Even "direct monitoring" through an interface will give some latency - the audio is still passing through the convertors in the interface after all. For true zero latency you need to monitor via an analogue mixer and use no hardware digital effects between instrument and amp/mixer.

In the real world, the difference between a PCIe interface and a very good USB one operating properly doesn't really matter. Sound travels about one foot a millisecond, so the difference between 2 and 5 milliseconds latency amounts to the same as moving your monitors or guitar speaker about a yard further away. Most people can cope with a few milliseconds latency pretty much the same way most people can cope with being a few feet away from their amp or a stage monitor. For me the crunch point comes at around 10ms.

Sonar, like pretty much all modern DAWs, will place tracks recorded at the same latency perfectly in sync no matter what that latency is by the way.

Sorry your sort of wrong on one point unless I'm misreading - Your interfaces inputs are analog and the monitoring system is too. It's exactly the same as with a mixer.
Maybe your talking about the DAW playback audio coming back to the interface?  Sonar automatically compensates for the system latency and there should be none at all as far as overdubbing a new track goes. So your interfaces input will always be dead on with the DAWs tracks. 
 
You can check this buy performing a loop back test. 
Send a Kick or snare drum track out and then patch it back to an input and re record it. Zoom in on the transients and you should find them perfectly lined up. If not, then you may need to adjust Sonars compensation settings but I think this is rare with any proper audio interface with good drivers. 
 
People are always misinformed about latency and when and were it really matters. 
 
For me with a so, so set up I only hear latency when input echo is engaged.
MIDI latency gets worse if you add certain plug ins like LP64. 
 
 

Direct monitoring on the interface taps the signal prior to the A/D converters.

grumbleweed4162

Is anyone out there is Sonarland using one and if so does it bring happiness and good results?

Grum.

Yes , I have and use the 2i4 . it is a very good unit for what it costs ...
the input pads are definitely a must have …
i do a lot of recording direct using a large variety of my personal guitars 
the input pads will give you a nice sweet spot where you can get a correct gain staging while still maintaining  a fair amount of headroom …
i play very dynamicaly ,  having the input pads come in handy for the phrases that i happen to dig into.
 
the mic pre's sound impart an almost HI Fi type of vibe / sound ,
before I got my 2i4 I ran a pre into my PCI sound card …..i have no need for it now …the pre is in my closet ….
 
I like that the 2i4 has an extra set of out puts …Focusrite touted that feature for the DJ's out there ….
I'm not a DJ  yet, I feel having the 2 extra outputs  is a nice additional feature  to have ...
 
hope some of that helps, 
Kenny

kennywtelejazz

grumbleweed4162

Is anyone out there is Sonarland using one and if so does it bring happiness and good results?

Grum.

Yes , I have and use the 2i4 . it is a very good unit for what it costs ...
the input pads are definitely a must have …
i do a lot of recording direct using a large variety of my personal guitars 
the input pads will give you a nice sweet spot where you can get a correct gain staging while still maintaining  a fair amount of headroom …
i play very dynamicaly ,  having the input pads come in handy for the phrases that i happen to dig into.
 
the mic pre's sound impart an almost HI Fi type of vibe / sound ,
before I got my 2i4 I ran a pre into my PCI sound card …..i have no need for it now …the pre is in my closet ….
 
I like that the 2i4 has an extra set of out puts …Focusrite touted that feature for the DJ's out there ….
I'm not a DJ  yet, I feel having the 2 extra outputs  is a nice additional feature  to have ...
 
hope some of that helps, 
Kenny

Cheers for that (and to everyone else with an opinion). Over the last couple of days I've been looking and thinking and.....

......in the end I ordered the Focusrite Saffire Pro 14, mainly due to the loopback feature and the S/PDIF. It also comes with the Focusrite VRM Box as a freebie and I can't say no to a freebie.
The downside is I now have a Firewire PCIe board to buy and fit!
It's a good job Mrs Grumbleweed is in a good mood and has slack purse strings .

Grum.

johnnyV
Sorry your sort of wrong on one point unless I'm misreading - Your interfaces inputs are analog and the monitoring system is too. It's exactly the same as with a mixer.

