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Mustang Audio

This page details some installation tips that I’ve put together in outfitting a 2005-2009 Mustang with a decent stereo system.

Click on any picture to view a larger version of the picture.

Here’s what I installed:

• Pioneer AVIC-F700BT in-dash gps /cd/mp3 head unit
• Polk db5251 5 1/4″ component speakers for the front
• Polk db571 5×7″ coaxial speakers for the rear
• Polk MM1240 12″ subwoofer
• Rockford Fosgate P400-4 4x50W amp for front and rear speakers
• Rockford Fosgate P200-2 bridged at 1x200W for the subwoofer

Tools

You need basic stuff – screw drivers, sockets, etc. And you need these two must-haves: wiring pliers and an automotive trim pry tool. The pry tool is great at prying apart our snap-together cars without nicking stuff up like a simple flat head screwdriver would.

Perhaps the best tool is a good sheet of instructions. So here’s a tip: buy something from Crutchfield. They will include a very good install guide for the Mustang, or whatevever your car is. Crutchfield’s guide is loaded with pictures and instructs you on how to take apart your dash and trim panels so you can install things. (FYI – I bought one of my amps from Crutchfield as a great deal on a factory refub).

Speaker Installation

The factory front & rear speaker are 5×7″ oval-shaped coaxial speakers.  It would be easiest to simply replace them with better quality 5×7″ speakers. But sound quality in round, component speakers is far superior to a) oval-shaped speakers, and b) coaxial-design speakers.

So I opted to put Polk 5 1/4″ component speakers in the front. I could have also done so in the rear, but opted for less expensive 5×7 coaxials from Polk, as sound quality in the rear matters a bit less than it does in the front.

Installation of the 5×7 speakers was a straightforward.

Installing component speakers up front requires more work. Sure the 5 1/4 inch driver fit the factory 5×7 location with the use of a stanard 5 1/4 speaker trim plate like this.

The factory speaker bracket had some troublesome plastic nubs in the way and they were easy to trim away.

How about the tweeters? No matter where you put them, some cutting is going to be required. Turns out this required more bravery than skill. It wasn’t hard. I was advised by a local shop to put them on the A-pillars like this.

This location for the tweeter allows sound to bounce off the windshield. The result is left-right stereo separation and imaging better than I thought was possible in a car. I am very happy with it.

So here’s how I did that. The A-pillars pulled right off (its amazing how much of this car is really just snapped together.) After some experimentation to verify clearance, I went ahead with the install. I started by taping from the underside to mark where I did not want to cut – on top of any internal support structure.

Next, I marked where to drill. I held the speaker bracket (upside down) in place and made a mark with a small phillps head screwdriver.

Next came the drilling. A 2-inch circle bit was the perfect size.

Finally, I dropped the tweeter holder in there, and screwed on a holder bracket from the underside. This fits nice & snug.

Then the tweeter just snaps right into the holder you see here. But don’t put the tweeter in until the A-pillar is installed on the car – it won’t be easy getting the tweeter back out.

Ta-da!

You’ll notice in that picture of the Polk 5 1/4″ components, there a box that goes with it. That’s the crossover. I installed my crossovers under the dash next to the driver & passenger footwells. I couldn’t find a good way to mount them with screws, so I used 3M Automotive Trim tape, which I understand holds with a death grip.

That vertical bar on the right of the crossover is the clutch. One pair of blue wires is an input that comes from an amplifier. The other pair of blue wires goes to the 5 1/4 inch speaker. The gray pair of wires where pre-installed on the tweeter.

Here’s the passenger side crossover. I taped it on top of the passenger side fuse panel box.

Running speaker wires from the component speakers to the crossovers was complicated. The tweeter wires were easy – they dropped straight down from the A-pillars to the locations where the crossovers are. But getting wire to the 5 1/4″ inch speaker was a real bear.

Start from the door side. Fish wire into the factory conduit which runs across the door jam. You’ll need to wiggle, fish, wiggle, fish. And then the wire hits a roadblock just before entering the car.

Here are someone else’s photos on that.

This bracket blocks entry to the car. So I pried out & pushed the tab as shown below to separate this bracket from the car.

At this point, you’ll discover that this pesky bracket is snapped on to yet another bracket inside the car which you won’t be able to pull through this hole.

So pull up on the tab as shown below to de-attach the interior bracket.

Now run your speaker with through the exterior bracket and into the car. Forget the interior bracket and just let it hang inside the fender well. I can’t tell that the interior bracket serves any useful purpose. When you’re done, the exterior bracket should snap back into place, and with a great deal of patience you can stretch the rubber conduit/grommet/boot back over the exterior bracket to keep the whole thing sealed up.

Electrical

I recommend not re-using factory speaker wire, as that wire is very small. It may work. Re-using it wouldn’t be the end of the world. But if you’re going to spend money putting in a good sound system, the least you could do is spend a few bucks on decent speaker wire. Don’t believe the hype on expensive speaker wire, or expensive wire of any other type of wire. The main concern is to pick out the right gauge (thickness) wire for the the speaker wire as well as power and ground cables. I chose 14 gauge speaker wire.

For RCA cables, you mainly want something that is described as being twisted & shielded, as this will reduce noise. Ignore all other hype and expense – trust me on this, I’m not just some guy who stayed in a Holiday Inn Express, I’m an electrical engineer. I chose Monster Cable 306 XLN RCA cable because 1) it was a cheap ebay deal, and 2) it contains 3 pairs of cable which was easier for me to install than the usual 3 cables with 1 pair of connectors each. Otherwise, I’d just about never buy a hyped up, expensive brand cable.

Choosing power & ground cables is a little less straightforward. Reusing factory readio power & ground connections for the head unit is fine. If you’re using one or more amplifiers, the big concern here is how to get power and ground connections to them. I consulted this cable chart and determined that each of my amps needed 8 gauge power & ground wires.

Rather than running 2 8-gauge power wires to the battery, I chose to run one 4 gauge wire to a fuse distribution block like this.

This Hitron HFB2G fuse distribution block is made to input a 4-gauge wire which it connects to 2 fuses and then outputs two 8-gauge wires. Based on Rockford Fosgate recommendations, I put 40-Amp fuses in the fuse block.

It is best to put power fuses as close to the battery as possible, preferably right next to the terminal. But this fuse block which I’d already bought appeared not to be waterproof, so I opted to put it inside the car next to the firewall. I messed up here. I should have purchased a weatherproof fuse distribution terminal and planted it right next to the battery.

So later, I ended up putting a single 80-Amp weatherproof fuse on my 4-gauge wire right next to the battery terminal.

Anyway, so the plan is 4-gauge wire from the battery to this fuse block, then 8-gauge wires to the amps.

With wires chosen, the next task was to figure out how to run them from the battery to the amp location in my trunk. The hardest part was figuring out how to get the wire through the firewall.

I discovered there is already a firewall wiring grommet shown here in the passenger side footwell. Better yet, this grommet had an unused nipple on it. I cut the end off the nipple and discovered it was just the right size to get a tight squeeze around a 4-gauge wire. Nice when things just come together.

My first experiment with this grommet was to remove it, push a wire through, and see where it comes out on the engine side. The red wire here shows where it came out.

See that fat pipe to the bottom right? That’s my header pipe inches away. I was concerned the wire being that close might melt.

Fortunately, I found a better route shown below. I put my blue 4-gauge wire through that hole and it dropped in right behind that grommet in the firewall. Perfect.

I had to remove the grommet to pull my length of wire through. Then I fed the wire through the nipple and reattached the grommet.

I also went back and put an “anti-short” grommet in that hole pictured above. This will help prevent the metal around the hole from rubbing through the blue outer coating and causing a short. Here’s what an anti-short grommet looks like.

I mounted my fuse block right next to the firewall grommet. The fender-side firewall had a nice gap behind it, which made it safe to drill & mount the block with sheet metal screws.

