Introduction
My previous car, a Suzuki Grand Vitara, was written off by my mechanic, so I purchased a Hyundai Tucson to replace it. The Tucson has a decent stock audio system (certainly better than many of the other stock systems I've had the displeasure of hearing), but I was soon thinking about what I could do to upgrade it. My basic plan is to put in a kick-ass system that is as stealth as I can make it, i.e. little or no visible signs of any upgrades.

Components
Head Unit: Pioneer Premier 980BT with CD-UB100 USB interface
Amplifiers: MTX4160, Pioneer GDM-510
Front Speakers: Silver Flute W17RC38-04 midbass drivers, Seas 27TFFNC/G tweeters, custom-designed crossover (Madisound) (stock front speaker locations), Aurasound NT1-204-8D tweeters and custom-designed 8kHz high-pass filter (stock sail panel locations)
Rear Speakers: Silver Flute W17RC38-04 midbass drivers, Seas 27TFFNC/G tweeters, custom-designed crossover (Madisound) (stock rear speaker locations)

This photo shows the stock deck. It looks like a standard DIN-sized deck (one of the reasons why I went with the Tucson - many of the other 2007 models appear to be equipped with non-standard decks, which will make the upgrade process a lot more difficult). Quite likely this is going to end up being the most visible part of the upgrade, because the deck I've chosen to replace it, a Pioneer Premier 980BT does not look anything like the stock deck.

The stock system is equipped with four 6.5" "full-range" speakers and two tweeters mounted on the sail panels.

The photo above shows the stock speaker grill for the left rear speaker. There's a slight "tunnel" between the grill and the stock speaker, which may affect the midrange response at bit.

Shown above is one of the stock speakers. It has one of the smallest motors that I've ever seen on a 6.5" speaker.  I'm guessing that it's a neodymium  magnet, hence the smaller structure.

The photo above shows the spare tire well, where the subwoofer is likely going to go (another reason why I chose the Tucson - most of the other SUVs on the market have the spare tire mounted on the rear door, rather than in the trunk). The subwoofer is going to be a sealed alignment using the two 12" drivers.

Speaker Installation

The photo above shows one of the stock sail-panel tweeters (left), and the replacement I selected for it (along with the x-over components). The original replacements that I selected were the Aurasound NT1-204-8Ds, but I replaced those with Dayton ND20FB-4s when one of the Aurasounds blew prematurely.  Those were finally replaced by a pair of Dayton ND16FB-6s.

The sail-panel tweeters are used with a passive high-pass filter at 8kHz, 12dB/octave originally designed for the Auras, and are basically used to offset the off-axis high-frequency rolloff effect from the main speakers.

The photo above shows the midbass driver from a Boston Acoustics R61 component system (used in my previous car), and the midbass speakers I've chosen to use in my new vehicle - Silver Flute's W17RC38-04. I've heard good things about this driver, and when I finally got my own to try out, I understood why - very smooth midrange: much better than the R61 midbass driver, which seemed to have a peaky upper end. Once I'm done with this particular project, I may find some other uses for those Boston Acoustics drivers - perhaps in my wife's car with an upgrade crossover to take care of the peakiness.

A side view of the two midbass drivers. The Silver Flute driver has a much larger motor and voice coil, and a cast basket (compared to the stamped steel basket of the Boston Acoustics midbass driver).

What the x-over for the main speakers looks like on paper. Nine components, not including the drivers

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The high-pass filter for the sail-panel tweeters is illustrated above.  Note - the Aurasound NT1s were replaced by the equivalent Dayton ND20s, and then subsequently by Dayton ND16s.  The ND16s are actually producing the best results, which came as a bit of a surprise, seeing that the high-pass filter was not designed with them in mind.

Laying out the crossover components for the main speakers.  This took about two days to get right!

One of the crossovers, completely assembled. Note: the 8kHz high-pass filter for the Aurasound tweeters is implemented on a separate circuit board.

One of the completed crossovers, installed on the right rear door. This thing is huge! I've reused the stock speaker terminal on the crossover, so I don't have to cut into any of the stock cabling.

Another view of the crossover - it's almost the same size as the midbass driver!

One of the midbass drivers. I made a mounting bracket for it out of 3/8" ply, spray-painted black.

One of the tweeter brackets (viewed from the rear). The channel on one side is for the speaker cable. The other side is trimmed down a bit to ensure that it does not come into contact with the midbass driver.

The same tweeter bracket, viewed from the top.  The two slots line up with the stock speaker grill.

One of the tweeter brackets, with the tweeter installed (front view).

One of the tweeter brackets, with the tweeter installed (rear view)

One of the tweeter brackets in its installed location.

A front view of one of the installed tweeters (right rear door). It's nearly invisible in this view, and it's totally invisible when the panel is in place on the door.  Mission accomplished!

A view of the midbass driver installed in the front right door. The main crossover and the sail panel tweeter crossover are located above the driver.

A close-up of the rear of one of the front grills. I had to shave it down a bit to prevent the midbass driver's surround from hitting the grill. This modification is invisible from the front.

One of the sail panels, with one of the new tweeters hot-glued into place.

The same sail panel from the front.  The new tweeter is all but invisible. Mission accomplished again!

Subwoofer Installation

The Hyundai Tucson's spare tire well is an ideal location for the subwoofer (if you're willing to give up the spare tire, of course). I opted to use a fiberglass and 3/4 ply box to make the best use of the space available.

The bottom of the enclosure:

The top of the enclosure, under construction:

Bracing the bottom section...

