tweeter issues, poor audio

i was thinking of adding a pair of 6.5" crachendos. if i added them i would not have room for the 6" tweets in the door so i am unsure as to what route to take. the cross over network i was intending to run off the head unit to start with and buy an active external xover if needed. could i take an RCA out that is filtered for mid range on the head unit and daisy chain 2 amps through a xover? or do they make an xover with 1 RCA in and 2 outs?

i want you to understand that size is not the all important factor in how loud a speaker is. the speakers sensitivity, or how well it converts power into sound, is dependent on a bunch of factors. depending on what frequency range you are going for, having a large speaker can work against you. you might gain volume by having a large tweeter but you will probably loose a lot of detail and clarity. thats why sub woofers are big and tweeters are small, big speakers are more efficient at producing low frequencies and small speakers are more efficient at producing high frequencies. a 6" tweeter? who needs that in a car man... you would be better off with multiple tweeters than a single huge tweeter. tweeters dont need the insane power handling that sub woofers are accustomed to, a tweeter will get plenty loud with less than 50 watts, what matters most with tweeters is proper aiming and elevation. a tweeter is very directional, if they are not aimed correctly at the listener you can easily lose 3db+ just because they are "off axis". not to mention having those massive tweeters will severely limit where you can put them. an ideal place for tweeters is high on the door panel or eye level in the A pillar. do this experiment and you will see what i mean, plug in a tweeter to an audio source and just listen to the difference as you point it towards your ear and then move it a few degrees to either side and you'll notice the difference in what you hear is a good bit less than when it's pointed straight at you. having a properly set up set of tweeters will make it so that you actually hear everything they are producing instead of having them aimed wrong and making them play much harder just to get the same result, not everything can be fixed by just adding more and more equipment and you'll save a ton of money and time by just setting everything up the best way the first time. you'd be amazed the difference you'll hear thats probably the most common mistake everyone that is into car audio has made, they assume that bigger or more is always better when in reality the exact opposite is usually true. the simpler your system is and the more expertly it is set up and installed the better it will sound. lots of pros on this forum run only a single set of components in the front doors and nothing at all in the back other than a sub. these simple 2.1 systems usually sound insane, maybe not the loudest but it sounds like a concert in the front seat. and its a much bigger wow factor when you tell someone that all that sound is coming from just a single set of speakers. more speakers or bigger speakers just make it harder on you to be able to set everything up properly and thus you lose any advantage you would gain because its not done right.

ok, help me understand how this stuff is meant to be setup. the sub will be 20-100hz and the 10" mids will be from 80-4500hz (they are rated to 4800), the tweets i have are rated from 1000-29000 so i set the xover on them at 3000 and then i should not have any gaps right? i see super tweets that max around 28000 so im not sure if i would need any more tweets would i? is that how this works?

well in a nut shell yes that is how it works but its not as simple as just overlapping frequency response specs. every speaker has something called a frequency response curve which is basically a graph of how loud the speaker plays each frequency. speakers dont play each frequency equally loud, depending on the design of the speaker it will play some frequencies much better than others. most cheap speakers have a response curve that is all over the place and more expensive speakers will have a much flatter response curve. it is important to take this into consideration when you are trying to use unrelated speakers and putting them together into a single system. for instance ill use your example of having a mid set at 3000Hz, if you can find the response curve for those mids it is possible that there could be either a large peak in output or a large dip in output, same goes for the tweeter. keep in mind this is just hypothetical, but if the mid has a large dip in output around where you set the crossover point then you will basically lose a noticeable section of audio and it wont sound right. now you might be able to adjust the crossover point to a different spot and solve the problem but by doing that you might end up pushing the tweeter too hard. thats why i say that using random speakers could end up bad because many time you wont have access to a response curve which basically makes it a guessing game to set up properly. not to mention that just because a speaker is rated for a certain frequency range doesnt mean that its good at it, you will usually want to stay away from a speakers upper and lower ranges unless you have a response curve that tells you otherwise. now even with all that said, it gets much more complicated than that because to make things worse every speaker also has an impedance curve which tells you what the resistance of the speaker will be while playing certain frequencies. a 4 ohm speaker does not stay 4 ohms while it is playing so that means it also does not draw a steady amount of power from the amplifier. without knowing this impedance curve it can be very easy to blow a speaker because the graph helps you see which frequencies will be potentially harmful to your speakers and it allows you to make better decisions with the crossover settings. that is of course the main function of a crossover to filter harmful audio from each speaker. now that i have roughly explained some of what goes into matching up speakers you can see why most people just go with complete component sets that have already been designed to work together from the jump.

how does one measure the curve? a good multimeter and a mic with some computer program?

the response curve is measured in a room that is acoustically dead so there is no influence from reflections and i believe they use a very regulated power supply to give a steady 1 watt of power and a microphone placed a meter away from the speaker and the output is then graphed by a computer program. i could be wrong but i think that's it. its not something you can just measure under normal conditions. im not sure what exact device is used to measure the impedance curve.

by the way, i am incredibly sorry if i am ruining your view of car audio systems. i know this can be a lot to process and i dont want to scare you into thinking this is some impossible task. all i really want to do is give you enough information so that you can decide if you want to go ahead with your plans. you can use what ever speakers you really want as long as you can put them in a good spot and the response and impedance curves are only tools to help you match and set up the whole system. if the manufacture doesnt publish these graphs then its not the end of the world, you just have to understand that you will have to make a guess on how to set the crossover and make sure that you take it easy on the speakers at first and listen for signs of distortion when the speaker cant handle what you want them to do. dont expect it to sound perfect the first time and be prepared to be playing with your settings for a while to find the right balance.