In episode 371 of the Production Expert Podcast, my find of the week was a church that my partner and I decided to buy, which we affectionately nicknamed Castle Grayskull…
We have plans to turn this redundant church into a house with an area dedicated to music and recording, (obviously). With renovations and the inevitable change in sonics fast approaching, I decided to capture an impulse response recording in an effort to preserve the original sound of the Castle Grayskull Sanctuary before we started the conversion work. I’d never done an impulse response recording before, so I started this project with a little good old fashioned research.
Let’s start with the basics. Impulse response (IR) recording is the process of measuring a room or acoustic space by playing a tone, or impulse, and recording how it excites the room, creating the reverb. The result is a custom convolution reverb that you can use with plugins. I wanted to create a full stereo convolution reverb to use with my Waves IR1 plugin, To achieve this I needed a left and right mic and left and right speaker.
The Set Up
Creating an IR requires a playback system with loudspeakers, microphones, a recording device, and a frequency tone sweep. To keep things simple and portable, I set up our Yamaha STAGEPAS 500 Portable PA system at the front of the sanctuary. For the microphones, my research suggested that cardioid or omni mics work best for IR capture. As a result, I chose a pair of Neumann KM86s as they have a switchable pickup pattern.
Choosing The Best Microphone Positions
To determine the best position for the microphones, I played a dry reference track of acoustic guitar and vocals through the PA and walked around the church listening to the reflections to find where I liked the sound best, which as you can see, was about 15 feet in front of the PA.
Then I listened to the reference track through the microphones and my recorder and tweaked the placement, so what I was hearing through my mics, matched what I was hearing in the church.
I ended up keeping the mics in omni for the recording because I liked how they were picking up the sound better than in cardioid.
Recording The Best Impulse Response
The Waves IR1 manual specifies recommends…
“Record your Left speaker with the Left mic (LL) and Right mic (LR). Then record the Right speaker with the Left mic (RL) and the Right mic (RR).”
I also recorded both Left and Right speakers with both Left and Right microphones just in case I needed it, although I didn’t end up using it.
In order for your convolution reverb plugin to process the audio recording correctly, you need to use the tone or sweep provided by the plugin manufacturer. Since I’m using Waves IR1-Full, I downloaded the sweep file from their website.
To find the correct sweep file for Altiverb or any other IR plugin, check the manufacturer’s website.
I triggered playback of the file from my smartphone and split the ⅛” output to feed both the PA and to my recorder, a Zoom F8n to have as a reference. I recorded at 24 bit 96kHz - the same parameters as the sweep file.
First, as recommended by Waves, I played the sweep just through the left speaker while recording both left and right microphones. Next, I did the same thing again, this time just with the right speaker, and then again using both speakers.
I repeated that entire process twice to make sure I got a clean recording, free of dogs barking and the neighbour’s lawnmower. Then, I turned up the PA to excite the room even more and recorded everything again.
Back In The Studio
After recording, I imported the files into Pro Tools and removed the parts of the recording I didn’t need but I did not normalize them. To keep everything organized, I named the files “LL_Left Speaker_Left Mic,” “LR_Left Speaker_Right Mic,” “RL_Right Speaker_Left Mic,” and “RR_Right Speaker_Right Mic.”
I exported the files and opened a recent session and the Waves IR-1 plugin to test it out.
To import IR files into Waves IR1, click Load in the top right corner, import IR. You can either import the files with normalizing or without. Since I hadn’t earlier, I let Waves IR normalize it for me. It will prompt you to select 4 files in the following order: LL, LR, RL, RR.
Boom! You’ve got a preset!
Now, I have a reverb that sounds pretty damn good for an old church and because we love you, here is the preset I detailed in this article for you to download. To hear the reverb here are two extracts from a track called Storms Inside Of Me by Sam Ness, one dry and the other with reverb using the Castle Grayskull IR.
For Pro Tools Users
The .tfx file is the one to use if you are a Pro Tools users, In the Plugin Preset menu, select ‘Import Settings…’ and then navigate to the folder you downloaded and select ‘Castle Grayskull.tfx’. You will then be asked to locate the ‘01.wir’ file that is also in the same folder. Once you have selected that you will have the Caste Grayskull impulse response loaded into your instance of Waves IR-1
For Other DAW Users
We have created a Waves preset format .xps file. Use the Waves Load option and select ‘Open Preset File…’ Navigate to the folder you have downloaded and select ‘Castle Grayskull.xps’. You will then be asked to locate the ‘01.wir’ file that is also in the same folder, once you have selected that you will have the Caste Grayskull impulse response loaded into your instance of Waves IR1.
If this has whetted your appetite for creating your own impulse responses then we checked we found that right now the Waves IR1 is on special offer for $39 instead of the normal price of $249. Be aware this offer may not still be available in the future.
What Do You Think?
Let us know in the comments what you’ll use these presets on! If you’ve captured impulse responses yourself please do share your experiences too.