I've just acquired my first hardware analog synth (MFB Dominion X), but am having some troubles triggering it from Sonar X3:
 
1: I've tried connecting the Dominion directly to my Axiom 25 midi controller: When playing it from the keyboard, it doesn't seem to have any delay, but when using the Axiom as a midi interface with Sonar, a random delay on the triggered notes appear. The delay is so high that it leaves the synth unusable (up to about 1/8th variation at 170bpm)
 
2. I've also tried connecting the synth to my the MIDI port of my PCIe RME HDSPe AIO audio card. Same result.
 
3. Flicking things like "transmit MTC" and MIDI sync on an off sometimes appear to have a short-time effect, but that may very well be coincidence.
 
I'm not sure if the problem lies in Sonar, but was wondering if anyone here have experienced similar difficulties?

It may be some settings in Sonar that are producing this delay, or it may be caused by one or more effects in a given project, or a combination of both.
 
Try the following settings for recording in Sonar:
 
Audio interface: Sample Rate 48 k, ASIO Buffer of 128
 
Sonar: Driver Mode of ASIO, Sample Rate of 48 k, Record Bit Depth of 24 bits.
 
The above is based on your having an audio interface.  IF you do not have an audio interface, I urge you to consider getting one.
 
You want to end up with a combination of settings that give you a Sonar-reported Total Roundtrip Latency of around 10 milliseconds, or just a little under that.  This will greatly reduce lag/latency when trying to record, such as the problems you are reporting.
 
Once you apply the above settings, try them out in a project without any effects, just to make sure it all plays OK in as simple a project as possible.  
 
It is important to understand that certain effects, by design, add MASSIVE latency to projects, and are NOT meant to be loaded into projects while recording.  These effects are instead meant for mixing/mastering, and will require the ASIO Buffer Size to be set WAY higher than for recording (1024 is common).  Effects such as Perfect Space and Boost 11 are examples of effects that add lots of latency, and are not meant to be used during recording.
 
So, try out the settings and post back.  :)
 
Bob Bone
 
 

I tried triggering the synth from an empty project, and that did indeed remove the lag. When reducing my buffer size from 256 to 128, I get a reported round-trip latency of 8.8ms in Sonar (I have to use 44.1 as my Kemper's SPDIF out won't play nice unless it's clock master, and it only supports 44.1).
 
This seemed to help a bit in my "loaded" project, but it's still not acceptable. My projects tend to have quite high track counts, with Slate VCC on all tracks and buses, in addition to Waves MPX and compressor-plugs on some of the buses. I guess a workaround will be to create separate, MIDI-only projects for triggering external devices, and importing the recorded audio from these.
 
Thank you for your help!

I think your effects are likely the cause of your lag.
 
44.1 k is fine, by the way.  I usually suggest 48 k just because it is a little better, but no biggie.
 
Take your loaded project, then hit 'E' which will toggle off/on all effects.  If your lag goes away with that, then it is caused by one or more of the effects, and not the number of tracks.  (hit 'E' again to turn effects back on).
 
Bob Bone
 

You're right. Bypassing all the effects solves the problem. Then comes the task of finding the effect(s) that cause it.
 
Do you think it is likely to be a single effect that is the culprit, or is it typically a cumulative problem?

The usual suspects included with SONAR are LP-64 EQ, LP-64 MultiBand, TS-64 Transient Shaper and Perfect Space. Also from Cakewalk the Concrete Limiter. Any 3rd party plug-in that uses a look ahead buffer.

Allright, thanks again - You've all been very helpful :)

Here's the scoop:
 
Some effects are designed to be used AFTER you finish recording, and move into the mixing/mastering phases.  These effects, due to how they do their thing, add MASSIVE latency to projects, and that means you can't really track/record with them present, because of the added latency.
 
Perfect Space and Boost 11 are a couple of examples of these kinds of plugins.
 
When you are mixing, it is perfectly fine to adjust your ASIO Buffer Size to be as high as 1024, if needed, to compensate for the added latency of mixing plugins.   But, when recording, you want to keep your latency down to at or under 10 milliseconds, for lag-free recording.
 
If needed, temporarily swap out some of the latency-intensive plugins, just until you are done with your recording of tracks, then you can add them back in for mixing.
 
Bob Bone
 
 

But this has only been a problem for me when triggering external MIDI modules from Sonar and playing VSTis from an external MIDI controller.
 
The latency has never been a problem when recording live percussion, vocals, guitars or other stuff in projects with the same plugins.

I cannot speak to what happens or had happened with other projects of yours - since the issues went away with the effects bypassed, even on one of your loaded projects, it seems likely that one or more of your effects is spiking the latency.
 
In addition, the simple project with not much in it played fine with the external controller, so the mechanics of the controller seem OK - it's somehow when the controller is connected and the effects are on.
 
Maybe there is something else going on, but from what I have seen posted thus far, the effects seem to be involved.
 
Bob Bone