Why NOT To Use Cardioid Mics! - Mike Senior

Mike Senior's Expert Tracking & Mixing Tips

Cardioid mics are tremendously popular amongst recording musicians, but can also work against you. In this episode, Mike Senior explains some of the reasons why, and illustrates how omni and figure-eight patterns can often give more useful results.

Chapters
00:00 - Introduction
01:39 - Proximity-effect bass boost
04:44 - Spotlighting 
05:48 - Low-end response at a distance
06:40 - Off-axis tonal coloration
09:06 - Insufficient spill rejection
10:56 - Plosives and handling noise
12:33 - The hand-held LDC trick
14:11 - Summary

If you'd like to listen more critically to the audio examples, you can download a high-resolution 24-bit/44.1kHz WAV of this whole episode from the podcast support page for this show https://www.soundonsound.com/techniques/why-not-use-cardioid-mics-mike-senior-podcast

Credits
This month's episode features recordings from David Tyo's 'Long Way Home'. You can check out more of David's great music here:

https://davidtyo.bandcamp.com/

If you'd like to try mixing 'Long Way Home' for yourself, you can download the full raw multitracks here:

https://cambridge-mt.com/ms/mtk/#DavidTyo

To read more about the low-spill figure-eight guitar-recording method, check out Neil Rogers's January 2014 'Session Notes' column:

https://www.soundonsound.com/techniques/session-notes-thomas-rumbold-reds

For more general advice about microphone polar patterns, try this March 2007 article by Paul White:

https://www.soundonsound.com/techniques/using-microphone-polar-patterns-effectively

Mike Senior Biog

Mike Senior is a professional audio engineer, regular SOS contributor, and author of the best-selling books Mixing Secrets For The Small Studio & Recording Secrets For The Small Studio. He runs the Cambridge-MT educational resources site (including the web's largest free multitrack download library) and hosts two monthly independent podcasts, Project Studio Tea Break and the Cambridge-MT Patrons Podcast.

Catch more shows on our other podcast channels: https://www.soundonsound.com/sos-podcasts

Creators and Guests

Host

Mike Senior

Mike Senior is a professional audio engineer, regular SOS contributor, and author of the best-selling books Mixing Secrets For The Small Studio & Recording Secrets For The Small Studio. He runs the Cambridge-MT educational resources site (including the web's largest free multitrack download library) and hosts two monthly independent podcasts, Project Studio Tea Break and the Cambridge-MT Patrons Podcast.

What is Recording & Mixing?

Welcome to the Sound On Sound Recording and Mixing podcast channel where you’ll find shows packed with Hints & Tips about getting the most out of the recording, mixing and mastering process.

More information and content can be found at www.soundonsound.com/podcasts | Facebook, Twitter and Instagram - @soundonsoundmag | YouTube - https://www.youtube.com/user/soundonsoundvideo

Mike Senior
Welcome to the Sound On Sound recording and mixing podcast channel.

I'm Mike Senior. Let's play a little game. Pick a microphone. It can be any mic you use regularly. Now I'm going to use my amazing mind reading powers to guess which one you chose. Ready? Okay, it's coming to me. I think you chose the RØDE NT1. Now there may be one or two of you listening who are now freaking out, thinking that I can actually read your mind.

But for most of you, the likelihood is I probably got it wrong. Even though I tried to play it safe by choosing something of a Project Studio favourite. What I can say, however, with a good deal more confidence, is that the mic you chose is almost certainly a cardioid model. Or at least that you use its cardioid polar pattern most of the time.

To a certain extent, this stands to reason. When you're overdubbing in perhaps less than perfect acoustic environments, having a directional mic means that you get less overdubs. Certainly if you're recording lead vocals, which tend to be recorded pretty dry. Cardioid mics also have the advantage of being more intuitive in ensemble recording situations, because you can point the mic at what you want and away from what you don't want.

And that makes as much sense to the performers as it does to the engineer. Unfortunately though, cardioid mics also have a number of other characteristics that can be less helpful in a recording situation. And in this episode, I want to talk about some of those, and why choosing a different polar pattern than cardioid can often therefore work in your favor.

Now the thing most of you probably already know about is that all directional mics, including cardioids, exhibit proximity effect. In other words, an extra bass boost that increases the closer the sound source gets to the mic. For example, here's a bit of vocal I recorded with three identical cardioid mics at different distances from the singer.

The first is only three inches away. The second is eight inches away, and the final one is about 12 inches away. Take my heart, and please don't break it. Love was made for you and me. Take my heart, and please don't break it. Love was made for you and me. Take my heart, and please don't break it. Love Was made for you and me.

