Is there a perfect speaker?

Yes. The Magico Q7. Now you know. Slight issue with it: it costs almost a quarter of a million dollars.

There seems to be so many parameters that can influence the sound of a speaker, that one wonders why anyone uses speakers. I have a pair of Acoustic Zen Adagios which I like very much. They seem to have one or two sonic flaws. Nevertheless, I am currently fooling with a new pair of speakers that are monitors, the Music Hall "Marimbas" which retail for $350... Why?? I have been intrigued for many years as how a well designed budget, or less expensive speaker can compete with some of the top guns on the market, or at least speakers I have owned.

I tried the same experiment 6 months ago with a pair of Wharfdale 10.1....a highly touted bookshelf. So far, I think the Music Halls are better sounding with a much wider frequency range. Neither were equal to the Adagios, though they came close in certain aspect of the sound like tonal neutrality

Occasionally, I get the urge to buy and try a vintage speaker of the 70's like a pair Dynaco A-25, or large Advents,or even a Rectilinear 12. However, in each case, the speakers have been either reconed and/or use newer tweeters. In addition, cabinets and grills are scratched, stained and whatnot. Sound crazy!! I know.!!! Several yeas ago, I bought a pair of the vinyl "Large Advents", and despite the horrible tweeter used in the original model, I still believe they had the most neutral sounding mid-range of many speakers costing 20-30 times their retail price.

I doubt this will provide a satisfactory answer to your tread, but may give you some insight into how each brand of speaker has its own sonic character and signature. The very good ones are worthy of an audition.

The only thing I'd add to what's been said is that as you move up the price scale, you're more likely to find speakers that do many things well, as opposed to just some. But even at that level, there are compromises, in part because technology is still limited and in part because the criteria for a good speaker aren't entirely unitary. For example, speakers interact differently with the room, and in some cases, there's no right and wrong to it; an omni, say, like the MBL's, might produce a wonderful sense of space with an orchestra, but too much ambiance for a folk singer.

Perhaps in as much as there is a perfect listener, then again, perhaps not.

As is obvious to even a casual observer, only God is perfect.Bach comes close though.