Audio Engineering Principles - By Moses

Audio Engineering Principles


1) dbu vs dbSPL

2) Crossover Points

3) Variable Gain Amplifiers (V.G.A’s)

4) Equalization Sections

5) Band-Pass Filters

6) Monitors

7) Microphones and Mic Polar Patterns

8) Compressors and Limiters

9) Gates and Expanders

10) Reverb, Delay, and the Haas Zone (the Precedence
Effect)




1. dbu vs dbSPL

To double your dbu simply raise 3 dbu (+3dbu).
To double your dbSPL you raise 6 dbSPL (+6dbSPL).
dbu is doubled (+3dbu) with each wall/floor/ceiling.
dbSPL is doubled (+6dbSPL) with each wall/floor/ceiling.
dbu refers to the mixers output from the mains (Left and Right) to the multi-track (recording device). Most analog mixers max-out at +6dbu (the good ones max-out at +10dbu). On digital mixers you automatically max-out at 0 dbu.
DbSPL refers to the amplitude of the sound that comes out of the monitors (the speakers). Sound at outdoor concerts and arena concerts usually measure in the 100-120 DbSPL range.


2. Crossover Points

A speaker cabinet with one crossover point is a two-way.
A speaker with two crossover points is a three-way.
A crossover point sends the frequencies above that point (or frequency) to one section of the speaker and frequencies below that point to another section of the speaker cabinet, before amplification.


3. Variable Gain Amplifiers (V.G.A’s)

i) Saw-Tooth Wave – Gives a saw-tooth pattern to the frequencies and amplifies them.

ii) Triangle Wave – Gives a triangular pattern to the frequencies and amplifies them.

iii) Square Wave– Gives a square-pattern to the frequencies and amplifies them.

iv) Exciters – Are a glorified V.G.A. Boosts certain high-end harmonics.

v) Flanging, Phasing, Chorusing and Delay are the results of a V.G.A device.


4. Equalization Sections

Parametric Equalization – Carries three qualities:

i) Frequency (set frequency measured by Hz).

ii) ‘Q’ or Slope (the angle within which a cut or boost is made)

ii) Amplification (how severe a boost or cut).


Graphic Equalization – Carries two qualities:

i) A certain number of set frequencies (A 30 Band Graphic E.Q strip has 30 set frequencies – which are measured in Hz).

ii) The dbu (amplification level).


5. Band-Pass Filters (Guard-bands)

i) High Pass Filters – Allows high frequencies to pass above a certain frequency and cuts those frequencies below that frequency/likewise Amplitude Levels.

ii) Low-Pass Filters – Allows low frequencies to pass below a certain frequency and cuts those frequencies above it/likewise Amplitude Levels.

iii) Filter Designs: 1) Chebeshev, 2) Bessel, 3) Butterworth, 4) Gaussian

iv) Main Supplier: Gemen


6. Monitors

Nearfield – Small monitors used in most control rooms of recording studios (usually NS10’s or Alesis). Gages the mix with high frequency bias.

Midfield – Mid-sized monitors used in many live shows at the Bar/Pub. Has a bigger base drum in the speaker than a nearfield. Typically used as mains in the control room to complement NS10’s (usually Tannoy or J.B.L).

Farfield – Carries the best fidelity of the three. It’s the largest speaker cabinet. Used for outdoor concerts and arena concerts as well. Usually carries a bass drum of a minimum 18’’ and has two crossover points (minimum).

Lesley Cabinet Speaker – A Farfield monitor that plays from a cabinet speaker that goes around and a-around. Is reminiscent of a vinyl player (a phonograph).


7. Microphones and Microphone Polar Patterns

Microphones

i) Dynamic Microphones – Direct current from the mic into the mic panel (mic in). This enables the mic to the mic-pre-amp for setting the mic level in the channel. Well known dynamic mics include Shure 57’s and 58’s.

ii) Condenser Microphones – Condenser microphones connect to the mic panel (mic in). At the start of the I/O Module you must give Phantom Power to prompt a response from a condenser microphone. You then use the mic-pre-amp to set the level for the channel. Known condenser mic’s include Neumann U87 and U47, AKG 414 and Silver Pencils (made by Sennheiser).


Microphone Polar Patterns

i) Uni-Directional – Mic takes in from only one direction on the mic.

ii) Bi-Directional – Mic takes in sound from two directions on the mic, usually at opposite sides.

iii) Omni-Directional – Mic takes in sound all around the diameter of the mic.

iv) Cardioid – Heart shaped diameter that is sensitive to the sounds penetrating in the cavity.

v) Hyper-Cardioid – Instead of being a heart shape there is an oblong piece placed inside a cardiod shape (heart shape – inside the cavity).


8. Compressors and Limiters (Guard-bands)

Compressors take in a certain amplitude (measured in dbu or dbSPL) and outputs at a lower amplitude by ratio.
For example – A 1:1 ratio means that for every 1 db in there is 1 db out.
A 2:1 ratio means that for every 2db-in there is 1db-out.
A 4:1 ratio means that for every 4db-in there is 1db-out.
A limiter is essentially a severe compressor. In other words, it will cut the signal if the amplitude is too loud.