Routing power wires, speaker wires, amp turn-on leads, and RCA cables to the amps in the rear of the car was straightforward (except for the door jam issue which I described farther up). The main thing there to keep in mind is to keep the power wire runs away from the speaker & RCA cables. This will reduce noise.

Ground wires for the amps should be kept as short as possible. (Darn, forgot to take a picture of this.) Here’s the rear passenger side of the trunk where I installed the subwoofer & amplifers.

Behind that subwoofer box & trunk-liner fabric is a factory-made section of sheet metal with holes in it. This section of metal & mounting holes was intended as the mounting point for a factory-option subwoofer. I grinded away paint & primer from one of these holes and used it as a ground location for two 4-guage, 18-inch long ground wires.

There are a couple of other miscellaneous electrical things required by the AVIC-F700BT uber cool GPS/Navigation head unit I bought:

• ACC (12V only when the ignition is on)
• A reverse signal which should be connected to something which has voltage 0nly when the car is in reverse
• GPS which runs to where ever you mount the GPS antenna
• Microphone installation
• Illumination which connects to something with 12V only when your lights are on.

I was surprised not to find ACC behind the factory radio. This was highly unusual. Instead, I pulled it from a spare fuse location in the passenger fuse panel as shown below with the “add-a-circuit” fuse I bought from a local parts store. At some point, I will also tap into this wire to use for a hardwire install of my radar detector.

For my reverse signal, I tapped into the diver side reverse lamp shown as the green wire in this harness right behind the driver side tail light. That red thing on the bottom is the handy wire tap widget that came with the AVIC-F700BT.

The GPS wire simply plugs into the back of the AVIC-700BT. I chose to mount the GPS antenna on the rear deck where the rear windshiled provides good visibility to the sky.

I punched two small holes in the rear deck and secured the wire with a black tie-wrap. That flat square comes with the antenna – its a ground plane which many people don’t use (not required if the antenna is mounted to metal), but it will make the antenna stronger. The GPS antenna isn’t glued or taped down, as the tie-wrap keeps it from moving.

The Illumination signal is something else I was surprised not to find behind the factory radio. A dimmer wire is provided, but that’s not what you want for the AVIC-F700BT. The AVIC-F700BT doesn’t support variable dimming. It just has a day mode and a night mode. The night mode comes on when you turn on your lights (indicated by the Illumination signal).

For the microphone installation, I simply ran with wire through the inside of the drivers side A-pillar and let the microphone hang over the top edge, pointing towards the cabin.

I found an Illumination signal behind my headlight switch.

The headlight switch panel pried right out with my trusty trim pry tool. Then I turned the panel upside down to find the Illumination signal.

I tapped the peach/white wire to get an illumination signal, as shown by the red wire tapper widget below.

The rest of the AVIC-F700BT install was straightforward, per the directions.

I did choose to completely remove the center console and put some rearward-running wires wires underneath it – RCA’s, amp turn-on’s, GPS, reverse signal. Front speaker wire was routed along the door sill panels. I put power wires near the passenger door sill, but farther under the carpet towards the front seat.

I also opted to put in a hardware hack which disables some lawyer-inspired safety precautions in the AVIC-F700BT. The hardware hack allows all the radio functions (like choosing a navigation destination) to work while the car is moving. Hey, why shouldn’t the passenger be able to operate the thing while I drive…

Instructions for the hardware hack are posted at the incredibly useful avic411.com forum.

Here’s the final product.

Mounting the AVIC in the Dash

For mounting I used the Metra 95-5812 mounting kit, which everybody under the sun recommended. Turns out the fit wasn’t all that great.

Click that picture for a closer look and you can see there’s a decent sized gap between the Metra’s bezel and the factory trim panel. Also, while the top if fairly flush with the car’s interior, the bottom of the bezel is recessed a bit.

The metra kit came with spacer tabs to address this. Spacer tabs from for the top are installed in the picture above. Spacer tabs for the bottom made the bottom stick out by about as much as you can see that its recessed in the picture, so I left them out.

