sound reinforcement final

when looking at a VU meter on a professional mixing desk, 0 (zero) references:

+4dBU signal

resistance of 4 speakers with 8 ohms each in a parallel circuit

2 ohms

Band P.A.

Designed to reinforce small to large venuesEasily scalableBest for groups of 10-2,000 people

gain to feedback

Measure of how loud a microphone can be amplified before you get frequency emphasis problems

This amplifier type uses pulse wave modulation (PWM) to amplify signals.

Class D

It is common to have multiple engineers during highly complex shows to work as a team and manage the mix.

True

It is generally agreed that most humans cannot hear Total Harmonic Distortion below 0.5%

True

Power compression is caused by two things: 1) The heating up of a driver's voice coil which causes the impedance of the speaker to increase. 2) As speakers are pushed harder they near their mechanical limits and they become non-linear.

True

The Class A Amplifier is biased so that the transistors are always conducting electricity, even if there is no input signal present.

True

The state and settings of a mixer at any instant.

Scene

Personal P.A.

Smallest; can usually fit into a carRange of 10-20 ft.

The process of copying and saving the mixer's state ant any time.

Snapshot

inverse square law

a sound wave looses 6dB for every doubling of distance

in-ear monitors

adv: less stage volume, more coverage because the musician can take their mix with them, less chance of feedbackdis: some people don't like how they sound because it closes them off from the audience

drive rack

all equipment used to process the signal after the master output on the console1. console2. EQ3. Limiting4. crossover5. delay6. amps7. speakers

class A amplifiers

always letting signal through

Drivers with large surface areas...

are more efficient at reproducing lower frequency sounds.

fixed installation

church, theater, doesn't change, stays where it is

bridged amp mode

combining the two channels, add the power outputs together. you hook up the + of channel 1 on the amp to the + of the speaker, and the + of channel 2 on the amp to the - side of the side of the speaker

When a direct radiator driver's cone moves at different rates because it is not rigid entirely rigid, it will cause...

cone breakup

pizo electric driver speaker

contains a crystal

Horns are used in conjunction with direct radiator drivers to...

control the dispersion of the sound increase the driver's efficiency reduce the midrange spread of the driver.

purpose of a horn on a loudspeaker

controls the dispersion of the sound, amplifies the sound, and improves the driver's efficiency

compressor can be used

individual channels on console

An input port...

is the physical XLR, 1/4 inch, fiber optic, or other connection into the console must be bound or patched to another input.

advantages of putting subs together in the middle rather than from both sides

less phase issues, not as many "hot spots and "low spots

limiter vs compressor

limiting has a certain level that nothing will go past, compression is not a certain level, it's relational to how loud the input sound is

parallel vs series speaker setup

literally just like in physics just know that

side chain input

lso called key input, uses signal from one channel to activate the input on another channelex. if you put compressor on bass and trigger it by the kick drum, or putting compressor on guitars triggered by singing so it's

squelch

mutes the wireless receiver when the signal is not present

ideal positioning for front of house mix

no further than 2x the distance between your main PA left and right speakers, and slightly off-center to avoid the power alley

advantages of stereo input channel vs reverb return chaneel

on the effects return there is no EQ and you can only send it to mon 1 and 2. if you bring it in on a stereo channel, you have EQ and you can route it wherever you want: mon, aux, effects, main... you can send it through multiple effects

distributed PA system

sends to multiple rooms, like in walmart

One way to get make it easy to hear vocals in a mix is to...

slightly boost frequencies around 2-9kHz remove frequencies from other instruments around the critical band.

compression driver speaker

small moving coil placed inside a rigid shell connected to a horn, basically small version of direct radiator with a driver inside

if 4 ohms is the resistance at 1,000 watts how many watts do you get on 4 4 ohm speakers

the total resistance is 16 so 1000/4 so 250

A speaker's polar plot will typically show..

the vertical and horizontal dispersion of a speaker.

The Amplifier's output wattage should be twice as high as the power handling capability of the loudspeaker.

true

coaxial driver

two drivers in one, overlapped on top of each other. both the woofer and tweeter share same center point, speaker's polar response is symmetrical, crossover distortion is hidden, all of the coaxial drivers need a built-in crossover

direct current (DC) burn

type of speaker failure caused by overdriving your speaker driver into clipping, indicated by voice coil... something (look it up)

sealed speaker enclosure

uses trapped air that acts like a spring to maintain equal pressure on the driverAccurate Sound, Good Transient

passive crossover

when the speaker has a crossover built-in. if it only has one input on the back that's not an NL4 but has a horn and a woofer, then it has a passive crossover

active crossover

when you have to have a crossover unit in your drive rack and can determine where the signal goes yourself

Dampening factor is only an issue for...

your low frequency audio content.

side fills

full range speaker that shoots from the sides of the stage towards the center to fill in large

balanced cable

has 3 contacts, hot cold and ground ex: XLR or Tip-ring-sleeve 1/4 inch

NL4 cables

has 4 contacts within the connector, used for a bi-amplified speaker connection... one stereo channel is going to tweeter and one is going to woofer

ported speaker enclosure

has a hole in it that's tuned to a certain resonant toneDeeper Bass Tone, Bad Transient

bass reflex loudspeaker

has a tuned bass port and a resonator

bass reflex speaker enclosure

has another cone on the back that is basically another diaphragm that is tuned to a certain resonant tone and operates with the other one to equalize the pressure

3-way system

subs mids and highs

What are the different types of distortion in a sound system?

