What I don't get is how I can change latency in the test section and what kind of result this has
The sound card will produce different latencies at different sample rates: the higher the sample rate, the lower the latency.
The 'true' latency in your system buffers is affected by changes in the 4D Control Panel settings, these are not affected by changes to change the buffer settings:
- Power your Xone:4D ON and connect it to your MAC system
- Open the 4D Control Panel application and select the TEST tab in the bottom half of the GUI.
- The Frame-size (buffer settings) are indicated as a number of samples.
- This setting can be altered via the drop-down menu options (from 64-1024):
- You will see that the Input/Output latency times will change depending on the Frame-size selected.
- You will also note that these latency times can also be lowered/raised by increasing the sample rate setting.
The optimum settings are something that you will need to experiment with to find the best settings for your own particular system/audio application/playing style, but to give you an idea of how latency may (or may not) affect your audio stream please see below:
Latency is a result of the physical limitations of the process of moving audio samples into a systems audio buffer prior to streaming (playing/monitoring) the audio source.
In this sense, latency can occur because of the number of samples that are 'required' by the buffer before streaming begins.
Because the latency in samples is defined by the card, then the faster the sampling rate, the quicker a fixed number of samples will pass through the buffer, hence: faster (higher) sample rates = lower latency.
The audio buffer size is set via the soundcard control panel and, because a lower buffer size means that fewer samples need to be buffered, so long as your system can handle low buffer sizes, the lowest is best.
This 'lowest' setting, however, will be dependent on your system's physical processing capabilities and can also be affected by other factors such as slow physical hard drive speed, unnecessary applications running on the system in the background, poor system 'housekeeping' etc.
You'll need to trawl the internet, or digital audiophile forums for more info on optimizing your system, Sweetwater’s Optimization Guides are often a good starting place: