1. Intensity Stereo
Uses only differences in intensity between two channels to create stereo image
Two microphone diaphragms are placed as close together as physically possible (“coincident”)
No time (phase) differences between channels
“Mono-Compatible”

2. XY Stereo
Diaphragms of two directional mic's are angled out towards the edges of the soundfield
“Discrete Stereo” - generates a left channel and a right channel
Different angles and polar patterns can be used
Best if maximum sensitivity of “L” channel coincides with null of “R” channel & vice versa
“Blumlein” - two bidirectionals at 90-degrees
“XY” - two cardioids or hypercardiods angled at 90 – 130 degrees

3. Mid-Side Stereo “Mid” microphone is aimed directly at sound source
Can be any polar pattern
“Side” microphone is aimed 90-degrees off-axis to sound source
must be bidirectional
“Matrixed Stereo” - generates a “sum” and “difference” channel
Cannot simply be panned left and right
Matrix generates an “in-phase” (center) and an “out-of-phase” (left and right) component

4. Show in class Polar patterns & Polarity
Omni + Bidirectional = cardioid
Mid + Side = Left;
Mid + (-Side) = Right
How to set up a Mid-Side matrix
“Mid” is panned center
“Side +” is panned left
“Side -” is panned right

5. Mid-Side can reproduce same patterns as different XY arrays
So why don't they sound the same?
Mid-Side can use different polar patterns (including omni)
Whatever is on-axis to a mic will be reproduced with best frequency response
XY = on-axis to edges of ensemble; off- axis to center and room
Mid-side = on-axis to center of ensemble; on-axis to room

6. Benefits to Mid-Side Recording
Mid-Side can reproduce same patterns as different XY arrays
depending on Mid pattern and Mid:Side ratio
More flexible (to some extent)
Especially when used as a “stereo spot mic”, amount of room and stereo spread can be decided in the mix without changing sound of instrument
Absolutely mono compatible
“Side” channels completely cancel out when summed to mono

7. Collapsing to mono XY Mid-Side
will reproduce same amount of ambience as in stereo
Will reproduce musical balance as heard in stereo
Mid-Side
Whatever is in “Mid” channel remains
Whatever is in “Side” channel goes away

8. Think of stereo in a different way:
Rather than “Left-Right”, think “Same-Different”
Things that are the same between L&R in a stereo mix will be reproduced dead center (“Mid”)
Things that are different between L&R in a stereo mix will be reproduced extreme left or right (“Side”)
You can make 3 tracks out of two
Record on source to hard left, another to hard right, one panned straight down the middle
Ability to process “Mid” channel separate from “Side” channel is an extremely powerful tool
Often used in mastering