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Convolution reverb IR: Recording


Here are some of my thoughts when I'm at location to record Impulse responses.


When entering a new place the first thing you will need to do is make some decisions. Where will the microphones and speaker stand, where from do you want to capture the IR? Is problematic background noises more audible more in some places? How many IR on the location will there be time for? Where is the closest power outlet?  If the location has for example a highway nearby you might need to consider using a shorter sweep file since the timeframe of silence might be short and you can a clean recording of a 15 sec sweep but will have much more trouble with a 50 second sweep. 


It's ideal to visit the place or environment at some time before the recording will take place, to se the challenges in advance and to scout for good recording positions. 

Distance matter. Measure the distance between the speaker and microphones and write it down so you have a information document on every place you capture IRs. It can help you a lot if you need to revisit the recording project some time after the recording tok place. 

Write down possible artifacts in the files, such as a car driving by. It will make it easier in post to know why the files behave in a certain way. 

Take some pictures of the setup. Mobile pictures works fine as long as you can se where you placed the equipment. 

When using a Zylia ZM-1 that has multiple output possibilities it can convert audio to any surround format in the software perfect align, this will help you and take care of phase issues when converting. 

Don't sweep to loud, try to find the a good combination of noise floor for that location without letting the speaker melt down. 

Prepare presets for what you can before. I have a mapp I just copy when I'm at a new location where I have clean Logic, Reaper and Impulse response utility's ready. 

Recording challenges


Phase issues can be troubling especially when using condenser microphones. You need to have this in mind during recording. I would say that phase is not as often a problem when using omni microphones with some distance between them. 

There is always possible to mixture with the recordings and phase in post production but it can be troublesome especially with more than two microphones. 

Wind, noise and weather can be a challenge when creating IR outdoor. 

Lack of time at location and technical issues. Try to have a backup plan for most of the technical stuff. For example: Interface with possibility to record audio files without a computer in worst case, extra batterys, extra microphone, extra cables etc.  


Closing Thoughts 

A Impulse response recording can be much fun and you will learn much the first times you perform them. I'm sure you will find own creative ways to improve the workflow and recordings after some field experience. 


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