Technical Features
Project TT Coupe: Audio Upgrade Part 1
By by: Joe Lucchio, photos by author
Feb 6, 2006, 08:37

With the possible exception of tires and wheels, audio upgrades are probably one of the most common modifications that owners perform on their vehicles. In the past, finding an aftermarket head unit with a CD player that could operate a multi-disc changer, an amplifier and some speakers was all you had to do. With the advent of in-car entertainment systems or “ICE,” there is really no such thing as a simple upgrade to your factory car stereo system. The process can be overwhelming due to the endless list of options that are out there. With today’s digital generation upon us, that aftermarket head unit now must also be capable of playing MP3 CD’s, feature Satellite Radio, control an iPod, as well as possibly allow video inputs for video game consoles and in-car navigation systems.

While car manufacturers have offered upgraded audio systems for years now, such as Audi’s BOSE system found in our Project TT, most of the digital requirements listed above are more recent than the TT’s BOSE system and as-such, aren’t available. For example, when you order Audi’s factory Nav+ system in the A3 and A4, it comes with two secure digital (SD) card slots for playing MP3’s, has integrated satellite radio controls offering the option of either Sirius or XM, and Audi recently released an iPod connectivity kit which allows for an iPod to be connected to and controlled directly through the factory stereo.

Having been spoiled by access to these features in other cars, we set out to find a way to add both satellite radio and iPod connectivity to Project TT’s factory stereo system, as well as provide a path for future upgrades such as an amplifier and a subwoofer or two. As we mentioned, Project TT is outfitted with the optional BOSE Audio system, which includes the Concert II CD head unit and a six-disc CD changer located in a compartment next to the left rear seat.

The factory BOSE system offers seven speakers, with component tweeter and mid/bass speakers in the doors, and two speakers located in the rear side panels behind the front seats. The seventh speaker is a small center speaker located in the defroster vent on the top of the dash. The BOSE amplifier provides 175 watts of power and is located in a compartment next to the right rear seat. The amplifier also incorporates BOSE’s Audiopilot Noise Compensation technology.

According to BOSE, “the Audipilot Noise Compensation technology for the TT includes a microphone inside the car which is constantly monitoring both the audio signal and any disturbing ambient noise. The BOSE digital electronics continuously optimize frequency response and dynamics and the volume is adjusted in different bandwidths, i.e. bass or high-frequency range as required to compensate for the variable dynamics of ambient noise. BOSE AudioPilot noise compensation technology enhances the music signal so it stays consistent, never being perceived louder than at the listener's initial setting, even as the noise level changes. While hearing all of the music, the listener never perceives a change and never has to adjust the controls.”

While this may be what they say it is supposed to do, in reality, the volume flucuations can be heard and can be quite bothersome. In fact, Audi has issued a TSB for models equipped with AudioPilot which disables the system by rewiring the connection to the BOSE amplifier. Assumedly, the newer generations of the system are not plagued with this problem.

We first looked into options that worked with the factory Concert II head unit, however, these were pretty limited our wish to add both satellite radio and iPod integration made things even more difficult. If we were to keep the factory head unit, we would have to find a location in the interior for an external satellite radio receiver and for the iPod. In addition, we would also have to include some type of switching device to allow for both units to function with the factory head unit. Not wanting to clutter up the TT’s handsome interior, we opted to forego using the factory head unit and move into the aftermarket realm.

This is where things got complicated. Since we wanted to do the audio upgrade in phases, we wanted to make sure that we could install the aftermarket head unit into the car and still utilize the BOSE amp and factory speakers without having to hack up the factory wiring harnesses. The most difficult decision was whether or not to choose a head unit that offered video screen capabilities in case we later wanted to add a navigation system. After looking into a variety of systems, keeping in mind that we didn’t want to install anything that would be visible in the cars interior and looking at the overall budget, we decided that for now we could live with a simple head unit upgrade that allowed us to connect both satellite radio and iPod modules.

With this in mind we started our search for the right head unit. After looking at our options, we settled on the Kenwood Excelon KDC-X889. We chose this unit because it offers both satellite radio control and external media control – read iPod – directly through the head unit when using Kenwood’s automated switch box. Kenwood’s iPod adapter kit was also one of the most reasonably priced on the market.

One downside though was that the Kenwood unit is that is Sirius Satellite Radio ready, and we planned on using XM Radio. This would require an additional module that would need to be used, not a big concern, except we were starting to worry about where we were going to hide all these components. We purchased the Kenwood KDC-X889 and KCA-iP500 iPod adaptor, and radio fitment kit/faceplate on-line at, the Kenwood KCA-S210A switch from and sourced the XM Direct XMD1000 tuner, XM micro antenna and Terk XM Smart Digital Adaptor for Kenwood car stereos locally.

With the parts amassing, we now turned our attention to how we were going to install the system and integrate it into Project TT using the factory BOSE amplifier and speakers, and find locations for all the modules that had to be installed. This proved to be no easy task.

