live sound systems

Question 1

give the standard way to measure freq response of a speaker

Answer 1

dB SPL at 1m with 1W of power when fed white noise

Question 2

how to predict the output in dB from a given speaker sensitivity and power input?

Answer 2

dB formula

sensitivity + 10log (watts input/1)

the denominator is 1 because the original power is 1W at 100 dB SPL

Question 3

how to calculate dB SPL at a different distance other than 1m?

Answer 3

the SPL dB equation

20 (log (new distance/1)

denominator is 1m because it referenced from 1m

Question 4

what happens to high freq content as you move off axis?

Answer 4

high frees drop as you move off axis from a speaker

Question 5

define polarity loss

Answer 5

the loss of sound as angle increases, disperse loss

Question 6

how does a polarity plot change as freq changes?

Answer 6

lower freq response speakers have a more consistent polarity plot

as freq increases, speakers ability to project sound in all directions diminishes

Question 7

define distance loss
how is it calculated ?

Answer 7

the loss of dB due to distance from axis, changing the angle

distance loss, dB = 20 log (new d/old d)

Question 8

what’s a dipole speaker?

what is a benefit of these speakers?

Answer 8

speaker with 2 elements in a horizontal plane

makes a speaker more directional by having areas of phase cancellation on the sides of the speaker, making it more directional towards the front

the distance between the elements is half the cancelled frequency
2D = λ