Lesson 2


Sound System Basics


We all have some type of sound system that we plan on using for our recording set-up. If you don’t, this lesson will give you some great insight into the nuts and bolts of putting together a good sound system.

This lesson is a little dry and long-winded, but just get through it and enjoy all of the new information that you will glean by studying hard!

Evaluating Your Current System

If you already have a sound system, you really need to evaluate it in terms of what it sounds like. The room that it is in will also impact the sound, but I am not going to spend too much time on acoustics for a recording/monitoring space. That is a whole other course!

To start evaluating your current sound system, hook up a CD player to an input and find some music that is professionally recorded and produced. The music should be familiar to you, and maybe even the type of music that you want to record some day!

If the system has EQ built into it, set all the EQ levels flat (more on EQ later). If the system does not have built-in EQ, don’t worry about it.

Play the CD and really start to critically listen to the music. Are all the frequency ranges well represented? Can you clearly hear each instrument in the mix? Listen to levels, distortion, and other signs that something may not be right with your system. An audio system is a lot like a musical instrument. You need to practice with it and become familiar with its operation. It also needs to be in the best working condition so that you are accurately hearing your audio.

Evaluating Your Recording/Monitoring Room

Face it, we all are pretty much stuck with whatever room our spouses/landlords will let us have to set up our computer, and sound equipment. Unless you are rich, then you can have a professional build you the perfect recording space. I am stuck in the basement, which is OK, until the furnace kicks on, or my wife decides it is time to do the wash.

What you really want to strive for, in your recording space, is to control sound and sound reflections. That is to say, limited reflected sound. Many studies have shown that reflected sound is “bad” sound when recording. Yes, practicing in the bathroom or gym, singing in the shower, and all large reflective rooms do make you sound better. But really, you are just fooling yourself. In recording, reflective sound is inaccurate sound! By controlling sound reflections, you allow the real sound of an instrument, voice, or speaker/monitor to come through.

Any hard surface in your recording space will cause sound to reflect. Walls, floors, and ceilings are great examples of reflective surfaces that can cause flutter, echo, and low-frequency buildup.

Test your studio for reflective surfaces by clapping your hands around different parts of the room. Listen for echo, ringing, and hollow sounds. Make a mental note to yourself.

You can help to eliminate and control reflective surfaces by using acoustical treatment materials that are either home-made or professional grade.

Types Of Sound Wave Reflection

There are three basic types of sound wave reflection:

Axial

Tangential

Oblique

All of the above terms refer to the direction that sound is being reflected from one hard surface to another.

In
axial mode, sound is being reflected from wall to opposite wall or floor to ceiling. This is the most common and worst reflection.

In
tangential modes, we find reflections that bounce off of two hard surfaces that come together, such as two walls of a room. These reflections are not as strong as axial reflections.

Oblique modes occur where three hard surfaces meet, such as a corner and a ceiling of a room. They are weaker than the other two modes, but can really mess with a bass sound, often making the bass louder than it really is.

Controlling Your Sound Space

It is a misconception that the best recording environments are totally dead spaces! In fact, some of the best recording studios are a blend of hard and soft surfaces. Professional 2” studio foam can go a long way in making your room sound better. But it is not the whole solution to the problem.

There are basically two ways to control sound in a room: sound diffusion (reflecting sound) and sound absorption (absorbing sound). Each plays an important role in developing a good sounding room. If you are interested in more information on acoustical treatment check out the following link on acoustic treatment and studio designs.

www.auralex.com

The Mixer

Mixers come in two flavors:

Split-Line

In-Line

Split Line Mixers have their faders off to the side.


In-Line Mixers have their faders and all controls running vertically
from top to bottom on the channel strip.

Screen shot 2012-04-05 at 7.31.56 AM
In-Line Mixer

Mixer Configurations

When you purchase a mixer, you’ll want to make sure that it will accept any, and all, input cables that you want to run through it. Do an inventory of all your gear and the types of connector cables that are going to be plugged into your mixer. If you own a piece of gear that has RCA outputs and your mixer does not accept RCA inputs, it could be a problem. You can always purchase cable converters and adapters for some situations. For others, you may not be able to use a cable converter. Just be sure that you know what gear you are going to be plugging into your mixer. When you purchase a mixer, be sure to check input configurations.

