Rumsey Chapter 16Day 3

Overview

Stereo = 2.0 (two discreet channels) THREE-DIMENSIONAL, even though

only two channels Stereo listening is affected by: THE

ROOM, LISTENING POSTION, SPEAKER POSITION

Most PRACTICAL way to listen

Principles of Loudspeaker Stereo PHANTOM IMAGES: We hear sound

from BETWEEN the speakers even though a speaker is not there

Multi-channel sound was first researched by BELL LABS

Remember: LOUDNESS, DELAY, and FREQUENCY help us to determine the location of sound

More on Phantom Images

Figure 16.2 Place speakers 30 degrees from

center on each side Create a perfect TRIANGLE with the

listener Best phantom imaging, or “Summing

Localization”

Binaural vs. Stereophonic BINAURAL refers to localization of an

individual source STEREOPHONIC is the way we use a

stereo source to create a simulation Fact file 16.1

More on Binaural

Tries to be NATURAL sounding by re-creating the EARS on your head!

Must accurately re-created the HRTF Problems happen because we must

keep our head STILL when listening There can also be problems with

exact reproduction “Binaural Haircut”

Two-Channel Mic Techniques Spaced Pair X/Y Pair “COINCIDENT Pair” Blumlein Midside (MS) Near-Coincident Pairs Decca Tree

Issues with Stereo Micing Fact File 16.5 Frequency Response and Level can

skew the stereo image PHASE will change the natural sound

reproduction and perception of space CROSSTALK: 18dB level difference

makes the signal seem fully left or right

Stereo Width

Fact File 16.6 NULL POINT: Changes “Fully left or

right” Widening the mics makes the stereo

image more extreme Wide mics = narrow angle between

fully left and right = wide sound stage

Mic Configurations

Fact File 16.7 END-FIRE and SIDE-FIRE

configurations End-Fire allows for the mic to

be directly pointed at the source

Side-Fire usually stands vertically

Spaced Microphones

Rely on the PRECEDENCE effect: The delay between the capsules

Also changes based on volume and frequencies

Can capture a very wide sound stage LESS ACCURATE natural imaging:

Must be careful to maintain accuracy if that is what you want

Dummy Heads

Actual model of the human head Use of Pressure Microphones Simulates how the human ear

captures sound

Stereo Studio Setup

Multi-Mic: Levels are panned to a “virtual” stereo position

Some sources still warrant natural stereo reproduction: Acoustic guitar, piano, drums

“PANNED MONO” creates an artificial stereo image

Close micing is used often, but must be done with care so as not to disrupt the stereo image