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Recording electric guitar with an amp can be a struggle without proper microphones and a decent sounding room, but there is a great workaround for this issue using impulse responses.
by Luka Sraka, November 2016
Recording Guitar with Impulse Responses
Recording electric guitar in this day and age is as simple as it gets. We have great impressive sounding guitar amp simulation plug-ins that are as much of a real deal as a nice amp recorded with a couple of quality microphones. That said, there are still some of us that think that there is some mojo in plugging your guitar into a righteous tube amp and recording guitar through it. But it is not as easy as it seems. If we want to record a great sounding guitar amplifier, we need an OK sounding room or at least some sort of acoustic absorption so we do not record too much room sound. We need an adequate microphone. And last but not least there is also the volume issue. Tube amps sound the best if they are set fairly loud, too loud for recording in an untreated room or for late night recording.
There is however a great way to overcome these issues. Using impulse responses is a great practical and creative alternative for micking your guitar amplifier.
What Are Impulse Responses?
Impulse Responses (IRs) are basically impulse recordings of actual spaces that translate into the equivalent of EQ curves and ambiance. We know impulse responses from reverb plug ins which use sampled acoustic spaces for example: a famous studio live room, or a church hall. We can load those IRs into a reverb plug-in and have the ambiance sound of those “sampled” spaces.
Impulse responses are not limited to spaces though. You can make an impulse response of a speaker cabinet. When you are capturing an IR from a speaker cabinet you are in fact capturing the whole chain, the D/A converter, power amp, microphone, preamp, cables, etc.
Luckily enough we don’t need to sample our own impulse responses, since there are great impulse responses on the market. Guitar cabinet impulse responses are usually captured with different microphones at different positions and different distances from a guitar speaker cone. Needles to say impulse responses are made with various speaker cabinets using various guitar speakers.
Using Impulse Responses
To record a guitar using impulse responses, you will need to get the amplifier signal before it reaches the speaker to your sound card. If your guitar amplifier has a direct out, you are pretty much set.
If not, you will need a device that attenuates the output of your guitar amp to a line level. Do not plug your amplifier speaker cable directly to your sound card by any means! This will end in damage to both of your devices, your sound card and the amplifier. There are different products on the market that accomplish this, to name a few: Hughes & Kettner Red Box, Rivera RockCrusher, Two Notes Torpedo line of products or any attenuator that has a line output. Keep in mind that a guitar amplifier always needs to see the load of your speaker. If you want to record silently, not using your speaker cabinet for monitoring you will need to invest in a load box, which takes the load from your speaker to the load box. Some of the mentioned products above have a load box built in and some don’t. Be sure to make some research before you attempt in recording your guitars this way.
When you have your guitar amp signal attenuated to a line level, you can connect it to your sound card and record. The recorded guitars will probably sound thin and harsh, since the guitar speaker is a vital part of shaping the sound of an amplifier. This is where the impulse responses come in.
There are different companies and individuals that make impulse responses and they vary in quality. One of the best known impulse response producers are the people from RedWirez ( http://www.redwirez.com/ ). They have a range of impulse responses from different cabs available but best of all they have a great free impulse response library that was made using a 4X12 Marshall 1960A loaded with Celestion G12M speakers. You have seventeen classic guitar microphones to choose from (all with different mic positions and distances) plus a range of ambient microphones.
You will also need a plug-in to load those impulse responses into. That can be done in any of convolution plug-in such as a reverb plugin, Logic Pro Space Designer comes in mind, but any of IR loading reverb will do. You can also use a specialized speaker cabinet IR loading software. One of great free plug-in for this use is the Ignite Amps NadIR Convolver ( http://www.igniteamps.com/en/audio-plug-ins ).Using a plug such as the NadIR enables you to load more IRs at once and blend them together and pan them, in the same way you would blend and pan the two microphones that you recorded your guitar amp with.
You can also use the speaker simulation part of your amp simulation plug in for the same purpose
The Advantages of Using Impulse Responses for Guitar Recording
Using impulse responses for guitar recording is very practical. It is realistic sounding, if you have an load box you are able to record guitars silently in the middle of the night, which means you can run your amplifier as cranked as you want to get the desired sound. It means that you have different microphone options, you can have the sound of a guitar cabinet recorded with a ribbon Royer R121 without spending upwards of a thousand dollars for a microphone. You can have IRs from as many different guitar cabinets you want, a 2×12 open back with alnico blue speakers, a 4X12 with V30 etc. without busting your bank account and cluttering your room.
Impulse responses are a great and creative way of recording your electric guitar amp. As always have fun experimenting and making music!