Manufacturers will often list a mixer’s configuration in numbers. For example, 8X4X2. The X’s between the numbers stand for the word “by”. So, 8X4X2 really means 8 by 4 by 2 and so on. This first number usually indicates how many inputs the mixer has. The second number indicates how many busses are available (more on bussing later). And the third number is the final output from the mixer. The above example indicates:

8 inputs into the mixer.

4 busses.

And a stereo output.

Professional Amplifiers

Although using a home stereo system is alright when you are first starting to record and monitor your sessions in Pro Tools. It is usually best to start to put together a professional playback system. Home stereo systems tend to color the sound and don’t give you a flat playback response.

It is best to buy a professional amplifier that is used specifically for recording purposes.

RMS Ratings

RMS stands for Root Mean Square and indicates the constant power supply that an amplifier is putting out. This rating is important, especially when you are monitoring audio for mixing and mastering. You will want to purchase a professional amplifier that has an RMS rating between 100 and 200 watts RMS.

While Tim “the tool man” Taylor’s statement “more power is good”, may work well for power tools, you will want to be careful that your speakers can handle the power that your amplifier puts out. Check the
RMS rating (usually printed on the back of your speakers) to make sure your speakers can handle the output from your amplifier. You should also check to see what the RMS rating is for your amplifier. It may be listed on the amp or in your owner’s manual. You really need to know this information so that you can match your amp with your speakers.

Speaker Wire Gauges

There is a wide variety of speaker wire available out there for the consumer. I recommend that you always use heavy-duty wire specifically designed for use with speakers. You also want to make sure that you have the proper wire gauge. In general, use thicker wire gauges for longer wire runs, and thinner wire gauges for shorter wire runs. Here is a brief chart that may help:



Length Suggested Wire Gauge

0’-25’ #18-gauge wire.

25’-50’ #16-gauge wire.

50’-100’ #14-gauge wire.

You don’t have to buy the most expensive wire out there. Any good quality wire will work. If you will be monitoring in stereo, please make sure that that you connect the red post on the back of the power amp with the red post on the back of the speaker with the same wire. The same goes for the black posts. If they are connected incorrectly, your speakers will be out-of-phase. This will cause inaccurate playback, especially in the lower frequencies.


Monitors For Recording And Mixing

The purpose of recording monitors is to reproduce the sound as accurately as possible without coloring the sound. This is usually done on near field monitors at close range to the listener. I would highly recommend purchasing near field monitors for a home set up. Far Field monitors are designed to interact with a professional recording space. Something most of us don’t have access to!

Most professional studio monitors are set up for theoretical flat response in anechoic chambers. Once your music sounds good on professional near-field monitors, it will usually sound good on any playback system that exists in the “real world”.

Buying Monitors

I would highly recommend reading published reviews from professionals who are working in the audio field who have had experience using different types of studio monitors. These reviews appear quite often in
Electronic Musician, Keyboard, Home Recording and other magazines that include articles and reviews on home recording. www.homerecording.com is also an excellent site to find out information on home recording studios and equipment.

Once you have read several reviews, try to narrow your choices down to two or three different monitors that fall within your price range. Audition each brand of monitor by bringing a CD of music that you are familiar with to the audio store so that you can do some critical listening to make sure that you are hearing everything that you should.

Listen for good stereo imaging, clarity, shimmer in the high end, and good bass response in the low end. Also make sure that you listen to a variety of volumes. Most of your mixing will be done at a moderate to low volume. Mixing at high volumes can fatigue your ears and also give you a false sense of a good mix. I almost always mix at low to moderate volume levels.

Active and Passive Monitors

Monitors for home recording studios come in two flavors: active and passive. Active monitors have an integrated power amplifier that is designed to work with that speaker type. There are several types of powered studio monitors on the market. These all-in-one units work quite well and deserve careful consideration. I have had great success with powered monitors.

