Getting the most out of Altiverb & Pro Tools.

As a response to several questions online and in direct mail to Audioease, they have posted the following guide on their forum:

The more seconds of reverb the more strain on your cpu.
The smaller the hardware buffersize the more strain on your cpu.
The more channels of reverb the more strain on your cpu.
The more instances of Altiverb the more strain on your cpu.

So to do things efficiently (assuming we’ll not use high latency mode, which is impractical for post pro.)

– Use mono-in to stereo-out Altiverbs rather than stereo to stereo ones. Especially when Altiverb is inserted in an AUX, you will get away with this sonically.
– a protools playback buffer of 512 samples or higher is recommended. expect to run up to 15 altiverbs at 48 kHz in one session on a g5 this way.
– Use Lesser Altiverbs in Aux channels rather than flipping one in every track you need a bit of ambience on. Rather than that send several tracks to 1 bus and put an Altiverb in there.
– when you use Altiverb in an aux, check the left bottom most checkbox in the Altiverb interface where it says: Load as aux. It will turn wet dry to wet and direct gain to -144 dB.

There may be a chance that you’ve previously installed the ProTools file called
StreamManager_128 instead of the regularly installed one. In that case Altiverb 5 will put a lot
more strain on your CPU. You can solve this by to manually removing the StreamManager_128
version from your /Library/Application Support/Digidesign/
folder before installing the regular one from the original ProTools disk.
For higher sample rates (88.2KHz and up) the _128 Stream Manager is not supported.

To reduce the amount of seconds calculated out of a reverb sample you may indeed cut the tail at, say, -80 dB. Often our samples go down to -120, which is nice for classical recordings, but overkill for most others. Do that by clicking the CPU tab and turning the Tail Cut knob.

On the first g5 that entered the market, the smallest single cpu one at 1.6 gig, a typical postpro verb will eat 6 to 7 percent of your CPU. A concert hall of 6 seconds takes up to 12 percent. You can almost half these values for modern top notch G5’s.

Automatable parameters show up in the automation menu when you click AUTO in pro-tools plug-in head right on top of the altiverb interface.
You can switch on individual parameters to be automated there.
They are: master in and out level, all EQ parameters, front and rear levels, and snapshot (load a full preset including the impulse response, introduces a short silence)
All other parameters interrupt audio and can therefore not be automated safely.

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