MKII Toyota MR2 Audio Installation How-To Guide

This page gives the details of a DIY aftermarket stereo installation in a MKII Toyota MR2. The installation is performed in a 1991 MR2 with the stock "Premium" system, but a lot of the information here is applicable to all MKIIs. This is not an all-encompassing guide; my intent is to simply provide one possible approach and provide some details that may be of use to anyone contemplating a similar install. Since every audio installation is unique, however, you will likely run into issues not covered here.

What this guide is: An account of the MKII MR2-specific aspects of the stereo installation. Removing the stock door panels, adapting the stock wiring harness, fitting an amplifier rack, running wires through the firewall... all the nuts-n-bolts aspects of an aftermarket stereo installation that are unique to a particular car.

What this guide ISN'T: Lots of things won't be covered here, such as the basics of system design and tuning, sub box fabrication, wiring basics, etc.... all these things are covered in great detail elsewhere on the web.

This was a long term project for me, so I have lots of pictures and comments. I've done my best to keep things organized, with varying degrees of success. This page contains:

• Introduction & scope of this guide
• Outline
• The Basics
  • Overview of the stock system
  • Recommended upgrade path
    • Head Unit
    • Tweeters and woofers
    • Rear speakers
    • Subwoofer
    • Amplifier
    • General wiring
• My system
• Amplifier installation
  • Building a amplifier rack
  • Wiring the amplifier
    • Wiring the power, ground, and amp turn-on lead
    • Signal wires / RCAs
    • Speaker/subwoofer wiring
• Removing the door panel
• Tweeter installation
  • 93+ Tweeter covers
  • Making custom tweeter mounts
• Woofer installation
  • Making a spacer ring
  • Installing the woofer
  • Modifying the door panel
• Subwoofer installation
  • Subwoofer box selection
  • Mounting & wiring the sub in the enclosure
  • Wiring the sub to the amplifier
  • The enclosure installed
• Head unit installation
  • Removing the stock head unit
  • Making a wiring harness
  • Adapting the antenna
  • Power and signal wiring
• Things I would have done differently

Disclaimers:

• The information here was current when I wrote it. Part numbers and part availability can change. If you notice something seriously wrong on this page, let me know and I'll try to keep it updated.
• Use this guide at your own risk. Not responsible for skinned knuckles, electrical fires, or profanity overheard by impressionable family members.
• This guide is a work in progress. Comments, corrections, typos, and alternate approaches are welcome and should be sent to "smspam @ comcast.net" with "MR2 audio" in the subject line.

Stock Premium System

My install consisted of:

• A Phoenix Gold XS4600 4-channel amplifier mounted in the front trunk
• Orion HCCA 5S component speakers in the stock locations (5.25" woofer in the door, 1.5" tweeter in the sail panel)
• A single Image Dynamics IDQ-10 subwoofer in a Q-logic QLT-.6510SX truck box behind the passenger seat
• A JVC KD-SH99 Head unit.

• I use MDF, or medium density fiberboard, for just about everything. You end up making a lot of curving cuts and drilling lots of holes, and with MDF you don't need to worry about going against the grain or hitting a knot. It also finishes smoothly. The downside is that it's pretty heavy, and makes a lot of dust when you're working with it. Plywood would probably work just as well in some areas, such as the amp rack.
• I try to be consistent in my terminology, but I use the following words interchangeably: Tweeter cover/sail panel; RCAs/signal wires/interconnects; mids/woofers/speakers; sub/subwoofer; and head unit/HU/deck. Hopefully everything will be clear from context.
• A lot of the pics are on the crappy side, because at the time of my audio install, my digicam was a bit on the crappy side. I've since upgraded, so if anything is unclear in the pics let me know and I'll try to get a better picture. This is assuming the part in question is readily accessible and easily photographed; I'm probably not going to be willing take my door apart and unmount the speakers to get a better pic.
• You can install the components in any order, but I recommend installing the amp first, since that's what everything else connects too. It's also good to have it already installed so you can use it to check the woofers & tweeters when you get to that step.

I used a scrap piece of solid core foam insulation to make my template. This is basically a big piece of pink styrofoam, roughly 3/4" thick, that can be bought in 2' X 8' sections at any hardware store for a few bucks. It comes in very handy when prototyping. It can be cut easily with any serrated knife. I started with a 2' X 4' piece of this stuff and started trimming it down, test-fitting it in the frunk repeatedly as I went. Once I felt it was close to the shape I wanted, I traced the outline onto the MDF and made my first pass. Here's a pic of one of the test-fittings:

I ended up having to make a few notches in the perimeter of the rack to run the various cables. I also took out two notches along the bottom to clear a coolant hose and the spare tire frame. Once I was done cutting, I painted it black and screwed down the amplifier and crossover.

Here's one more detail that will be of interest to...pretty much nobody. The crossover frequency of my amp is adjusted by replacing DIP resistors which are accessed from the underside of the amplifier. Since I didn't want to have to unmount the amp to get to these, I drilled out two large holes in the amp rack for access:

Here's some pictures of the finished product as mounted. The wiring is covered in the next section.

• Make good connections, crimp hard, and when in doubt, solder. The wiring will be subject to a good amount of vibration, and you don't want anything coming loose.
• Use gold plated connectors when possible. They're really not that expensive and resist the elements better.
• Once you've figured out what you need, buy supplies from one of the big discount online audio supply stores, such as Partsexpress.com. The retail mark-up on connectors, wires, and other basic supplies is obscene, especially at places like Best Buy or Circuit City. You can buy wire by the foot off a spool pretty cheaply at Lowes or Home Depot.
• Avoid drilling new holes when possible. Use a grommet any time you run wires through a firewall.
• Secure wire runs in several places with zip ties.
• Leave yourself some slack, perhaps as much as a foot, on each end of a wire run. You might need to make changes later, and you don't want the wires pulling tightly on the speaker/amp terminals anyway.
• Leave enough slack in all wires at the amp rack end so that you can remove the rack without having to disconnect anything, in case you need to get to your spare. Or, get a bunch of quick disconnects.

For the power lead, I spliced in an inline fuse holder about a foot from the terminal.

The RCAs run from the bottom of the amp through the notch in the bottom of the amp rack. I marked the subwoofer RCAs with a band of blue electrical tape on both ends so I could distinguish it from the component speaker RCAs.

In general, the Frunk is a veritable mine field of potential noise sources. The power steering pump is the most noxious offender, though. You may have to try routing you cables a few different ways to get a noise-free install. In hindsight, it might have been easier to use a different grommet for the RCAs, perhaps one over on the passenger side. Once you find a routing that works, secure your RCAs with some zip ties to keep them from shifting around.

The amp side connections are made with gold plated crimp on ring terminals.

• Red : Left Tweeter
• Blue : Left Woofer
• Green : Right Tweeter
• Yellow : Right Woofer

The left and right woofer and tweeter wires run along the outside edges of their respective footwells to the kickpanel, where they join the door wiring harness as shown in the picture below. This pic is of the passenger's side wiring, the driver's side is a mirror image.

This is a good time to test the amplifier. I didn't have my head unit installed yet, so I used a portable CD player with a mini-to-rca plug as a source. I jumped the Power lead to the turn-on lead with some alligator clips to get the amp to turn on. If you don't have your speakers hooked up yet, you can connect them temporarily and run them in free air to test, or use a pair of home theater or computer speakers. Just make sure whatever you use has enough impedance and can handle the power output of your amp. There's no point in doing any fine tuning at this stage, but it's good to at least make sure everything is working.

Removing the stock door panel

The stock location is not the best for imaging, but it's not that bad either. I specifically chose a component set with a low tweeter crossover frequency to help "blend" the sound together. The ORION HCCA 5S manual recommends a tweeter-to-woofer separation of no more than 24". The stock locations on a MKII MR2 are 16" center-to-center.

