audio engineering 1 lab 5 eqs in signal...

Audio Engineering 1 Lab 5 EQs in Signal Processing Subtract Hz to fix a problem

Add Hz to cover up / hide a problem

Bradford Cox – Audio Engineering 1, Collin County College Page # 1 AE1_Lab05c_EQs.docx

Objective: By the end of this lab you will be able to hide, display and call up any EQ and to deduce how to use it to your advantage. To be able do duplicate EQs to other Insert positions. Loading and Saving your EQ settings.

Open the AE1_Lab5_EQ project. It is just Kick, Snare, High Hat, Bass & Piano. You can use any project you like, but this lab will refer specifically to that session.

In not knowing how the previous session was saved we need to verify that certain things are being shown in this session. Go to the mixer (CMD + =) to toggle Mix/Edit windows.

In the Edit Window the View Selector is located just above the tracks. In the Mix Window it is located in the lower left corner of the Mix window as shown below. The Edit window and Mix window have this option.

Mix window

Edit window

When you click on it this pops up Click on the View selector and click on the ALL option. You will see the screen fill up with all sorts of data. We only need Inserts A-E, Sends A-E & I/O. You could go through this same process of clicking in the view selector and un-checking various components, but there is a faster way. Go to the Mixer +/or Editor and OPT + Click on the name header of the ones you want to no longer display.

This also works for the different time rulers. Just OPT + Click on the ones you want to get rid of. The timeline ruler allows you to add components you want just like the Window View selector. Play around with these displays and see what is available. Eventually we only want Inserts A-E, Sends A-E & I/O. Everything else off.

What is an EQ?

EQ stands for equalization. It is the tool that an engineer uses to add or remove frequencies in a given instrument or sound effect. There are Graphic EQs that are a bunch of faders, similar to a mixing console, that will boost or cut specific frequencies and ONLY those frequencies. These are very common in car stereos for the consumer market. In the professional market they graphic EQs are used to compensate for the anomalies in a given room or space so that the room sounds as close to a flat response as possible or any other accentuation desired by the people who own the room. A typical multiband graphic EQ would be one from the Rane Corporation like this model 60S




Rane Model 60S - http://www.rane.com/jpg/me60sfp.jpg

More typically what you will come across is called a parametric equalizer. Parametric means we can adjust ALL parameters in any way we see fit. What is a parameter? It is a knob, switch or button that does only what we tell it to do. We set this value and that value and we can enable or disable its function. An example of a parameter would be a light switch on a dimmer. We can choose to use or not to use that light. Then when we do choose to use that light we tell the light how bright to be or not to be. In a parametric equalizer we can set the kind of influence, the amount of influence, the broadness or narrowness of the influence and where the influence is to take place. In Pro Tools we can even automate the parameters; meaning that we can have them change over time to better fit our needs.

It is important to understand the basics of an EQ and what all the different things do in an EQ. There are several key terms you have to be familiar with in order to grasp what an EQ is going to do for or TO you.

Envelope = The kind of influence or change to be done. There are several envelope types in an EQ and they all do something differently. You must be able to recognize them by picture and describe what they actually do, for two reasons – 1) Audio Engineers look incompetent if they don’t. 2) It is on the test. In general there are three types if EQs; Filters, Shelves and Notch (band pass). Lets talk about each. Did I mention these will definitely be a test?

Filter / EQ type – What it really does EQ Curve (icon/graphic) HPF = High Pass Filter. Its function is a Low Cut Filter. All frequencies at a dialed in Hz and below will be removed. LPF = Low Pass Filter. Its function is as a High Cut Filter. All frequencies at the dialed in Hz and above will be removed.

High Shelf – Gain (Boost or Cut) Highs and do nothing to the lows. All frequencies at the dialed in Hz and above will be modified where all frequencies at the dialed in Hz and below will have no change.

OR

Low Shelf – Gain (Boost or Cut) Lows and do nothing to the highs. All frequencies at the dialed in Hz and below will be modified where all frequencies at the dialed in Hz and above will have no change.

