Developing critical listening skills


I’m not really an audiophile, but a long time music fan who values quality gear as a way to enjoy the music I love, so please forgive me if this seems naive. I’ve been experimenting with a lot of new gear lately, and with different resolution files, trying to see what differences I can detect. When evaluating hi-fi equipment, I have a good idea of the things to listen for, but find it very difficult quantify and compare differences. For instance, I just added new cables to my desktop system, and I think they sound better (wider soundstage, and more natural, less forced presentation), but I have a hard time identifying differences in a quantifiable way and really don’t know whether it is just an optimism bias. I can’t accurately remember how the sound was specifically different. I’ve always just listened to music on decent systems, but never tried to develop my critical evaluation skills: actually developing a systematic way to isolate, identify, contrast sonic differences. All the guidance I can find is very vague and general. Things like "spend a lit of time listening closely", or invest in the right hardware. I’ve already done both in spades. Are there some specific sort of reliable, audible tests that can be performed to build my skills? Any guides? I just purchased the Chesky Ultimate Demonstration Disc, and Sheffield Drive and A2TB Test Disc.

Similarly, trying to AB test files, and see if I can really hear a difference between 44.1/16 and a 256kbps file derived from the original, I honestly have a hard time. What should I be listening for? After a lot of listening to the same track, I think I’m starting to hear differences in the bass guitar, where the image a little smaller, and less resonant in the compressed file. Also, the cymbals are a little more sibilant, and with less depth and decay. But it is very subtile, and not too successful in an A/B test. Specifically what parameters should I be listening for (and how to I isolate & memorialize these characteristics repeatably) to start to build my listening?
svenerik
https://harmanhowtolisten.blogspot.com

steakster, when Harman (Floyd Toole) did their big speaker/listener experiment a few years back, the reviewers who did participate performed rather poorly. That is obviously not indicative of all reviewers. I am glad you found one of the diamonds and he was willing to share the experience with you. 
@svenerik
A few simple pointers might help
(...)trying to AB test files, and see if I can really hear a difference between 44.1/16 and a 256kbps file derived from the original, I honestly have a hard time
It helps if you listen to loud music (because our hearing is "flat" at higher amplitudes), listen to s/thing you're familiar with (see elizabeth above); you also need a system capable of reproducing low-level detail, which I imagine your system is.
Listen for:
- sense of space between instruments and volume (not loudness, i.e. does the tenor sound like a tenor or a mouse?)
- 3-dimensional soundstage, wide and deep?- Bass: is it clear? Not overpowering, but clear- Do you hear low-level detail
- Do you get listener fatigue very quickly?
There are many other considerations, but these are the simplest I think.
Three ideas:

When was the last time you had your ears professionally cleaned?

Listening to music through headphones might help you
develop critical listening skills.  By "taking the room out of it,"
you can focus on "what you hear" more easily.  

Lastly, if you have another person to share your perceptions with,
his may be helpful.  "Do you hear this?" and similar questions and comments
can direct your attention towards making important discriminations...

Lot of good advice on this post. I second Robert Harley's book. After reading his chapter on becoming a critical listener a whole new layer opened up for me.

rwortman makes a good point too. The quality of the recording make a substantial difference. I listen to one song after another and it sounds like the music is coming from the center, then another song comes on and it's distinctly left channel/right channel.

elizebeth nailed it though; use a few songs that you know backwards and forwards for reference.
All you need to do is listen "it is like riding a bicycle" it is not rocket science there is no special skill required you were born to listen.