91-92 vs. 93+ Tweeter covers

One cheap and easy upgrade for 91-92 owners is the 93+ tweeter covers. These are much larger than the stock 91-92 covers and have a grill instead of drilled holes. They are available from the dealer and are a direct swap for the old style covers. Some side-by-side pics of the covers appear below, the 91-92 covers are on the left and the 93+ covers are on the right. The 93+ covers allow you to mount a larger tweeter, and may give you more freedom in aiming the tweeter more towards your ears. I've also heard people say that the finer mesh grill in the 93+ covers transmits sound better than the drilled holes in the 91-92 covers, but I can't vouch for this myself.

67491-17041 Door - Outside mirrors - Inner cover (Right) $14.55

67492-17041 Door - Outside mirrors - Inner cover (Left) $14.55

Custom tweeter mounts from MDF

Let me preface this section by saying I went to way too much trouble making these mounts. I didn't mind, since I enjoy wood working and had all the necessary tools, but there are much easier ways of mounting the tweeters. For instance, some people have used plumbers tape or even just double-sided tape with good results.

The mounts were made from 1/2" MDF. After I'd removed the stock tweeters, I cut a small triangle out of cardboard to get a rough estimate of the shape of the space. I used this as a template to cut the MDF. I then used a belt sander to shape the MDF more accurately to fit in the recesses. I used the stock tweeter bracket to transfer the mounting holes to the MDF pieces and then drilled new holes. Also, several partially drilled holes were needed on the back to clear the heads of the mirror mounting screws, to allow the MDF pieces to mount flush. To find where clearance holes were needed, I drew on the heads of the protruding screws with a black marker. I then pressed the MDF piece into place, and then drilled wherever marker had transferred onto the back of the MDF. This was basically trial and error, so I'm afraid I don't have any exact measurements. I also cut a small notch in the back to run the tweeter wire. Here's a picture of the unfinished tweeter mount, the cardboard template, the tweeter mounting cup, and the 93+ tweeter cover for reference.

I unplugged the stock tweeter plug, tucked it out of the way, and ran new wires along the stock wiring path. I soldered the tweeter leads to the speaker wire, but in hindsight it probably would have been good to buy another set of disconnect terminals. There's sort of a channel in the door panel that you can run the wire along, I've hi-lighted it light blue in the pic below. The thicker wire to the right of the tweeter wire is for the power mirror. There's a few more pictures of the wiring setup in the woofer section.

As mentioned above, pretty much any 5.25" and a lot of 6.5" woofers will fit in the door. The only thing you have to watch out for is drivers with really deep baskets, since you may rub up against the window glass when it's rolled down. This brings up an important point:

• Be sure to roll the window down before beginning the install

The first step is to remove the stock mounting ring. Use it as a template and trace the outer edge onto a sheet of MDF. You can also use the stock ring to mark the location of the holes for the 3 screws that will hold the spacer ring to the door. Next, trace the inner circle of the spacer, based on the required mounting hole diameter for your chosen woofer. My component speaker set came with templates for tracing out speaker holes, basically a cardboard doughnut looking thing. If you don't have one of these, you can just use a compass and the specs for your particular woofer. Try to center the hole on the spacer as best you can. The stock ring, cardboard doughnut template, and resulting spacer outline is shown below as drawn on a manilla folder. I did this after the fact for the sake of this web page. Obviously, you want to save yourself a step and just trace directly onto the MDF.

The last step is to cut out the inner speaker hole. First drill a small starter hole inside where the speaker hole will be. Then use a jig saw or coping saw to roughly cut out the hole. To finish up the inside, I used a drum sander mounted in a drill press. This allowed me to get the speaker hole nice and round. Just go slow and work your way outward until you hit the line. You could also use a hand file or Dremel for this step.

Here's a pic of test-fitting the spacer ring:

Before putting the door panel back on, it's a good idea to check the speakers. Play some music at a relatively high volume and make sure there's no rattles or distortion, and that both the woofer and tweeter are working.

