X308/300 Stereo Upgrade introduction

Introduction

Despite its many creature comforts, one of the weak points of the X300/X308 range is its limited stock stereo system.  Whilst a number of improvements were made for the launch of the X308, and additional refinements offered through the optional premium system, the XJ’s stereo remained a poor match for the luxury and technology offered by the rest of the automobile.

The following is a brief description of the upgraded system I recently installed in my MY2000 North America spec. X308.  Most of the described work is also applicable to the X300 series.  The goal in designing this system was to alleviate the weak, hollow sound of the stock system while retaining a stock appearance. 

So, Where to Start?

The most logical place to start with upgrading the sound system is the head unit.  Today, a wide-variety of fantastic head units can be purchased relatively inexpensively.  Nearly all mid-priced head units will drastically outperform Jaguar’s stock and premium systems.  However, installing a new head unit in an X300/X308 requires some custom fabrication to make the aftermarket unit fit in the proprietary space occupied by the stock system.  A new head unit means you will also lose the use of the steering wheel controls (a few high-end units aside) and, to the best of my knowledge, lose the use of multi-disk CD changer in the trunk unless you use an Alpine head unit.

For my installation, I choose to keep the stock head unit to maintain aesthetics and functionality.  To keep costs down, I upgraded my system in three steps: 1) speakers; 2) amplifier; 3) subwoofer. 

1) Speakers

Replacing the stock speakers in an X300/X308 is a simple, if labour-intensive job.  To begin with, you will need to remove each of the door panels.  Jaguar thoughtfully attached these using only two screws and a series of barbed plastic plugs.  The first screw is located under a plastic button in the center of the black plastic door handle cup and the second on the underside of the armrest near the rear edge. 

To remove the panel, simply slacken the screws, pop the plastic cup from the door handle and then CAREFULLY work your way around the outer edge of the door to free the barbed plugs.  It pays to be gentle on the outside edges – though the armrest features a spring clip that takes some force to release.  If you work carefully, you will not have to remove the veneer from the top of the door panel. Simply shift the door panel up and forwards to clear the handle.  To make sure nothing happens to the veneer, apply a layer of masking tape around the door handle opening.

Once the door panel is off, mark and release all the electrical connections.  You will now see that the tweeter is attached to the door handle assembly and the mid-range speaker to the door panel.  The tweeter is held in place by an integral clip.  Simply press on this to release the tweeter.  The mid-range is held in place by four #8 screws around its outer edge.  Slacken and remove.

Now for the fun part – the Jag’s stock speakers are of an abnormal size.  They are just over 6.125 inches (155mm) in their outer diameter, where as most 6 inch speakers are about 5 – 10 mm less in diameter.  This makes it difficult to easily swap speakers as only a few manufacturers (Orion, Boston Acoustics?) make slightly oversize 6 inch speakers.  Even more frustrating is that 6.5 inch (165mm) speakers are a tight fit in the front door panels and nearly impossible to fit into the rears without modifying the door panel map pockets.  Oh, and you only have about 2.75 inches (70mm) of depth to play with before you have to cut the foam speaker baffle molded into the door’s moisture barrier.

I chose to mount a set of Phoenix Gold Octane-ZR 6-inch component speakers.  These are good quality speakers for the money (though not the best) and feature a 24-dB/Octave passive crossover network that neatly fits in the door panel.  The tweeters are 25mm in diameter and feature a silk dome for smooth response.

The Phoenix Gold tweeters fit neatly in the “prongs” that formerly held the stock tweeter.  In my case the fit was snug enough to not have to worry about clipping or screwing it in place.  However, I did run a bead of silicone around the outer edge of tweeter to keep it from rattling in anyway. 

The mid-range speakers were a different story.  Given the outer diameter differences between the stock and replacement speakers, none of the factory screw holes quite lined up with the replacement speaker and the speaker gasket did not seal properly to the door panel.  To overcome this, I made up a set of .25 inch (6mm) thick by .75-inch (18mm) wide reduction rings.  The ring was sealed to the door panel with silicone and flat head screws counter-sunk into the stock screw holes.  I then carefully drilled new holes for mounting the replacement speaker. 

The passive crossover network for the new speakers was mounted on the back of the door panel, just to the side of the map pocket.  I used industrial quality Velcro tape to hold the crossover in place.  Normally, one would not want to mount the crossover in the door because of moisture issues.  In this case, the stock moisture barrier and the map pocket protect the crossover very well.  All of the speaker wire terminals were given a coating of brush on electrical tape to guard against corrosion and vibration.