A closer look at the top section, under construction:

Testing the fit of the top section. The black box in the back is my test enclosure holding an Elemental Designs 13Kv2-D4 subwoofer:

Another test fitting, this time with the driver cutouts:

08-NOV-2008: The picture below indicates the current status of the enclosure - carpeted and braced, and holding an Elemental Designs 13Kv-2-D4. The enclosure is about 3.2 cu.ft. and I tuned it to 22 Hz with a 3" flared vent. The combination of the woofer's measured specifications, the alignment and the Tucson's transfer function should result in a sub that has a flat response from 60Hz down to below 20 Hz.  Above 60 Hz, the response will slope gently downwards to 100 Hz (-9dB).  This is a temporary arrangement - the 13Kv.2-D4 and vent will be replaced with two 12" drivers (I still have to decide on the replacements).

08-FEB-2009: I've cleaned up the subwoofer installation a bit, though I'm still using the same Elemental Designs subwoofer. I'm hearing some noises from within the enclosure, which may be because it isn't bolted down to the spare tire well yet. I still haven't decided on what replacement subwoofers to use, though I'm leaning towards the Infinity 122.7W or perhaps the Infinity Perfect series.

03-MAY-2009: I finally purchased the Infinity 122.7Ws.  The first picture shows them installed in the original enclosure. The second picture below shows the enclosure being rebuilt with a few extra layers of fiberglass on the baffle, and the second picture shows the Infinity 122.7Ws installed in the re-carpeted enclosure.  I had to remove the previous carpeting in order to apply the fiberglass to the baffle.  I opted for black carpeting this time, for greater visual effect. I also used some flash-band at the bottom of the enclosure to reduce rattles. The results have improved the response of the subwoofer, but it's still not as great as some of my better builds.  It will do for now however.

06-FEB-2010: This is how the subwoofer system currently looks.  I'm using one Infinity 122.7W and the box is vented to just above 20 Hz.  This gives an almost sealed-like performance with a bit of better power handling at the low end of the pass-band. Efficiency is a bit low however, so I may end up changing it out for something else.

Amplifier Installation
I reused the two amplifiers from my previous installation - an MTX4610 providing a rated 20Wx4 into 4 ohms for the main speakers and a Pioneer GDM-510 providing 500W into 4 ohms for the subwoofers. The MTX amplifier will eventually be replaced, as I don't think it's powerful enough for me to get the most out of the new speakers.

I ran the power cables for the two amplifiers through a grommet located on the left hand side of the vehicle, inside of the fender. The larger cable is for the subwoofer amplifier, the smaller one for the amplifier for the main speakers.

This picture shows the subwoofer amplifier in its installed location - below the left front seat.  It fit quite nicely there, with plenty of space for ventilation.  The location of the connection points will make it very difficult for someone's foot to accidentally dislodge anything.

This picture shows the main amplifier in its installed position - below the driver's seat.

I'm currently using a 200A circuit breaker to control the power for both amplifiers.  I will be replacing this with a smaller breaker (or two smaller ones), once they become available: a 200A circuit breaker is way overkill for this project.

Head Unit Installation
 
The picture above shows a modified Scosche HY1608B adapter that I used to mount the Pioneer head unit in the dash. Scosche claims that the HY1608B is the right adapter for this purpose, but my experiments suggest that using it unmodified would leave open gaps at the top and bottom of the deck as the mounting gap is too narrow.

A close-up view of the modification.

The head unit, mounted in the modified adapter.  No open gaps above or below the deck.

The hole in the dash where the head unit is destined to go.  Getting to this point takes about 45 minutes of removing screws, clips and connectors.

Getting all the wires together...

The head unit and mounting adapter  in place, without the head-unit's faceplate.

Another view of the head unit.

Issues:

Background whine
Once I completed assembly, I noticed that there was background alternator whine, albeit at a low level - but just high enough to be annoying. I eventually got enough enough with it to tear down the front of the dash and and ground the RCAs to the deck (a typical fix for this kind of problem).  Once I put everything back together, I noticed that the negative leads for the front and rear speakers were not fastened properly to the speaker terminals - likely the real cause of the noise.  I fastened them down properly.  The system now has absolutely no audible background noise, even at high volume levels.

Auto Time Alignment not functioning properly
Possible phasing problem between front and rear speakers
Imaging is a bit off ("hole in the center" type of sound at times)
I'm getting some really strange results with the deck's auto time alignment feature.

When I ran the auto-EQ and time alignment feature, it returned the following adjustments for the speakers (right-side driver listening position):

However, using my own measurements (physical distance as well as phasing), I ended up with the following:

I'm not sure what's causing the problem, but it might be a phasing issue, as I'm noticing what might be phasing problems between the front and rear speakers, and a "hole in the center" type of sound at times. 

Buzzing / Rattling from front doors and rear hatch
As expected, the front door panels buzz at lower frequencies.  The fasteners for these panels are for for just keeping them on the doors, rather than making an airtight rattle-free connection between the panels and the doors.  I'm presently contemplating a number of different ways of tackling this, including making sub-enclosures for the speakers to isolate them from the doors.

Subwoofer enclosure vibrates too much for my liking
Yes, amazingly enough, even with all of the bracing that I put into the enclosure, the damned thing still vibrates. The only thing I haven't done so far is bolt the enclosure down to the floor, which I plan to do shortly. If that doesn't work, I'm going to add an extra layer of 3/4 ply to the baffle.