Mounting a subwoofer in the cockpit of a MKII

• Most importantly, will you have enough room to slide your seat back and/or recline it enough to be comfortable? What about your passengers? The best sub in the world is pretty pointless if it makes your car uncomfortable to drive / ride in.
• Do you ever use the space behind the seats for storage? If you have T-Tops, where do you put them when you take them out? How often do you use the storage box behind the passenger seat? Will having to move the subwoofer to get to the storage box annoy you in the long run?
• Can you still get to the engine hood release lever behind the driver's door? If you have to move the sub box to get to it, will this also annoy you in the long run?

1. Buy a generic, ready-made box.
Dozens of ready-made boxes are available from places like Sound Domain, Crutchfield, and Ikesound. Look for truck-type boxes, which are shallower and fit better. Make sure there's enough mounting depth to fit the subwoofer you've chosen, and carefully measure the area behind the seats. All MKII interiors should be the same, but in reality I doubt that's the case. The shelf area is roughly 7.5 inches deep by 20 inches wide, but measure your own to double check. It's also a good idea to buy the box from a place with a good return policy, just in case it doesn't fit the way you hoped. It's also hard to predict the impact on seat movement without having the box in your car. The place I bought my box from (Crutchfield) was nice enough to let me take it out into the parking lot to test-fit it before purchasing.

2. Buy a custom box specifically made for the MR2
Shawn M. makes custom boxes designed specifically for the MKII MR2, in both 8" and 10" sizes. With the 8" versions, you don't loose any recline room, and the T-tops can still fit behind the seats. Details can be found here: Shawn M. MR2 sub enclosures. Another option is to spec out your own design and take the measurements to a car audio store or cabinet maker. This option may actually be cheaper than building the box yourself IF you don't already own the necessary tools.

3. Build your own
The most time consuming, but also potentially the cheapest and most rewarding, especially if you already have access to the necessary tools. There's lots of great resources for box building out there, so rather than go into detail I'll just say "measure twice, cut once" and then point you to Google. I had already had my fill of working with MDF from the amp rack, woofer spacers, and tweeter mounts, so this option wasn't terribly appealing to me personally. Maybe next time.

I went with the first option, and bought a Q-Logic QLT-.6510sx from Crutchfield. It was reasonably cheap, had enough depth and the proper airspace for my chosen subwoofer (Image Dynamics IDQ-10), and it fit perfectly on the shelf behind the passenger seat (see pictures below). The dimensions of the QLT-.6510sx are 20" wide x 15" high with a 7-1/2" bottom depth and 5" top depth. The airspace is 0.65 ft^3. NOTE: I've been informed that Q-Logic has discontinued the QLT-.6510sx and is now selling a QLT-.6510se ("second edition?"). The se is slightly wider and deeper, at 21-1/8" wide X 13-7/8" high with a 8-1/8" bottom depth and 5-1/4" top depth. I've been told that this newer box does not fit nearly as well. A Google search still turns up some places selling the sx, so perhaps some old stock is still available. Anyway, be sure of what exactly you're getting, and check the return policy in case you're not happy.

Installing the sub in the enclosure

First, pull out the ashtray and remove the two screws shown below.

Salvaging a 14-pin connector from the stock head unit

This step is optional, and will result in the destruction of the stock head unit. If your HU has been annoying you lately, this could be a good thing. In the end you'll liberate a difficult-to-find connector for the stock 14 pin harness, which can be handy later. I didn't take many pictures of this process, all you're really doing is disassembling the HU into component atoms. It's built up of interlocking layers of metal cages and circuit boards. Just go slowly, unscrewing every screw you can see. Your target is the bottom circuit board with the 14 pin connector on it. There's a small metal band that holds it in place, the liberated connector and vanquished band are shown here:

1. Splice a more readily available 14 pin plug into the stock wiring
There's a good write-up of this approach here. You can get away with a connector with fewer than 14 pins, since odds are you won't be using all of the stock connections anyway (BEEP and MUTE come to mind). I'd go ahead and use a 14 pin connector, though, just so you have all the connections available in case you or a future owner decides to go back to a stock stereo.

