Loudspeaker Design Cookbook, Vance Dickason

84 Pages·2011·3.82 MB·English

Introduction to Loudspeakers
and Enclosures
D. G. Meyer
School of Electrical & Computer
Engineering
Outline
• Background
– How loudspeakers work
– Waveforms
– Wavelengths
–– SSppeeeedd ooff ssoouunndd
– How sound propagates
– Sound pressure level (dB)
– Summation of audio signals
– Phase wheel
– Beamwidth
– 3D directivity “balloons”
How Loudspeakers Work
How Loudspeakers Are Made
The Waveform
Transmission
l
= C/F
C is speed
ooff ssoouunndd aatt
ambient
conditions
Transmission
How Sound Propagates
Acoustic Decibel (dB SPL)
• In acoustics, the ratios most commonly
encountered are changes in pressure level,
measured in dB-SPL:
m mmm
dB-SPL = 20 log (p/p ) where p = 20 N/m2
10 o o
• As distance from a sound source doubles,
tthhee ddBB--SSPPLL ddeeccrreeaasseess 66 ddBB ((tthhiiss iiss ccaalllleedd
the inverse square law)
• Adding/subtracting dB levels:
– ––– – –––
SPLa SPLb = 10 log [ 10 db-SPLa/10 10db-SPLb/10]
10
• Doubling acoustic power corresponds to a
3 dB increase in SPL
• Doubling perceived loudness corresponds to
a 10 dB increase in SPL
Transmission