OR

Band Pass or Notch (sometimes called parametric) - Boost or Cut any frequencies. The frequencies at the dialed in Hz will be affected and nothing happens to the other frequencies. OR




There is a knob called the “Q” also known as the bandwidth. The Q’s function, basically speaking, is to say how many other frequencies are going to be affected by the other values you dialed in. The Q’s range of influence is measured in dB per octave. Qs of higher values are more steep, used for lopping off frequencies or notching out a specific problem. Qs of smaller numbers are more slope like and sound more natural to the human ear. Start with a Q setting of 1.0 (1 1/3 octaves). This setting covers about the frequency range of an instrument. For more percussive instruments a narrower (higher Q number) Q is more common. For more melodic instruments a broader (lower Q number) would be used. This chart that gives ballpark influences of the Q / Bandwidth.

The “Knee” is the transition point of the filters where the EQ starts or ends it’s effect on the sound. For an example, an HPF (High Pass Filter - which really means it is a low cut filter - we have to tell the EQ what frequencies to get rid of. It could be 100Hz it could be 1000Hz. A true parametric equalizer will let you type in any number within the frequency range of human hearing you want. The value of that frequency starts the knee point. The Q says how abruptly the frequencies below the knee are lopped off or said another way – do the frequencies disappear immediately (sharp knee) or do the gradually disappear (sloped knee)

The goal of a good EQ setting is to enhance the natural properties of the instrument. Though, EQs can be used for special effects like in Green Day’s “American Idiot” there is a special EQ setting on the voice to make it sound like a megaphone, cell phone or some other processing.

In film and TV EQs can be used to make recordings of one day sound like the recordings of a different day. Sometimes those days can be months apart. Sometimes the recording was on location and the new recording is in a climate-controlled studio. These are totally different atmospheres.

Earlier in the semester you were given several frequency charts. One chart is laid out in such a way that if someone listens to your mix they may say something like “That sounds to boxy to me”. A phrase like that is fine, but what does that mean? If you look at that chart you can find the word boxy. You will see that generally speaking, people who describe a sound as being boxy it is an indication that the frequencies between 500Hz and 5kHz are too loud. To remove the boxy sound you would use a bell curve set to about 3k with a small Q and dial the gain down. Maybe 3dB maybe 9dB, whatever makes the fix happen. You may have to sweep to slightly higher or lower frequencies, depending on the problem. Remember, these are guidelines. Nothing is set in stone. This is an art form and your taste is what makes you valuable. Modern Recording Techniques, 7th Edition, Page 485 has a chart of typical equalization guidelines in that if you want to increase or decrease body, fullness, sibilance and so on modify the gain of “these” frequencies.

The EQ: To the right is a picture of the Pro Tools free EQ called EQ3-7Band. The term “band” means there are seven incidences or modification points where one can manipulate the tonal characteristics of a sound. A three band would give you three incidences or modification points to manipulate the tonal characteristics of a sound.

Q Setting Bandwidth 0.7 2 Octaves 1.0 1 1/3 Octaves 1.4 1 Octave 2.8 1/2 Octave




Meters – display the strength of the signal coming in and the signal going out.

Gain – Input & Output = You can boost or cut how much signal is going to or coming from the EQ. 0dB = Unity Gain

HPF & LPF – have two settings, either a notch that only cuts or a filter. Dial in the frequencies you want to eliminate and the range of influence (Q). The grayed out “IN” button means active or inactive, when the “IN” is blue, the filter is active as in the red LF section.

Notice that this next section has five different colors, labeled differently. The knobs all do the same thing, the difference is WHERE they do their thing. LF = Low Frequencies, LMF = Low Mid Frequencies, MF = Mid Frequencies, HMF = High Mid Frequencies, HF = High Frequencies.

The bottom section is somewhat of a parametric equalizer in that you can dial in the frequency you want to manipulate but only within that sections frequency range. In a true parametric equalizer any knob can be set to any value. Since these knobs have a fixed range of influence this kind of an EQ is called Semi-parametric. Q says how many OTHER frequencies will be affected. FREQ lets you dial in which frequency you want to manipulate. Gain lets you boost or cut that frequency. The IN is a button that turns on or off that portion of the EQ. In the LMF (orange) area, click the IN to turn it on, set the gain to be 18dB and the Q to be 1. Now set the HMF (green) gain to be -18dB, and click the IN so that it is blue. Look at the curve. This is telling you that the Low Mids will be increased by a certain gain and the High Mids will be reduced by a certain gain. This graphic representation of the modification is sometimes helpful in learning what an EQ is doing to your audio.

How can you learn what different frequencies sound like? Good thing to know? Absolutely, it is critical to know what instruments play in what ranges and to know what makes any particular instrument warmer or brighter.

