsals and gigs back in analog days. I don’t have any nostalgia for analog recording and playback systems at all. I think even low end digital systems can capture marvelous recordings. So when I look at gear, I look for good specs: low noise, broad flat frequency response, wide dynamic range, low distortion. I’m not interested in colorful components, mics and preamps with a sound, I want the sound to be the sound of my guitar.

      But the last word is that I’m just learning and I hope you find something useful in my posts.