Trouble monitoring with headphones as I record the track

I haven’t used Ardour for about 3 years. I’m using it now again and it seems to work better than before. But, I’m not an expert in this field, more of a musician that just wants to record original music for myself. I don’t know what I’m doing wrong, but when I try to monitor what I’m playing or singing into the system there seems to be a delay (latency?). It’s off to the point where it’s so distracting and hard to hear what I’m doing. I’m using a macbook and a Focusrite Scarlet 2i2. I don’t remember having this problem before when I used Ardour in the past. ???

There is always a delay when you route audio through the CPU. The amount of delay is defined by the buffer size (also known as the period size in JACK) that you use with the audio interface (“soundcard”). For live monitoring, you need to reduce the buffer size as small as possible - the smallest possible value is a function of everything about your computer (not, however, its CPU speed; see for lots more detals about this). For most people, 64 samples is close to “no detectable latency”, but many computers will not be able to go this low.

Dobro you’re in the same position as mine, meaning to be more a musician than a audio technic.
I’m on Linux 64bit and use a Fast Track Pro, actually I only open Ardour without dealing first with Jack because I discovered I have less latency and xruns problems.
I’m recording at 48KHz, 128 buffer size and 2 periods. I don’t have latency or anyways it’s as low as I cannot hear it.
But it depends on the computer for the most. I have a i5-6200U @ 2.30GHz cpu with 8GB ram.
With the computer I had before, I wasn’t even able to make it recognize the soundcard (though it used to work on Windows).

Thanks Paul for the help. For directing me where I can start to get a better understanding of all this. I flipped the switch on the interface to direct monitor and on Ardour changed the buffer from 1024 to 512 and that sees to help a bit. Sample rate is 44.1KHz My Macbook is 2.7GHz with 8 GB a little over a year old. This time using Arduor I noticed that Jack is no longer required. Is this correct? Or do I need it for better performance? If I change the buffer should I change the sample rate too? Should I try and go lower with the buffer without any adverse affects? It’s a big learning curve for me ( 15mph ).
Thanks for your input Telover every little bit helps.

Using “Direct Monitor” means that audio is not routed via the CPU - there is an analog pathway within the audio interface that is used for monitoring. Sometimes this is what you want, sometimes it isn’t.

JACK is required only if you want to connect Ardour to other applications.

If your sample rate is 44.1kHz, there’s no reason to consider changing it. At 96kHz, it is harder for your computer to deal with very small buffer sizes. There are no hard answers about what the “best” settings are for your computer, since it depends on your computer (hardware and software), which stand a fairly good chance of being close to unique.

for me a suitable solution is to use both: direct monitoring to get the attack of a played note directly (e.g. on the guitar) and the sound, routed via ardours process-/plugin-stack, mixed to the monitor-speakers also (a few msecs later) to get the “atmosphere”. The sound-device must be able to play both streams simultanously.
This is only a workaround, but for me it fits.