A very good way is to develop relative pitch. Sit at a piano and sing your lowest note, whatever it is, doesn’t matter, just the lowest note you can produce. Match that note on the piano in the correct octave. Refer to the chart below or at the link below and learn what the frequency of that note is.

Repeat this for the highest note you can sing, comfortably. You now know what your frequency range is and you have the numbers for those extremes. If you are musically inclined you can deduce all notes based on how far away it is from your lowest frequency or highest frequency.

I have even seen people train their ears by getting a pitch pipe, blowing a note, saying and singing that note over and over again until they can sing the note then blow the pitch pipe and it matches exactly.

http://www.independentrecording.net/irn/resources/freqchart/main_display.htm is an interactive frequency chart. Drag your mouse over the instrument and the data appears on the right side of the chart.

Another way to learn pitch is to put the signal generator (Pull down menu Audio Suite>Other>Signal Generator) and it starts playing a sine wave at 1000 Hz. You can make the Hz any number you want, between 20Hz and 20kHz. See if you can match the pitch. Learn how your throat adjusts to various pitches. When you get to the stage of being able to mix or engineer at the speed of creativity you will use your voice to deduce various pitches for notching stuff out, or bring up missing frequencies.




Below is a frequency chart of all 128 MIDI notes. A 4 69 440 is in the middle of a piano keyboard and will give you a point of reference. Wave length is in centimeters. To get inches divide by 2.54. Then multiply by 12 to get feet.

A 440 Hz wave length = 78.4cm - Divided by 2.54 (2.54 cm is 1 inch) = 30.866 inches. Divided by 12 = 2.57 feet

............. ..................... ......... Wave Note ...... MIDI ........ Hz ......... length C - ......... 0 ................. 8.176 ........ C# - ....... 1 ................. 8.662 ........... D - ......... 2 ................. 9.177 ........... D# - ....... 3 ................. 9.723 ........... E - ......... 4 ............... 10.301 .......... F - ......... 5 ............... 10.913 ........... F# - ....... 6 ............... 11.562 ........... G - ........ 7 ............... 12.25 ............. G# - ...... 8 ............... 12.978 ........... A - ......... 9 ............... 13.75 ............. A# - ....... 10 ............. 14.568 ........... B - ......... 11 ............. 15.434 ........... C 0 ........ 12 ............. 16.352 ... 2100 C# 0 ...... 13 ............. 17.324 ... 1990 D 0 ........ 14 ............. 18.354 ... 1870 D# 0 ...... 15 ............. 19.445 ... 1770 E 0 ........ 16 ............. 20.601 ... 1670 F 0 ........ 17 ............. 21.826 ... 1580 F# 0 ...... 18 ............. 23.124 ... 1490 G 0 ........ 19 ............. 24.499 ... 1400 G# 0 ...... 20 ............. 25.956 ... 1320 A 0 ........ 21 ............. 27.5 ....... 1250 A# 0 ...... 22 ............. 29.135 ... 1180 B 0 ........ 23 ............. 30.867 ... 1110 C 1 ........ 24 ............. 32.703 ... 1050 C# 1 ...... 25 ............. 34.648 ..... 996 D 1 ........ 26 ............. 36.708 ..... 940 D# 1 ...... 27 ............. 38.89 ....... 887 E 1 ........ 28 ............. 41.203 ..... 837 F 1 ........ 29 ............. 43.653 ..... 790 F# 1 ...... 30 ............. 46.249 ..... 746 G 1 ........ 31 ............. 48.999 ..... 704 G# 1 ...... 32 ............. 51.913 ..... 665 A 1 ........ 33 ............. 55 ............ 627 A# 2 ...... 34 ............. 58.27 ....... 592 B 1 ........ 35 ............. 61.735 ..... 559 C 2 ........ 36 ............. 65.406 ..... 527 C# 2 ...... 37 ............. 69.295 ..... 498 D 2 ........ 38 ............. 73.416 ..... 470 D# 2 ...... 39 ............. 77.781 ..... 444 E 2 ........ 40 ............. 82.406 ..... 419 F 2 ........ 41 ............. 87.307 ..... 395

