Download April 23, 2009 - St. Joseph Music Foundation

AS APPLIED TO ELECTRONIC MUSICAL
PRODUCTION AND PERFORMANCE
Part One – Basic training
JIM DuBARR – INSTRUCTOR
MICHAEL FUSON – COURSE CONSULTANT
CREATED BY JIM DuBARR ENTERTAINMENT. ALL RIGHTS RESERVED. USE OF ALL MATERIALS CONTAINED HERIN IS
AUTHOIZED TO ALL MEMBERS OF THE SAINT JOSEPH MUSIC FOUNDATION FOR PURPOSES OF EDUCATION ONLY.










DEFINITIONS
OHMS LAW
SOLVING EQUATIONS USING OHMS LAW
WHAT IS FREQUENCY
MORE ABOUT FREQUENCY
THE FREQUENCY SPECTRUM
SPEAKER CONSTRUCTION
FREQUENCY AND SPEAKERS
CROSSOVERS
EQUALIZERS
 IMPEDANCE
 IMPEDANCE MATCHING
 SERIES AND PARALLEL CONNECTIONS
 POWER HANDLING CAPABILITIES
 RMS vs. PEAK WATTAGE
 TOTAL HARMONIC DISTORTION
 READING SIMPLE SPECIFICATION SHEETS
(Specs)
 CURRENT
 RESISTANCE
The flow of electrons
within an electronic
circuit.
Opposition to the flow of
electrons in an electronic
circuit.
Measured in Amperes
Measured in Ohms
Electronic symbol – I
Electronic symbol – R
Also known as amps.
Also represented by
Omega
 VOLTAGE
 POWER
The potential, or pushing
power, of electricity
available to a circuit.
The measure of the ability
of an electronic circuit to
accomplish a task.
Measured in Volts
Measured in Watts
Electronic symbol – E
Electronic symbol – P
Also symbolized as V
Also symbolized as W
 CURRENT – AMPS - I
 VOLTAGE – VOLTS - E
 RESISTANCE – OHMS - R
E
 POWER – WATTS - W
I
R
With any two variables, the third may be found by using
the following simple formulas;
E (Voltage) = I (Current) x R (Resistance)
I (Current) = E (Voltage)
R (Resistance)
R (Resistance) = E (Voltage)
I (Current)
Frequency is the essence of Sound
Frequency is defined as the time between the reoccurrence of
the same event
Sound waves create pressure waves in the air that vibrate the
ear drum, causing us to “hear”. These sound waves are
sinuodal, or modulate from zero to a positive level, then to
an equal negative level, then back to zero again. The
period of time it takes for this cycle to occur is called the
“frequency”. In electronics, this is measured by what is
called a “sine wave”, which resembles a sideways “S”.
Frequency is measured in units called Hertz, abbreviated
as Hz, also called Cycles per Second.
LOW FREQUENCY
Low frequency sound
waves are long, and
repeat less frequently.
Low frequency sounds ,
like that of a bass, vibrate
the ear drum less often,
so we hear low sounds.
HIGH FREQUENCY
High frequency sound
waves are short, and
repeat more often. High
frequency sounds, such
as lead guitar, vibrate the
ear drums more often, so
we hear a higher sound.
 Low Frequencies
20 Hz to 250 Hz
 Midrange Frequencies
250 Hz to 2 kHz (2000 Hz)
 High Frequencies
Above 2 kHz to extent of hearing capabilities.
PLACEHOLDER FOR PICTURE OF SPEAKER
Low Frequency
 Larger magnets and coils are
necessary to produce low
frequencies.
 More power is necessary to
energize these large coils,
which are actually resistors by
nature.
 Power is measured in watts,
low frequency speakers
require more wattage to
produce sound.
High Frequency
 Smaller magnets and coils are
needed to produce high
frequency sound waves.
 Less power is needed to
energize the smaller coils of
these speakers, consequently
there is less resistance in this
circuit.
 Less wattage is necessary to
power these speakers, a
smaller Power amp can be
used.
 Crossovers are adjustable frequency dividers which allow
selected frequencies to pass, or be blocked from passing, to
speakers.
 In simple terms, crossovers provide a means of allowing
only lower frequencies access to larger bass speakers while
blocking higher frequencies. At the same time they allow
only higher frequencies to pass through to the smaller
speakers and horns, while blocking the lower frequencies,
which could damage the smaller speakers.
 Crossovers can be two way, or three way which additionally
allows control over frequency distribution to Midrange
speakers .
 Equalizers allow the user to control the volume of
individual frequencies distributed to speakers.
 Equalizers allow for fine tuning of the force of sound
waves produced by the speaker for each of the
adjustable frequency ranges by providing resistance to
the chosen frequency being adjusted.
 Using Ohms Law, we can see that more resistance
means less voltage.
 Understanding speaker construction, the speaker will
vibrate less, producing less powerful sound waves in
the adjusted frequency range.
Typical 32 Band Equalizer
Two-Way Crossover
Please take this time to jot down any questions you may have.
This presentation will be available online through the Foundation’s website. A
comprehensive five part course is available through the Foundation as well. There
is no cost for these services, however donations to the Foundation will be
accepted. Questions (and possibly tutoring) can be addressed to the following
links after tonight’s presentation. Thank you for attending!
Jim DuBarr – [email protected]
Mike Fuson – [email protected]
Impedance is simply the combined resistance of all
components of any given circuit.
Since it is resistance, it is measured in ohms.
Multiple speaker enclosures usually contain an internal
crossover to separate frequencies between the different size
speakers in the cabinet.
The resistance of this crossover, combined with the resistance
of the speakers themselves, represents the impedance.
 To insure proper operation of speakers and power
amplifiers, it is important to match the impedance of the
speakers to the output of the power amplifier used.
 Failure to insure proper impedance matching may damage
speakers and power amplifiers, and at a minimum will
shorten the useful life of the items.
 Most matching can be done easily by either choosing the
corresponding output on the power amplifier, or in some
cases setting a control on the power amplifier for the
correct output impedance. Many power amplifiers match
impedance automatically through sensing circuits.
 Most speaker enclosures are 4, 8 or 16 ohm impedance.
 How you connect multiple speakers together can have
an effect on total impedance of the circuit.
 SERIES – one cable connects the power amplifier to
the first speakers input. The second speaker is
connected from the first speakers output to the input
of the second speaker. In this scenario, if the first
speaker’s impedance is 4 ohms, and the second is 4
ohms, the total impedance of the circuit is 8 ohms.
 PARALLEL – separate cables connect each speaker to a
separate output of the power amplifier. Each speaker
maintains it’s own impedance rating.
Because there are no universally accepted standards, most professional loudspeaker
manufacturers use different test methods to arrive at a power handling specification.
 This rating does not necessarily correspond to the best amplifier size to use nor is it a
measure of the "safe" amplifier size to use under actual operating conditions.
 There are three separate and very distinct issues regarding selecting amplifier power for
loudspeakers.

