Lots to respond to:
WRT Haas effect - Agreed it also has to do with spatial positioning and amplitude relationships, but it basically states that 2 similar sounds of similar amplitude spaced anywhere from 5-30ms (broad window there!) can be heard as "one sound" but will affect perceived origin or "width" of said sound. I liken this to the sound of the acoustic drums in the air (also incurs a small time delay from drumhead to ear - say 3ms for 3' @ speed of sound) compared to the sound of the drum in the headphones. I'm not likely to hear 2 distinct sounds until I get around 20ms RTL or so, and I should be able to play into that groove if I'm worth my weight ... Believe me - I would not accept my system if I was always on the verge of "Flamming" in my heapdhones - I'd still be on Analog!!!
The "impulse response offset" of hitting a dead clave (or whatever) into an Earthworks mic and trying to get the smallest duration "Flam" I can detect just isn't something I'd ever have a desire to record as "Music" - so I don't really find that relevant for my workflow. I base my statements on real-world application of Wet ITB monitoring, and how the overall feel holds up - not a hypothetical thought experiment that would never happen "naturally" in my studio. No complaints from the talent - and I'm the biggest critic as the Drummer I record most often! If I'm happy, then I know most others will be ecstatic with the setup!!!
RE RTL - I tested the MF-I's ASIO Analog-to-Analog RTL (@ 32-Samples) with the Centrance Latency Tester and got the 3.1x ms RTL. My HDSPe MADI/SSL setup is about the same, but I need to manually specify the delay of the AD/DA offset as the MADI Driver doesn't know which converters I'm using (see point below about PDC vs Record Offset Placement). I haven't done a true "Loopback" on a full session, but I can tell the latency is still very low, and I got to my ~5ms RTL figures by adding the few latent plug-ins I run plus a small bump.
AFAIK, Simply inserting a "0 Offset" plug-in doesn't add any delay to speak of. It might add one sample, but most actually report "0". Bussing might add another sample. So even in a complex project, that *might* add up to 20-30 samples total? I believe it will be far less. But you are correct that I need to actually setup a test to confirm what I get "Through the DAW" in my larger projects. I can definitely hear the distance-based-latency on room mics compared to the direct acoustic sound (distance comes into play, approx 15ms due to 15' distance plus my RTL in this case), but I can't hear any latency from direct sound to tight mics or overheads in the headphones.
To verify, I can record an analog loopback as a test, or I can actually record a common Mic to 2 different DAWs, plus record the Main DAW's Mix to the second DAW and get an RTL. I'll have to mind my P's and Q's to make sure I'm not omitting any AD/DA conversion latencies or otherwise getting fooled by the record offset placement (using 2 separate DAW's should eliminate that variable). No time this week, but maybe this weekend.
PDC - Refers to "Plugin Delay Compensation", and will increase latency of any live inputs to "line up" the plugin delays across tracks. Even if you insert a latent plug-in on a track you aren't currently arming, it will STILL offset the armed track to keep everything lined up (at least in Cubase - Logic might be different as it does some wierd stuff to cope with low latency!). So - don't use any latent plug-ins while tracking! It will KILL the low RTL you are working so hard to maintain :-)
"Record Offset Placement" is what most DAW's do automatically based off the ASIO's reported AD/DA and ASIO offsets. This is what allows your performance to line up EXACTLY with the backing track as you heard it during the performance. This should not affect RTL when monitoring (AFAIK), but will ensure what gets played back is the same thing you heard during the performance WRT relative placement of the backing tracks against your performance.
All I can tell ya is it works every time in my setup. I sold my old mixer, and rely strictly on the DAW for all of my monitoring/bussing/DSP needs, and supplement with a "very analog" front-end for the interesting/tasty flavors Digital can't produce on its own. I don't even think I'd want to get a nice console at this point! :eek:
MADIface-XT+ARC / 3x HDSP MADI / ADI648
2x SSL Alphalink MADI AX
2x Multiface / 2x Digiface /2x ADI8