Fig. 10. — The settings for capturing an impulse response using Ableton Live’s IR Measurement Device.
Making Impulse Responses Using Ableton Live’s IR Measurement Device
Another way to make IRs of clean amps is with Ableton Live Suite. The trick is to use Max for Live’s IR Measurement Device and Max’s Convolution Reverb plug-in.
1) Find the IR Measurement Device in the Max for Live/Max Audio Effect location, and then drag it to an audio track.
2) On the track, enable the input for your microphone. Next, select the In button in the Monitoring Row and then the output that will connect to your amp. Now record-enable the track.
3) On the IR Measurement Device, use the pull-down menus to select the following: Mono to Stereo (assuming you’re only using one microphone), Amp -30, Sweep 30s (good quality), and IR Time 1s (unless you’re capturing spring reverb or a large room sound along with your clean amp, in which case you’ll want a longer IR Time of 2 seconds or more). See Fig. 10.
4) Run a cable from the output that’s selected in the record-enabled audio track to your guitar amp input, turn your amp volume all the way down, and turn on your amp.
5) In the Test Tone section of the IR Measurement Device, use the pull-down menu to select Freq: 125 Hz, and press the button to turn on the test tone.
6) Now gradually turn up your amplifier until you hear the 125 Hz low-frequency test tone, which is about a low B (5th string, 2nd fret) on your guitar. Without changing the amp volume, unplug the cable from your guitar amp, and plug a guitar into your amp with its volume knob wide open.
Play a low B. The subjective volume level of the B note and the 125 Hz test tone should be about the same. If the test tone is too loud, reduce the output from your interface. If it’s too soft, raise it. The goal is to match both the test tone and guitar volumes as best you can. We don’t want Ableton’s sine sweep to cause the amp to distort.
7) Set up a microphone as if you were recording your amp. Put it right up to the grille cloth, unless you prefer a roomier sound, in which case you’ll place the mic further away. Connect the microphone cable to an input on your audio interface. Set the interface’s input level to avoid overloading.
8) Press the Sweep button. (Consider earplugs for this step!) During the sine sweep, monitor your input recording levels to make sure there is sufficient level, but that it has not overloaded during the sweep. If levels are too low or too high, press Stop, make adjustments, and start Sweep again.
9) Make sure the Trim and Normalize button is selected, then press Save on the bottom right of the plug-in screen. Name your impulse and save it to a location of your choice.
10) On a new audio track, find the Convolution Reverb plug-in in the Max for Live/Max Audio Effect location, and drag it to the track. Now drag the impulse you created directly on to the Convolution Reverb plug-in window. Dial the Dry/Wet mix to 100 percent but keep everything else set to default values.
Fig. 11. — Ableton Live’s Convolution Reverb with a Deluxe Reverb II IR. Note that the Dry/Wet knob is set to 100-percent wet.
Fig. 11 shows a screenshot of Ableton Live’s Convolution Reverb with an IR made using a Deluxe Reverb II with its onboard spring reverb set to 5 1/2.
Check, Check ... One, Two
If you want to test the accuracy of your impulse, record your guitar with the same settings and mic position you used to create the IR. Now set up a track with your new IR loaded into Space Designer, Convolution Reverb, or another convolution plug-in, and record into that track going direct through your interface. Listen to both tracks while toggling between them. If the two tracks are level-matched, you should not hear any significant differences—except that the IR will not have amp hiss or hum.
Now you’re ready to make multiple IR clones of your favorite amps set to different clean settings. When inspiration strikes, these IRs will be available for easy recall. Rock on, guitar amigas and amigos!