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:

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.


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:

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

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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    67 Responses to ' Mic Comparison – a Tutorial '

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    1. Felipe said in post # 1,

      on January 16th, 2014 at 2:50 pm

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

      Right or wrong?!

    2. Fran Guidry said in post # 2,

      on January 16th, 2014 at 10:15 pm

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


    3. Chris said in post # 3,

      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.

    4. Armon said in post # 4,

      on November 9th, 2014 at 5:22 am

      Well my favorites, at least for acoustic guitar given these recordings, are L then J then K, can you provide the key?

    5. reklamusic said in post # 5,

      on December 17th, 2014 at 2:33 am

      Hello! So much time passed, will we know the key? 🙂

    6. Fran Guidry said in post # 6,

      on March 22nd, 2015 at 11:00 am

      I finally figured out that Gmail was putting blog posts in the spam folder instead of my inbox for the last few months. I believe I’ve responded to all the key requests and other comments and found a solution to the problem. My apologies.


    7. Mauro D said in post # 7,

      on September 11th, 2015 at 9:02 pm

      I preferred the sound of K the most. I’d also like to see the key.

    8. Fran Guidry said in post # 8,

      on September 12th, 2015 at 9:31 am

      Just sent the key, Mauro.


    9. MK said in post # 9,

      on November 13th, 2015 at 7:17 pm

      Great recordings. I preferred the comforting, pleasing sound of K. But there is something to be said for the upfront and clean nature of L too. I’m guessing the L is the Rode?

      I am considering between the CAD M179 and AT3035 for my own future purchase. Could you email me the key? Thanks.

    10. Daniel Martineau said in post # 10,

      on November 14th, 2015 at 9:18 am

      My choice J then L and K Find J sharper , K more coloured with more mids. If I could choose 2 I would go for J and K to have 2 different tonality. So…which one are they?

    11. Fran Guidry said in post # 11,

      on November 14th, 2015 at 10:46 am

      Thanks for stopping by. I just emailed you the key.


    12. Fran Guidry said in post # 12,

      on November 14th, 2015 at 10:47 am

      Daniel, I just emailed you the key. Thanks for visiting and commenting.


    13. Dean said in post # 13,

      on February 23rd, 2016 at 6:50 pm

      Hi Fran,
      I realize this is years later but can I please find out the answer? It keeps me up at night. Thanks

    14. Fran Guidry said in post # 14,

      on February 23rd, 2016 at 7:09 pm

      Thanks for stopping by, Dean, I just emailed the key.


    15. Dan said in post # 15,

      on May 17th, 2016 at 3:54 am

      Hi Fran,

      Great day!

      I am really interested with the answers too. Hope you could share it with me.


    16. Pierre said in post # 16,

      on June 9th, 2016 at 11:00 pm

      Hi Fran I own a Rode NT1 which I think could be L (??) and I would love the keys. Thanks for a very nice and interesting video!

    17. Alex said in post # 17,

      on June 18th, 2016 at 2:57 am

      thanks for the compare! can I see the key? thanks

    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.



      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.