Chambers

The first reverb emulators were actually specially designed echo chambers that had a speaker on one end and a microphone on the other. The sound was fed to the speaker and then recorded through the microphone. It was very simple in concept, yet it took up a lot of room. I wouldn’t really call this an emulator, though, because the reverb was very real and not simulated via an effects unit or computer.

Figure 8-1 Direct sound, early reflections, and reverb.

Plates

An early reverb emulator design was a large steel plate encased in a wooden box. These units were around four feet high, one foot wide, and 15 feet long. While smaller than a chamber, they were still large by today’s standards. The sound was sent to a device that worked like a speaker and was attached to the middle of the plate. Microphone-like devices were attached to each side and captured the sound after it moved through the plate. Both chamber and plates created reverb-like sounds but could not easily be changed to mimic a specific location; therefore, they didn’t really make good tools for matching looped dialog to production dialog. Spring reverbs, popular in guitar amps, work on the same principle as plate reverbs but on a much smaller, and lower quality, scale.

Digital Reverbs

Once digital audio started to become more commonplace, it became easier to create effects that used delays to create reverb. In an actual space, reverb unfolds in a semi-predictable manner.

The original sound reaches your ears, then early reflections arrive after bouncing off nearby objects and surfaces. Then, the sound fills the space and arrives at lower levels from all directions. Once that happens, it quickly begins to die out. A digital effect can mimic this by using a series of repeated delays at various levels to create a reverb-like sound. The more layers of delay, the denser the reverb. The more complex the delay system, the more realistic the result. The Soundtrack Pro Reverb and the PlatinumVerb work on this type of system. They are decent reverbs that work well in a variety of situations, which we’ll get to in a little bit.

Convolution Reverbs

This type of reverb is on the newer end of reverb history. It uses impulse responses (IRs) from actual places to create reverb. These IRs are usually created in one of two ways, the first being through an actual impulse in a particular space. Either a starter gun being fired or a balloon popping do the trick, but a full-range sound (covering all the frequencies from low to high) is needed to create an accurate impulse. This impulse can be used directly in a convolution reverb to simulate the reverb for the original acoustic space.

The second method is to broadcast a sweeping sine wave through the audible range of sound and record how it sounds in the physical space. The way to do this is to place a speaker in the room, attached to a computer that plays a sine wave sweeping through the audio range (this sounds like a tone that starts really low and slowly rises until it is higher than you can hear). To record the sine sweep, you’ll need a microphone that is also hooked up to your computer. You can subsequently take the original sine wave sweep and the recorded sine wave and use them to create an impulse using a deconvolver. The deconvolver analyzes the differences between the two signals and converts the results into an impulse that contains enough information to recreate the sound of the room. The good news is that Soundtrack comes with a convolution reverb plug-in and an impulse response utility that allows you to create impulses for use. The reverb is called Space Designer and is one of the more powerful tools in Soundtrack Pro.

The Early Reflections Section

The Early Reflections section is used to set the predelay for the early reflections, which is a delay that pushes back the initial reverb sound. At high settings, this can easily separate the reverb completely from the dry original. The effect that this is good at creating is the bounce of sound, such as a gunshot or other loud sound, off a distant wall. The sheer distance is much easier for the ear to understand when the reverb follows the dry sound after a short pause. These settings only apply to the early reflections, which are the reflections that happen first as sound bounces off the surfaces which are nearest.

Figure 8-4 Early reflections.

The Room Shape setting allows you to change the general shape of the virtual room. You can see this reflected in the graphic in the center of the plug-in. The more complex the shape, the more complex the reverb. Sometimes, a nice simple shape creates a reverb that will remain in the background and not draw attention to itself.

The Stereo Base defines the wideness of the reverb, with higher settings creating a very wide sound and lower numbers creating a mono reverb. This is based on virtual microphone placements in the room, with higher settings representing microphones that are further apart. Since this reverb is not a perfect model of a virtual space, the concept is rather more hypothetical in nature.

The Room Size slider changes the size of the virtual room. In conjunction with the decay time, you can create some very interesting sounds. For instance, if you set a very short reverb decay but a very large room size, it will make the processed sound larger without placing it in a large room. This, as you might imagine, can be confusing for the ear and is typically done for specific reasons like making footsteps seem larger than life or creating a dark effect on someone’s voice.

The Reverb Section

Once we are past the early reflections, we enter the Reverb area, which is what describes the sound when it is no longer bouncing off nearby objects but has bounced in so many places that it begins to fill the space and comes from all directions. Just like in the Early Reflections section, there is a delay setting for this portion of the reverb which is used to put a brief pause between the early reflections and the reverb, but I rarely adjust this parameter beyond whichever preset I am using. However, if the predelay and reverb sounds are blending together too much, you might try extending this setting to help with separation.