There are also “Digital-Ready Monitors” on the market. This is an advertising ploy to get you to spend more money. Speakers work in the analog world and can’t tell the difference between digital and analog input. Stay away from these! An excellent online store with great information and reasonable prices on most audio equipment can be found at
www.zzounds.com.

Connectors For The Home Studio

Screen shot 2012-04-05 at 7.32.55 AM RCA connectors are typically used for home stereo equipment. They may also be found on some of your lower-end audio equipment. Be aware that these types of connectors may add a lot of noise to your recording chain. Short cable runs are desired. If that is not possible you should run the unit through a DI box (more on that later). You may also use an adapter to get RCA connectors into a mixing board. Radio Shack carries adaptors for almost any situation. Using an RCA to quarter inch adaptor is fine. Just be aware that you may still hear quite a bit of noise.

Quarter-Inch Phone connectors are typically used for guitar, keyboard, synths, and tone generator outputs and inputs.

Screen shot 2012-04-05 at 7.35.06 AM Quarter inch mono connectors have one ring on the connector. Be aware that they will function in a stereo output, but you will only hear one channel.

Screen shot 2012-04-05 at 7.35.52 AM Stereo Quarter Inch connectors have two rings (called ring and sleeve) and are used for stereo outputs. When fully inserted into a mono output, they will not function. Pull the connector about halfway out and you will hear sound. It is better just to use a mono connector in a mono output. I recommend short runs for these connectors as well. Noise in the recording chain can be a problem. For longer runs, connect to a DI Box (I know, more on that later).


Screen shot 2012-04-05 at 7.36.19 AM XLR Connectors are used for high-end audio equipment, microphones, mixers, and speakers. They are also known as Balanced Low-Z connectors, although, those terms refer more to the cable than the connector. XLR cables emit low, or no-noise and can be used for longer cable runs. Anytime you can purchase a piece of gear that has XLR inputs and outputs, do it! The extra money spent for these connectors is well worth it.




Powering Up Your Home Studio

This may seem simple, but by following this procedure, you may save some money by not having to replace speaker cones on your new monitors.


To power a system up:

turn on you mixing board first, and then turn on your power amp.

To power a system down:

turn off your power amp first, and then your mixing board. This will save you ware and tear on your speakers.

Grounding

The purpose for grounding equipment is safety! With proper grounding, you won’t get shocked or die while in your recording studio. That is a good thing! The only problem with grounding is that it may add noise to your recording system by creating a ground loop. A ground loop is a 60 Hz low hum that will be pretty noticeable in your system.

There are several methods for avoiding a ground loop. The safest method is to make sure that you have separate electrical lines running through your studio space earmarked for studio gear only. This method allows you to have your gear grounded while avoiding potential ground loops. Ground loops occur when several pieces of gear share the same electrical outlets or electrical lines. It is best to hire an electrician to install added electrical lines in your home.

Another less desirable method for breaking a ground loop involves
lifting the ground loop by using a ground lift, which can be purchased at any electrical or hardware store. If installed correctly, this is a great way to break the loop and keep you grounded.

You may also break a ground loop by removing the ground plug. This method removes the ground loop noise but also removes the ground and improves your chances of getting shocked!

Removing the shield from the 1/4-inch cable closest to the mixing board input may also get rid of a ground loop hum. This may remove the ground loop noise, but leave the offending piece of gear ungrounded.

Any lights, especially Florissant lights, will also add noise to your studio if they reside on the same electrical line as your studio gear. Try to place them on a separate electrical line. If you can’t, you may have to lose that Lava Lamp!


Screen shot 2012-04-05 at 7.36.55 AM Input Stages and Impedance

This is where microphones, instruments, and other pieces of gear get plugged into your mixer. It is very important that you match your input and output impedances when you are setting up your recording studio. This will allow you to record the best possible signal into Pro Tools.

Microphone inputs come in two flavors:
high impedance and low impedance. When used correctly, both impedances will get the job done.

By definition,
impedance is the resistance to the flow of current as measured by Ohms.

You can think of the two impedances in terms of water pipes. Low impedance can be represented by a large pipe. It has low resistance and more water can be pushed through a large (low impedance) pipe.