F# 2 ....... 42 ............ 92.499 ...... 373 G 2 ........ 43 ............ 97.998 ...... 352 G# 2 ...... 44 .......... 103.82 ........ 332 A 2 ........ 45 .......... 110 ............. 314 A# 2 ...... 46 .......... 116.54 ........ 296 B 2 ........ 47 .......... 123.47 ........ 279 C 3 ........ 48 .......... 130.81 ........ 264 C# 3 ...... 49 .......... 138.59 ........ 249 D 3 ........ 50 .......... 146.83 ........ 235 D# 3 ...... 51 .......... 155.56 ........ 222 E 3 ........ 52 .......... 164.81 ........ 209 F 3 ......... 53 .......... 174.61 ........ 198 F# 3 ....... 54 .......... 184.99 ........ 186 G 3 ........ 55 .......... 195.99 ........ 176 G# 3 ...... 56 .......... 207.65 ........ 166 A 3 ........ 57 .......... 220 ............. 157 A# 3 ...... 58 .......... 233.08 ........ 148 B 3 ........ 59 .......... 246.94 ........ 140 (Middle C on a piano) C 4 ........ 60 .......... 261.63 ........ 132 C# 4 ...... 61 .......... 277.18 ........ 124 D 4 ........ 62 .......... 293.66 ........ 117 D# 4 ...... 63 .......... 311.13 ........ 111 E 4 ........ 64 .......... 329.63 ........ 105 F 4 ......... 65 .......... 349.23 .......... 98.8 F# 4 ....... 66 .......... 369.99 .......... 93.2 G 4 ........ 67 .......... 391.99 .......... 88 G# 4 ...... 68 .......... 415.31 .......... 83.1 A 4 ........ 69 .......... 440 ............... 78.4 A# 4 ...... 70 .......... 466.16 .......... 74 B 4 ........ 71 .......... 439.88 .......... 69.9 C 5 ........ 72 .......... 523.25 .......... 65.9 C# 5 ...... 73 .......... 554.37 .......... 62.2 D 5 ........ 74 .......... 587.33 .......... 58.7 D# 5 ...... 75 .......... 622.25 .......... 55.4 E 5 ........ 76 .......... 659.26 .......... 52.3 F 5 ......... 77 .......... 698.46 .......... 49.4 F# 5 ....... 78 .......... 739.99 .......... 46.6 G 5 ........ 79 .......... 783.99 .......... 44 G# 5 ...... 80 .......... 830.61 .......... 41.5 A 5 ........ 81 .......... 880 ............... 39.2 A# 5 ...... 82 .......... 932.32 .......... 37 B 5 ........ 83 .......... 987.77 .......... 34.9 C 6 ........ 84 ........ 1046.5 ............ 33

C# 6 ...... 85 ......... 1108.7 ............ 31.1 D 6 ........ 86 ......... 1174.7 ............ 29.4 D# 6 ...... 87 ......... 1244.5 ............ 27.7 E 6 ........ 88 ......... 1318.5 ............ 26.2 F 6 ........ 89 ......... 1396.9 ............ 24.7 F# 6 ...... 90 ......... 1480 ............... 23.3 G 6 ....... 91 ......... 1568 ............... 22 G# 6 ..... 92 ......... 1661.2 ............ 20.8 A 6 ........ 93 ......... 1760 ............... 19.6 A# 6 ...... 94 ......... 1864.7 ............ 18.5 B 6 ........ 95 ......... 1975.5 ............ 17.5 C 7 ........ 96 ......... 2093 ............... 16.5 C# 7 ...... 97 ......... 2217.5 ............ 15.6 D 7 ........ 98 ......... 2349.3 ............ 14.7 D# 7 ...... 99 ......... 2489 ............... 13.9 E 7 ........ 100 ....... 2637 ............... 13.1 F 7 ........ 101 ....... 2793.8 ............ 12.3 F# 7 ...... 102 ....... 2960 ............... 11.7 G 7 ....... 103 ....... 3136 ............... 11 G# 7 ..... 104 ....... 3322.4 ............ 10.4 A 7 ........ 105 ....... 3520 ................. 9.8 A# 7 ...... 106 ....... 3729.3 .............. 9.3 B 7 ........ 107 ....... 3951.1 .............. 8.7 C 8 ........ 108 ....... 4186 ................. 8.2 C# 8 ...... 109 ....... 4434.9 .............. 7.8 D 8 ........ 110 ....... 4698.6 .............. 7.3 D# 8 ...... 111 ....... 4978 ................. 6.9 E 8 ........ 112 ....... 5274 ................... F 8 ........ 113 ....... 5587.7 ................ F# 8 ...... 114 ....... 5919.9 ................ G 8 ....... 115 ....... 6271.9 ................ G# 8 ..... 116 ....... 6644.9 ................ A 8 ........ 117 ....... 7040 ................... A# 8 ...... 118 ....... 7458.6 ................ B 8 ........ 119 ....... 7902.1 ................ C 9 ........ 120 ....... 8372 ................... C# 9 ...... 121 ....... 8869.8 ................ D 9 ........ 122 ....... 9397.3 ................ D# 9 ...... 123 ....... 9956.1 ................ E 9 ........ 124 ..... 10548.1 ................ F 9 ........ 125 ..... 11175.3 ................ F# 9 ...... 126 ..... 11839.8 ................ G 9 ....... 127 ..... 12543.9 ................

