How to create/record an Impulse Response

by | Mar 29, 2018 | Post from Product Developer, Guides | 0 comments

Creating an Impulse Response of your cabinet can be quite useful when it comes to mixing or recording, specifically at home.

It gives you the ability to switch around and tweak your sound after you have recorded without the hassle of having to re-record what you had previously recorded. It also eliminates the loud noise generated from a physical speaker which limits your choice of location when it comes to producing music.

To start recording an Impulse Response of your cabinet you will need to have an Amplifier with an Effects Loop, A Soundcard capable of sending and recording a signal simultaneously and a Microphone, so you can hook it up with your computer/DAW and actually get a good signal in and out.

Once you have hooked up everything together with your rig, you are ready to mic up your cabinet and start looking for that “sweet spot”.

Easiest way to do this is have one person playing the guitar with headphones on, hearing the input of the Microphone while giving directions to another person who is moving the Microphone across the cabinet.

Once you finally found the spot you want to record, you will now change around some things in your rig so that the computer can send a signal through your amp/cab and also pick the signal back up using the microphone that you’ve placed earlier.

  • First you need to have a cable going from 1 of the Outputs of your soundcard, into your Amplifier. You need an Amplifier that has a Effects Loop, this is where the cable goes – into the Return of the Effects Loop. This allows you to bypass the pre-amp of your amplifier and only use the power-amp that drives the actual cabinet.
  • The Microphone should already be in place and going into your input of the Soundcard.

Now that you have a rig set up and ready for recording and creating an Impulse Response, What you need to do now is download a Deconvolution software so that you can create an Impulse Sweep you will be sending through your cabinet.

The Impulse Sweep is basically sending frequencies through your cabinet from 10hz up to 10khz letting you record how the cabinet reacts to each of the frequencies.

For PC users you will have to download and use Voxengo Deconvolver.

Here is a great Video that explains how to use Voxengo – and record an Impulse Response in general really well.

For Mac users that happen to use Logic, there is a native program within the Logic App called Impulse Response Utility that helps you with this exact thing.

Open up the Impulse Response Utility and you will see the following;

Choose the correct input so that it has the input of the microphone, and the output so that the signal is sent out of your Soundcard and into your amplifier’s Effects Loop.

Choose the channel corresponding to your output regarding the sweep, and switch between the different Test Tones to make sure that they don’t peak the signal and adjust your sweep level accordingly.

When everything is to satisfaction you click “R” to arm the rig for recording.

Make sure everyone and everything  near the speakar/microphone is silent so the sweep recording doesn’t get disturbed.

You can adjust the length of the sweep, i usually just keep it at around 10 seconds to make sure every frequency gets picked up. The Reverb time should be set as low as possible.

After you’ve recorded your sweep you can trim the recording down by dragging on the visual screen, try and trim away the start until you see where the audio-waves start to form.

Doing this makes it easier to use the Impulse Response you have created together with other Impulses in the future if you would want to blend and mix around with them.

Now that you are done recording and trimming, click “Create Setting”.

It will be saved as a .SDIR file which is used by Logic’s Space Designer plugin. What we want to do now is convert this file into a .WAV file.

For this i use a program called X Lossless Decoder(XLD).

It’s a tool for Mac OS X that is able to decode/convert/play various ‘lossless’ audio files.

Opening the .SDIR file through XLD automatically creates a .WAV version of that same file, Resulting in your new Impulse Response.

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