High impedance can be represented by a small water pipe. It has high resistance and less water will get through the pipe.

If you send a low impedance signal (a lot of water) into a high impedance input (small pipe) you can’t get all that water into the pipe no matter how hard you try. The signal will be weak.

A high impedance instrument plugged into a low impedance input is not so good either. The high impedance instrument is expecting to see lots of resistance at the input. When it gets low resistance at the input it will try harder and overdrive the input. The result is a lot of distortion.

Just remember, low impedance outputs to low impedance inputs and high impedance outputs to high impedance inputs. Life is good!


Screen shot 2012-04-05 at 7.37.21 AM Balanced Low Impedance microphone inputs are also called low Z or +4dBm and use XLR cables and connectors. This is professional standard in recording studios, is used for longer cable runs, professional PA applications, and tends to be much less noisy than other input specifications.

Screen shot 2012-04-05 at 7.37.53 AM Unbalanced High Impedance microphone inputs are also called high Z or –10dBv and typically use quarter-inch connectors. This is used for semipro gear and shorter cable runs.

Some recording equipment will have a switch to let you select your input or output.

A
+4dBm low Z output is too strong for a –10dBv high Z input and will result in a distorted recording signal.

A
–10dBv high Z output is too weak for a +4dBm low Z input and will result in a weak, noisy, recording signal.


Screen shot 2012-04-05 at 7.38.19 AM Adaptors

If you find that you don’t have the right input connectors. It is OK to use adaptors for your cable connectors. Just remember, that an adaptor will not change your impedances, which brings us to the DI box!



Screen shot 2012-04-05 at 7.38.55 AM Direct Boxes or DI Boxes

So what do you do if you have to route a high Z guitar or synth output into a low Z mixing board input? Use a Direct Box! These also come in two flavors:
Active and Passive.

Active DI Boxes have an amplifier that will enhance bass and treble. Active DI Boxes require a battery or Phantom Power (more on that soon).

Passive DI Boxes require no power and do not enhance the sound.

Most models of
DI Boxes also come with a ground lift switch.


Screen shot 2012-04-05 at 7.44.08 AM Phantom Power

This is a dc voltage (11-48 volts) that typically powers the preamplifier of a condenser microphone or other device, such as a DI box. Most mixers supply
Phantom Power and may have a separate switch dedicated for that purpose.

Phantom Power requires the use of a balanced XLR cable. Phantom Power requirements will vary from mic to mic; so make sure that you check your microphone specifications to insure that your condenser mic is getting the power it requires.

Line Level

When you input a signal from a microphone into your mixing board XLR inputs it is called
Mic Level. Mic Level signals are too weak for a mixing board and they need to be amplified by a mic preamp to something called Line Level. This way the signal is strong enough to work with the mixing board. More on mic preamps later in this lesson.

Instrument inputs on your mixing board (Quarter Inch Phone Inputs) are already at
Line Level so they will not need to go through a mic preamp.

Screen shot 2012-04-05 at 7.44.52 AM Getting Sound Into Your Mixer

Once you have mastered your little mixer, you can pretty much master any mixer! The controls are all basically the same, there are just more of them!



Screen shot 2012-04-05 at 7.45.17 AM The Preamp

This is the first place the signal goes from your microphone as it enters the mixer (or a Pro Tools interface like the M-Box).


Screen shot 2012-04-05 at 7.45.46 AM Pro Tools M-Box with mic preamps.


The
preamp amplifies the mic level so that it becomes line level so the mixing board can work with a strong signal.

The
preamp is actually a small amplifier circuit. The controls for the preamp are generally located at the top of each channel on your mixing board. The preamp may also be labeled as:

Mic gain
Trim
Mic preamp
Input preamp
Gain.

They all do the same thing. Remember that a mic level must be amplified to a signal strength that the mixer can work with (line level).

The
preamp usually does not need to be turned all the way up. To amplify a mic level signal, a preamp circuit usually sends the signal back through itself. This process can add noise and then amplify the noise. That is why it is best not to have the preamp turned all the way up. Try to get a strong signal with as little pre-amplification as possible! That way, you won’t be adding a lot of noise to your audio signal.

