What creates the effortlessness in sound reproduction?

Huy, it is mostly the amplifier, speakers and room. You need an amp that can effortlessly drive the speakers to 110 dB. This will depend on the efficiency of the speakers. The speakers have to be peak free or even a little depressed (3 dB) in the upper mid range (3000 Hz) and the system has to have excellent bass performance. If all these criteria are met you will have that "effortless" performance unless there is a severe deficiency up stream. The program sources and pre amp are important but they have much less effect on the overall sound unless there is a significant problem. Also in my experience class A amplifiers are more "effortless"

Class A amps are certainly "snappy." Mine (Dennis Had Inspire Firebottle HO SEP) is anyway...a short path to the mojo transferring a clear upstream signal to earball pleasing immediacy.

Thank you everyone for the input!

@erik_squires : You are absolutely right about the feeling "It is like sitting on top of a mountain ridge and looking out for miles to the horizon"

I will try to go with room treatment and then amp replacement.  I will update if I have some improvements :) 

Huy

OP :

Highly recommend you reach out to GIK Acoustics.
Best,
E

lots of good comments about effortlessness already.

the word that comes to mind for me is ’headroom’; effortlessness in music reproduction requires all pieces of your system puzzle to operate in their best region of efficiency. if a piece in the chain is being stressed that causes distortion and inhibits the free flowing ease and authority which equals effortlessness.

another aspect of effortlessness is bottom octave extension past the needs of any musical material. this margin of error allows the music to matter of factly do deep bass without strain. having 10hz-20hz system performance requires extension below that.

effortlessness also comes from power grid optimization and anti-resonance treatments which allow the musical focus to hold together as it scales and not get muddled by strains on A/C power or hash and distortion from high SPL resonance feedback.

i could go on and on.

effortlessness has been a central theme of my system evolution. take a look at details of my system to see what i mean by that.