1.
2.
3.
LOUDSPEAKER POWER HANDLING RATING
SELECTING AN APPROPRIATE AMPLIFIER SIZE
PREVENTING LOUDSPEAKER DAMAGE

If an audio system is operated improperly, damage to or failure of a loudspeaker can occur
even with an amplifier sized well below the loudspeaker’s power rating.

Contrarily, if an audio system is operated properly, damage to or failure of a loudspeaker
can be avoided even with an amplifier sized well in excess of the loudspeaker’s
continuous (or RMS, average, etc.) power rating.
 RMS, or Root Mean Standard, describes the point in a
signal, or frequency when distortion begins to occur.
 This can be heard by turning a radio up to full volume and
listening. Once the volume is decreased, you hear less
unnatural noise other than the sound itself.
 RMS is 70.7% of the peak Wattage.
 Example: 100 watts peak=70.7 watts RMS. Above 70.7
watts, distortion will increase proportionally to the
maximum allowed by the design of the circuit. Simply put,
a volume knob incremented 1-10 will begin to produce
distortion of the signal when turned to 8 or above.
 Music is made up of both Fundamental and Harmonic
Frequencies.
 A note produced by a musical instrument, A for example, is
producing a fundamental frequency of 440Hz or cycles per
second. It is also reproducing harmonics of that frequency that
are multiples of the fundamental frequency, such as 880Hz,
1220Hz, 1760Hz and so on.
 Each of the harmonic frequencies is lower in level or volume
than the fundamental, but they serve to give each instrument its
unique sound.
 When the total harmonic distortion of an amplifier is measured,
the difference in the level of the harmonics at the output stage of
the amp is compared to the level of the harmonics at the input
stage, and the difference is the extent of the distortion.
Behringer B212XL

SYSTEM DATA

High-performance woofer

B212XL: 12" (305 mm)


B215XL: 15" (381 mm)


Tweeter compression driver

B212XL and B215XL: 1.75" (44 mm)


Frequency range


B212XL: 65 Hz to 18 kHz

B215XL: 55 Hz to 20 kHz


Power rating


B212XL: 800 W Peak Power


200 W Continuous Power

(IEC 60268-5)


B215XL: 1000 W Peak Power


250 W Continuous Power

(IEC 60268-5)


Impedance


B212XL and B215XL: 8 Ω


Sensitivity (1 W @ 1 m)

B212XL: 95 dB (Full Space)


B215XL: 96 dB (Full Space)


Dispersion
B212XL: 90° x 60°
B215XL: 70° x 40°
Crossover frequency
B212XL: 1.9 kHz
B215XL: 2.0 kHz
DIMENSIONS/WEIGHT
Dimensions (HxWxD)
B212XL: approx. 21 2⁄3" x 13 5⁄8" x 10 5⁄8"
(approx. 550 mm x 345 mm x 270 mm)
B215XL: approx. 27 1⁄3" x 17 1⁄3" x 13 1⁄16"
(approx. 695 mm x 440 mm x 335 mm)
Weight
B212XL: 24.0 lb / 10.9 kg
B215XL: 38.7 lb / 17.6 kg
THANK YOU FOR ATTENDING TONIGHTS
PRESENTATION
2009 – Jim DuBarr Entertainment – All Rights Reserved – Unauthorized Duplication is Prohibited