Many boards will have an LED light that blinks when the preamp is overloaded. This is a
Peak Level Indicator and is used for indicating peak level strength that is getting close to overloading the preamp.

The best method for setting a
preamp is to have the LED blinking occasionally, then turn it down a little. It is usually OK if the LED light blinks a couple of times during a recording. Let your ears be the judge.


The Attenuator or Pad

Sometimes when you are recording, the signal into your mixer is too strong and even with the preamp all the way off, the signal is still distorting and overloading the input. This may also happen when you are recording a loud instrument like a kick drum or snare drum. When this happens you would use an
attenuator or pad. This is almost always found at the top of the channel strip on the mixing board. The Attenuator restricts the signal into the preamp by 10, 20, or 30dB and is usually labeled as –10dB, -20dB, or –30dB.

Using an
attenuator or pad will allow you to record an unusually hot signal with no distortion. Not all mixing boards have this feature so it would be wise to look for this if you are purchasing a mixing board.

Screen shot 2012-04-05 at 7.46.16 AM The VU Meter

Meters are used on mixing boards to tell us how much signal is getting into the board.
VU meters are the most common. VU stands for Volume Unit and this type of meter reads the average signal level not peak levels or fast transient attacks. The VU meter has a needle that measures a scale from –20VU to about +5VU. The sweeping motion of the needle across the scale restricts the meter from measuring peaks and transients. VU meters are typically used in analog recording.


Screen shot 2012-04-05 at 7.46.33 AM The Peak Meter

Peak meters or Peak LEDs meter fast attacks and transients from more percussive instruments. Since there is no needle to move, the small series of lights will turn on quickly to measure a peak or fast attack. Peak meters are typically used for digital recording.

Signal Path

Signal path is the route that an audio signal takes to get from point A to point B. It is essential that you understand the signal paths involved in your recording studio set up. I always diagram my signal path in my recording set-up. It may be simple or complex depending on you set-up. Look at the diagram below for a simple example of a signal path.
I would strongly advise that you diagram your studio to better understand your signal path set up.

Screen shot 2012-04-05 at 7.46.57 AM


Managing Your Signal Path or Gain Staging

When you are recording, you want to make sure that you understand how to get the best possible signal into Pro Tools. This next section will help you understand how to do this. This is commonly referred to as
Gain Staging.


Screen shot 2012-04-05 at 7.48.44 AM Input Faders

When you have your preamps set up correctly, you will use the input faders on your mixing board to set the recording levels into Pro Tools. The
input faders should be used to adjust recording levels going into Pro Tools and not used for adjusting your signal strength into the preamp.


Screen shot 2012-04-05 at 7.49.08 AM The Pan Control or Pan Pot

The
Pan Pot short for panoramic potentiometer, is used to move sounds around in the stereo panorama. Sounds are positioned anywhere in the left to right spectrum located between the left and right speakers. Pan controls are usually sweepable from full left to full right and anywhere in between those points.

Screen shot 2012-04-05 at 7.49.40 AM Solo and Mute Controls

A
Solo button turns off all tracks except for the soloed track. This will let you hear one track at a time. You can also solo more that one track or a group of tracks.

A
Mute button is an off button. This will turn the selected channel off. It is much better to mute a track using the mute button than to move the fader down on the channel. You may not be able to get back to your original fader position after you bring the fader down to turn the track off.



Screen shot 2012-04-05 at 7.49.58 AM EQ or Equalization Controls

These controls are usually located at the center of your channel on your mixing board.
EQ is also commonly referred to as tone control; highs, mids, and lows. Mixers with EQ controls typically have an in/out or bypass button. When the button is pushed in, the signal is routed through the EQ. When the button is out, the signal bypasses the EQ. If you are not using any EQ on a channel it is best to bypass the EQ.

In the ideal recording world, one would never have to use EQ to shape a sound because you would record the sound with the best mic in the best room, so no EQ would be needed.

In the “Real World” there are many situations that call for EQ, especially since we rarely have access to expensive microphones, mic preamps, and fantastic studio recording spaces.

