Tyco 579-769 specifications 51º

Speaker Basics, Continued

Speaker Coverage	Using the polar information of the speaker, in combination with the distance between the speaker
	and the listener, you can determine the area that a speaker can cover. The “Coverage Area” is
	defined as the plane where the SPL at the edge of the plane drops 6 dB below the on-axis SPL,
	as illustrated below:
	Simplex 4902-9721
	Ceiling Mount Speaker
	Polar Plot - 2kHz 0º
	6dB/division

10' high ceiling
	93dB			93dB
		Dispersion Angle	51º
			of
			f	5.0'
			i
			x
	97dB		s	97dB
		Critical Polar Angle
				10.0'
	D2			D2
Listener level	93dB	99dB @5' 1W		93dB
			Distance off axis

Coverage Diameter

12.8' 6dB variation

Floor

Figure 2-5. Speaker Coverage

Coverage area is determined by a combination of speaker polar loss and the inverse square loss off-axis. To illustrate, consider a speaker with no polar loss, i.e. the speaker’s SPL is the same over all angles. As the listener moves away from the center of the speaker, the distance to the speaker increases resulting in a lower SPL. From the Inverse Square Law, the off-axis SPL is 6 dB lower than the on-axis SPL when the distance from the speaker to the listener has doubled. From simple geometry, it can be determined that the maximum useable coverage angle is 120 degrees:

Ceiling Height

60°

2
x
	C
	ei
	li
	n
	g
	H
	ei
	g
	h
	t-
	Li
	st
	e
	n
	e
	r
	H
	ei
	g
	h
	t

Listener	-6dB edge of
Height	coverage area

Figure 2-6. Maximum Theoretical Coverage Angle

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