Is a FLAT response the IDEAL?

No you can't. An EQ will change both the direct sound and the room response. Fix one and you can break the other.

The OP is not talking about room response. He just wants to know if flat is right or wrong. I have answered that. 

An EQ has already been used even before you plug in your speakers. The mastering engineer and the mixing engineers would have used plenty of EQ unbeknown to the audiophile. The EQ would have been used to balance the sound but you will need to retune the sound because everybody has diffferent hearing, different room and different speakers.This is why every speaker on the market has a different frequency response curve. Every speaker designer has their own opinion about what sounds good and so every speaker is tuned according to their preference and their room. The goal of an audiophile is to go out and find a speaker which is miraculously tuned exactly to your requirements and that of the speaker designer, which is highly unlikely wouldn't you say?

AFAIC the only way you could truly get true reproduced flatness in record playback is if your listening room and playback equipment are identical to that which recorded it. other than that it is a crapshoot. the most you can hope for in the real world is to avoid the noted audio sins of shriek and boom and to have sound clean enough and close enough to relative neutrality that you can discern something of what the original recording engineer heard in his studio control room. you are NOT gonna hear but an approximation of what went on in the studio auditorium itself, not even with krell and wilson on hand. it is, with the exception of minimally mic’ed direct to stereo recordings in real spaces, all a game of manufacturing and consuming sonic sausages.

Sigh…

(1) Aspiring to make the the room response flat is desirable because it helps to remove the particular way that a particular room alters the sound of recorded media upon playback—it’s a room-specific endeavor, not a global ideal, and the point is not “it sounds good.” The point is accuracy. If the recording is bad no equalization will make it sound “good;” EQ to your heart’s delight to make it sound “good” to you;.

(2) OP obviously didn’t read the Wikipedia article from which he or she copied the graph; if he or she did, it would clearly be understood that the RIAA curve is a solution for the challenges presented by the vinyl record medium to accurately reproduce the recorded sound—it has nothing to do with room response; it is not a good or bad, like or dislike, subjective, choice, judgement, kind-of-thing. It’s more akin to zipping a computer file and unzipping it when needed—nothing sexy or controversial about that.

Nice unsupported accusations about me there.

Here’s some quotes from Wiki

“The purposes of the equalization are to permit greater recording times (by decreasing the mean width of each groove), to improve sound quality, and to reduce the groove damage that would otherwise arise during playback.”

And…

”RIAA equalization is a form of pre-emphasis on recording and de-emphasis on playback. A recording is made with the low frequenciesreduced and the high frequencies boosted, and on playback, the opposite occurs. The net result is a flat frequency response, but with attenuation of high-frequency noise such as hiss and clicks that arise from the recording medium. Reducing the low frequencies also limits the excursions the cutter needs to make when cutting a groove. Groove width is thus reduced, allowing more grooves to fit into a given surface area, permitting longer recording times. This also reduces physical stresses on the stylus, which might otherwise cause distortion or groove damage during playback.”

I suggest this is a much wider discussion than what has been raised so far. Your point could have been served by sharing this: 

I like flat, try to achieve it when possible.  Currently....*shrug*....tolerable, a whack space, basically.

Preferred with beverage, no.  Spouse isn't. *L*

@kenjit Truth, to beauty. 👍

@emrofsemanon , ditto...but take a breath, or at least, Caps. ;) *whew*L*