I was looking into replacing my 6.5" door speakers with 110 watts RMS 330 peak, adding a set of 4" speakers at 50 watts RMS 150 peak, and one tweeter somewhere up front as well at 50 watts RMS and 150 peak. With all that adding up to 210 watts RMS to each front door. All speakers are 4 ohm impedance. When I get the amp what would be the best way to wire them? Parallel or Series? What would the total ohms be in the end and would a 400 watt 2 channel amp be sufficient? I want the most sound I can get.
First question is.. do you really need 10 speakers per door? There exist 2-way and 3-way speakers that will blow away anything you have heard before. Next issue is, the midbass, midrange, and tweeter, they are all designed to play different frequencies. A midbass speaker playing high enough frequencies may sound harsh to the ear. A tweeter playing low enough frequencies will simply blow up. So you need a device that separate the frequencies between speakers. This is what crossover boxes are about. The next issue is that your random midbass, midrange, and tweeters can have completely different sensitives. The (passive) crossover's second job is to match the levels of your speakers. Therefore do not listen the advice that you need to buy a passive crossover box separately. In a well designed speaker system, the crossover box is designed specially for a set of speakers it will be connected to. If you pick a random crossover box, it will probably will not sound good.
The second way of running multiple speakers is to use an _active_ crossover, which can be either digital or analog. It can be part of an aftermarket active crossover, processor, high end stereo, and some times part of an amplifier's pre-amp section. The active crossover splits the frequencies between channels _before_ the amplifier chain. In this case, the amplifiers will need to have a separate channel for each driver (e.g. for midbass, mid , and tweeter, you will need 3-channels per side).
And by the way, I hope your 6.5 is NOT a coaxial speaker. A coaxial speaker is a full range speaker that does not need help of any extra tweeters midranges, etc. What you want is a midrange or midbass woofer (something that's without its own tweeter) since you will be using a extra tweeter.
My advise to you is simply to buy a set of component speakers (together with their own crossover box). I personally wouldn't bother with 3-way if running passive and without advanced processing. A nice 2-way component set should run well enough. Skip the cheap mass brands. Look into Hertz, Focal, Hybrid Audio, Morel, etc. But if you really want a 3-way passive system, there certainly exist a few vendors that offer them. There were a couple of posts about them this past week.
