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Posts Tagged ‘Impuls Response’

If you’re doing home recording, like me, you don’t have a lot of money to spend on expensive recording equipment or even just gear like amps and cabinets and especially, microphones. You need to find economical ways to lay down your sound. Well, I recently discovered Impulse Responses, which are digital profiles of real cabinets that you can use with GarageBand, either using the amp models or, using your own amp running into a load box (if it’s a tube amp) and using the IR as your virtual cabinet.

But to use them in GarageBand, I had to do a little digging. There were tutorials out there, but some skipped over some important information or the posts were so old that they were literally missing content. So I had to figure out a lot of stuff on my own, and once I did, I decided to do a tutorial myself.

First, you need a convolver plugin

A convolver is software that convolves an audio stream with an impulse response. To put it simply, this plugin allows you to load IRs for use in GarageBand. There’s no real magic here other than the great sound that the IRs provide. IRs are WAV files; though they’re actually special WAV files. If you tried to listen to them, they sound like clicks. The convolver plugin takes that WAV file and makes it usable in GarageBand as a speaker cabinet.

The one that I use – and seems to be the one that is most recommended (probably because it’s free) – is called LA Convolver by Lernvall Audio. You can download it here. It’s a ZIP file, so you’ll have to decompress it. Once you’ve done that, then you need to follow some discrete steps:

Copy or Move the LAConvolver.component file to the [Macintosh HD]/Library/Audio/Plug-Ins/Components folder.

Other tutorials said to open up GarageBand and you’ll see LAConvolver as an Audio Units plug-in. But that didn’t work for me until I restarted my Macbook. So I recommend that you restart or shut down and restart before you open up GarageBand.

Once you open GarageBand, LA Convolver will be available as an Audio Units plug-in under Lernvall Audio as shown below:

If you still don’t see it, then it’s possible that GarageBand was set up under your user profile on your Mac. For that, you’ll need to place the LAConvolver.component file into [Macintosh HD]/Users/<your user name>/Library/Audio/Plug-Ins/Components. This is what I had to do.

If LAConvolver was successfully added, then when you select the LA Convolver menu item, you should see the following plug-in dialog box:

We’ll get into loading IRs a little later. But first…

Next, you need to get some IRs

I’m a big fan of Pete Thorn, and he recommends using OwnHammer IRs. They have a free set that you can experiment with, but I just pulled the trigger on the Core Tone Bundle that consists of IR models of Fender, Vox, Marshall and Mesa cabinets.

Once you download your IRs (they come as Zip files from OwnHammer – not sure of other producers), I recommend that you move the Zip files to a convenient place. I put mine under a folder I created under the Music folder on my computer: [Macintosh HD]/Music/IRs:

Once you get the Zip files to a convenient location, you need to unzip them. With OwnHammer zips, they decompress to an OwnHammer folder. As you can see in the image above, I renamed the uncompressed folders to the cabinets so when I decompress another Zip file, it won’t overwrite my other IRs.

Understanding the IR Files

At least with the OwnHammer IR files, you might get confused by the sheer number of them as shown below for the Fender Deluxe Reverb (click on the image for a larger view):

The reason why there are so many is that the IR’s come in different flavors. For the files numbered 0 to 10, these represent mic placement on the cone; 0 being dead-center to 10 being at the edge. These are the predominant file types. There are also a couple of others such as “FRED” that set the mic on the edge and angle it 45-degrees, and ROOM, where the mic is set at a distance and you get some room reflection (I love this, by the way). In the image above, I’m showing the “Mics” folder which includes IR files for individual microphones, while the “Mixes” folder includes a combination of a couple of mics.

According to OwnHammer, the numbers don’t represent a specific distance from the center as the numbers increase. They’re rough positions, so if you chose “OH 112 DVRB FN-AXA 57-05.wav,” you’d choose an SM57 positioned roughly between the center cone and the edge. The graphic below illustrates this:

As you’d expect, the further away from the center a microphone is positioned, the warmer the sound gets; in other words, you lose highs.

Now it’s time to choose an IR to use in GarageBand

There are a couple of ways to set up your guitar sound. The first is to input your amp directly, using a load box whose line out runs into your audio interface. Then you can just add the LAConvolver plug-in to your track, choose the IR you want to use, and you can start recording away!

But if you’re like me and are often pressed for time, using the Amp Designer plug-in in combination with LAConvolver is very easy. This will give you a complete software-based signal chain. Of course, the weakness here is that you can’t use pedals, but if you just need basic sounds, this will work nicely. So here goes:

First, create a new, blank track. Select “Record using a microphone…” option. You don’t want to use the canned guitar/bass option because once you disable the cab and use the IR, I found that it messes up the signal and your track volume goes WAY down. Once you set up the amp and IR though, feel free to add other plug-ins.

Next, add the Amp Designer plug-in to the track. Choose the amp model you want to use.

Set the cabinet choice to “Direct.” This is extremely important because you want to bypass the cabinet completely and use the IR as your cabinet.

Now, add the LAConvolver plug-in by going to the Audio Units menu and selecting “LA Convolver.” Once you do this, you’ll get the LAConvolver plug-in dialog:

Next, choose your IR. Click on one of the channel rows, then click on the “Choose” button. You’ll then get a File Chooser dialog. Navigate to where you stored the uncompressed IRs and select an IR. For me, I chose the following:

You’ll see that there IRs for Atomic, Fractal, Kemper and Line 6, plus generic Wav-200ms and Wav-500ms. Not sure what the difference is as of yet, but I just chose the Wav-200ms at 44.1 kHz, 112 DVRB, FN-AXA, Mixes, and the OH 112 DVRB FN-AXA 57-05 IR file, which uses two mics position between the center cone and edge.

Note that each IR has two channels in LA Convolver. This is actually pretty cool because you can choose an IR for one channel, and another for the other channel. But for my setup, I used the same file on each channel.

Once you’ve chosen your IR files, the dialog should be filled in like so:

I haven’t played much with the Wet Gain other than just testing out the output volume which could be useful if the gain is too high and starts clipping the track.

So that’s it! Record your tracks! Granted, you’ll have to do quite a bit of testing to find just the right IR. I spent about an hour trying out different ones until

If there’s anything I’ve missed, please let me know and I’ll add it!

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