[MENTION=301805]champco[/MENTION] My experience with sound does not span anything close to the 50 years you have. However, I have been designing and building high performance speakers for 10 years. I've spent countless hours measuring drivers and designing passive crossovers. Running full frequncy sweeps hundreds of times opens your eyes on what is actually needed for a quality sound system. I've replaced my car audio systems since my first car back when I was 16 and have helped several friends improve their car systems. I also sang throughout my high school and college days in groups ranging from a five man a cappella group to a 100 voice mixed choir with full symphony. I feel I have a fairly good understanding of the creation and reproduction of sound.
Couple of things here with your posts and your desire to improve the sound. While it is possible the tuba on the CD you mention plays down to 25Hz, I think it's doubtful. The fact you tore a stock driver apart in a Durango means very little for the frequency you were playing. Very few stock auto systems have a system capable of playing below 35-40Hz with any authority. Old, dried drivers in a Durango could easily be torn by playing a freq around 250Hz as 25Hz, all depends on the excursion and design of the driver. Depending on the speakers, they may have had a foam surround. The foam will often fall apart after being exposed to the hot, cold and possible UV elements of being inside an auto. Heck, talk radio turned up loud enough could tear an aging foam surround apart. Even a folded paper surround gets brittle after a few years. Most car audio systems have cheap components, even if they are top-tier brands. It's like biggie sizing your value meal. At McDonals you pay $1 more, and they give you $0.19 more of fries and soda. Same this with OEM car audio. You pay $250+ more and they give you $3 tweeters in each door with a $0.50 resistor to block the bass instead of a 6x9 with a wizzer cone for the higher frequencies.
Getting back to my original statement, a $99 pair of aftermarket speakers will easily improve the sound quality of the system in almost every car. The drivers will be better built, foam or paper surrounds will be replaced with a Non-fatiguing butyl rubber surround. Paper drivers will be replaced with injection cones and small magnets will be replaced with power magnets with quality voice coils.
But like I said before, listen to the speakers before you buy them and ask a local shop for their recommendations. The local shop will likely know about the system replacing. Bose for example uses inferior speakers, but EQ's the crap out of the signal to create a 'good' sounding system. Bose also normally uses a driver with a very low impedance. This forces an amp to work harder, but also creates more power. In this sort of situation, if you would replace a 2-ohm Bose speaker with a 4-ohm aftermarket, the aftermarket speaker could over produce certain frequencies due to the Bose EQ, and the speaker could play quieter because it's only a 4-ohm load instead of a 2-ohm load. But, assuming no extra EQ'ing is done and you are replacing a speaker with the same impedance, even a cheap aftermarket speaker will sound as good or better than almost any speaker that came with the car.
BTW the human voice range is easily 300-3000 hz. Well above 2500Hz
A bass singer in a group I really enjoy has been recorded singing as low as 44Hz, quite a bit lower than your 300Hz range. Hitting notes below 300 Hz is very simple for most singers, male or female. Not sure I agree with the "humna voice range is easily 300-3000Hz" range comment. Listen to the youtube video I posted above, skip to the 3000Hz (1:40 time mark). It's takes a special voice to hit those notes.
The average man’s speaking voice, for example, typically has a fundamental frequency between 85 Hz and 155 Hz. A woman’s speech range is about 165 Hz to 255 Hz, and a child’s voice typically ranges from 250 Hz to 300 Hz and higher. Of course, each of us has a wider range of sounds that our vocal cords can produce, and if we choose to sing, that range can extend up to four octaves.... But what’s surprising in all this is that the entire range of men’s and women’s voices remains between about 65 Hz for a male with a very deep bass voice to the highest note of a female coloratura soprano, just above 1,000 Hz, at 1,280 Hz. (A female high-pitched scream can go quite a bit higher, to around 3,000 Hz.) - See more at:
http://www.axiomaudio.com/blog/audi...e-and-children’s-voices/#sthash.wTf32pIx.dpuf
Again, this is why I say a speaker that can accurately reproduce 40-15K Hz range is about all you need in a car. Heck, you are at least 50. You may not have much hearing left above 15K. I'm 37 and I know I've lost a lot of hearing in the upper range. It's part of growing old.