What I need to do is grind down the bottom spacer tabs to about half their original height and install them. That would make the whole thing flush.

But I’ve still got an ugly gap. I’ll keep an eye out for another trim kit, but I doubt there’s one out there.

Subwoofer

First up as I waited for various mail-order things to arrive is subwoofer box construction. I’ll be installing a Polk Audio MM1240 12″ subwoofer in the location where an optional factory subwoofer could have existed.

Here’s what my semi-final product looks like. This box fits right up against factor subwoofer box mounting holds next to the right rear fender panel.

Obviously, the panel that the subwoofer mounts to is missing. I don’t have my sub just yet. But I’ve got all the measurements and specs I needed to build this box. So you see where the sub goes.

This box has been carefully designed by me to contain exactly the 0.88 cubic feet (after accounting for the volume which the back of the sub displaces) which Polk recommends. Getting the dimensions and volumetric specs right is a big deal. Subwoofer sound and performance is going to depend heavily on that. More on the dimensions later. Different brand subs, regardless of size, require different amounts of space. So check your manufacturer’s recommendations!

Attached to the box is space to mount one amplifier vertically and another horizontally. The vertical plain is just the right size for a RockFord Fosgate P400-4 amplifier complete with proper cutouts to pass power, speaker, and RCA connections to the amp. The horizontal plain is sized for a Rockford Fosgate P200-2 amplifier. Once installed, both amps will sit flush with the edges of the subwoofer box.

Not obvious from the picture above is that a simple rectangular subwoofer box won’t fit in the car – at least not without wasted space. Here, have a look below…

See, the top of the fender slopes toward the middle of the trunk. So I had remove an angle out of what would otherwise be a normal rectangle (this too has been accounted for in the box’s 0.88 ft^3).

Now, on to the actual construction.

Let’s start with a word about materials. I built this using:

• 3/4″ MDF board
• 2 inch #6 drywall screws (do not use wood screws – they’re tapered and will make the MDF split)
• 7/64″ drill bit for pilot holes
• 3/8″ drill bit for countersinking
• Titebond Original Wood Glue

Much care needs to be taken when putting screws into the edge of MDF board, as the stuff is easy to split. You want the pilot hole to be the same size as the core of the screw. And you want a screw that doesn’t taper (drywall screws). Ideally, just get use confirmat screws which are made for working with MDF board.

A word to the wise on countersinking – drill the countersink hole before drilling the pilot hole. If you drill the pilot first, the coutnersink bit is going to pull up a lot more material than you want and give you headaches. And before drilling, use a piece of scrap to trace the outline of where the underlying board edge is going to be. This will help you aim for the center of the board’s edge.

And before you put any screws in, run generous sloppy bead of wood glue along the top edge of the MDF board. The glue combined with the screws will make a strong bond.

OK, on to brass tacks… so what dimensions make the box fit sung in the corner of a 2005-2007 Mustang coupe, while providing precisely 0.88 cubic feet of volume for a Polk MM120 subwoofer? Glad you asked… (again, click on any of these pics for a larger version)

Each side is 14″ along the subwoofer-side edge, 12.45″ along the bottom, 10 7/8″ from the subwoofer-side corner to the corner where the 45 degree cut starts, and 12.5″ long from the bottom corner on the fender side to the corner where the 45 degree cut starts.

The bottom is an 11.7″ x 11.5″ rectangle. The 11.7″ sides are for the wheel well side and tail light side. The 11.5″ sides are for the fender side and the spare tire side.

The top is a 11.5″ x 9 3/4″ rectangle with one 11.5″ side having a 45 degree cut on it. And the 9 3/4 dimension starts on on “regular” corner and extends to the top edge of the 45 degree cut as shown above.

Ok start building…

The bottom, sides, and fender-side pieces fit together as shown above. That’s simple enough.

Next, put the top in.

Then you’ll need to make a piece to fill in that corner. That works out as follows.