There are two reasons for using EQ



    Screen shot 2012-04-05 at 7.52.18 AM Hertz

    To begin to work with
    EQ you need to better understand Hertz or frequency. When we talk about Hertz or frequency we are referring to a musical waveform as it completes its 1-second cycle with a crest and a trough. We will cover this in much more detail in lesson 3.

    The human ear can typically hear a range of frequencies from about 20Hz to 20,000 Hz (20 kilohertz or 20kHz). Musical instruments also fall into this frequency range. The lowest note on a piano is 28Hz and the highest note on a piano is 4186 Hz. When you are working with EQ, you have to know the frequency ranges of each instrument. For example, cutting a frequency of 40Hz from a piccolo sound will not have any great effect since the piccolo does not contain that frequency.


    Screen shot 2012-04-05 at 7.52.50 AM


    Screen shot 2012-04-05 at 7.53.07 AM Equalization Curves

    When you are using EQ on a mixing board, you are usually relegated to 3-5 knobs to cut/boost EQ. Be aware that by boosting or cutting a particular frequency, you are usually boosting or cutting nearby frequencies as well. For example, a 500Hz boost on most mixing boards will boost a range of frequencies from about 200Hz to 1000Hz, with 500Hz being the middle frequency. Most mixing boards have EQ knobs labeled as
    highs (frequencies above 3.5kHz) mids (frequencies between 250Hz and 3.5kHz) and lows (frequencies below 250Hz). When you use the EQ knobs on a mixing board know that you are adjusting a pretty broad range of frequencies!


    Screen shot 2012-04-05 at 7.53.32 AM Bandwidth

    Bandwidth allows us to select how much of the frequency range is being cut or boosted. Bandwidth is also referred to as The Q. Most equalizers don’t have a bandwidth control. But Pro Tools EQ plug-ins and Parametric Equalizers (see below) allow us to control the size of the bandwidth when we are working with EQ. Bandwidth is usually described in terms of octaves. A wide bandwidth (2 or more octaves) is good for overall tone coloring. A narrow bandwidth (less than half and octave) is best for finding problem frequencies and cutting them.


    Screen shot 2012-04-05 at 7.54.14 AM Sweepable EQ

    Many mixers have
    sweepable EQ (also called semiparametric EQ). Sweepable EQ has two basic controls per sweepable band:


      This is a nice feature to have on a mixing board. You will pay extra for this feature, but it is well worth the money.


      Screen shot 2012-04-05 at 7.54.38 AM Parametric Equalizers

      This is by far the most flexible EQ. It is just like the
      sweepable EQ but with one major difference. Parametric Equalizers allow you to select the range of the bandwidth that you want to boost or cut. You can be very precise when you target a frequency that you want to alter.


      Screen shot 2012-04-05 at 7.55.04 AM Graphic EQ

      This has the most visual interface of all the equalizers. Each slider usually controls a one-octave bandwidth. Depending on the model of
      Graphic EQ that you buy, you are relegated to a certain number of bandwidths. A 10-band model is pretty much the norm but you can also purchase a 31-band model. This type of EQ is generally used on home and car stereo systems.


      Screen shot 2012-04-05 at 7.55.36 AM Notch Filters

      This type of filter is used to find and eliminate problem frequencies like a 60Hz ground hum or other noise.
      Notch Filters have a very narrow bandwidth and most often have sweepable EQ.

      Screen shot 2012-04-05 at 7.56.05 AM Highpass and Lowpass Filters

      A
      highpass filter allows high frequencies pass through while cutting low frequencies, usually below 80Hz. This type of filter is great for getting rid of low rumble noise or a ground hum

      A
      Lowpass filter allows low frequencies to pass through while cutting high frequencies, usually above 8-10kHz. This type of filter works well for cutting cymbal leakage onto a drum’s tom tracks. Both of these filters are commonly called Shelving Filters.



      Screen shot 2012-04-05 at 7.56.31 AM Compressors and Limiters

      Compressors and limiters are used in today’s music to even out the transients and increase the overall volume level of a recording.

