Well, I am glad to see this thread has evolved into something interesting, even if it took a little work to get there.
Some comments without quoting the original posts:
Yes, enclosure construction (and with low frequencies, the specific design chosen) is critical to any driver's performance. It's a system; the driver alone is only part of the equation and we rarely use true infinite baffles or piston driver dipoles. But that's the starting point; everything comes from that essential set of characteristics.
It's true that this forum (and Audioholics in general) is more attuned to Home Theatre than most. It does colour people's replies to threads. I am not into Home Theatre much ... for one, the cheapskate in me bristles at the cost I would have to outlay to get the same resolution I can achieve in two channels. For another, given I have but one main system, I will always compromise to the HiFi side over the HT side.
I am suspicious of DSP, not because I don't think it works (it does) but because I prefer elimination or minimization to correction. Something I learned a very long time ago is in audio, your issues often center around translations in format, as you are going to introduce aberrations inherent in the translation, added to the problem you were trying to address, which themselves now need to be corrected or dealt with. So, given a choice, if you can keep it analog (it starts analog, it ends analog, and those are not optional) then work that to it's natural conclusion first and see if that does the trick. **
DSP is easier, but it's not automatically "better". Analog is hard, no question, but in most cases your problem can be addressed in that domain. If not, find out why and try again.
It's similar with my approach to Car Audio ... I try to re-create the Sound Quality (SQ) I achieve at home, rather than rattle the paint off the trunk and pop the glass in the back window. So although I do use Low Frequency extension, I take advantage of the Room Gain in an automobile to flatten the LF rather than artificially boost it (the path to high SPL is in the subsonics). Subjectively, I find in a vehicle that a little LF bump helps, with emphasis on "a little"; there are high levels of vehicle-generated LF noise that needs to be overcome (if you ever have taken an unweighted frequency spectrum measurement of a car simply going down the road, you know what I'm talking about).
Living as I have, with one foot in the HiFi world and one in the live music / music production one, and with finally settling on a very different professional career outside of audio* but one where noise was an issue to be aware of, I am acutely aware of the dangers of high SPLs in car audio, where you are, in a very real way, sitting inside a pressure vessel.
I too was once young and stupid, and back in the day when the usual practice was to generate the sound from stage rather than a house PA, one common practice was to go up to the system and listen to each 15" driver to see which one was buzzing or dead. If you think about it for a minute, that means SPLs in the 120 or more dB range six inches from your ear from the working drivers. Not a bright idea, but it was the way it was done.
I was an early user of foam hearing protection (all you could get then), and if I didn't have that, I'd take cigarette filters and use them instead (Everybody smoked then; doctors smoked in the hospitals, everyone smoked on aircraft, let alone elsewhere indoors. finding two fresh cigarettes to break up was never a problem). Every dB helps.
Today, I can still hear steady state sine waves into near 18 KHz, I can hear "that noise" the flyback transformer supplies make on CRT TVs or monitors sitting at the viewing position (something many here will never experience).
I was part of the first generation that truly was exposed to high SPLs in concert settings. When the Beatles played Shea Stadium it was little more than a bunch of 30-watt VOX amps arrayed on stage (no, I wasn't there; I was five when they played Ed Sullivan).
Ten years later, at a concert in 10th grade consisting of Manfred Mann, Savoy Brown and a third warmup band that didn't yet have an album out and nobody had heard of yet, Kiss grandstanded with the loudest set I had ever heard. At 19, I had quit half way through the 12th grade to concentrate on an audio career, I landed a job by annoying the owner to death, part time, building cable. Two years later I was a partner. Five years after that, I was a freshman in University.
When I see kids today with In-Ear Monitors (IEMs) and headphones using them long term, often with supplemental amplification ... some people wear them on the entire job shift ... and when a car driving down the street announces itself with pressure waves ... well, all I can say is those people won't like what happens next.
* A lot of hours around loud piston, turboprop and jet engines. It did involve long spells between contracts, so when I was back at home, I would get calls to work shows right to recently, where my health introduced roadblocks. I had, for a time, a studio in the top floor of my house. I still have some audio clients from more than 30 years ago who call for consultation.
** It's not simply a matter of avoiding a translation to digital and back again. If you record a live set to magnetic tape, that's a translation. If you transcript a master tape to vinyl, that's a translation. And so on. Each translation introduces unique distortions. We work to minimize these distortions to what we hope are inaudible levels, but sometimes we simply cannot, and at that point we fall back to Band-Aids®, which themselves introduce their own problems that need to be addressed. Sometimes the Band-Aids® stack up, always a bad idea.
