Issues With Low Latency Mode In Pro Tools

01-13-2014 05:59 PM

Kenny McLellan sent us an email explaining he is having problems with the low latency monitoring mode in Pro Tools 11. He says…
When I make an audio track and wish to input monitor with record enabled, if I turn on low latency mode I cannot hear the audio. The meters are indicating that there is a signal present etc. If I turn low latency off, then I can hear the audio. I have been using this method for years with my 003 and have never had this problem before. I am aware that I can lower the buffers etc but this affects my mix when i have an abundance of plug ins running etc. I have checked the routing etc and all is OK. Having done some more research, I have just discovered more about low latency monitoring. It seems that the Mbox 2 LLM does not work with PT11 and with 003 LLM mutes the audio. Avid advised me to use 11.0 driver with Mountain Lion, PT 11.1 and PT 10.3.8. They then replied asking me to check the routing etc. I told them I have been using LLM for years never had any problem with LLM until now, and I am waiting on answer from Avid.
Kenny points to Avid’s answer from their knowledge base dated 24th June 2013 says..
Low Latency Monitoring does not function with Mbox 2 Pro in Pro Tools 11.0.0. No audio will be heard on a record-enabled audio track if Low Latency Monitoring is enabled in the Options Menu. To work around this problem, choose a low HW Buffer size in the Playback Engine Dialog when recording audio instead of using Low Latency Monitoring.
However looking at the Mbox Pro drivers information for v1.2.2 released on September 25th 2013.

  • Fixed problem where Mbox Pro Control Panel would become unresponsive if it was launched before Pro Tools
  • Fixed problem where Low Latency Monitoring would duplicate signal
  • Fixed problem where Pro Tools would not take proper control over Stereo Mix controls in Mbox Control Panel
  • Fixed problem where monitoring of record-enabled channels in Pro Tools with Low Latency Monitoring enabled would not function until a recording was made

There is a later driver - v1.3 but that is only for OSX Mavericks, not for Mountain Lion.
As to the 003 family and the low latency monitoring mode, the solution seems to be to push the HW buffer size down to 64 samples, which should work for the MBox Pro too. Remember that with Pro Tools 11, this only adjusts the input buffer, as one of the improvements with PT11 is to split the input and output buffers, so with PT it should be possible to disable the LLM and set the input buffer to 64 samples as the output buffer is fixed at 1024 samples which should enable lots of plug-ins to be used without problems.
What are your experiences, is it working OK for you either with the Mbox Pro or the 003 family? Let us know what your experiences are, and please include details of your configuration.