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3-D Sound and Spatial Audio MUS_TECH 348. Stereo Loudspeaker Reproduction

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  • 3-D Sound and Spatial AudioMUS_TECH 348

  • Stereo Loudspeaker Reproduction

  • Intensity StereoSide Image

  • Intensity StereoCenter Image

  • Typical Pop/Rock and Classical Spatial Distribution

  • Off-Center Listening

  • Precedence Effect

  • Mono Compatibility

  • Why cant we just reproduce binaural recordings over loudspeakers?

  • Binaural Recording with Loudspeaker Reproduction

  • Stereo Loudspeaker Reproduction Creates Notch at 2kHz

  • How to Eliminate Crosstalk?1) Use a baffle

  • 2) Use out-of-phase signals

  • 180 Out of Phase Signals

  • 180 Out of Phase Loudspeakers

  • Alternatively

  • How to make Loudspeaker Reproduction Transparent?

  • 3) Crosstalk Cancellation from Manfred Schroeder (late 1950s)

    Exact SolutionMake loudspeaker listening more like headphonesAll sounds externalized

  • Schroeders Cross-talk Cancellation System

  • Schroeders Cross-talk Cancellation System

  • One Step at a Time: Equalization of Loudspeaker ResponseEQ FilterResult

  • But

  • Introduce cross-talk cancellation signal:

  • ButThere is crosstalkfor the crosstalkcancellation signal!

  • Full Cross-talk Cancellation Solution:

  • Sweet Spot

  • The Problems?Off-center positions. Only one sweet spot.Individual Differences. Listeners HRTFs, including H30 and H330, dont match.High frequency cancellation. Wave lengths are so short that very slight shifts in position throw everything off.1/H30. Inverting the notches creates big peaks that probably dont match the listener.Room Acoustics. Indirection sound reaches the listener.

  • Off-Center Seating in Larger SpacesGoodEach seating position has unique time of arrival delay and level differences. Only the center seats can provide spatial imagery.

  • Off-Center Seating in Larger SpacesThe separation of the stereo loudspeakers creates different ranges of differences for time of arrival delay.

  • Off-Center Seating in Larger SpacesDelayed signal from loudspeaker can create a wide range of subjective impressions!

  • Off-Center Seating in Larger SpacesThe range of time of arrival delays for typical loudspeaker separatations puts the delay in the range of these different subjective impressions

  • Loudspeaker Reproduction in Natural EnvironmentsLoudspeakers themselves create indirect sound.

  • Frequency and Time Response of Loudspeaker in an Empty RoomImpulse response and amplitude response from the loudspeaker to the listener in an empty test room.

  • Figure 2 shows change with a few absorption panels in place.

  • More,

  • Figure 6 finally shows a rooms with only slight indirect sound between the loudspeaker and the listener.

  • Figure 6 impulse response and amplitude response.

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