All told, each door took me about 60 to 90 minutes to finish.  This was with copious coffee breaks, so I am confident that with experience the swap could be made in 30-40 minutes per door.

2) Amplifier

When installing a set of upgraded component speakers, it is imperative that they are fed a clean, high-powered signal.  Otherwise, they will sound hollow and eventually self-destruct because the stock head unit will likely “clip” trying to provide them enough power. 

For example, with my system, the stock speakers sounded great at about volume level 10 and would start to distort around 20 or so.  The replacements needed at least volume level 20 to be sufficiently audible.  However, at higher settings, the stock head unit would distort.  The other problem is that the EQ curve of the stock head unit feeds in increasing amounts of treble as you turn the volume up.  With upgraded speakers, this often sounds “tinny.”

The solution is an amplifier.  Jaguar was kind to X308 owners and provided us with a nice carpeted shelf just above the CD changer in the boot to install an amp.  This shelf is supported by two 1-inch wide steel brackets mounted to the body – making it ideal for carrying a heavy amplifier.  The only down side is the shelf’s available space.  It is only about 20 inches (510mm) long and 10 inches (255mm) wide.  An amplifier also produces a fair amount of heat and must have several inches of clearance in order to cool properly.  This limits the maximum height of the amp to about 2.75 inches (70mm) if it is to fit neatly above the CD changer.

Because I elected to keep the stock head unit, I also had to find an amplifier that featured hi-level inputs.  If you find an amplifier that fits your needs but does not have hi-level inputs, do not despair.  You can use a Line-out Converter (LOC) to switch the hi-level speaker outputs to a low-level RCA connection.  If you do use an LOC, be sure to keep the RCA cables as short as possible and far away from the body harness to avoid electromagnetic noise.  Unlike most cars, the X300/X308 has multiple harnesses and relays throughout the car, including in the boot, under the rear parcel shelf, and behind the rear heel boards.  Toss in heated rear seats and you have the perfect recipe for creating noise in your new system. 

If you are not planning on adding a subwoofer, a wide-range of four channel amps are available.  Try to avoid buying anything that seems too good to be true.  A good amp will be pricey and a cheap amp will make you regret it.  Some solid names include Alpine, Blaupunkt, Soundstream, Kicker, Clarion, Kenwood, JBL, Infinity, Eclipse and Memphis.  Alpine, Eclipse and Memphis all make very nice four channel amps that fit well in the boot. 

In my case, I wanted to add a subwoofer.  To make life easy, I choose to go with a five-channel amplifier.  Unfortunately, there are really only a handful of five channel amps that will fit in the X308 cleanly (Kicker [700.5], Memphis [Belle and Baby Belle], Hifonics [Zeus series Zxi8006] and JBL).  I choose the Kicker ZX700.5.  This is the latest Kicker five channel and is exactly 20x10x2.75.  It is also a nice gray-black color that fits very well with the boot.

Hooking up the amp was a bit of a chore.  First, you have to tap into the stock wiring harness for the speaker signal from the head unit.  Jaguar thoughtfully put one of the main connectors for the speakers behind the left-hand heel board under the rear seat (right hand for UK spec cars).  It was a simple matter to splice into the harness.  Remember, you have to two sets of wires– one from the wiring harness to the amp and the other from the amp back to the harness.  Disconnecting the stock plug and tapping into the two sides, respectfully, allowed me to do this without destroying the stock harness.  Consult the JTIS for the wiring diagrams for your car.

The new speaker wires were carefully labeled and fed through a tiny (10mm by 10mm) pass through located under the rear squab in its upper corner.  The new speaker wires were then bundled, cable tied at 4-inch intervals, and secured in the boot.  At this point, I turned the radio on and tested each of the connections to make sure there were no shorts or problems.  This step can save you an enormous amount of trouble down the road.

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Left: View of the boot wing with its carpeting removed to reveal the “shelf” supports above the CD changer.  Note the two sets of new speaker wires. They are connected in this picture to test their integrity prior to installing the amplifier.  No gaffer tape was used in the actual installation!