Now you might say, well, so what if I get a bit more or less bass on my recordings? I can just add a bit of EQ. And that's all well and good, as long as the instrument doesn't move. With singers in particular, you're dealing with a moving sound source. As much as I'd like to clamp a singer's head in a vice while recording them, I probably wouldn't get the most emotional performance that way.

And when they move, the amount of low end in the vocal tone changes. For example, here's a snippet of the raw vocal from the downloadable multitrack of David Tayo's song, Long Way Home. We'll take the long way home, and baby we'll take it slow. Notice how the words, baby we'll take, are significantly warmer sounding, presumably because they were sung slightly closer to the mic.

Have another listen. We'll take the long way home and baby, we'll take it slow. The problem with that variability of tone is that it makes it quite difficult to get the vocal level solid within a mixed context no matter how hard you compress. For example, here's a little rough mix I've done of that multitrack project, where I've hammered the lead vocal compression pretty hard, and yet the tonal variability still makes the warmer lyrics seem louder.

If I even out the low frequency levels first using an automated EQ, I can make that vocal sit much more solidly in the balance without changing anything else. A bit like this.

But frankly, that's a bit of a tedious processing job. And one way it could have been avoided... would have been to use an Omnimic instead, because Omnimics don't really suffer from proximity effect. And if you're worried about the extra room sound, just sing closer to the mic. Incidentally, if you'd like to try mixing that track for yourself, check out this episode's show notes, where I'll put a download link.

Another problem with using cardioid mics, particularly for close micing, is that they pick up only quite a small area of the instrument they're pointed at. This is something I normally refer to as spotlighting, because of the way a spotlight only really lights up the thing right in front of it. With wooden bodied instruments in particular, which send out frequencies in very complicated ways from different parts of the instrument, a cardioid therefore picks up only a fraction of the information that the instrument's putting out.

And again, this is a situation where an omni mic can often produce more natural sounding results. For example, here's a recording of the same guitar performance with two of the same model of small diaphragm condenser mic, both about 8 inches from the 12th fret of the instrument. But one of those mics had its cardioid capsule, and the other one its omni capsule.

I'll play the cardioid first, followed by the omni.

The Omni recording just feels like a more holistic representation of the instrument. Omnis can also outperform Cardioids if you're micing from a distance, because once you get out of the range where the proximity effect boosts the Cardioids low end, It'll typically feel a bit bass light compared to an omni.

Furthermore, the way the directional polar pattern is created usually involves a certain amount of low frequency phase shift that can make what low frequencies the cardioid does capture feel less natural anyway. Here's an audio example that demonstrates the kind of difference I'm talking about here.

What I've done is I've recorded the same piano recording with two sets of the same model of small diaphragm condenser mic, but one pair's using the cardioid capsules and the other's using the omni capsules. I'll play the cardioids first and then the omnis.

Another problem with cardioid mics, particularly the budget large diaphragm condensers that are used in a lot of project studios, is the way they colour off axis sounds. Now let's imagine for a moment a typical side address cardioid microphone, as seen from above, and then mentally overlay a clock face on it, with the mic in the middle.

And now let's compare the tone that's picked up with a singer in the on axis position at 12 o'clock, against the tone of the same singer at the 4 o'clock off axis position. I'll roughly match the level of the two so we're just comparing the tonal qualities. O is for the only one I see. O is for the only one I see.

It's a truly horrible sound. And yet it's a mid priced condenser mic. Certainly not the cheapest mic in my locker. If I switch to the mic's omni or figure 8 patterns though, the tonal change is much less. Have a listen. First I'll play the off axis cardioid again, then the off axis figure of 8 and off axis omni.

I've roughly matched the levels again to make the tonal changes more obvious. O is for the only one I see. O is for the only one I see. O is for the only one I see. Now these kinds of off axis tonal considerations may not matter much if you're just recording a singer close up in a dry room. But the moment you start picking up any appreciable room ambience, which of course comes in from off axis, that element of the sound is more likely to be undesirably coloured if you use a cardioid.

Similarly, if you've got several instruments recording in the same space, the spill from one instrument into another instrument's mic will usually come in off axis, and again will suffer from any off axis tonal colorations of the mic. To be honest, in general, Project Studio users tend to be too scared of spill, in my opinion, because as long as a spill sounds natural, it can actually enhance the sound of your final result.

Whereas using lots of cardioid mics to try and reduce the level of spill can actually backfire, because the spill they do pick up sounds so nasty. So not only do you not get the enhancement of nice sounding spill, but you also get the damage done by the nasty sounding spill. Now, of course, I realize that there are plenty of situations where you might want to actively reduce levels of spill on a particular mic.

