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Question 1

what is audio?

Answer 1

an electrical energy that represents sound in an analogue or digital domain

Question 2

what is the difference between sound and audio?

Answer 2

sound is a mechanical energy and audio is an electrical energy

Question 3

what is an aux track/send?

when is an aux considered a return channel?

Answer 3

a bus path that can send audio from a channel, independent of that channel, pre or post fader

aux return is when the auxiliary is routed back to the main mix and not to an output channel

Question 4

what is a VCA?

Answer 4

voltage controlled amplifier or in the digital domain DCA, digital controlled amplifier
a VCA group is an independent fader used to control the value of multiple channels simultaneously
without altering the individual channel faders and without having to make a subgroup
no inserts, pan pots, auxes, returns, sends, simply. a. fader.

Question 5

name 2 ways in which you would use a VCA group

Answer 5

1. grouping similar instruments together so they can be controlled at once
2. creating sub mixes, route desired channels to VCA then route the VCA to a separate channel and control the VCA using that single faderi

Question 6

give 5 examples of output mixes that could be present in a live scenario

Answer 6

line array PA amplifiers
subwoofer PA amplifiers
on stage monitoring (wedges)
IEM monitor mixes
headphones for FOH

Question 7

describe the signal flow from audio source to output in a 4 PA speaker system

Answer 7

audio source is captured by a mic, synth, audio file, and sent to the mixer via an input channel, then thru processing, DSP or whatever, then two output channels are dedicated to the left and right mid range/tweeter PAs and two outputs are dedicated to the left right sub amplifier , amplifiers then feed their corresponding speakers

Question 8

what frequencies do the following drivers cover:
subwoofer
mid range
tweeter

Answer 8

below 500 Hz
from 500 Hz to 4kHz
anything above 2kHz

Question 9

what is a crossover?

Answer 9

a device that splits audio signal into difference frequency ranges

either by HPF or LPF or bandpass if in a 3 way system

Question 10

where can a crossover be found in a signal pathway?

Answer 10

before or after amplifying (active or passive)
can be found as a physical device or a DSP (built-in digital crossover in a processor)

Question 11

in a 2-way system what is important that both crossovers have?

Answer 11

a matching cut-off frequency, or crossover point. normally around 80Hz or 100Hz
if the sub produces too much high freq information, the sound source will be localised, low freqs are omnidirectional, and can compromise the stereo image created by the mids and tweeters

Question 12

what is the goal of a crossover with regard to the listener?

Answer 12

divide the signal such that when audio is outputted through the speakers, the crossover can’t be heard, sounds as if it were coming through one speaker, flat response

Question 13

what is an active crossover?

Answer 13

a crossover in which each driver gets its own channel amplification (passive speaker system)

found before the amplifier

signal leaves the crossover split into its freq bands and each set of freqs goes to the desired amplifier and then driver

Question 14

what is a passive crossover?

Answer 14

a crossover found after amplification, a network of capacitors and inductor coils (and other electrical components)

a full range of freqs leaves the amplifier and then the signal is split into freq bands

Question 15

give pros and cons of active crossovers

Answer 15

active
- preserves energy since it is only amplifying the necessary bits

• does not come ready to plug and play

Question 16

give pros and cons of passive crossovers

Answer 16

passive
- ready out the box, plug and play

• wastes power because it is filtering a signal that has already been amplified, amplifying unnecessarily

Question 17

what role do inductors and capacitors play in a passive crossover?

Answer 17

inductors have lower impedance for low frequencies so they let low freqs pass and block high/mid freqs

capacitors have a lower impedance to high freqs so they allow high through and block low/mid freqs

caps and inductors in series block both low and high and are used to create bandpass filters

Question 18

what does a crossover alter inevitably?

Answer 18

crossovers will alter phase

for every 6dB/oct of attenuation on a crossover filter, phase will change by 45°

Question 19

which connector is used for speakers? how many pins?

Answer 19

the NL4 connector, with the clip on
it has 4 pins
1+ 1- 2+ and 2-
1+ and 1- used for low freq positive and negative and the 2 pins are used for mid-high freqs

Question 20

describe a 2x3 crossover system

Answer 20

2 meaning two inputs left and right, stereo
left is sent to
left sub, left mid range and left tweeter
right is sent to
right sub, right mid range and right tweeter
so 6 outputs, 2x3 = 6

Question 21

in a live setting (duh), how do we check for dead spots in the space?

what can be used to cover the dead spots?

Answer 21

using a SPL metering device or spectral analyser

there should be no more than 6dB pressure difference across the space

delay speakers and fill speakers are used

creates a more consistent sound for the whole audience

Question 22

what type of output can be used to send audio to delay speakers?

Answer 22

matrix outputs

Question 23

what type of output is used for delay and fill speakers?

Answer 23

matrix output

Question 24

give 3 differences between delay and fill speakers

Answer 24

primary function - delay provides consistent sound for the entire audience and fills fill in areas where the main speakers are not sufficient

placement - delays are placed all over the place and fills are typically at the front of the stage

delay - delay speakers have a delay but fills do not

Question 25

why would we roll off the low end of front fill speakers?

Answer 25

the PA mainly delivers the low end so it is not needed in the front fills usually

Question 26

describe the Haas effect or the Precedence effect

what is a common delay time used for this?

Answer 26

the technique on which a delayed signal is sent to speakers further from the stage at a value of ms such that when sound arrives from the front PA at that speaker, they are in time

creates the illusion or effect that the sound is coming from the stage when it is in fact coming from delay speakers

commonly 10-20 ms, 30-50 is a common echo effect and 60-250 is a slapback echo