The correct / best target curve is indeed an interesting discussion, is there perhaps an existing thread on that topic here on Audioholics where we can continue that?
Note also again that it is important not to confuse my personal preference with "design goals" for the speaker. The in-room target curve is something every customer is free to set for themselves, it is not limited by the design of this speaker, on the contrary as mentioned before there are powerful built-in tools allowing you to do this according to your personal preference.
I don't recall a thread about target curves, but there might be one.
Personally I dislike the concept of target curves. I'm hard core, and believe there is truth (precision), and error.
So I should tell you a little about myself. For some odd reason I became obsessed with sound reproduction from my earliest years. I had an obsession with it. I built my first speaker age 7. So I have seen very nearly 70 years of development.
So for most of that time, the home constructor had to use hand math calculations and fine tune by ear. 1984 was a turning point for me, when I obtained the floppy discs of Bullock and White's design software. I designed my first computer assisted design speakers. Those speakers are now my surrounds, having been my recording location monitors for many years.
As you know things progressed, and we now have measuring microphones and associated software.
In the late eighties Stereophile had a competitive "Audio sound off." I designed and submitted a pair of these speakers.
Much to my surprise they won first prize. The winner received assistance with production. So I organized a production run and had custom packaging made.
The small first production run sold out promptly. When I went to start the next run, I found out that Focal had stopped production of the bass/mid drivers.
That cured me of going into the loudspeaker production business for good. I sincerely hope you fare a lot better than I did!
Although that winner was a ported design, I have mainly concentrated on the development of transmission line speakers. The reason is that I know of no other alignment that produces such accurate and realistic bass with very uniform dispersion throughout the room, and with great efficiency with excellent control of driver excursion.
I think one of the issues a speaker designer has to really understand is where to put and distribute your power resources. I can not understand why this is not discussed more often, as it is crucial to making a robust design.
The starting point has to be the distribution of the fundamentals of musical instruments. Of course the fundamentals demand the largest portion of the power as the higher fundamentals demand progressively less of the power.
As you can see a huge number of instruments have fundamentals in that 80 to 400 Hz range.
Now this is in the area where with narrow cabinets BSC needs to be applied. So this greatly increases power demands in that, what I call, the foundational region.
This is not so much a problem for amplifiers, but loudspeaker drivers, especially those with drivers under 7" and some 8". These days there are a lot of speakers in that category.
Shortcomings in this region are NOT shown by speaker measurements we usually have for review, subs excepted. In my view the need for this is much greater in the other speakers. In my view few drivers produced today, have motor systems up to the task, which is why I have a very short list of acceptable drivers. It also requires more than one driver as a rule, and that extends into the midrange. The result if the drivers are not up to it, is serious dynamic compression and increased distortion.
If I am again suggesting there is far too much attention paid to subs versus the three to four octaves above you are absolutely right. When I do waste dealers time and hear other systems, I find that the sub is too loud to try and cover the above shortcomings, This is NOT accurate reproduction and the overall sound is not balanced.
Now before software help was available I decided that I would invest in accurate recording equipment and first class microphones. I also made the decision that is still unusual, to make phase coherent intensity difference recordings, rather then the ubiquitous phase difference recordings more often than not sprouting microphones growing like mushrooms.
Most of my recordings were made of live recordings for public radio station KFJM Grand Fork ND, and the the Dakota public broadcasting system. In the days prior to software and computer aids this was an excellent tool for loud speaker evaluation. Prior to 1984 recordings were made with a Revox A700 and a bespoke Brenell Mk VI with parabolic heads without pressure pads. Tape was Ampex Grand Master running at 15 ips stereo on 1/4 tape with dbx 1 noise reduction. The microphone was a Neumann SM69 FET usually set up in M-S mode, most often, or figure of 8 mode. Spot mics were used sparingly, if at all, and only cracked open. These recordings were extremely useful for loudspeaker evaluation, for multiple reasons.
Here is part of my last analog recording with the Revox and Brenell machines on location. These machines are still in my system. After this a changed to a VHS based digital system.
I have YouTube video on my channel of parts of this recording with explanations. Thorbjorn, you may be interested to know this video contains a work by a much loved Norwegian Immigrant to Minnesota, F. Melius Christiansen. The work is O Beautiful Savior. This work is much loved in Minnesota and the Dakotas.
This recoding was made entirely with the SM 69 FET in M-S mode. The mixer was by Tapco/Electrovoice. I show the video of my DAW. In the lower right you can see the band by frequency power band intensity. Now remember this is only a choir and smallish Baroque orchestra, and large forces are even more weighted to that 80 to 500 and even above power band. The below 80 band is trivial by comparison. However one can not dismiss that power band as it is essential to realistic reproduction. For reasons that are still not clear, it has long been observed that the 20 to 80 Hz band contributes immensely to giving a recording a sense of space and ambience. The reason for this phenomenon has never been entirely clear. The recordings I made were always monitored by speakers, and did as I hoped, give me enormous insights as to what was really required of speakers.
Here is the video of which I speak.
The first 11 minutes or so, are my verbiage, which you are welcome, and may be encouraged to skip. If you watch this carefully, it will give you significant insights as to what is required of loudspeakers, at least excellent ones.
As usual there are caveats. I do not listen to music of the pop culture as a rule. However local engineers who work in that genre really like this system and have used it as a reference.
This system is used for movies and they contain music from the popular culture often, and it reproduces that well and with excellent intelligible speech quality.
So to cut to the chase. What is my opinion of Target Curves. I say quite unequivocally that they are nonsense. You don't need a curve, you need a flat straight line and the flatter the better. However there is some license on the last octave or so 20 Hz to 40 to 50 Hz, in the area of room gain. To get extremely "hair shirt" in this region can make reproduction excessively dry. So a small amount of leeway in this area is required. I think this is actually best judged by ear, on a room to room basis.
I absolutely do not agree with the hot sub and attenuation above sub range. That in my view has come about by pandering to speakers with inadequate power response on the two octaves or so above sub range. I will state this again for the record that this defect likely affects the majority of speakers, with the resulting lack of balance at power, limiting realistic reproduction. This became clear to me as a result of the invaluable experience of making live recordings.
So this has been a long winded way of saying we need more straight lines and less curves.