I didn't think about writing a thread for this, so pictures are scarce. Oh well. I used stock photos from websites to fill in some gaps. I simply don't have pictures for some steps; sorry.
This write-up is long, so I have to split it into 2 posts.
I wanted to write this to share my experience. There seems to be a lot of 2001+ NB2 guides and feedback, but 99-00 NB1 models are a bit different inside the door panels and the electronic plugs we have to work with. I also want to show people that it's possible to get a decent audio setup without giving up too much.
I like to do things in hardest-first order. So while reading this, keep in mind that I intentionally did all the hard steps first, just to get them out of the way. That's just my philosophy of doing things!
Massive Audio CK-6 Stage V
Massive Audio NX2
In an ideal world, the Miata would have a lot of space, good acoustics, and great theft prevention. Yes well, take all those ideals and throw them out the window with this car. Accept the fact that you won't have a perfect audio setup no matter how much money you spend. Also, accept the fact that real-estate is a premium in the car, so compromises must be made for audio quality, practicality, and security.
This combination offers a good compromise between sound quality and the rest of the drawbacks with the car. These speakers respond well at 40 hz and go up from there. Typically, anything under 80 hz is considered "real bass," or frequencies so low that the average human can't locate its source. Yes, a subwoofer would definitely fill the low end, but where would you put it? The trunk, so you lose some of the already laughable trunk? Plus, you'd have a big box that screams "steal me." No thanks! When combined with a clean, beefy power source (like the Massive NX2), these component speakers offer plenty of mid-bass, a little bit of real bass, and clarity in the mids and highs.
The selection of the amp was also critical. This amp, even with its high power and sound quality, is small enough to fit in the NB trunk tunnel, even with a roll bar! This will fit behind the carpet trim piece in the trunk. This means it's a completely stealth installation; nobody will see it. As far as the eye can see, you have a stock, crappy speaker setup! And you even get to keep all of your trunk space!
Give up a subwoofer, gain immensely in practicality and security. The speakers, with enough power, sound great without a sub. Not having a subwoofer is also wayyy cheaper! That's the choice I made and I'm happy with it.
This installation method is great for future-proofing your audio setup. Do the hard work once, then swapping speakers and amps should be a matter of minutes, including setups with separate crossovers, such as mine.
How it's done:
The factory wiring is worthless for anything other than OEM speakers, or other weak things. Unless you want the crossovers in the door, which has been done with success by other people, then it's impossible to use the OEM wiring. Personally, I didn't want the crossovers in the door due to moisture and future flexibility (adjustments, swap-outs, etc). Plus, even if I did, the OEM wiring probably couldn't handle the power that the speakers require. I used 14 gauge wiring for my entire install.
First, prep your speakers. Solder speaker wire to the terminals. Crimp waterproof terminal/interconnects to the ends. You can pick whatever scheme you want, but I chose male terminals for the speakers, and later I'll put female terminals in the doors. Here are the terminals I'm talking about:
Remove your seats, b-pillar covers, door sills, and the plastic trims that go by your feet. Remove the dead pedal on the driver's side, too. Remove the plastic snaps holding in the carpet around the area behind the seats pull back on the carpet, leaving it all exposed. Remove the trunk trim piece that hides the battery/wiring and the passenger trunk tunnel. Run speaker wire from your trunk through the hole between the package shelf and the seat belt, then all the way to under the dash. Leave plenty of slack! This will be the wiring for your right speaker. Route it through the carpeted areas. Do the same for the left side. Keep them labeled, especially in the trunk!
Okay, here we go. Remove your glove box. Next, we need to remove the AC/heater blower fan assembly. Here's a pic from the bottom side:
This part is the most frustrating and difficult. You could remove the entire dash for easier access, but I was able to do it without doing so. You'll need a small 10 mm wrench. Unplug two electrical cables from the blower assembly. Unhook the cable from the door lever and unsnap it from the bracket. There's a large metal strap with a snap-clamp on it. Unsnap the clamp and it'll be loose; push it completely against the blower fan. There are two 10 mm nuts you'll need to remove; they're easy to find and easy to remove once you're laying on your back under the dash. Then there's a 10 mm bolt toward the top, above the large connector/cable. This thing is nearly impossible to get to; good luck! It's gotta be pulled. No way around it. Once it's removed, you need to wiggle, push, pull, and otherwise finaggle the entire blower unit out of its place and out of the car. Pat yourself on the back; you've completed the second hardest part of the install! The hardest part is when you're done and now you need to put this thing back in. LOL!
Now you'll be able to see the plug that leads to the door. Notice how the NB1 plug/connector does not have the green, half-ring shaped latch that the NB2 has:
Sit up and open the door. Look at the rubber boot covering the exterior part of the plug:
Here's where I'm a bit scarce on pictures, so I'll try my best at describing the steps. Pry away the rubber boot from the plug. The rubber has a recess that fits over a lip on the plastic plug, so you need to lift up on the rubber with a screwdrivers, then simultaneously use needle-nose pliers to start pulling away at the boot. Once you get it started, it becomes easier. Once the boot is off the connector, push it toward the door to completely reveal the plastic connector. You'll see a small green peg at the top of it. Grab it with needle nose pliers and pull HARD, straight out of the connector. Once it snaps out, you can remove the entire connector; remove it.
Now you need to remove the door. There are plenty of tutorials online, but I'll give a brief overview. There's a pin holding the door-stop lever in place; hammer it out from the bottom. I stuck a metal stud under it to help me hammer it out. Then there's 4 bolts (off the top of my head, 10 mm, but I'm not sure) connecting the door to the hinges, 2 per hinge. If you remove them from bottom to top, you don't need to support the weight of the door until you're loosening the top bolt. Once the door is off, set it down on something soft right next to where it came off. I used a thick blanket.
Now that the door cabling and plug are easier to access, pull that green snap completely out of the plug. Yes - pull hard, completely remove it! Now look at the plug receptacle on the car. See where the green part used to snap into? Snip away the plastic tabs, then drill a larger hold into the plastic above the existing square hole.
Estimate the amount of wiring you'll need for the woofer and separately for the tweeter. Notice how the tweeter wiring needs to be a bit longer, plus extra slack to you can install/uninstall the door panel. Go ahead and over-estimate; you can always trim excess. Cut these pieces and take them with you.
Go back to your door. Grab the rubber boot on the connector and fully compress it. From the inside of the door, push the speaker wire through the boot. Do the second wire the same way (slightly tighter fit). Here's a pic:
Pull the wiring through so that they kinda/sorta ends up in the positions they should be in. Stretch the rubber boot back over the lip on the connector (don't forget this!). Make sure to label them somehow so that you know which goes to the tweeter and which goes to the woofer.