      A
      Compressor and limiter both operate on the same principle. The only difference between the two is the degree to which they affect the signal that exceeds the threshold.

      A
      Compressor functions as a gentle volume control much like you would turn down a channel fader to lower the volume when recording a track that is too hot.

      A
      Limiter is more extreme. It radically decreases the level of the signal that passes above the threshold, almost like slamming down a fader quickly to lower the volume in a big way.



      How Compressors and Limiters Work

      Compressors and limiters are nothing more that automatic volume controls. When the compressor receives an overly hot signal level it triggers an automatic level control to decrease the signal strength, and as a result, it also decreases the volume of the signal

      When the
      amplitude (signal strength) reaches a certain level (voltage) it pushes through a user set threshold. As the signal exceeds the threshold, an amplifier within the compressor then turns the signal level down according to the user defined compressor/limiter settings.

      The Compressor

      The goal of the compressor is to control the volume of the signal level in the same way that a recording engineer would work with the fader while listening to the track playback. When a compressor is used correctly, you should not even be aware that it is there!

      A compressor allows the engineer to record an entire track at a hotter level than if the compressor were not used. Pop music makes great use of compression so that it can get a hotter signal out of your radio or TV station. Ever notice that commercials seem to be louder than regular TV programming? That is because most commercials make use of a compressor and deliver a louder signal to the listener.

      If the compressor decreases the level of the hottest part of the track by 3dB, the entire track can be recorded 3 dB louder without distorting the tape or exceeding a maximum digital recording level.

      This results in a louder more robust audio track that really sticks out. The loud passages are controlled and the softer passages are brought up, resulting in a more even sonic effect.

      Musically speaking, the compressor can be a great tool. For example, the lead vocal in a pop song should be audible, understandable, and “in your face”; this is just what compression does. A compressed lead vocal line sounds much more up front in the mix.

      Any instrument with a wide dynamic range is usually compressed while recording and during the mixdown process.


      The Limiter

      The limiter controls level and amplitude much like a compressor but in an extreme way. For example, when recording a bass player playing a jazz tune with an easy consistent playing style, you probably would not use a compressor. But, if that same bass player is playing a funk tune that requires bass slaps or snaps, a limiter would level out the amplitude peaks caused by his aggressive funk playing.

      Limiters are often used to control the level of an entire mix.
      If a limiter is used correctly it is usually imperceptible to the listener. It quiets the transient peaks and maintains a full “in your face” sound throughout the entire song.

      Controls

      Threshold

      The threshold setting determines where the compressor begins to recognize the signal and act on it. The compressor turns down any amplitude that exceeds the user-set threshold, in direct proportion to the ratio selected by the user.

      Attack Time

      The Attack Time controls the amount of time is takes for the compressor to turn the signal down once it has passed the user-set threshold.

      Release Time

      The Release Time is the time it takes for the compressor to let go, or to turn the signal back up to its original volume once the signal is out of the threshold.

      Ratio

      The ratio setting defines the degree of compression or limiting applied.

      If the audio signal exceeds the
      User-Set Threshold by 10 dB, and the ratio is set at 10:1 the resulting signal exceeds the threshold by only 1 dB instead of 10dB!


      If the audio signal exceeds the
      User-Set Threshold by 15 dB, and the ratio is set at 5:1 the resulting signal exceeds the threshold by only 3 dB instead of 15 dB. In a 5:1 user set threshold the math is as follows:

      5 dB lets 1 dB through
      5 dB lets 1 dB through
      5 dB lets 1 dB through

      15 dB lets 3 dB through.

      The difference between a compressor and a limiter lies in the ratio setting.

      Ratios of 10:1 and below result in compression.

      Ratios of more than 10:1 result in limiting.

      Compressors and limiters can be the same piece of equipment.


      Microphones

      I could dedicate an entire course just for the study of microphones. However, there is not enough time for that within the scope of this course. You will need to understand some basic principles and terminology regarding microphones and their usage to help you produce better sounding recordings. I will limit my discussion to two different types of microphones:

      Condenser microphones.
      Moving-coil microphones.