 
Most (if not all) interfaces pass incoming audio through the convertors in the hardware before handing it on to the output. They take the PC out of the routing, but not their own convertors and digital internal mixer. This is why the more honest of them (like Focusrite) talk about "near zero latency" monitoring. Nowadays the internal processing is so fast it nearly always doesn't matter. Take a look at the block diagrams many interfaces come with, and the analogue inputs and outputs are both attached to the convertors.
 

johnnyV
Maybe your talking about the DAW playback audio coming back to the interface?  Sonar automatically compensates for the system latency and there should be none at all as far as overdubbing a new track goes. So your interfaces input will always be dead on with the DAWs tracks. 

 
Unless the interface has built in extra "safety buffers", on top of the ones the driver allows you to configure, which the driver fails to report to the DAW. This seems to be more a feature of USB interfaces than Firewire or PCIe. Then there are a few interfaces where the reported and actual measured latencies seem to bear little relationship to each other at some settings.
 
Oblique Audio's RTL Utility is a useful free tool for testing interface latency if you've not come across it. Easier than looping audio from a DAW, means there's no DAW internal calculations affecting the result and lets you run through loads of different latency settings very quickly.
 

johnnyV
People are always misinformed about latency and when and were it really matters. 
 

It matters when it gets in the way. Exactly how much latency causes a problem varies from person to person and even the instruments in question.
 

johnnyV
MIDI latency gets worse if you add certain plug ins like LP64. 

 
I think you mean audio latency? At least, that's what the help and manual describe plug in delay compensation as. If you use a VSTi synth then yes, there will be more latency between pressing a controller key and the sound emerging, but I suspect Sonar spits out MIDI at the "normal" time then delays the audio output from the VSTi - since audio tracks have to be delayed as well that would seem the easiest way to do things. I'll be honest and say I've never actually checked this though, I rarely use VSTis other than drums from time to time and avoid latency inducing plugins while tracking because I generally monitor via Sonar so it's not something I've given much thought to. I'll have to see if I can come up with a few experiments to find out what happens to MIDI with pdc active.
 
Hm. We seem to have drifted well off-topic....

No not really off topic as your information is very educational and I myself am always looking for a clear picture on latency and audio interfaces. This thread is about shopping for an interface and latency is certainly important if your going to toggle that input echo. 
 
The topic of audio interfaces often includes conflicting statements regarding Round trip and plain old system latency. And as you clearly seem to be one of the few who has a handle on this I stand to agree 100% with what you have said.  And to tell the truth I was only was assuming that my interface is hardwired inside to the outputs after passing through an op amp or two. But I guess digital circuits are cheaper to build so that does make sense. 
 
I used my Yamaha 01v for 15 years before reading that it has 2ms of latency. Guess its moote if your sitting 50' out in the audience doing FOH. It's not like we would see the drummer strike the cymbal and hear it a few seconds later.  But I was concerned about this in the studio as I use it a lot and for monitoring too. But then I run it into my SPDIF which therefore bypasses my interface converters which would have added about the same amount anyhow. 
One will also remember the old tape systems offset the record and playback heads and synced them electronically. I seemed to remember that system had it's flaws as well. 
 
And I have that Oblique Latency utility, Funny thing was it worked fine with my Tascam interface but I couldn't get a reading with my Scarlett. 
 
Anyhow thanks for your clear and to the point corrections to my post. 

Yes, latency is the crucial thing if you need to monitor via a DAW, yet like guitar pedals and manufacturer claims regarding their bypass it can be very difficult to seperate marketing speech from hard information.

And just because an interface is capable of e.g. 48 sample round trip times doesn't mean that the computer someone happens to have is capable of running it at that glitch free. Once we had to worry about tape machine running speeds, bias, print through on spools, cleanliness etc. Now we have to worry about PCI bus latency, BIOS tweaks, cpu sleep states etc.

Once in a while I think the old boys back in the 1930s who just set up a bunch of direct to disc recording machines, pointed the horns at the musicians and recorded the performance direct then repeated as many times as they needed to maybe didn't have it so bad after all.