The corner piece is 11.5″ long and 2 5/8″ wide. The 2 5/8 is measured between the top edges of the 2 45 degree cuts as shown above.Eh, never mind my unsmooth skil saw skillz. And never mind those holes drilled into the 45 degree cuts – they’re not supposed to be there. For countersinking, at an angle, I found it easiest to drill 2 adjacent countersink holes perpendicularly into the board, allowing the screw to drop in vertically (or horizontally) without rubbing anything . Have a look below.

If all you wanted was a rectangular-ish subwoofer box, you’re done! Well except for that subwoofer-mount part that I haven’t done yet – its a simple 14″x13″ rectangle that will fit over the edges of the top, bottom, & sides…and oh yeah it will have a big hole for the subwoofer.

If you’d like amplifier shelves mounted to this thing, keep reading…

Here’s where we’re headed with the amplifier shelves.

Below are the top shelf dimensions with two support pieces that will be needed.

The 8″x10″ top shelf fits a Rockford Fosgate P200-2 amp with about 1/2″ extra room around each side. This shelf couldn’t have been much bigger because it would have otherwise bumped into the fender well.

Here’s the vertical shelf.

The vertical shelf is just big enough to fit a Rockford Fosgate P400-4 amp and also accommodate the ramp up in the trunk floor. The shelf is 15″ across the top edge, 11 3/4″ down the edge next to the subwoofer, 4 5/8″ along the short bottom edge, and 7 1/4″ along the edge closest to the back seats. To place the wiring holes, I place the amp on top of the shelf and drew holes where wires needed to come out.

The next thing to do is to draw lines on the side of the subwoofer box which will indicate where these shelves will attach. I wanted my amps to sit flush with the subwoofer box, and since each amp is 2 1/4″ tall, I recessed each shelf 2 1/4″ from the sides of the subwoofer box.

Note the lines I drew that showed me where the shelves needed to go. I attached the angled 2×4 and scrap piece of MDF first so I’d have something to attach the top shelf to. Once in place, I also added 2 screws from the inside of the subwoofer box into the edge of the top shelf.

While you’re doing all this, I recommend you make some marking indicating where screws are so you don’t run screws into each other when you install the next shelf. Also make a note of where the amplifier mounting screws are need to be so you can leave space for those as well.

Here, I have mounted the vertical shelf. I used two angled 2x4s for and a piece of MDF scrap for extra support.

All of this fits very nicely in the car. The wheel well comes out of the floor at about the point where you see the yellow extension cord above. It then goes up and curves toward the back seats, almost touching the bottom of the top shelf.

Notice there are no wiring holes in the top shelf. This wiring side of the top shelf amp will face the fender and there’s just enough space (shown above) between the top shelf and edge of the subwoofer to get some wires up there.

There you go! Now all that’s left is to:

• drill a hole in the subwoofer box to get speaker cable to the sub
• caulk all the sub’s speaker wire hole and all creases
• bolt the box to the factory subwoofer holes next to the rear quarter panel
• cover the box with some nearly-matching carpet using spray adhesive made for carpet

Here’s the finished product in the trunk.

Look closely to the upper right of the box, and you can see a mounting bracket which I made from some fencing bracket at Lowe’s. I simply made a right-angle turn to a flat braket, and drilled appropriate holes in it. It mounts to a factory mounting point for a factory-option subwoofer.

I also made a mount point through the side of the box opposite the subwoofer and next to the fender. I inserted a bolt through a pre-existing factory subwoofer mount hole and secured the bolt with a nut. With the bolt secured and the woofer not yet mounted to the box, I pushed the box into place, threading a hole in the back of the subwoofer box with that bolt. Then I secured the box to that bolt using a washer & nut.

Then I bolted down the aforementioned bracket to the top right, mounted the woofer to the box, and I was done.

The Final Product

I’m thrilled with the way that it looks and sounds. I wouldn’t change anything, except for that Metra trim kit that doesn’t have a nice tight fit with the head unit.

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• About...

  Shane Crowe is a proud Mississippi State alum and electrical engineer. He is married with two children. A retired ice hockey player, Shane loves college football, home theater, the Internet, and working out.

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