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