Twenty questions about recording in stereo
20 QUESTIONS about (drum roll please)
recording in stereo
APPLICATIONS OF ALL OF THE STEREO TECHNIQUES:
XY AB M-S
AMBT ORTF
BLUMLEIN
click to see microphone polar patterns: http://www.sengpielaudio.com/Visualization-Blumlein-E.htm
stereo recording links: http://www.stereosoundbook.com/pages/chapter4.html
1. WHAT ARE THE THREE QUALITIES OF A MUSICAL IMAGE THAT ARE CONVEYED WHEN USING STEREO MIKING?
- DEPTH OF EACH INSTRUMENT
- PERSPECTIVE (DISTANCE OF THE INSTRUMENTS FROM THE LISTENER)
- AMBIENCE (SPATIAL SENSE/ REVERB OF THE ACOUSTIC ENVIRONMENT)
2. WHAT DOES ORTF STAND FOR?
“Office de Radiodiffusion Télévision Française”
3. WHAT IS THE TECHNIQUE?
USING TWO CARDIOID MICROPHONES WITH CAPSULES SPACED 6 1/2 INCHES (17 CM) APART AT 110 DEGREES
4. WHEN IS IT USED?
- BACK OF THE ROOM
- POOR ACOUSTICAL ENVIRONMENT OK
- CONCERT TAPING AT DEAD-CENTRE OF VENUE
5. WHY?
- GOOD STEREO IMAGING
- SIMPLE TECHNIQUE
- PRODUCES AN EVENLY SPREAD STEREO IMAGE WITH GOOD LOCALIZATION WITHOUT THE NEED FOR SPOT OR AMBIENT MIKING\
- GOOD FOR NEWBIES!!
6. WHAT IS ANOTHER NAME FOR THE X-Y STEREO MICROPHONE METHOD?
- COINCIDENT PAIR
- INTENSITY STEREO METHOD
7. WHAT IS THE X-Y TECHNIQUE?
TWO DIRECTIONAL MICS ARE MOUNTED WITH GRILLES NEARLY TOUCHING AND DIAPHRAGMS, ON ABOVE THE OTHER , SYMMETRICALLY ANGLED FROM THE CENTRE LINE
FROM “HOME RECORDING FOR MUSICIANS FOR DUMMIES”:
When you record using the X-Y technique, keep these points in mind:- The stereo image (the placement of the instruments in the sonic environment) isn’t as wide or realistic as it is in real life. The X-Y technique is easy to set up and results in a decent sound, so (as with all things in life) you have to deal with the compromise this ease creates. No solution to this exists, so if a wide stereo image is important to you, consider using a different stereo technique, such as the spaced pair or perhaps a Jecklin disk.
- Don’t use two mics when one is enough. After you get a pair of nice mics for X-Y miking, you’ll want to use them on everything. A stereo-mic approach to a classical guitar composition is nice, but honestly, recording the acoustic guitar in a rock ballad with five other instruments playing isn’t necessary and just makes life more complicated when you mix the song.
- Keep some distance between the mics and the sound source. The X-Y technique has no benefit over a single mic if you place your mics within a couple of feet of the sound source. You simply don’t have enough space for a stereo image to develop until you’re at least 6 feet from the instrument or group of instruments. In fact, you should be at least 10 feet from the sound source before using the X-Y stereo miking approach.
8. WHAT IS THE BLUMLEIN ARRAY?
A COINCIDENTAL PAIR METHOD USING TWO BI-DIRECTIONAL MICS ANGLED AT 90 DEGREES APART AND FACING THE LEFT AND RIGHT SIDES OF THE BAND/ENSEMBLE
9. WHAT IS MS RECORDING?
- A FORM OF THE COINCIDENTAL PAIR TECHNIQUE WHERE A MIC (USUALLY A CARDIOID MID) IS FACING DIRECTLY AT THE SOURCE TO PICK UP ON-AXIS SOUND WHICH IS SUMMED AND DIFFERENCED WITH A BIO-DIRECTIONAL MIC FACING LEFT AND RIGHT PICKING UP OFF-AXIS SOUND
- TWO SIGNALS ARE COMBINED VIA THE M-S MATRIX TO PROVIDE A VARIABLE CONTROLLED STEREO IMAGE
- ADJUSTING THE LEVEL OF MID VERSUS SIDE SIGNALS, A NARROWER OR WIDER IMAGE CAN BE CREATED
10. WHERE WOULD YOU USE THE MS TECHNIQUE?
- WHEN LOCALIZATION ACCURACY IS IMPORTANT
- LIVE CONCERTS WHERE YOU CANNOT PHYSICALLY ADJUST THE MICS DURING THE PERFORMANCE. STEREO SPREAD CAN BE REMOTE CONTROLLED
