one might say that you get what you pay for.. another might say that you are lucky and picked a pair of capable speakers.
i am currently running my stock 6.5 inch speakers down to 50hz and all the way up to 20khz.. i run them as hard as i can, just before the vocals start to distort.
they dont have any output at 20khz.. but they are getting a signal.
they stop around 10khz
but if i move the crossover up to 80hz.. i get a bit more volume.. and if i cross them up to 100hz i can get even more volume out of 'em.
its a situation of compromise.
one thing i am absolutely certain of ..
if you are running the speakers that low, you are never EVER gonna get to hear the 'audiophile' details that make people say 'i can now hear parts of the song that i never knew where there'
because wasting all the voice coil on the bass is gonna run the utilization up to 110%
if you think keeping the vocals from distorting is somewhat difficult.. keeping nuances and transients is exactly the same IF the speaker can reproduce them at all in the first place.
better speakers will produce the hidden details.. and when you crank 'em up those details fade away, then the speaker usually slaps the bottom or the voice coil overheats and needs replaced.
sometimes a speaker will also distort the vocals.. but not all speaker is created equal.
i mean.. i am an easy going kinda guy.
i once got laughed at and poked fun of because i had my two twelve inch infinity reference subwoofers crossed over at 120hz and was enjoying some 'no doubt' (gwen stefani band from the 1990's)
i was getting a lot more bass guitar at the same volume of the rest of the bass.. and i didnt have my equalizer calibrated, therefore my subwoofers were a lot louder than the midranges.
but it sounded FUN and i was enjoying myself.
however.. one concept to clearly understand is that car audio speakers are not headphones .. they are not designed to produce the full range of sound.
the less they have to do, the more they can focus on the details of what they are doing.
and again, not all speakers are made equal.. some speakers will be so stubborn that you wont hear much of a difference compared with playing the speaker full range or using a crossover on both the low end and the high end.
an easy place to find such an example is with component speakers.
if you ask too much of them .. they will lose their detail.
sometimes they sound yellow or brown.. other times they distort with an obnoxious and uncontrollable flapping of the cone going in and out.
SOME SPEAKERS sound a lot better when they use all of the xmax.
other speakers sound a lot better when they use little/none of their xmax.
its like... there is a dozen different ways to wrap the copper around the former to create the voice coil.. and that determines how the speaker sounds and what it can and cant do.
but anyways..
i have had 2-ways in the car
2-ways in the house
and then 3-ways in the house
i can already tell you that the only way to get a midrange to do the job of BOTH a midrange and a woofer .. is to have a bass reflex box that amplifies the low end.
having the door as a speaker box (sealed at that) is not gonna reproduce anything close to what a properly built ported fiberglass box would do mounted onto the door panel.
i dont wanna be a jerk.. but if your speakers are so capable .. you might as well have won the lottery, because there are hundreds of speakers to choose from.
the junk such as pyramid and boss all the way up to the small companies i have never heard of before.
the only real way to know what you are getting is to test them out for yourself.. at the car shop or the audio store.. or buy them and install them yourself and try 'em out to see which one is better (too expensive for me)
and again, in all honesty..
you are not gonna be able to cross those speakers over at 600hz and be able to tell if they sound any better because there is so much missing from the frequency spectrum that it is hard as hell to determine if what you are listening to is actually any better.
its a situation where having the midrange crossed over at 600hz will play tricks on your brain and you will constantly be forced to believe something isnt right.
because something ISNT right.. you are missing frequencies from 600hz all the way down to 50hz
you could try.. and with some determination and maybe a little sweat.. you might come to a conclusion.
but dont expect to listen for 10 seconds and instantly know that there is something better going on.
.....and if you can notice right away that things sound better, you seriously have a situation on your hands where you didnt do something right the first time and need to make some adjustments to fix the mess.
trying to make cheap flee market speakers sound their best is, above all, the luck of the draw.. which speaker you bring home that is designed to play better than the rest of the speakers available.
and then taking that speaker and trying to find the sweet spot for high pass crossover and low pass crossover slopes so that you can maximize the final result
i might be able to get a lot of decent bass from the stock speakers if i treat them like subwoofers.. but if i try to do that **** with vocals added, the result isnt gonna be the same because the volume coming from the speaker will have to be adjusted.
it isnt uncommon to find a do it yourself speaker to have two tweeters.. mainly because one tweeter cant play as high as the other one.. and the other tweeter cant play as low.
its a lot more economical to split up the power from the amplifier with a crossover and have a speaker dedicated to a small chunk of frequency spectrum.
yet.. yes, i know that there are speaker companies who are begging to make speakers that are going to turn my words into absolute rubbish.. and so they shall since evolution is among us.
but finding those rare oddities can be hard.. and those that know of them probably wont right a review worth reading.