Tech Notes

Porsche 997.1—Replacing a Factory PCM 2.1 System

Part 1: the Bose Amp and Head Unit

By Conrad Van Hyning

The Start

After purchasing a 2007 997.1 911 Carrera and becoming familiar with the antiquated factory PCM 2.1 infotainment system, I set out to replace the factory head unit with a modern Sony AVX-5600 head unit with FM radio, Bluetooth, iPhone, and Apple Car Play (~$500). My original plan was to replace only the PCM head unit and integrate the new Sony 5600 head unit with the original factory Bose amplifier and speakers. After some research, I settled on Crutchfield (www. crutchfield.com) as my go-to project retailer, a leader in sales and support of a project such as this.

However, it became apparent after more than hours of frustration and complete replacement of both Sony and Axxess products that the the Axxess interface wasn’t going to work in my 997; the incompatibility was ultimately blamed on the sat-nav optical interface. Fortunately, Crutchfield allowed me to bail out on the entire Bose integration plan, accepting all products for return with no questions asked.

Phase Two

to me and this requirement was also far-reaching in that it determined much of what was both necessary and possible the rest of the way. Second, the amp had to have decent power and enough channels to effectively replace the original 10-channel Bose amp while also supporting the Bose subwoofer. And, third, the amp specs had to be compatible with the existing Bose channels and speakers.

The only amp I found that came close to meeting the requirements is shown here, the Clarion 2510 marine five-channel amp with 500 watts total output (~$400). This amp is 4” longer than the factory Bose amp and 2” narrower. In fact, nearly all aftermarket car amps are much too large to fit nicely in the pocket for the 997 Bose amp behind the carpeted cover in the front boot. And, this amp didn’t fit in the cover either; I had to dispense with the factory tire repair goo and cut out the Styrofoam backing on the cover to allow the amp and wiring to fit. I was happy to sacrifice the tire goo and a bit of foam.

While interfacing a new stereo head unit with a factory amplifier and factory speakers might sound straightforward, with Porsche PCM 2.1 with sat-nav and Bose sound it definitely is not. The PCM head unit with sat-nav uses an optical interface (light) to drive the Bose amp rather than an analog electrical interface. According to Crutchfield, there was only one wiring interface available to integrate a modern car stereo head unit with an optically driven Bose amp: the Axxess AX-PO90052 (sold by Crutchfield at ~$350).

After some soul-searching, and some research finding that Porsche 997 Bose sound systems were decidedly unloved, I decided to replace the Bose with an aftermarket amplifier and do whatever else was necessary to integrate the Sony 5600 head unit into my 997. I was obviously wholly committed and my awesome Crutchfield support engineer began advising me on every step.

I established several requirements for the new amp. First was that the amp had to replace the Bose amp in its original location without exposing the amp as an obvious aftermarket replacement. This was very important

Clarion 2510 Amplifier

The next step was to disconnect and remove the Bose amp and mount the Clarion amp on the steel backing plate behind the cover in the 997 boot. I shade-tree engineered this mount by drilling new holes in the backing plate and attaching the amp on the right side with screw clips. On the left side, where the amp extended beyond the plate, I got creative and used (horrors) industrial quality zip-ties to bind it to the plate. amp were joined to the four wires from the battery compartment. The RCA audio cables had to be connected to a much shorter set of stubs from the opposite side of the amp, so the RCA cables had to drop to the bottom of the boot and enter the amp cover some distance to make the connections with the amp’s RCA cable stubs.

Wiring the head and battery to the amp involved some wire-routing engineering creativity. What is described and shown in the pictures here are what I think is the best (perhaps only) approach to route the power and audio cables from the head unit or battery to the amp. I estimate the wiring and routing to the amp took a total of about 10 hours.

Clarion amp fitted in modified boot cover pocket

Wiring the amp was the next challenge. The plan had to take into account new power wiring between the battery and amp and also new audio wiring between the head unit and amp. Audio wiring was necessary because the original factory audio wiring was optical, so there was no existing wiring to take advantage of between the dash and the amp. I chose RCA cables for superior shielding and sound quality, along with a single 16-gauge wire for the amp wake-up circuit.

It was immediately apparent that four 10-gauge power wires (two positive and two negative) for the Clarion amp routed to the battery would impact the routing plan for the audio cables. A compromise had to be made: it wouldn’t be possible to route the power and audio cables separately to reduce interference as there wasn’t space in the boot. I had to route and bundle them together with high quality shielded audio cables and hope for the best.

There is ample room to route three pairs of RCA audio cables from the head unit compartment in the dash forward to the firewall to a 3” rubber firewall plug about 4” above the pedals. Once through the firewall, there is ample room behind the battery to route the wires to the right side of the battery compartment, then forward to the intermediate firewall between the battery compartment and the boot storage area where there is another 3” plug through the intermediate firewall at the evaporative emission control box.

Routing through the intermediate firewall required not difficult, temporary removal of the evaporative emission control box to allow the cable bundle through the plug. Routing was then right-to-left across the back of the boot in a wiring conduit channel in the intermediate firewall behind the carpet.

The audio wiring and routing described required from Crutchfield three pairs of high quality 9’ RCA cables and a 9’ 16-gauge wake-up wire for the amp. The power wiring and routing for the Clarion 2510 required two 8’ red and two 8’ black 10 gauge insulated braided copper wires from AutoZone. Also required are several rolls of good quality electrical tape and a lot of patience and perseverance.

There is adequate room in the channel for four 10-gauge power wires and three pairs of RCA cables and a wakeup wire. Once across to the left side of the intermediate firewall in the channel the bundle was then dropped down along the right side of the vacuum brake booster and along the master cylinder. It was in the area just forward of the master cylinder that the 10-gauge power and ground wire stubs from the

When the audio and power wiring was complete, the battery connections for power and ground wires were made and the amp fuse was in-lined in the power wires. Because of the two power and two ground wires for the amp, both factory battery terminals were replaced in favor of terminals sold by AutoZone that were better suited for the connections. The 90-amp fuse was in-lined in the power wires on the right side of the battery and glued to the body and the ground wires were routed under the battery mount plate to the left side of the battery.

This concludes Part 1. In the forthcoming Part 2 I’ll describe the Sony 5600 installation in the dash PCM cavity and the speaker wiring and replacements necessary to convert the ten channels from the original Bose amp to five channels from the Clarion amp, while continuing to support the subwoofer and all but one of the existing Bose speakers.

Conrad Van Hyning joined PCA in 2022. He drives a 2007 997.1 in Meteor Gray Metallic.

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