I've recently added a second audio interface to my main rig (UAD Apollo Twin USB). It appears that the only way to get multiple audio interfaces to work within the same SONAR session is to use WDM/KS mode instead of ASIO. However, while everything seems to be working OK, I have encountered this really weird side-effect. Whenever I press Play, it now takes over 2 seconds before playback begins. This doesn't appear to be a latency issue. Once playback actually starts, I can record audio and MIDI just fine with better than acceptable latency.
 
I have already tried the following:

• Creating a blank session with no plugins
• Turning Off/On 'Open all devices'

Changing the 'Open All devices' setting seems to improve the delay from 4 seconds to around 2 secs, but it still is a ridiculous amount of time.
 
Any suggestions appreciated...
 
-e.B
 

Disable Dynamic Arming? (Preferences > Project > Record > Allow Arm Changes During Playback/Record)

I think the November update has a bunch of improvements for drivers, including WASAPI improvements.  You might want to try that?
 
My guess regarding the delay is that it's probably writing a bunch of data into the buffer before it starts playing.  Doing a quick search, it looks like WDM drivers were created back in 2000 for 32-bit systems, and was mainly designed for CD-ROMs and stuff like that.  Anyway, WDM drivers have always had crappy real-time performance on my system so I avoid them.

2 AudioInterfaces is "always" a huge problem. Not only with Sonar.
The Audio program must control two different drivers und must synchronize them.
I would avoid this in any case.
 

THambrecht
The Audio program must control two different drivers und must synchronize them.
I would avoid this in any case.
 

Unless the two interfaces have an external clock

My loopback tests of a few interfaces always showed that WDM mode was out of sync. 

brundlefly
Disable Dynamic Arming? (Preferences > Project > Record > Allow Arm Changes During Playback/Record)

This change made a HUGE difference. Now the delay is well below 1 sec, probably closer to 500ms or so. While not ideal, it is now much more acceptable.
 
Thanks!
 
-e.B

THambrecht
2 AudioInterfaces is "always" a huge problem. Not only with Sonar.
The Audio program must control two different drivers und must synchronize them.
I would avoid this in any case.
 

Actually, other than the aforementioned playback start delay, the two interfaces are working remarkable well together. I'm now running at 4ms latency with reduced CPU load, which is better than ASIO on the same interface (VS700).
 
-e.B

gcolbert

THambrecht
The Audio program must control two different drivers und must synchronize them.
I would avoid this in any case.
 

Unless the two interfaces have an external clock

I using sync via the ADAT Out of the VS700 into the ADAT In on the Apollo Twin USB. While it can sometimes be tricky getting the Apollo to 'sync up' initially, once they do, things become rock solid.