1. Overdriven sound 2. Harmonic Distortions 3. Intermodulation

osha dB level requirements

110 dB SPL A-weighted = 30 minutes

how far apart should wireless frequencies be?

1MHz, unless it's assigned automatically for you

VHF frequency range

30MHz to 300MHz

illegal frequency bands

700-799 MHz

Air is trapped inside of the enclosure that allows for a buildup of pressure behind the driver. This trapped air acts like a spring to return the driver's cone to it's original resting state.

Acoustic Suspension

Data that is generated die to sending the audio through sending the signal from the ADC to a routing module.

Audio Stream Data

Which of the following are considered the foundations of the mix? (Mark all that apply)

Bass Drums Leadvox

Which of the following is not a Digital audio format?

CAT5e/CAT6

Portable P.A.

Can be taken from one location to another

Data that is generated as a result of the user setting a parameter.

Control Data

The transitional boundary between the direct and reverberant audio field in a room is called the...

Critical Distance

_____ allows us to take any analog input and route it to any digital input port.

DIR

This is a baffle that allows sound waves to exit from both sides of the driver to reproduce the final sound.

Dipole speaker system

A ____ radiates it sound directly into the air with out the assistance of a horn, chamber, or duct.

Direct Radiator Driver

Most digital consoles offer which of the following options?

EQ Busing DCA's Internal effects Matrix Sends

Tour/Stadium P.A.

Extreme end of PA systemsRequires small army of people & trucksUse same components - just more & bigger versionsNeeds more set up time & knowledge

A disadvantage to digital mixers is that they share multiple I/O (Analog to digital converter) boxes.

False

Direct radiator drivers are highly efficient at transmitting sound, they can be up to 80% efficient.

False

A ______ protects users from electrocuting themselves by constantly monitoring the current flow through itself.

GFCI circuit

When considering an Amplifier's signal to noise ratio, an engineer must take note of the weighting system used to measure the noise. If a ______ is used, the midrange frequency content will be emphasized more than any other weighting system.

ITU-R-468

__________allows for the sharing of physical controls across multiple functions on the console.

Layering,or Fader layering, Pages, or Fader Pages

Why should an engineer mute channels when they are unused?

Muting prevents spill and possible feedback.

This enclosure has an opening to the outside that functions as a Helmholtz resonator.

Ported enclosure

crest factor

Ratio between the peaks and average signal level

____ is the specification that will tell about the efficiency of a speaker.

Sensitivity

____ is the art of removing or boosting frequencies of each instrument to give it it's own space and separation.

Spectral Mixing

class D amplifiers

Switching techniques=higher efficiency, waste no power

What happens if you exceed the maximum output voltage of a power amplifier?

The output signal will clip.

headroom

The system's ability to do the work you want it to do, the space between the crest factor and the point of distortion, determined by equipment you're using

In a digital mixer no audio physically runs through any control device on the control surface.

True

A high dampening factor means my amplifier will have more control over stopping and reversing the movement of my speaker's driver.

True

An active speaker system will have an amplifier, crossover, and protection built into it.

True

power alley

a buildup of frequencies because of where speakers are setup, usually right down the middle

UHF freq range

above 300MHz

When I am operating my amplifier in stereo mode...

both channels of the amplifier operate independently.

(Chose all that apply) When operating an amplifier in bridge mode...

both channels of the amplifier operate together to double the output voltage. you will hook up the + terminal of channel 1 and the + terminal of channel 2 to your speaker

class A/B amplifiers

can operate in class A mode or class B mode B= turn on and off with the presence of signalA = always letting signal through

how to calculate speaker delay settings

distance divided by speed of sound (1140 ft/sec), then move the decimal 3 spaces to the right.guessing would be around 1ms per foot

When "Daisy Chaining" speakers together you are actually hooking up the speakers...

in a parallel wiring setup.

limiter can be used

in drive rack so you don't clip and damage the speakers

critical distance

point where the direct source and the reverberation is at equal amplitude

purpose of limiting the drive line

protects speakers from damage

static vs. dynamic mixing

static is where you put all of your faders set for the show and leave it where it is, dynamic is where you ride the faders during the show

2-way system

subs and highs

A class B amplifier will more than likely never be used in live sound because...

the amplifier creates a crossover distortion.

power output

the power an amplifier can produce into a stated impedance load

complex crossover

using both an active and passive crossover

harmonic distortion

when 2 related frequencies combine to create a new frequency that's not part of the original audio