Orinj Convolution

Orinj version 4.0.0

The Orinj Convolution applies the impulse response of some system – amplifier, reverb or other – to the signal and thus changes the signal as if the signal is put through that system.

For example, Orinj is distributed with an example impulse response, that of the classic Ampeq 835 bass amplifier combo. Applying the Ampeq impulse response to a signal mimics what would happen to the signal if it was put through that amplifier. This includes a decrease in the magnitude of some of the high frequencies, a slight reverb, and so on.

Using the Orinj Convolution

The Orinj Convolution can be added to tracks in the multitrack session view, tracks in the loop building view, and to waves in the single wave view. In the multitrack session view and in the loop building view, first select the track to which you want to add the effect. In all these views, click on Effect, Filtering, and then on Orinj Convolution in the Orinj menu. You will see the following dialog.

The Orinj Convolution dialog

When this dialog becomes visible, the Orinj Convolution effect has been added. Adjust the parameters of the convolution, which are described below, in the dialog above and click Close.

Orinj Convolution parameters

See Orinj Effects for an explanation of the Title, Track, Presets, Bypass, and Lock channels controls. The remaining Orinj Convolution controls are described below:

  • Load: Use this button to load an impulse response. The convolution has no pre-loaded impulse responses and will not have an effect until you load an impulse response. Orinj is distributed with two impulse responses – that of the Ampeq 835 bass amplifier combo, recorded 12 inches away from the combo speaker with a microphone placed at the center of the speaker. Both files reside in the "impulses" folder of the Orinj installation. Both files contain the same impulse response, but one is shorter and does not contain the full tail of the impulse response.
  • Gain: Use these controls – the box and the slider – to set the additional gain of the impulse response. Impulse responses may introduce gain into the signal. The Ampeq 835 impulse response, for example, will introduce anywhere between 5 dB and 8 dB gain to a mid-range guitar recording, depending on the frequencies in the guitar recording. The gain controls of the Orinj convolution are a way to compensate for this gain so that the signal does not clip. The gain is measured in decibels and can be between -10 dB and 10 dB.
  • Zoom In and Zoom Out: Use these buttons to zoom in or out in the impulse response graph. These buttons have no effect on the actual convolution and impact only the impulse response graph.

See Orinj Effects for additional notes on: where Orinj effects can be used, using boxes and sliders that impact the same parameter (such as the box and slider for the left channel delay), applying effects to mono and stereo waves, and using effects during playback. See Orinj Working with effects for additional information on creating, modifying, moving, removing, and processing effects.

Impulse response format

The Orinj Convolution expects that impulse responses are stored in standard wave files.

Impulse responses sampling rates and resolutions

The Orinj convolution effect is designed to be used with impulse responses with any sampling rate or standard PCM sampling resolution. The impulse response will, however, be resampled at the signal sampling rate and resolution before it is applied to the signal. For example, an impulse response recorded and computed at 96 kHz and 24 bits – even though it is probably more precise – will be recomputed to 44.1 kHz and 16 bits, if the signal itself is at 44.1 kHz and 16 bits.

Impulse response length

Longer impulse responses probably better represent the system they are intended to describe. Long impulse responses, however, require a lot of computations. Impulse responses that are longer than about 25 milliseconds may be difficult to compute during playback, depending on the computer, and will cause breaks in the playback. Such impulse responses can be pre-processed prior to playback with the Effect Process command of the menu. Shorter impulse responses can be computed by Orinj during playback.

Impulse response channels

Even though this is rare, the Orinj convolution can use impulse responses that describe two different channels (according to the wave file format).

Impulse responses of various types of systems

Certain audio processing systems – amplifiers assuming no distortion, microphones, usually equalizers, reverbs – are linear and do not vary in time. They can easily be described completely by their impulse response. The Orinj Convolution effect is designed to work with any such constant impulse responses.

(Other audio processing systems – compressors, distortion – do not impact the signal in a linear fashion and do vary in time. Impulse responses for such systems are not likely.)

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