Extra Cabs for Your Amp Sims – That You Didn’t Know You Had!

An amp
sim’s cabinet is a crucial element for shaping your guitar’s tone. Amp sims
come with stock cabinets, and many sims can load third-party impulse responses.
But there’s also a way to multiply the number of cabs in your amp sim’s
existing roster of cabs. And, perhaps best of all, the new cabs are free.

How It Works

A cabinet’s
frequency response is anything but flat. There are multiple peaks, dips, and
resonances that create its “character.” We can take advantage of these
differences to “morph” two of your existing cabs into a different cab.

This works by feeding your sim’s amp into two parallel cabs
and flipping the polarity (phase) on one of the cabs. If both cabinets
are identical, then the sound cancels because one cab is completely out of
phase compared to the other. But, if the cabs are different, then what
they have in common cancels while the differences remain. This can create
anything from fairly normal-sounding cabs to tones that are seriously crazy.

The total number of morphed cabs you can obtain equals the
number of cabs in your sim minus one times the number of cabs. For example, if
your sim has 16 cabs, then there are 15 x 16 = 240 possible combinations. Or consider
the Line 6 Helix — it has 41 cabs, so there are 1,640 possible cab
combinations.

Fig. 1 shows the spectrum for two Line 6 cabs fed by pink
noise: a 4×12 Greenback 20 (top) and a Soup Pro Ellipse (middle). The bottom
curve results from flipping the phase on one of them.

Figure 1: The spectral response for (top to bottom) a 4×12 Greenback 20, a Soup Pro Ellipse, and the out-of-phase response. Note the frequency-response gyrations in the out-of-phase version.

The following audio example plays the 4×12 Greenback 20, the Soup Pro Ellipse, the out-of-phase response (with a narrow cut at 5.6kHz to tame the high-frequency whistle — more on this later), and, finally, the original out-of-phase response without the narrow cut.




How to Separate
Cabs from Amps

Manipulating
cabs independently requires being able to separate the cabs from their
associated amps. Most sims do this in one of three ways. Some DAWs, like
Digital Performer, treat the amps and cabs as separate types of insert effects
(fig. 2). Pro Tools’ Eleven MK II combines amps and cabs but also makes the
cabs available as separate effects.

Figure 2: MOTU’s Digital Performer treats amps and cabinets as separate insert effects. Note that the cabs are in a “room” environment with a collection of mics.

A more common approach is integrating the amp and speaker
into a single effect. In this case, isolating the cab involves turning off
“power” to the amp, essentially bypassing it. Fig. 3 shows this with PreSonus
Ampire, Waves PRS SuperModels, and IK Multimedia’s AmpliTube.

Figure 3: The cursor arrows are pointing at ways to turn off amps. Clockwise from top: PreSonus Ampire (where you specify “none” for the amp), Waves PRS SuperModels, and IK Multimedia AmpliTube 5. The last two have virtual power switches.

A third method takes an à la carte paradigm, where
you build a rig that can pair amps and cabs — or insert them separately. Line 6
Helix, Native Instruments Guitar Rig, Overloud TH-U, and others take this
approach.

Switching Phase

Now we need
to route our cabs, regardless of how we obtained them, in parallel — as well as
to be able to flip the phase on one of them. Guitar Rig, AmpliTube, Helix,
TH-U, and others make this easy by integrating phase switching into the sim
(fig. 4).

Figure 4: Clockwise from upper left: AmpliTube 5, Line 6 Helix, Guitar Rig 6.

Each of the setups in fig. 4 takes a similar approach.
AmpliTube has a mixer for two cabs where one channel can switch phase. Helix is
set up with two cabs in parallel, which go into a mixer. The B path’s phase can
be inverted (lower right). Guitar Rig has a splitter module; an amp is being
split into two cabinets, and the B cabinet has a phase invert button (again, in
its lower right).

Studio One and Ableton Live can create effects chains,
which house a collection of amps and cabs and accommodate phase switching (fig.
5).

Figure 5: This Ableton Live effects chain splits an amp output into an effects rack with parallel cabs.

In fig. 5, the amp feeds into an effects rack with two cabs
panned hard left and right. The next stage is a Phase Invert utility. Setting
this to stereo, reversing either the left or right channel, and then summing
the left and right channels together provides the needed mono signal for an
out-of-phase effect (remember, Live tracks are inherently stereo, and we need
mono for this).

Pro Tools offers yet another way to work with amps and cabs
by using Eleven MK II and the Trim plug-in in Multi-Mono mode (fig. 6).

Figure 6: Pro Tools can set up two different cabs, and flip one out of phase, in a single channel.

Eleven MK II is mono, and the cabs are also mono, so you
can treat them as separate insert effects. But Multi-Mono mode is a clever way
to do out-of-phase cab tricks with a guitar track (note that, if the initial
guitar track is mono, then you’ll need to convert it to dual mono).

With Eleven MK II, unlink the left and right channels.
Choose the same amp for the left and right channels but different cabs (or
different amps if you want — no rules!). Insert a Trim plug-in after Eleven MK
II, unlink its channels, and reverse phase on only one of the channels. Pan the
mixer’s left and right pan pots to center to return to dual mono from stereo.

What’s Next?

When you
first try this technique, you may find the tones to be more “interesting” than
“useful.” But some simple tweaks can tame your new cabs and add useful
variations.

If there’s a lot of cancellation between the two
cabs, then you’ll lose some level. The amp sim itself might be able to increase
gain sufficiently, but, if not, insert a utility type of plug-in to raise the
gain.Change levels on one of the cabs. Even
very slight changes alter the cancellation characteristics, which can “weight”
the sound more toward one cab. This is like morphing the two cabs into a
different cab that has more characteristics of one cab than the other.Changing any cab parameters, such as a virtual
mic or mic position, makes a huge difference in the final sound — more so than
you would expect from changing these types of parameters with a single cab.Don’t overlook using bass cabs with guitar cabs.
Because the guitar cabs will likely not have as much low end, it won’t cancel,
which results in a beefy, bassy cab sound.Some of the sounds from throwing two cabs out of
phase may sound almost cool except for some peak that’s way too high
because neither cab had that frequency in common or a big dip because both cabs
did have the frequency in common. Following the cab with a parametric EQ
(and narrow Q settings) can work wonders for lowering response peaks, bringing
up deep cuts, and tailoring the sound to perfection.

Now, some people might look at this article and think it’s
stupid. “Duh... why not just get some third-party IRs and load those if you
want different sounds?” Well, you can, but that means all your sounds will be sounds
that already exist — not your sounds, and certainly not new sounds
no one has heard before. Admittedly, being creative takes a bit more effort,
but your reward is that the sounds will be uniquely yours. And fair warning:
some of the results will sound pretty weird, at least initially. But then
you’ll also find ones that are awesomely unique, and even some of the weird
ones may become productive members of your musical society with a little EQ.
Why be normal?

Let’s close with an audio example. This has two parallel cabs set up in the Line 6 Helix. One cab is out of phase, while the other cab switches among various cab options without any tweaks or edits (you’ll definitely notice when there’s a switch to a different cabinet). So, you’ll hear the good, the bad, and the ugly — but you’ll also get an idea of how this technique can deliver a ton of new cab sounds.


The post Extra Cabs for Your Amp Sims – That You Didn’t Know You Had! appeared first on inSync.