Input monitoring latency

This is something I should already know but I have never had need thusfar in all my years using Sonar to have to use live input monitoring as I lay down a track. I have always just used line 6 POD products for all my guitar amp and effect tones. I've never used anything like Guitar Rig or Amp Farm ... any of those things ...
 
So, when I recently tried to run a live convolution reverb plugin (perfect space) with a speaker cabinet impulse response loaded and got a nasty half second delay in my guitar tone I had no idea how to address the problem. I gather you have to bring your recording and playback buffer sizes way down during tracking, but when I adjusted them from 1024 each to 64 ... and even 32 and it had no effect on this buffering latency, I was really scratching my head.
 
There is also a "ASIO Buffer settings" area on my soundcard's MixControl (Focusrite Scarlett 18i20) software that has a range of settings between 1.0 ms and 20 ms. How are those related to the recording and playback buffers in the preferences panel?
 
I am obviously doing something boneheaded, I just can't tell what it is. What do I need to do to get a latency acceptable enough to allow me to lay down live guitar tracks without this latency? Is it even possible to play live with plugins going with a laptop like mine? I am a clueless goon on this one ...
 
Laptop specs are as follows: Sonar X3 Producer 64-Bit, Focusrite Scarlett 18i20 Soundcard (USB), Dell Inspiron 5748, Intel i-7 processor 2.0 GHz, 8 MB Ram.

There is also a "ASIO Buffer settings" area on my soundcard's MixControl (Focusrite Scarlett 18i20) software that has a range of settings between 1.0 ms and 20 ms. How are those related to the recording and playback buffers in the preferences panel?
 
Focusrite uses a different system than normal with those numbers. It's been a while but I do believe 10 ms is the same as 256ms. This is the "safe" default. 
I run mine at 7ms (128?)  which is stable. I can go lower on some simple projects but at the risk of a dropout.  
The Mix Control menu is where you set your ASIO buffers. You have to see how low you can go before your system becomes unstable. Your laptop is not very powerful so I doubt your going to be able to set it very low. 
 
Focusrite scarlett interfaces are not top performers with RTL and you'll see what your is here. 
 

Try TH2 producer. Their IR works without a noticeable latency. Start off with one of the supplied IRs and get your system tuned. I record with amp sims and fx and monitor thru input echo. My DAW is beefier, but my laptop is just a bit faster.
 
TH2 producer opened with preset 001 factory, if that's the case for you delete the amp and the reverb fx and change the cabinet to IR. 

Anybody know of any free plugins that let you run IRs?
 

That does look pretty cool. And at that price, it may as well be free.
 
I was asking for something free to try an experiment to see if just a different app may have a positive effect on latency.
 
Here's what I am looking at now. I know, I was just on here asking for free, and now I'm about to drop over a grand ... but this UAW OX Box is way cool.
 
It has built into it the very cabinets that I need ... the 4x10 Bassman / Super Reverb thing, the 1x12 Deluxe thing ... a champ ... I am in heaven. It also has room settings for a bigger distant miking sound. And it lets you run different impedance amps.
 
https://www.sweetwater.com/store/detail/OX--universal-audio-ox-reactive-amp-attenuator-with-speaker-modeling
 
 

I will look into that. I don't even know what that is actually.

Check this out ... it's totally free and it runs on low CPU power and is 64-bit. Using the bundled PerfectSpace covo reverb I was never able to input monitor a plugin live, but using this to load IRs seemed to work much better. You can even load two IRs at once ... like say you want a mic on the speaker and then one around back ... you can even pan those two mics. I was pretty tickled with this.
 
https://www.kvraudio.com/...t/nadir-by-ignite-amps

scottcmusic
So, when I recently tried to run a live convolution reverb plugin (perfect space) with a speaker cabinet impulse response loaded and got a nasty half second delay in my guitar tone I had no idea how to address the problem.

Maybe you're already past this, but as note for reference: Using Perfectspace brings it's own latency setup issue, and almost every time I have done a new Sonar install/setup I forgot this as well, until I did as you mention and tried using it as a live processing element for a project. Again, maybe you have moved on from this, but either use a different plugin for live IR use (recommended) or go into the Perfectspace help and follow directions for setting the internal latency to it's lowest setting. -I did in fact get it to work OK in tandem with 48K 128 sample audio interface environment, but as it is still a 32-bit plugin and not designed particularly towards live processing, it's not the best choice. I'll bet that's what delayed your guitar tone initially, not necessarily the I/O latency (but that does also have to be tended to of course!).  -Jn-