Power to the amp was also simple.  The wire for the remote turn on was run parallel to the fuel tank and spliced into the switched power for the automatic antennae.  Jaguar also, thoughtfully, provided a power distribution block to the side of the spare tyre in the boot.  There are four studs in this block, split into two pairs that are each protected by a 250amp fuse.  Two studs provide power to the starter and main computer and a third to the security system, etc.  This leaves one stud open – making it perfect for tapping into for the amp.  The below photos show the block with and without its cover. Clickable thumbnails

Power flow is crucial to the efficient operation of an amplifier.  Therefore, I used a fine stranded 4 gauge copper wire to provide power to the amp.  A 90amp fuse was located about 14 inches from the distribution block to protect the amplifier.  All of the terminals were cleaned with 400 grit wet/dry sandpaper and coated in anti-oxidant paste to ensure the best power flow possible (and to avoid future corrosion).  Grounding is provided by another 4 gauge copper wire.  To keep things neat and tidy, the ground is only 6 inches (150mm) long and grounded directly to the body.  The area was sanded to remove all paint and expose bare metal.  To guard against corrosion, the ground terminal was fastened into place with a stainless steel #8 screw and covered in brush on electrical tape. 

Here is the completed power cable installation.  Note that the main amplifier fuse (circled in yellow) is in close proximity to the distribution block and screwed to the boot wall.  The inset shows the power, ground and remote on wires.  These have since been placed in a plastic loom for better aesthetics.  Note how each emerges separately from the carpet to avoid any chance of shorting.

All of the wires were then carefully fed through slots cut into the boot carpeting.  I kept my cuts to less than 1 inch so they would be all but invisible.  The boot carpeting was then reinstalled and a carrying plate for the amplifier made up out of ¼ inch plywood.  The plywood was matched to the base of the amplifier and attached to the metal supports above the CD changer using six #8 stainless steel screws (three per support). Be sure to use flat head screws so that the amplifier can sit flush against the wood.  All the wires were connected (ground cable first!) and the amp bolted to the plywood carrier.  Finally, the amplifier’s fuse was installed in its holder.

Clickable thumbnails Before powering up the amp make sure that the gains and crossovers are all turned to their lowest setting.  Then, carefully turn the system on and check for any shorts.  Once satisfied power up the system and follow the instructions for setting the gain and crossovers. 

3) Subwoofer

Unfortunately, even in the best of all worlds, component speakers cannot produce the sort of sub-bass frequencies (20-500Hz) that add a feeling of power to a sound system.  XJ owners have two choices to over come this limitation: 1) Install a subwoofer or mid-bass speaker in the rear parcel shelf; or 2) Install a subwoofer in the boot.  Searches on the Internet also turned up a handful of custom installations where the rear parcel shelf was replaced with a handmade subwoofer box; an expensive but beautiful solution.

The stock subwoofer location on an XJ is located just off center of the rear package shelf.  It measures approximately 5x8 inches (125mm x 175mm).  However, because of the fuel tank, the mounting depth is only about 2.75 inches (70mm), which is far too shallow for most subwoofers.  Solutions to this problem include mounting a component mid-range speaker in the hole (either a 5.25 inch or a 5x7), creating a custom blanking plate out of hard board to take a mid-bass speaker or tracking down one of the OEM subwoofers. 

Kicker, JL Audio and Orion make 6.5 inch mid-bass speakers (JL labels theirs as a subwoofer) with shallow enough mounting depths to fit in the stock hole.  The only drawback is that a shallow-mount 6.5 can only move a small amount of air and handle only moderate power.  Therefore, the amount of bass it produces is minimal.  However, if you do not listen to bass heavy music, it is a good choice.  If you do not mind cutting up the car, several 6.5’s can be mounted in the parcel shelf and wired in parallel to produce a good thump.

The box itself was made of ¾ inch marine plywood; cross braced and held together with lap joints, marine glue and stainless steel screws.  All joints were sealed with silicone and the exterior covered with gray carpeting.  For added bass response, the box was loosely filled with polyester batting.  The box is held in place by three stainless steel screws along the back edge of the box into the floor of the boot and a pair of stainless steel carriage bolts at the front.  The carriage bolts feature triple nuts and washers so that I could create counter-tension against the clamping force of the rear screws to eliminate vibration.  All of the screw/bolt holes were sealed with automotive seamsealer to prevent water intrusion and corrosion. 

The Results

The final product is a very nicely balanced package that cleanly reproduces music.  In fact, it is almost too clean.  Some newer pop music sounds almost antiseptic on CD because the sound system reproduces every electronic nuance.  This means that I have to fiddle a bit with the stereo settings when changing CDs to get the tone right, where as the old system was so muted that changing the tone controls did little to the overall sound quality.  On the plus side, CDs of analog recordings are glorious.  Classics like Black Sabbath, Cream, Pink Floyd, and Hendrix sound wonderfully rich.  Most house music also sounds lovely – provided the bass line is not too heavy.  Otherwise, the boot shakes a bit too much and rattles nearby windows, making me feel like a teenager.