How Reverb works
How Reverb works:
I recently was asked to post something about reverb and how to use it best. I'm not going to claim to know all there is to know about reverb but I'll do my best to share what I know. I'll also try not to use too much geek speak when explaining things. let's start by defining some of the most important features.
Reverb decay - This is how you control how long the reverb lasts before it fades out. Depending on what you are going for, this can be long and washy, or short and barely noticeable. keep in mind though that even though you might not immediate hear what a reverb is doing, the brain is exceptional at picking up these subtleties & can make a huge difference between a flat, sterile and lifeless sound & a realistic sound. By controlling these, it's possible to use reverb rhythmically. You can have it fade after a 1/4 bar or 1/2 bar. Slightly adjusting this can create a bit of swing or groove to your mix.
Diffusion - Diffusion is created when a sound reflects off a surface. A flater surface will have less diffusion because it simply hits the wall and bounces back. If you are in a cave, the surface is going to have all kinds of angles causing your sound to bounce and echo in a more complex way, creating a reverb that is less like the original sound. Less diffusion will have a brighter sound while more diffusion will make the reverb darker.
Reflection - Reflection is similar to diffusion in that it has to do with the angle at which soundwaves bounce around. As soundwaves spread throughout a space and bounce off all the encompassing surfaces, they will undoubtedly bounce back into eachother causing the waveforms to change, phase cancel eachother out, or to double up and increase in volume. Each of these reflections hit the ears at different times creating the full effect.
Predelay - This is the time between the original sound playing and the reverb reacting to that sound. Adding predelay can help the attack of a sound come across much cleaner as it's not yet effected by the reverb. A longer predelay can create a short echo or a slapback type effect.
Types of reverb -
Plate reverb - A plate reverb is named that way because they used to send sound to a "plate" of metal which it would reverberate off of. It doesn't take up as much dimensional space & thus doesn't bury & blur sounds in the way other types of reverb do. It tends to blend with the sound more and helps give sounds more impact. It's a cleaner reverb in that it doesn't take up as much space. It can be great for a smooth sounding vocal that doesn't get lost in the mix. Although plate reverb is great, you will want other reverbs used to add depth and dimension to your mix.
Gated reverb- This isn't really a type of reverb, but more the effect that is put after the reverb effect. This allows you to make a sound bigger but not have a long tail (or decay). This effect was used a lot in the 80's (some might say overused). By setting a gate effect after your reverb, you can adjust the gate to silence your sound once it goes beneath a certain volume. This effect can be used to clean up your mix so it doesn't get too muddy. Too much reverb used in the wrong way can drastically lower the quality of your mix.
Spring reverb - This type of reverb was popularized in guitar amps. The sound is created by metal springs and gives a vintage feel to some instruments. Great for a more lo-fi vibe. It's not smooth like other reverbs, but can add a different character to instruments.
Hall reverb - Adds depth and dimension & fills in gaps in the mix but keeps in the background where it doesn't clutter the mix. Using a large room size but a shorter delay time can help with a cleaner mix (even though it is not a natural sound found in the real world). Using too much can push important sounds to the back of the mix, but can add further thickness and space to sounds with long decay like pads or piano. Slower songs can typically handle longer reverb times.
Room reverb - Similar to hall but typically has a shorter decay and smaller size than hall reverb. Good for guitar or drums to give it a realistic space in your mix. A realistic space can be important when using acoustic instruments.
Convolution reverb - Imagine if you wanted to "sample" the reverberation of a specific location, be it a stadium or a bathroom. Convolution reverb makes that possible. This can give you some very interesting options. Perhaps adding the space of a wooden barrel or the inside of a metal pipe. This could be a powerful asset in creating both real world environments or alien environments & can be a sound designer's best friend. Since this reverb is essentially sampled and then applied to a sound, there isn't a whole lot of flexibility to a specific reverb setting but can offer results unavailable any other way.
Chamber reverb - Also known as an echo chamber, this reverb was created by sending a speaker into a specially designed room and a microphone strategically placed to capture the reverb effect and added to the original signal.
Reverse reverb - This effect is where you hear the reverb effect before the original source sound. Used a lot as a vocal or drum effect. This can be accomplished pretty easily in the digital domain by reversing your original source sound, adding reverb to the reversed sound, rendering the results and once again reversing so that the reverb plays in reverse while the original sound plays forward.
In most situations, you will want to set your reverb at the end of your effects chain. Basically you'll want to dial in your clean sound before smoothing it out with reverb. If you are wondering whether to add reverb or delay last, I'd suggest reverb. This will give you the most natural sound and make it easier to get the effect you are looking for (unless you are going for something unusual). In some cases I will add a compressor after the reverb to boost it's effect.
Reverb on send/returns - By creating a send track you can set up 2 or 3 reverb types and assign a specified amount of any or all of them to whichever instrument you want. Not only will this save CPU on your computer, it is great for placing multiple sounds in one space (like your drums). Since all your reverb will be sent to your send track, you will have more control of it's overall volume & eq.
I personally like to eq out reverb frequencies below 120hz. Sometimes higher depending on the instrument.
Another use for a reverb send is to switch it to mono and pan your reverb just like you would an instrument. You can keep it in one spot or automate your panning. You can do this with more than one reverb send if you like. this should give you some interesting results.
Using more than 1 reverb on a sound can give you more a realistic effect at times. this would typically consist of a short reverb and a long reverb.
Create great pad sounds with reverb by creating a long reverb of several seconds (even 10-15 seconds can sound good) and setting the wet/dry setting to 80%-100%. The reverb smooths out whatever sound you run through it. I like using a simple synth melody or vocals but have gotten great results from less conventional sounds as well.
Sidechaining reverb tricks - This is another widely used trick in dance music. For this effect, you would typically want to have a reverb send/return track and throw your sidechain compressor on the track. Sidechain it to your kick drum for that pumping effect or you can sidechain it to the original dry sound you are adding reverb to. This will push the effect down while the original sound plays for a cleaner sound and then the reverb will rush in after the original sound stops playing. You can get varying results by adjusting the threshold.
Accent your groove with Reverb - By adjusting the attack and release envelopes. You don't have to just use reverb to add dimension to your song, you can have it assist the overall feel of your song by adding it to any instrument that could use it. You'd be surprised with the results you get when using this trick correctly. You can set your decay to fall to silence just before the next beat or bar or any multiple that works for you. I like 1/4 note or 1/2 note intervals. Making slight adjustments can give your groove a more rushed or laid back feel. By adjusting your predelay, you can change the groove as well.
Experiment and have fun with this wonderful but often misunderstood effect.
Happy music making,
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