2. Bypass the stock wiring entirely.
If you're running an aftermarket amp, you'll only need 4-5 of the wires in the stock harness anyway, and they can be pulled from elsewhere. This is essentially what I did.

3. Cannibalize the 14 pin female adapter from the stock HU
If your stock premium HU has quit on you, and you don't mind sacrificing it, you can salvage a useable connector from the back as mentioned earlier.

4. Shell out for an adaptor.
After many years with no adaptor available, Autoleads has stepped up and begun offering a plug-n-play solution for the 1991 premium sound system. The part # is PC9-406, and details can be found here

I mostly bypassed the stock wiring, but I did end up pulling switched power from the stock harness using a cannibalized connector. The pinout of the stock adaptor and the wiring codes appear below for reference.

NOTES:

(1) The AMP and ANT pins are used to operate the power antenna. If you're keeping the antenna, connect these two leads to a turn-on lead from your head unit. If your head unit has separate amp and antenna turn-on leads, you can connect the antenna lead to the harness AMP & ANT so that the power antenna only raises when listening to the radio, not CDs. Also note that some owners have reported that the ANT lead is black with a red stripe, not green with a black stripe as listed in the BGB

(2) Pins 2 & 8 are listed as unused in the BGB. The information in the table comes from the thread about splicing in an alternate connector linked to above.

(3) This pin is supposedly the signal ground, so this lead is used if you're trying to use an aftermarket HU with the stock amplifiers

(4) Pin #14 is listed as "RR-" in the BGB, but I'm inclined to believe this is a typo and it's really RR+ and therefore consistent with the other speaker wires.

It should also be noted that if you're using the AMP (1) & ANT (7) leads, or the ACC (9) lead, you'll need to retain the stock amplifiers. I'd recommend leaving them in regardless, unless you're on a big weight reduction kick.

In the end the only pin I used from the stock harness was #9, switched power. I soldered a short piece of wire onto the back of one of the pins salvaged from the stock head unit connector, and then plugged it into the stock harness as shown:

The premium system uses what Toyota calls a "diversity" antenna for radio reception. There are actually TWO antennas, the power antenna mounted next to the spoiler on the passenger's side, and an additional antenna in the windshield. If you ever wondered what the thin wire that runs down the center of the windshield was for, now you know.

The power antenna uses a standard "F" connector and should plug directly into most aftermarket head units. Just connect a turn-on lead to the AMP and ANT leads in the stock harness and you're set. In my case, however, the power antenna had long since quit. I didn't feel like replacing it, but still wanted decent radio reception, so I decided to take advantage of the windshield antenna, which uses a "mini/GM" connector. The antenna plugs are shown below.

• Subwoofer - I would have put a quick disconnect terminal in the wiring near the box itself, and put a handle on the box as well to allow for easy removal during autocross and track days.
• Amplifier - Again, quick disconnects for the speaker & power wiring so I could easily remove the rack as need be. Also, I probably should have just used plywood for the rack. It would have been lighter and cheaper. Plywood doesn't finish as nicely as MDF, but it's under the hood and I never have to look at it anyway.
• Head unit - My next upgrade will probably be a new head unit. There's nothing wrong with the single-DIN MP3 capable unit I have, but a lot of new decks have come on the market since I bought it a few years back. I'd like to take advantage of the stock double DIN opening and fill it with a DVD/Navigation HU with a touch screen interface.
• Tweeters - As I mentioned above, making the mounts was probably more trouble than it's worth. I could have just used plumbers tape, or modified the stock mounts with a bit of bending.
• Woofers - I'm not sure I would have bothered painting the spacers, since they don't really show.

This concludes this how-to guide, I hope it was helpful. Once again, feel free to contact me with comments, corrections, suggestions, or questions at "smspam @ comcast.net". Be sure to put "MR2 audio" or some variation thereof in the subject line, or else it likely won't pass my SPAM filter.

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