COURSERA-IMP : ASSIGNMENT 1 - CARDIOID MICROPHONE POLAR PATTERN

Why I'm Doing This Course

It's so cool to discover Coursera and particularly this Introduction to Music Production course by Loudon Stearns from the Berklee College of Music. By taking this course, it is my hope that the knowledge I've gained through trial and error and lots of reading will be reinforced by learning the basics from a "master".

This post is my submission for the Week 1 Assignment.


For the benefit of my "classmates"

My name's Mario Gozum, based in Maryland, USA. I've been doing home recording, on and off, since 2005. For the week 1 assignment I will share what I've learned about microphone polar patterns by using my own condenser microphone as the "test subject".


Getting Familiar With My Condenser Mic and Its Polar Patterns

I record mostly with my Behringer C-3 Dual-Diaphragm Condenser microphone because it offers me three choices of polar patterns, from Omnidirectional, Figure-8 and Super Cardioid. Since I have a less than ideal space for recording (i.e. living room, bedroom, bathroom, closet), I gravitate towards the Super Cardioid setting.

First, what is a cardioid microphone?

Instead of redefining it, I'm going to grab some excerpts from Wikipedia. They can explain it better that I could.
"A cardioid microphone is effectively a superposition of an omnidirectional and a figure-8 microphone; for sound waves coming from the back, the negative signal from the figure-8 cancels the positive signal from the omnidirectional element, whereas for sound waves coming from the front, the two add to each other."
And in my case, one of the Behringer C-3 polar pattern setting is spec'ed as a Super Cardioid:
"A super-cardioid microphone is similar to a hyper-cardioid*, except there is more front pickup and less rear pickup."
(* Just follow the link to the cardioid wiki if you want to find out more about Hyper-Cardioid)






Putting the Theory to the Test

The Behringer C-3 is a side address microphone with a dual diaphragm design. On the super cardioid setting, the rear sensitivity is greatly reduced. If I understand it correctly, the diagram indicates that the front side is relatively sensitive to sound sources ranging from -25db to -5db, as far as 70-degrees off-axis. Then at 90-degrees off-axis it gets less sensitive and then completely rejects sound sources at about 113-degrees off-axis.

I'm going to test the theory based on the diagram. But since I'm doing this in my bedroom I have a feeling that I will not achieve complete sound rejection at 113-degrees since the sound will be bouncing off the walls and some of them will hit the axes that have higher sensitivity. Then add the fact that the microphone will be in close proximity to the sound source.

The setup:
Sound Source (boom box right speaker) >
Behringer C3 on cardioid pattern setting, set at about 6 inches from source >
Note: The picture shown is not 6 inches from the speaker, but it's meant to show the switch set to super-cardioid. I moved it closer to the speaker after I shot this.

Line 6 UX2 >
Laptop running POD Farm > Audacity
My ultra mobile home studio.

The source is an excerpt from "Fast In My Car" by Paramore playing through the boom box. However, it was around midnight so I couldn't play it loud (boom box volume was set at 8 out of 40). I made sure I was getting around -18db on the UX2's VU meter by turning up the mic gain. The POD farm mixer was set to output the dry signal into Audacity.

The plan was to start the mic on axis with the speaker cone, then turn it to 90-degrees, then around 113-degrees and lastly, 180-degrees.

Here are the results:

The differences are evident just by looking at the wave representation on the track.


On axis (UX2 VU meter peaking around -18db)


At 90-degrees (UX2 VU meter peaking around -30db)


At approximately 113-degrees (UX2 VU meter peaking around -24db)


At 180-degrees (UX2 VU meter peaking around -22db)


Then I did a little editing so we can hear all four clips back to back.




The Take Away

As I predicted, complete rejection was not achieved at 113-deg because of the proximity to the sound source and is most likely being picked up by the rear and a little by the front. In fact, the best rejection for this test was at 90-degrees.

By doing this test I've become more familiar with my condenser microphone's cardioid profile and will definitely help me with mic placement in the future.


Other References

Here's another interesting reading material I'd like to share as it explains what the diagrams mean.
What You Need To Know About Microphone Polar Patters - Harmony Central


Self Assessment

I wish I could've had better conditions doing the sound tests. Maybe a video would've enhanced this post but I was in a bit of a time crunch. It's 1:03AM as I write this sentence. I hope to do better on the next assignment.

Thanks for reading my assignment submission and I hope I was able to impart some of my new found knowledge to you. Feel free to explore my older posts here and if you have time, please listen to a couple of my songs (reverbnation widget to your right) that I recorded by just diving into the DAW and pretty much doing it by trial and error.

I'm looking forward to learning from my classmates as well.