9. Gates and Expanders (Guard-bands)

A gate allows the microphone to be on only above a certain amplitude. For example; If the gate is set at 60dbSPL that means that the microphone won’t be transmitting any signal below 60dbSPL but will transmit any signal 60dbSPL and up.
An expander will take a certain amplitude in and output it at the same or greater level. It works the opposite as a compressor.
A 1:1 ratio means that for every 1dbu-in there is 1dbu-out.
A 1:2 ratio means that for every 1dbu-in there are 2dbu-out.
A 1:4 ratio means that for every 1dbu-in there are 4dbu-out.


10. Reverb, Delay, and the Haas Zone (Precedence Effect)

i) Reverb – When the channel’s ‘spacial’ intonations are changed. We’re looking at a very subtle change that effects where the music seems to be playing in (whether that be in a cathedral, arena, or amphitheater.

ii) Delay – Echo, which is the result of a sound repeating itself.

iii) The Haas Zone (Precedence Effect) – Known to be a subtle delay (anywhere between 5ms – 35ms). In this delay period the sound is played through the one side monitor anywhere between 5ms-35ms after the first side played. This emphasizes the first sound and makes it seem to appear to be the louder of the two sounds, when in actual fact both sounds were at the same level. This is known as ‘precedence effect’.

Camps - By Moses

By nature, a Summer Camp encompasses children of many denominations, and is governed by commitee. For example, in Canada, most Summer Camps are multi-cultural and have these principles in place. However, as recent as 30 years ago in Ontario, Canada most Summer Camps segregated their 'Black' population from going to Summer Camps north of Toronto. It was also known that to be Jewish, was not acceptable in some Summer Camps in Ontario. During and around this time began the inception of Northlands and B'nai Brith Summer Camps (exclusively Jewish clientele). Since we're in 2010 we seem to have turned the corner in societal predudices, and therefore have no need for segregated Summer Camps. Keep in mind that once the snowball effect takes shape, we'll have segregated Christian, Muslim, Jewish, Hindu, Buddhist, and 'Black' Summer Camps (Christian summer camps started the ball rolling). With tensions arising from the anniversary of the 9/11 attacks, can we really afford to feed the frenzy of gentrification among these race issues?
In Israel, the concept behind Kibbutziim is to promote multi-culturalism within a Jewish State. While there may be 500 full-time residents on a Kibbutz, each Kibbutz (similar to a Farm/Camp - with families living amongst the confines) draws volunteers from around the World. This is to show equality towards all Nations.
A Summer Camp in Southern, Ontario, Canada is inherently different than a Kibbutz in the Negev, Israel, as the populous has different multi-cultural elements. However, the sentiments are exactly the same. To show equality towards each denomination is essentially to show equality to each Nation. We may see different ergonomics pertaining to the immigration of Canada and Israel. It is paramount though to not disciminate with respect to the people within your Nation. For example within Southern Ontario there are large Chinese and Black populations. To discriminate these people from a summer camp is ludacris and obtuse. The same argument would hold true of a Kibbutz in Israel. Discriminating against taking in volunteers from Sweden, or Japan for that matter would cause an uproar. We should be moving towards Worldwide passports in todays' age. It would stand to reason that in ten years time to be Lebanese-Israeli or Lebanese-Palestinian will occur, breaking down the barriers of a gentrified Nation and further promoting equality towards all Nations. What do we tell the children when they ask, is that person of Arabic descent my equal?

Disable This! Newsletter 3 - by Moses and Farhan Aboubaker

This newsletter is being written to promote Farhan's website (which will be up and running in the next month. The name is 'Almuawak', which means cripple in arabic). It is a statement of equal rights for the 'disabled'. The goal is to break down the sterotype that people with 'disabilities' face.

We are looking for people who want to network amongst the 'disabled', not for political gain. Stories of 'disabled' struggles are welcome, and we're trying to promote gainful employment for people with physical limitations. In other words we're trying to create positions for those that have been shunned in the past.
It is imperative that there are on-going discussions relating to these topics, and we are in the process of conducting a documentary of 'disable this!'. This website will also focus on civil liberties issues (like that of the after effects of the G-20 summit in which many were imprisoned). We would like to hold institutions accountable for their conduct amongst their clientele (whether that be a Chartered Bank, the police force, or Government services like Wheel-Trans).
People that join the website should be pro-active in being a member. One such way is to use the site to advertise their business or credentials. Farhan's T-shirts and Hoodies are one way for Farhan to express a sentiment of equal rights through being an entrepeneur. His business is in place to make a statement that the physically 'disabled' should no longer be sidestepped as a drain on the system, rather people with disadvantages that should still succeed through career choice.
It is important to empower the 'disabled' towards EQUAL RIGHTS as the Canadian Charter of Rights should be kept for ALL Canadians (no preferential treatment for the 'able bodied' majority).

To the Viewer - By Moses

The articles I'd written on Affirmative action (in placing high ranking African-Americans into Ownership positions) was for the purpose of creating an even playing field. As one viewer commented to me, there were some statistical innacuracies. Of roughly 200 statistics, 15 were slightly off. Please, by all means enjoy these articles once again knowing that there are ZERO innacuracies, as they've been revised.

Yours Truly,

Moses (a.k.a Stacey Marc)