First, we needed a harness that would allow us to connect the Kenwood head unit to the factory wiring. After much searching we found a Metra Electronics harness which would appear to work for us. The Metra 70-1787 is a two piece harness, with one part that connects the constant and switched power, illumination and ground and a second part that converts the BOSE inputs to simple RCA style inputs which could be connected directly to the Kenwood Unit. We would also need a powered antenna adaptor, and it appeared the Metra 40-VW53, was what we wanted. We then sent and email to Christian at, who specializes in VW and Audi car stereo integration to source both the harness and the antenna adaptor. Christian confirmed that the harness and adaptor were what was needed and shipped them on their way.

Once we had all the parts in hand, we now had to find a place to put them, as well as find a location for the XM antenna and Ipod. Again, our goal was to conceal all the modules, antenna and iPod. The Ipod connector, switching module, XM Direct tuner and Terk XM adaptor had to be located relatively close to the head unit. Originally, we had hoped to fit at least one or two of these components under the seats, but due to the design of the seats, there is simply no room. The next possible location would be somewhere in the dash below the instrument cluster. The lower dash piece on the TT is pretty easy to remove.

With the lower dash segment removed, we took the liberty of installing the European equivalent which is different than the stock US version. It includes two compartments, one small one under the light switch and also a place under the steering column for the owners’ manual. It also attaches to the car differently using a U-shaped bracket that goes over the back of the steering column. The US lower dash segment connects using two aluminum supports that mount on either side of the piece to the back of the fire wall area. This is important to note because we would not have been able to place the modules in this location if we had retained the US lower dash piece.

With the lower dash segment removed, we test fitted the iPod adapter and switch box on top of the left side of the lower dash and the XM tuner and Terk adapter on the right side. They all appeared to fit in these two locations so we next test fitted the cables over the steering column and then into the radio compartment. To make things easier, we simply zip-tied the iPod adaptor on top of the switch box, and the XM adapter on top of the XM tuner, then installed them in their respective areas and ran the cables to the correct locations.

Next, we needed to find a location for the XM antenna and iPod. We decided the best location for the iPod would be in the small compartment under the ashtray and in front of the shifter, so the cable was routed to that location. In order to get the connection inside the compartment, we cut out a small indention in the rear of the compartment, slipped a grommet over the cable and inserted it into the indention and provided enough cable so that we could pull the Ipod forward enough to connect it and disconnect it easily from the cable. It fit in with no problems and the cover opens and closes with no obstruction.

Knowing that there was room for a small speaker in one the upper vent grills on top of the dash, we removed the other vent cover to find a small location covered with a small metal plate. The XM micro antenna fit right into place with no trimming or cutting necessary and since it’s magnetic, doesn’t move at all. However, routing the antenna wire would require either removing the small metal plate and trimming it or simply removing the small plastic retaining clip on the end of the antenna wire and threading it through down to the lower portion of the dash. We opted to remove the small plastic retaining clip, routing the wire and then reinstalled the clip before plugging it into the XM direct tuner.

With all parts in place and the interior disassembled, it was time to connect the head unit. One stumbling block was finding switched power and illumination for the Kenwood head unit – since those functions on the TT’s equipped with the Concert II head unit are controlled by the can-bus system and are not part of the power harness like they are on earlier models. We routed a switched power line to the fuse block and wire tapped the illumination line to the light dimmer switch. We used Fuse #27, which is not used on the coupe for the switched power and simply plugged a flat connector into the fuse slot. We also had to connect the powered antenna lead to the antenna power line from the head unit as well as the amplifier power-on line to the BOSE harness.

With everything connected, we connected the battery back up and held our breath. To our delight, everything powered up and worked as advertised. We had no problem receiving the XM signal even inside the garage, the iPod was working as it should and the CD’s played loud and clear through the system. The AM and FM tuners worked perfectly, with much better reception than the factory system. After playing with the myriad of settings on the Kenwood head unit, we found the sound to be clearer and cleaner than the factory head unit as well, even with the stock BOSE amp. The Kenwood unit allows for simple switching of modes with the press of a button or use of the included remote. Also, when in iPod mode, the name of the artist and track scroll across the unit. You can search by artist, playlist, genre, album etc. However, the best part about it was that you cannot see any indication that there is an Ipod or satellite radio in the car.

With Phase 1 of the stereo upgrade complete, we have begun planning Phase 2. In the next phase we would like to add a multi-channel amp, some new speakers and a subwoofer system. At this point we most likely will remove Project TT’s rear seat, and build an enclosure in its place to house the amp and possibly the subwoofer(s). The size and number of amps and subwoofer will be determined in part by the amount of space we have. We may opt for one or two amps and one or two subwoofers. The replacement speakers however, will be stock size and located within the stock locations. Right now though, we will enjoy the upgraded system and all the new musical choices we have at our fingertips.

Related Links:

Project TT Coupe Main Page

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