      Screen shot 2012-04-05 at 7.57.09 AM Condenser Microphones

      The condenser microphone is the most accurate recording microphone. It responds to fast attacks and transients with great accuracy and does not color the sound in any way. The large condenser microphones that are used in major recording studios are very expensive and well worth the money!

      Whenever you want to capture the true sound of an acoustic instrument, the condenser microphone should be your mic of choice. Condenser microphones capture a broader range of frequencies, from a greater distance, than any other microphone type. In general, you don’t need to be as close to a condenser mic to capture a good full sound. Other mic types require you to be right on top of the microphone to capture a good full sound.

      While condenser microphones work well in the recording studio, they perform poorly in a live sound situation, often picking up all of the sounds that are close to the mic.



      How Condenser Microphones Work

      Once you understand some basic information on how microphones work, you will have a better idea on which type of microphone you need to use for recording or for sound reinforcement applications.

      A condenser microphone is a fairly simple device containing an electrically charged metal-coated plastic membrane. When a sound enters the mic, the audio signal causes the membrane to vibrate. Behind the membrane is a solid conductive plate. When the membrane is moving (vibrating), electricity is stored between the membrane and the solid plate. As the plastic vibrates, the area between the two plates changes and creates a discharge of electrical current. This discharge is an exact electrical duplicate of the sound wave. We now have an electrical version (mirror) of the original audio wave. The membrane is very thin and responds quickly to changes in an audio signal. That is why a condenser records a signal so accurately!

      The electrical (mirror) signal is now sent (mic level) to your mixer and then boosted (line level) so the board can work with it.

      A condenser microphone requires phantom power or a battery to charge the metal-coated membrane with electricity. They will not function without some type of power supply. I prefer using phantom power because you will always have a constant, correct power supply. Batteries tend to grow weaker with age, and the power supply can fluctuate. This may cause the mic to work incorrectly.


      Screen shot 2012-04-05 at 7.57.40 AM Moving-Coil Microphones

      Moving-coil microphones are the mic of choice for most live sound reinforcement situations. They are also used in the recording studio as well for recording drums, guitar amps, and other loud instruments. They can withstand a great amount of volume without distorting their circuitry.

      Moving-coil microphones color the sound much more than condenser microphones. This coloration usually occurs in the frequency range of about 5kHz-10kHz. As long as you know that this colorization of sound takes place, you can sometimes use it to your advantage. That high frequency range coloration typically adds clarity and presence to many vocal and instrumental sounds.

      Moving-coil microphones tend to sound very thin when they are more than a foot away from the intended sound source. Moving-coil microphones sound best when they are very close to the sound source. Therefore, they are great in live sound situations where you don’t want a lot of bleed over from other sound sources. They are also typically used for vocals in live performance venues.

      How Moving-coil Microphones Work

      Moving-coil microphones require no phantom power to run. While running phantom power through a moving-coil microphone will not damage the microphone, the mic may not function properly. It is best to make sure that you have your phantom power turned off when using a moving-coil microphone.

      On the inside of a
      moving-coil microphone, a copper wire is wrapped into a cylinder. The cylinder is suspended around a magnet. The copper wire moves up and down responding to pressure changes created by an incoming sound wave.

      As the coil moves around the magnet it receives a magnetic image that mirrors the changing air pressure from the sound wave. The magnetism (magnetic image) that is created is the signal that is sent through the mic cable and into your mixers input (mic level).

      Wow! This lesson was a lot to digest, but I hope that you have a better understanding of sound systems and some of the devices that work in your recording studio.

      Project 2:

      Describe your mixing board and monitor setup if you have one.


      Recap: Lesson 2

      This week you should now be more familiar with:

      Types of sound wave reflection.
      Mixers and mixer configurations.
      Speaker wire gauges.
      Monitors for recording and mixing.
      Connectors for the home studio.
      Grounding.
      Input stages and impedance
      Direct boxes.
      Phantom power.
      How to get sound into your mixer.
      Gain Staging and Signal path.
      EQ and equalization controls.
      Compressors and limiters.
      EQ and compression guidelines for recording.
      Condenser microphones.
      Moving-coil microphones.

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