I recently talked about impulse response on guitar and how you can use it to get better and more realistic sounding guitar. A similar principle can be applied to your reverb to simulate the spaces used on your favorite records, so let’s identify why is impulse response in reverb.
What is Impulse Response in Reverb
Impulse response in reverb is a way to replicate or simulate the sounds of a real world or virtual space from its echos and reverberation and apply it to your own audio.
Commonly referred to as IR, impulse response is all about taking the sonic characteristics of one environment and applying it to another, as in the case of the previously mentioned guitar.
This is handy if you don’t have access to a particular space anymore, if you’re recording your audio in a less than ideal environment, or you want to make your DI or midi recordings sound more realistic.
In the case of guitar, it was about capturing/recording a clip of clean, dry, and unprocessed guitar using our cabinet to capture that cabinet’s sound to apply to future guitar tracks we weren’t recording through that cabinet.
The “Impulse” in the case of impulse response reverb is referring to some kind of uncomplicated and easily replicated source material, like a clap, to capture its sound in that acoustic space.
With that in mind, you can create your own impulse response reverb from a space you are recording in, then apply it to the audio you recorded in a different space.
This is essentially a simple, two step process.
How to Make a Reverb Impulse Response
The first step is capturing the sound of the room you want to apply to unaffiliated audio.
To make a reverb impulse response, set up a microphone in the room you want to capture the reflections of and create a loud, simple one-off sound. A loud, one-off clap is the most common source material, but I’ve seen plenty of other examples, including popping a balloon.
A neutral microphone which won’t add any coloring to the sound is best, and the location of the microphone plays a big role in shaping the IR reverb makeup you’re creating. This makes sense considering that impulse is going to sound different if the microphone is in the center of the room versus in the corner.
You can try setting it up in the middle to capture the entire room as evenly as possible, or you can set it up in the best acoustic space in the room.
Where you create the response relative to the microphone also affects the sound. You may want to try a number of setups and apply each of them to your audio to determine which you think sounds best.
Of course you don’t need to create your own, as doing a basic search for “Impulse Response Reverb files” will yield limitless free packs full of hundreds of IR files which sample every environment you can imagine.
Once you’ve got your WAV file of that isolated, recorded impulse, this takes us to actually applying a captured sound to existing audio.
How to Use a Reverb Impulse Response
With the WAV file in hand, you simply apply this to your reverb of choice which is compatible with impulse response files.
In my favorite reverb, FabFilter Pro-R 2, you’ll find an option to import an IR WAV or AIFF file in the bottom of the preset section.
After importing a sample IR WAV file I found online of a clap in an elevator shaft, Pro-R 2 created a simulation of that environment via its settings based off of the sound and reflections of that impulse that was the clap:
By pulling the reverb characteristics of the live room of your favorite professional studio (for example), you can bring a similar sonic characteristic to your mix.
Use this on an Aux/return track and blend it in to however many tracks you like in your mix to taste, or drop it as an insert on your master bus to bring just a flavor of that space’s reflections across your entire mix.
I did a recent overview on using reverb on the master bus, most notably the blend amount and EQ settings I like to use to just add a touch of that space while bringing a sense of cohesion across the entire mix by way of sharing that communal space on every track.
Impulse Response Reviewed
Impulse response reverb has a number of benefits.
- It can make all of the tracks in your mix sound like they were recorded in a common space, even DI and midi tracks.
- It can recreate the acoustics of professional studios.
- It can make your audio sound like it was recorded in a better place than it was, or a place you don’t have access to anymore.
- There is a huge library of free IR reverb files available on the internet to recreate virtually any environment you can think of in your own mix.
Check to make sure your reverb plugin of choice can make use of IR files then create your own to add your room sound to tracks which weren’t recorded in your room, or get one of the limitless ones available online to add that extra sense of realism and quality to your mix.
