Roundtrip latency is probably the measurement that most audio interface owners are most interested in when it comes to recording. Roundtrip latency is the amount of time it takes for your signal to pass from the input, through the A/D converter, into the DAW, out of the DAW, into the D/A converter and reach the output of your audio interface so that you can hear it.
A low roundtrip latency figure is important when you want to monitor your input signal with processing applied from plug-ins in your DAW. e.g. you're playing through a guitar amp simulator and want to hear the effected signal, rather than the 'uninspiring' clean raw sound of your guitar.
Whilst some people are more sensitive to it than others, it is widely agreed that, on average, the effects of roundtrip latency (a perceived delay to the sound) are not noticeable below 10 ms. Above 10 ms is when most people start to become affected by it.
To put this all into some kind of context, sound travels at ~1000 feet per second. Therefore, sound takes about 1 ms to travel 1 foot. One practical way to look at this; you're performing on stage with a floor monitor and you're 5 ft 11 tall - you are inherently experiencing almost 6 ms of latency from the sound coming out of the monitor to it reaching your ear.
On Mac, SSL 2/2+ MKII uses Mac's own Core Audio Driver (as recommended). On Windows SSL 2/2+ MKII uses our own SSL USB ASIO/WDM Driver which you install. Whilst the Windows driver can achieve a slightly better performance, SSL 2/2+ MKII delivers great roundtrip latency performance on both Mac and Windows that certainly won't be noticeable when the DAW buffer size is set to 32 or 64 samples.
Important - Often people are concerned by the input and output latency figures reported to them by their DAW (normally found on the page where the audio interface is selected). These figures are notoriously inaccurate as the software has to make certain assumptions about the system which are often wrong and lead to over-estimation. Also, Windows users looking at latency figures in the USB Control Panel should be aware that this is the ASIO driver only and does not take into consideration the DAW buffer & hardware converters. Please refer to our published figures below for an accurate measurement of roundtrip latency.
SSL 2/2+ MKII is able to achieve the following roundtrip latency figures at 96 kHz.
Measured at 96 kHz, with a 32-sample buffer:
Mac: 5.8 ms
Windows (safe mode off): 3.65 ms
Window (safe mode on): 5.9 ms
Tips
- Whilst increasing the sample rate will further reduce the roundtrip latency, 96 kHz offers the best balance of low-latency to amount of disk space required.
- If the amount of disk space is a concern, the roundtrip latency performance at 48 kHz is only a few milliseconds more than 96 kHz and this is still more than good enough for most people.
- On Windows, safe mode off allows you to further reduce the roundtrip latency.
- You may have to increase your DAW's buffer from 32 to 64 samples throughout your tracking session as it gets busier, but this should have a negligible effect.
- Try to use plug-ins that do not introduce large delay compensation, as this will increase the latency.