Figure 8-5 The Reverb section.

The Spread setting is similar to the Stereo Base of the early reflections. Use it to widen the reverb or to make it narrower. Crossover is a parameter of the reverb that causes more confusion but offers more excitement. It allows you to split the reverb into two bands for slightly separate processing. The crossover determines the frequency split point and the Ratio slider immediately to its right determines what happens with each band. At 100% the bands are equal in length. With settings below 100%, the low frequency band (as determined by the Crossover slider) is shorter. When above 100%, the low frequencies are longer than the high frequencies. My first question was ‘why?’ This appeared to be a confusing set of parameters that would only make things harder. What I realized is that the parameters make a couple of specific things really easy to do. The first is to create reverb that sounds like it is coming from a distance. Think about any action movie in which you hear explosions from a distance. Most of what you hear is the low frequencies. With this Crossover slider, you can set the frequency to be somewhere around 200 Hz and then set the ratio to over 100%, and as a result the low frequencies will ring out longer than the high frequencies. This creates a very realistic effect of things happening further away.

The Low Frequency Level slider allows you to turn up or down the low frequency band as defined by the Crossover slider. If the reverb is too muddy, this would be a perfect slider to turn down. If you are looking for some good low frequency rumble, then feel free to turn it up.

The High Cut slider allows you to reduce the higher frequencies. It is a low pass filter which cuts all sound above the set frequency. If you want the reverb to sound like it is in a normal carpeted room, cutting some of the higher frequencies will help. Leaving all frequencies untouched gives an effect that sounds closer to a metal or stone room. If, following the example in the crossover section above, you would like to create the sound of distant rumbling, then cut more of the high frequencies.

Figure 8-6 Density, diffusion, and reverb time.

The last three sliders are very important because they do a lot to determine the sound of the overall reverb. Adjusting the density of the reverb increases the number of reflections. Typically, you will want to set this higher to create more realistic and complex reverbs, but sometimes you may want to lower it to create a simpler reverb. The diffusion is defaulted to 100% and I rarely change it. The diffusion affects the consistency of the reverb and low settings result in grainy and unusable reverb sounds. Turning the diffusion down to a low setting gives a great place to explore for special effects. The reverb time determines how long the reverb should last. This is an area that will require a good ear and a good monitoring system because too much reverb tail really affects how the reverb sounds and either makes it muddy (with too much) or unnoticeable (with too little). Finding a good balance is critical to achieving usable sounds. See the section after we explore Sound Designer (see page 162) for tips on getting good reverb settings for different applications.

Master Controls

You can control the mix of early reflections and reverb using the slider at the top. The overall dry/wet signal can also be controlled by using the sliders on the right.

Figure 8-7 Master controls.

These two areas are important because they allow you to control what actually leaves the reverb effect. The first slider, which controls the balance between the early reflections and the reverb, allows you to create a space that is heavier on the early reflections. The end result would be a much smaller space that doesn’t sound as natural. If you want a reverb sound that is the most natural, leaving the slider in the middle is a good option.

The Output sliders control the wet and dry levels for the entire reverb. You will need to listen carefully to how it sounds while adjusting these sliders, because the results are very subjective. The best advice I can give is that it is common to set the reverb wet signal too high in comparison with the dry signal. If you are unsure, find a level that sounds good and then turn the wet signal down a little.

Interface

Figure 8-8 Space Designer.

The interface is deceptively simple. The primary area is a graphical representation of the impulse originally created either in a physical space or as a result of the Space Designer Synthesis tool. At the end of this chapter, I will explain about the Impulse Response Utility, which can be used to create presets, so see that section for more information on impulses. The center section of Space Designer is very useful because you can see what the different settings are doing to the sound of the reverb. This section has several different views: Volume Env, Filter Env, Density Env, and EQ. By clicking on each of these buttons, the overlay which is semi-transparent over the actual waveform of the impulse switches to represent the different sections. The Volume Env(elope) controls the volume level over time; the Filter Env controls the cutoff frequency of the filter section; the density represents the level and amount of synthesized reflections; and finally the EQ is a standard equalizer. Let’s cover the most important features first and then we’ll get to some of the fun stuff.

Level Adjustments

You can easily pick a preset from the list and use Space Designer without ever tweaking any settings. However, you will need to adjust its output level to make it fit in your mix. The interface is different in stereo/mono mode versus surround mode, so we’ll need to look at both. In stereo/mono mode, you will find two sliders on the upper right side: Dry and Rev. The Dry slider adjusts the level of the original signal being fed into Space Designer. The Rev slider adjusts the level of the reverb effect being generated by Space Designer (see Figure 8-9).

Figure 8-9 Output sliders.

You can adjust the reverb level in several ways. If you are feeding the audio to a bus by using a send, simply turn the send level down using the Send Level slider in the Effects tab in the left pane. You will need to select the track that has the send on it and then expand the Send area in the Effects tab by clicking the arrow next to the Send check box (see Figure 8-10).

Figure 8-10 Send parameters.

Figure 8-11 Space Designer track fader.

You can also turn down the Rev slider (see Figure 8-9). Lastly, you can turn down the fader on the track which holds the Space Designer plug-in.

I prefer to send a full signal to the reverb (leaving the send at 0, which is the default), and then adjust the reverb level using the Rev slider or the track fader. If you are using a send then the Dry should be turned all of the way down to prevent having the dry signal on the original audio track and on the bus. If you are inserting Space Designer on the audio track itself, you will need to turn the Dry up so that you can hear the original audio. The other alternative is to have Space Designer plug-ins on every track or clip in your session, which can be complicated because you’ll need to create the same settings on each and it might hit you too heavy on the CPU usage.

Figure 8-12 Input section.

On the left side of the interface you should see a slider that adjusts the stereo image of the reverb input. If you leave it up, all stereo information will be retained. Moving it to the middle combines the input into a mono file. Sliding it to the bottom will switch the left and right channels. I typically leave this in the default position.

In surround mode you will see a number of different sliders. The way to use Space Designer in surround mode is to insert it on a track or clip that is either a surround item or that is being sent to a surround submix. These sliders affect which channels the reverb will be heard in (see Figure 8-13). The first slider adjusts the level of reverb in the center channel. If you are placing reverb on a dialog track then you will want to leave this fairly high, but you have some flexibility with it.

Figure 8-13 Sliders in surround mode.

Figure 8-14 Surround Input slider.

The Bal slider adjusts the front to rear balance. Pushing this up places the reverb entirely in the front left and right speakers. The Rev slider sets the overall level of the reverb. Typically, you will set this quite low. If you set it high, it will overpower the dry signal and sound wrong. The Dry slider does the same here as in stereo/mono mode: it turns the unprocessed audio signal up and down. When Sound Designer is inserted on an audio track this should be set to the top, but if it is an insert on a bus track it will be set to the bottom. When Space Designer is in surround mode, the slider on the left side switches to an LFE slider (see Figure 8-14).

The LFE slider adjusts the level of the LFE in relation to the input of Space Designer. By default this is set to 0, which means the LFE passes through without actively creating additional reverb. I recommend leaving it this way to prevent the low frequencies of the source material from creating a lot of low frequency reverb. Instead of adding power, it would make things sound extra-muddy.

Figure 8-15 Impulse response length parameter.

Length

The next thing to adjust is the length of the impulse. If the reverb tail is too long then it will create a muddy mess. I tend to pick a preset that is slightly longer than I need and then shorten it to the perfect length. To shorten the impulse you can use the Length setting. When using an IR sample you can never make the length longer than the actual impulse file. When using a synthesized impulse (which is covered below), you can make it as long or as short as you like. The trick is in knowing how long or short to make it. Unfortunately there is no magic bullet for this issue.

Equalization (EQ)

The EQ panel is the next area of Sound Designer that it is important to understand. A preset may be good for what you are trying to do, but with a little EQ you can make it great. The approach to take is simple: if the reverb is sticking out too much, then turn down the high frequencies; if the reverb is not sticking out enough, then turn up the high frequencies. If there is too much bass sound coming through the reverb, then turn down the low frequencies. That is just about the extent of typical reverb equalization. Of course, you can always do more as the need arises. For more on equalization, see Chapter 7.

Figure 8-16 EQ view.

The remainder of the features of Space Designer are better understood with examples. So, instead of further outlines, I am going to push you to the DVD where the rest of the features for normal use are explained and demonstrated.

Additional Space Designer demo.

Synthesized Impulse Responses (IRs)

What I am going to do now is explain how to create a synthesized IR for use in creating custom reverb presets. Instead of loading an IR created in a physical space, Space Designer is able to create an IR based on settings input on the interface. It uses the Volume Env, Filter Env, Density Env, EQ, and Length settings to create an IR that matches those settings. When you make changes to these parameters and then press the Synthesized IR button, a new IR is created to match. This is an extremely powerful tool to have access to. To help you understand why this feature is powerful and how you might use it, let me describe an example situation.

Surround Reverb

Placing a surround reverb onto a dialog track is generally a bad idea. Dialog is typically panned to the center channel in a surround mix, and hearing dialog tails coming from the rear is often confusing for the ear unless done with a high level of subtlety. However, placing an exploding car into a surround field with an appropriate surround reverb might be just the ticket. Just don’t overuse the ‘surround’ reverb option.