Norton I really don't think making sheet aluminum boxes is worth the effort. Cabinet material should be as vibration resistant as possible. Even for these tiny speakers, 1/2" MDF board would be the minimum. Since you already have a powerful sub, I'd say leave the rear speakers open and install high pass filters on them to fade out the lows which cause severe distortion at higher power levels. You'll have to check with a high end car stereo shop or search online to find these. They can be as simple as a coil of magnet wire, wound to the desired inductance, or a more complex electronic unit requiring 12vdc to power the circuitry.(How much money would YOU like to spend today, Mr. Customer.) Without remembering what the stock speakers looked like, it may or may not be worth replacing them if you're on a tight budget. If you have $$$, see below.
---Sound quality is a lot like pizza. Everyone has their own taste.---I like mine bright and crisp. Deep and powerful causes more hearing damage, much as I enjoyed it.
The mono sub will need some listening time to set up. The general guideline for a subwoofer crossover point is at or just above the lower bass limit of the primary speaker system. This is often between 80-150 hertz. The Spark set-up is a different animal, though. The rear drivers themselves could have a low frequency rating of 100 hz but because of the open design, (i've never even imagined a setup like this, it's so...........unkosher!) you may not actually hear the sound until (I'm guessing) 200-250 Hz.
I may do some real world testing to get more accurate figures for this discussion when I get my car. (month or 2?) I have an audio signal generator that will offset my damaged hearing. LET THIS BE A LESSON TO YOU KIDS.....As far as a reccomendation, I went to http://www.crutchfield.com and picked out my "dream speakers"
**** EDIT **** Cancel recommendations here. See later post.....
For the rears, I'd go with either the ******** or the *******. What I look for is high efficiency (also called sensitivity or SPL for "Sound pressure level"): 92db or higher is excellent for high volume per watt from amp. Next is a rubber woofer surround. This lasts much longer than foam or *plain* paper. Then a two way crossover. A single capacitor only filters out low frequencies from the tweeter. This is whats most commonly found on 2,3, or4 way car speakers. The cap and coil is a "true"crossover because it also filters high frequencies from going to the woofer. Not major, but a nice bonus on a few of the higher end speakers. (Standard practice in home speaker systems) ** If I'm buying online, I will look for high customer review ratings in large numbers.** Last thing for me is how they look. A speaker can be a thing of beauty. Just look at the Polk db461p. (Go ahead and zoom in, I won't tell your wife) Also you'll want **-4 ohm rated drivers from what I've heard. **** SPARK = 4 OHM RATED, not 2.****
As for the 4" fronts, first find out what space you have to work with. If it's open under there, I'll be going with the *********** (They're just too pretty!) and I'll be using a high pass filter around 100 Hz to reduce distortion.
Enough for now. I'd better hang up. The wife just caught me looking at speakers, again. Hope this is worth the reading time. (I don't really have a wife. *I did have some pet trout, but that wasn't very emotionally rewarding so I ate them*).
David - Very sorry for the..."out of spec" recommendations. See below if you wish.
