There are two typical ways to achieve this:
- By inserting delays on the other signal paths, so that all paths are delayed equally.
- By having some tracks (the ones with latency effects in their paths) play back earlier.
We compensate for
- effect devices that are between a source device (such as an instrument) and its mix channel,
- effects connected between the To/From Insert FX jacks on any channel device
- effects connected between the Parallel Out jacks of one channel and the input of another.
In addition, the FX sends from channels are delayed where needed, so that they are in sync at the Master Section.
The latencies/delays are also used for positioning audio correctly when bouncing to a new track and when recording audio (with monitor off). We also delay the metronome click so that it isn't heard ahead of the audio.
- A Delay Compensation On/Off switch is found to the right in the Transport Panel and in the Master Section of the mixer, next to the Master Fader. This is OFF when you open an old song, but will be ON in new songs (when we get around to doing new template documents).
- When this is on, the "Total Path Delay" (how much a signal is delayed from playback until it's heard) is shown below this switch. All shown values are in samples, but the tooltip also shows them in milliseconds.
- On the backside of the audio track/mix channel devices in the rack, if you unfold the Programmer section, is a display showing the insert fx latency for this channel. This is the summed latencies of the effects between the To/From Insert FX jacks.
- There you will also find an setting for manual adjustment: If you find that you get phasing or other artefacts even though Delay Compensation is on, it may be because an effect doesn't report the correct latency. You can then add or subtract from the reported latency with this control.
- There is also an indicator there, which lights up if the routings don't allow the latency to be calculated. A tooltip tells you more.
- At the bottom of the Insert FX section of the channel strips, the Channel FX latency is shown (if any). This is the summed latencies of the effects before the channel input and the effects between the To/From Insert FX jacks, plus the manual adjustment setting. For the Master Section, it's only the summed latencies of the Master Insert FX.
- Routing in Reason is free and can be really complex. That's why we've had to limit the Delay Compensation a bit. The following cases are not included in the Delay Compensation:
- Effect devices that don't directly feed a main mixer channel. For example, if you have connected several instruments via effects (with different latencies) to a Mixer 14:2, these will not be part of the compensation.
- Channels whose output signals don't pass the Master Section. I.e. the channel (or its output bus) is using Direct Outs.
- Send Effect devices. Although the sends are compensated, we don't care about inherent latency in the Send Effect devices themselves. For typical send effects like delay and reverb, some latency is typically not a problem.
- Effect devices fed from one channel, that feed another channel/bus (cross routing).
- "Special" Insert FX routings such as split (parallel) signal paths between the To/From Insert FX jacks or loopbacks, may make it impossible to calculate a correct latency value. The indicator on the back of the mixer device and its tooltip indicate this.
How to test Delay Compensation
- Find effects that report latency (the MClass Maximizer in Lookahead mode is a safe bet, but there are lots of REs and VST effects that do it too).
- Add such effects to some channels, and leave other channels without effects. Compare the timing with and without Delay Compensation activated.
- Test this with parallel channels and busses - make the channel routings complex!
- Test manual adjustment of channel latency.
- Try finding effect routings that cause the "Non-standard Routing" indicator to light up on the back of the channel device!
- Are sends correctly delayed?
- Bounce in Place and Bounce Mixer Channels - is the rendered audio in sync?
- Record audio with monitoring off. The audio should be positioned correctly (just like Record Latency Compensation in the preferences compensates for audio hardware i/o latency).