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In this post, I’ll show you how to capture guitar speaker cabinet impulse responses with a DAW and some equipment you probably own already. This process also will work the same for bass guitar speaker cabinets. We’ll cover how to use your DAW, a white noise sample, your amplifier head (it must have an effects loop!) and a microphone to make a digital representation of your speaker’s output.

12 July 2022 – Written by Michael R. Myers

Tags: #mykmyrs #mikem #homerecordingwithmikem #impulseresponse #ir #guitar #daw #waveform11 #tone #whitenoise #amp #effectsloop #guitarcabinet #speaker #bass

Skill Level: Advanced

DISCLAIMER:This post is not sponsored by any company or individual. I purchased all hardware and/or software discussed here with personal funds at my own discretion. The content of the post is my personal opinion and experience with the products mentioned/illustrated.

What You’ll Need to Get Started

In order to capture your own impulse responses, let’s take a look at the following items you’ll need.

• A USB audio interface connected to your computer. I use a Behringer UMC202HD unit.
• A clean white noise audio sample. You can easily find one with a web search.
• A DAW for playing and recording. In this post, I am using Tracktion Waveform 11 Pro.
• An electric guitar or electric bass
• A guitar or bass speaker in a cabinet. I used a Celestion G12L-35 (8 Ohm) from an old Crate cabinet.
• A microphone to record the impulse response
• An audio application, such as Audacity, to edit your impulse responses

First things first

I am entirely a beginner at creating custom impulse response files. From my results and experiences, making great-sounding IRs is an art and requires a lot of practice to get all the pieces into their proper place. This post is the result of research, trial and error and probably more luck than anything else. If I have misstated or written things that are not correct, please let me know and I’ll happily edit my erroneous information. My goal is to help others learn techniques to aid their music production needs.

This post is written at an advanced level, where many things are assumed that you already know. If you are a beginner, you may want to look on YouTube or search for other sources that really go into depth for each step.

Be aware that you can, and maybe should, use a dedicated power amplifier instead of the power amp section of an amplifier head. Since I do not own a neutral power amp, I had to use the power amp from my amplifier. As a reminder, DO NOT use the input jack of a combo amp in place of a power amplifier or amp effects return jack!

Now, let’s get started to capture guitar speaker cabinet impulse responses with your rig.

Set Up Your Physical Gear to Prepare to Capture Impulse Responses

1. Attach your USB audio interface to your computer and make sure any drivers you need are installed and it is configured for audio input and output.
2. Attach your microphone cable to an available input in your audio interface. In my studio, I use Input 1 on my interface.
3. Attach your audio output cable for the LEFT speaker on the rear of the audio interface into the amp head’s RETURN jack of the effects loop, or into your dedicated power amp.
4. Attach a speaker cable from the amp head into the speaker cabinet.
5. Place the microphone in front of the speaker in your cabinet. For the first capture, place the microphone in the center of the speaker and against the fabric covering it.
6. Now that the guitar, amplifier and microphone are set up, let’s move on to configuring the DAW software.

Configure the DAW to Play and Record the Impulse Response

1. Configure your audio sample rate and latency settings. For this example, I used a rate of 44.1 KHz and latency of 64 samples. Some people capture impulses at 48000 or 96000 in addition to 44100. This part is up to you to decide. Remember that more sample rates means many more files to capture and process.
2. Configure your audio ports so that the microphone signal is coming in through Input 1. The output of the interface should be itself.
3. Place the white noise sample you downloaded onto a track in the DAW. I put some empty space before the start of the white noise clip, and after it, as a padding for recording.
4. Create a separate audio track for your microphone’s input.
5. Test your set-up by playing the white noise track in a loop. Do you hear the white noise pop sound coming in on the microphone track? Remember to check the mic’s input levels and make sure it is not clipping. On my DAW, I keep the level in the green portion of the level meter.
6. When you are satisfied with your mic’s level, record the mic on its track. This audio is the impulse response of your guitar speaker with the microphone in the center of the speaker. It will show at the left side of the recorded track.
7. Move the microphone into a new position on the cabinet/speaker and repeat the process from step 3. Do this as many times as you like, each time moving the microphone to a new position to capture a different spot.

Exporting Your Captures

1. When you have captured all of the microphone locations that you wanted, you are ready to export your microphone captures as wav files.
2. For each microphone track, export it and make sure you set them to be a wav file, normalized and in mono. There are a lot of tutorials and videos where authors direct to use -3 for normalization or to use -6. The fact here is that it is a personal choice, and I think only trial and error in your studio with your gear will give you the “right number” to normalize to. I focused only on making sure that the finished IRs did not clip.
3. After your tracks are exported as individual files, the editing portion begins.

Trimming Your IRs

1. Much like the strong feelings about normalization levels, different authors have differing opinions on where to trim the impulses for maximum sound quality.
2. Open your first capture, from the center of the speaker, in an audio editor such as Audacity. This will allow you to zoom in deeply to the content of the wav file and make a trim at the start of the file.
3. I zoomed in and removed everything up to the last dot that was flat, right before the audio started to go upwards. I then removed everything after the 0.20 time marker. You can experiment here on your own whether longer IRs are better because this is another case of trial-and-error to find your best values.
4. I then exported the audio file as a 24-bit wav into a dedicated folder. These files are the actual IR files that can then be used with any IR loader application.
5. In your DAW, use an IR loader to select one or more of your IRs and see how your IRs sound.

Summary

In this post, we covered how to capture guitar speaker cabinet impulse responses with your guitar speaker cabinet. While a bit time-consuming and subject to many trial-and-error captures, capturing your own IRs is a great skill to have in your studio. Capturing IRs of your cabinet can be helpful in the event you need to re-record parts of a track. IRs can also help you come up with a standard sound for your tracks or an album. IRs open a whole set of options and can help you have a more consistent sound on different platforms/devices. Hope you captured some great IRs, and feel free to let me know how yours turned out.