The Pro Tools EQ: Practical application.

In the AE1_Lab5_EQ project, solo the kick track and put the EQ-3 7 Band on Insert 1. Leave the gain at unity. Hit play and you will see that the input and output meters are identical in activity. Stop, activate the HPF and set the Q to be 24dB per octave. Select an area to loop play (KP + 4) and set the frequency to be 500Hz. Click the IN button so that it is grayed out. Hit play and you should hear




the Kick as recorded. Now, click on the IN button to turn the HPF on (IN will turn blue). You should hear the low end of the EQ disappear.

Deactivate all IN buttons (make them gray). In the LF section (red) click on the notch (bell) icon. Set the Q to be 1, set the FREQ to be 60.0Hz and set the GAIN to be 6dB. Press play. During playback activate the IN button. You will hear the body, low end, boom of the kick accentuated and the OUT meter will be much greater than the IN portion of the meters. Red lights are bad. The red lights can be turned off by pressing OPT + C. It doesn’t get rid of the problem, it just turns off the red lights.

Deactivate all IN buttons. See if you can locate the frequency of the punch of the kick. Think to yourself, is it lower or higher frequencies than the body of the kick? Make that sound out loud or at least in your head. In the HMF (green) section turn the GAIN to be 12dB, set the FREQ to be 6.5kHz or so, leave the Q to be 1 for now. Press play and toggle the IN button. Do you hear a change? Describe it. Try sweeping the FREQ to be higher or lower values, how does that effect your kick? Try decreasing or increasing the Q value. What happens to your sound?

Refer to the charts given to you in class and the charts on page 485 of the textbook; refer to these often until you no longer need them. The charts cover instrument frequency ranges, frequency groups, key word descriptions e.g. if the sound is too much / not enough _____, then cut/add _______ frequencies. Dial in those frequencies on those instruments and listen to how it changes the tonal characteristics (timbre) of the instruments. If there is a problem with the track, can you dial it out? Can you sweeten or enhance the natural properties of a particular instrument if you know what its frequency range is?

Mixing is an art form. I can only show you how the tools work and guide you in the efficient use of those tools. It is all a matter of personal taste. If your taste matches the masses then you get paid to do what you do. If your tastes conflict with the buying public, there won’t be much work out there for you. There are no right or wrong as everything is situational. An EQ setting for “this” band will not work for “that” band. If you have what you want to do already in your head then the rest is mechanics. Always ask yourself, what is wrong with this part? Is it too loud, soft, bright and in your face, dark and disappears in the mix…? Once you identify the problem you need to deduce if the solution is a gain (loudness) problem or an EQ (timbre) problem or a combination of both.

People smarter than me have said “You cut frequencies to fix a problem, boost frequencies to hide a problem”. The good mixers and higher paid mixers cut more than they boost.

Get the free spectrum analyzer from BlueCat (http://www.bluecataudio.com/Products/Product_FreqAnalyst/) and put onto your personal system. You can see and hear what is going on and how you influenced the change.

Google “EQ Frequency Ranges” and see what other people are saying and doing about frequency content.

Try the cell phone EQ. Write down in real words a description of the sound from a cell phone, e.g. lacking lows, strong in lows, lacking mids… you get the idea. Now dial in parameters that match your description. How does it sound?

What to hand in: Save your work. When you are done with everything do a Save As and call it AE1_YourLastName_Lab05.ptx

audio engineering 1 lab 5 eqs in signal...

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