- MONO-COMPATIBILITY IS DESIRED
- BROADCAST AND FILM APPLICATIONS
11. WHAT IS THE A-B TECHNIQUE?
- TWO IDENTICAL MICS (CARDIOID OR OMNI-DIRECTIONAL) ARE PLACED 3-10FEET APART, AIMING DIRECTLY AHEAD TOWARD THE BAND/ENSEMBLE
- THE GREATER THE DISTANCE BETWEEN THE MICS, THE GREATER THE STEREO SPREAD
- POTENTIAL FOR UNDESIRABLE PHASE CANCELLATION OF THE SIGNALS ESPECIALLY WHEN CONVERTING TO MONO- A MONO REFERENCE SOURCE SHOULD BE USED TO CHECK FOR PHASE PROBLEMS
12. WHAT HAPPENS IF ONE INSTRUMENT IS CLOSER TO ONE MIC THAN THE OTHER?
- SOUND REACHES ONE MIC BEFORE THE OTHER
- BOTH MICS PRODUCE ALMOST THE SAME SIGNAL BUT ONE MIC SIGNAL IS DELAYED WITH RESPECT TO THE OTHER
13. HOW DOES THE BRAIN DECODE THIS ?
- IT DECODES TIME DIFFERENCES INTO CORRESPONDING IMAGE LOCATIONS
- IT TAKES ABOUT 1.5 MILLISECONDS OF DELAY TO SHIFT AN IMAGE ALL THE WAY TO ONE SPEAKER
14. HOW DO YOU CONTROL THE IMAGE USING INSTRUMENT PLACEMENT?
- TO REPRODUCE THE INSTRUMENT AT THE RIGHT SPEAKER, SOUND MUST ARRIVE AT THE RIGHT MIC ABOUT 1.5 MILLISECONDS BEFORE IT REACHES THE LEFT MIC
- PLACE MICS 2FT APART
15. WHAT HAPPENS WHEN YOUR SPACING BETWEEN MICS IS FAR APART – 10 OR EVEN 12 FT FOR EXAMPLE?
INSTRUMENTS SLIGHTLY OFF-CENTRE PRODUCE INTERCHANNEL DELAYS GREATER THAN 1.5 MSEC, WHICH PLACES THEIR IMAGES AT THE LEFT OR RIGHT SPEAKER
16. WHAT IS THE TERM(S) COMMONLY USED TO DESCRIBE THIS EFFECT?
- EXAGGERATED SEPARATION
- PING-PONG EFFECT
17. WHY WOULD YOU USE THIS SPACED PAIR A-B MIC SET-UP?
- TO MAKE OFF-CENTRE IMAGES UNFOCUSED OR HARD TO LOCALIZE
- TO ENSURE CENTRED INSTRUMENTS ARE STILL HEARD CLEARLY IN THE CENTRE EVEN WHEN OFF-CENTRE INSTRUMENTS ARE DIFFICULT TO PINPOINT BETWEEN SPEAKERS
- SONIC IMAGES ARE TO BE DIFFUSED OR BLENDED RATHER THAN SHARP
- TO PROVIDE A WARM SENSE OF AMBIENCE WHERE IT FEELS LIKE THE ROOM REVERB IS SURROUNDING THE INSTRUMENT
18. WHAT ARE THE MAIN DISTINGUISHING FEATURES OF THE COINCIDENT PAIR TECHNIQUE?
- LEVEL DIFFERENCES BETWEEN CHANNELS PRODUCE THE STEREO EFFECT
- IMAGES ARE SHARP
- SIGNALS ARE MONO-COMPATIBLE
19. WHAT ARE THE MAIN DISTINGUISHING FEATURES OF THE NEAR-COINCIDENTAL-PAIR TECHNIQUE?
- LEVEL AND TIME DIFFERENCES BETWEEN CHANNELS PRODUCE THE STEREO EFFECT
- STEREO SPREAD TENDS TO BE ACCURATE
- IMAGES ARE SHARP
- IMPROVEMENT OVER COINCIDENT METHODS FOR PROVIDING A GREATER SENSE OF “AIR” AND DEPTH
20. WHAT ARE THE MAIN DISTINGUISHING FEATURES OF THE BAFFLED-OMNI TECHNIQUE?
- USES TWO OMNI-DIRECTIONAL MICS A FEW INCHES APART, SEPARATED BY A BAFFLE
- LEVEL, TIME AND SPECTRAL DIFFERENCES BETWEEN CHANNELS PRODUCE THE STEREO EFFECT
- IMAGES ARE SHARP
- STEREO SPREAD IS ACCURATE
- LOW-FREQUENCY RESPONSE IS EXCELLENT