With or without Room Correction/DSP

[Curvature]

I don't know if they have limits for effectiveness regarding EQ. But i do know that when placing them correct an using DSP the improvement is hugh in my room. There are interesting interviews in stereophile with proffesional musicians. Don't think it's a coincident that lots of professional musicians like Paul Wells, Billy Drumond, John Escreet favours Vandersteen speakers. https://www.stereophile.com/content/musicians-audophiles-paul-wells. https://www.stereophile.com/content/musicians-audiophiles-john-escreet I think they are quite capable to hear differences/quality atleast better than me.
But shure that their are modern speakers that could do probably better unfortunly i don't have the time (or probably money) to audtion them all. For that ASR is a good scource.

What I'm suggesting doesn't require money or making purchases based on imagined expertise of others: study the background.

 

[Hipper]

I use a digital equaliser, a Behringer DEQ2496. I've had and used it some sixteen years and it's my best Hi-Fi purchase.

At first I just followed the manual and used its own measuring set up. That was OK but over the years I've learned better. Now, after careful positioning and copious amounts of room treatment, I just employ the Behringer to finish the EQ job based on REW measurements.

I measure in two parts. First, just the bass region, 0-500Hz. I use the Behringer to flatten this as much as possible using mostly it's Parametric EQ. After that I look above 500Hz. I don't try to flatten this area perfectly but use the Graphic EQ and broad adjustments, rather like tone controls. I adjust this region not only according to measurements but I would say more on the basis of what I can hear (I'm 69 and can no longer hear anything above 10kHz and the 6-8kHz region is also weaker).

Broadly though I aim for a flat frequency response. Others suggest having a sloping curve, say 6dB higher at the bass end. Of course not all recordings are alike but for me 'flat' works with what I play.

The result of all this is mainly a smooth bass and that allows the mids and highs to work their magic.

I should add that room treatment does something I don't think EQ/DSP can do so well and that is reduce decay times. I now think this is a very, if not the most, important improvement that can be made to the sound your hear.