AS APPLIED TO ELECTRONIC MUSICAL

PRODUCTION AND PERFORMANCE

Part One – Basic training

JIM DuBARR – INSTRUCTORMICHAEL 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.

DEFINITIONSOHMS LAWSOLVING EQUATIONS USING OHMS

LAWWHAT IS FREQUENCYMORE ABOUT FREQUENCYTHE FREQUENCY SPECTRUMSPEAKER CONSTRUCTIONFREQUENCY AND SPEAKERSCROSSOVERSEQUALIZERS

IMPEDANCEIMPEDANCE MATCHINGSERIES AND PARALLEL

CONNECTIONSPOWER HANDLING CAPABILITIESRMS vs. PEAK WATTAGETOTAL HARMONIC DISTORTIONREADING SIMPLE SPECIFICATION

SHEETS (Specs)

CURRENTThe flow of electrons

within an electronic circuit.

Measured in Amperes

Electronic symbol – I

Also known as amps.

RESISTANCEOpposition to the flow

of electrons in an electronic circuit.

Measured in Ohms

Electronic symbol – R

Also represented by Omega

VOLTAGEThe potential, or

pushing power, of electricity available to a circuit.

Measured in Volts

Electronic symbol – E

Also symbolized as V

POWERThe measure of the

ability of an electronic circuit to accomplish a task.

Measured in Watts

Electronic symbol – P

Also symbolized as W

CURRENT – AMPS - IVOLTAGE – VOLTS -

ERESISTANCE –

OHMS - RPOWER – WATTS - W

E

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 Frequencies20 Hz to 250 Hz

Midrange Frequencies250 Hz to 2 kHz (2000 Hz)

High FrequenciesAbove 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 – jimdubarr@stjoelive.comMike Fuson – mikefusn@swbell.net

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. LOUDSPEAKER POWER HANDLING RATING2. SELECTING AN APPROPRIATE AMPLIFIER SIZE3. 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.

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