Probably the biggest reason in any kind of ensemble recording situation is because if you get too much spill on a certain mic, it becomes not very useful for balancing the thing it's pointing at. So if, say, my upright bass mic is covered in piano spill, I won't be able to adjust the level of the bass in the balance without also rebalancing the piano.

But even when you're trying to minimize spill, a cardioid mic isn't necessarily the best option. Because the actual rejection you get at the back of a cardioid mic is not particularly great. It's probably in the order of about 15 dB. A figure 8 polar pattern, on the other hand, has a much deeper rejection null.

Or to be precise, a rejection plane perpendicular to the firing line of the mic. Fellow Sound on Sound contributor Neil Rogers demonstrated this very powerfully in a recording feature he did a few years ago. He used a figure of eight microphone for acoustic guitar, but where the player was also singing.

By directing the microphone's null plane at the singer, he was able to reduce the spill level tremendously. Have a listen.

Yes, you can still hear the singer, but he sounds like he's in the next room. Not, as in real life, only two feet away from the microphone. It's insane how deep that rejection null is on a figure of 8 mic. So bear that in mind before you instinctively reach for a cardioid in future. Finally, there are a couple of other little things that cardioids really aren't that good at dealing with.

The first is plosives. Those wind blasts you get on P and B sounds in particular, and which create low frequency thuds when they hit the microphone diaphragm. It sounds like this. Peter Piper picking peppers. Now there are various ways of avoiding plosives while recording. Putting the microphone slightly off axis so it doesn't get hit by the blast, or using a pop shield to break up and diffuse the wind blast before it even reaches the mic.

On the other hand, you could just switch to an omnipolar pattern instead. Because Omnis are far less susceptible to windblast noise. Let me just repeat that example you heard a moment ago, and I'll follow it with another recording of exactly the same thing, but with the microphone's polar pattern switched to Omni.

So first Cardioid, then Omni. Peter Piper picking peppers. Peter Piper picking peppers. The other thing Cardioids aren't typically great at dealing with is handling noise. You know, any vibration that reaches the microphone via its casing and then gets transmitted straight to the diaphragm as low frequency rumble.

Again, this is something that omni microphones deal with much better than cardioids. For example, I took the same microphone I used for those plosive tests. And just gently drummed my fingers on the outside casing. First with the cardioid pattern, and then with the omni pattern. Check out the difference.

As you can hear, it's pretty much chalk and cheese. Incidentally, the fact that an omni microphone is typically insensitive to handling noise, plosives, and proximity effect, makes it possible to pull off quite a handy little vocal recording dodge. You see, you sometimes get problems in a studio situation, where singers who are used to performing live with a band find it quite unnatural to be stood in front of a large diaphragm condenser mic on a stand.

You know, they're used to pogoing around the stage while swallowing a handheld dynamic. So the trick you can try here is to get one of those foam windshields and put it over a large diaphragm condenser mic that's been switched to omni. You can then give that to the singer to hand hold for studio recording purposes.

The Omni pattern will naturally reject a good deal of the handling noise, and the combination of the wind sock and the Omni pattern's natural resistance to wind noise will help to mitigate the plosives, while the lack of proximity effect on the Omni means that the vocalist can get pretty much as close as they like.

Now if you're thinking, don't be daft, that couldn't possibly work, have a listen to this bit of vocal, which was condenser, in exactly that way. When you put your arms around me, I get a fever that's so hard to bear. You give me fever. I would just add one little practical proviso about that recording dodge, though, and that is that water vapour from the singer's breath may begin to make the windshield damp after a while.

So it's not a bad idea to have two available so you can swap them over to allow drying time and to protect the mic diaphragm from condensation build up. So to sum up, there are plenty of reasons why a cardioid microphone might not be your first choice in the studio. If you're working close up, you might encounter difficulties with proximity effect or spotlighting.

Whereas further away, the low frequency response might not really cut the mustard. And in any kind of ensemble recording environment, the off axis coloration of cardioid microphones may hold you back from getting the most natural sounding end results.

That's all for now. Thanks for listening, and be sure to check out the show notes page for this episode, where you'll find further information including web links and details of all other episodes. You can also download a 24 bit WAV version of the show from there, if you'd like to hear the audio examples at higher resolution.

And just before you go, let me point you towards www. soundonsound. com slash podcasts, where you can explore what's playing on our other channels. I'm Mike Senior, and this is a Cambridge MT production for Sound On Sound magazine.