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Old 04-10-2005, 01:33 AM   #5
Scooby Specialist
Member#: 25837
Join Date: Oct 2002
Chapter/Region: South East
Location: Atlanta, GA
1996 SVX L AWD
Laguna Blue Pearl

Default Subwoofer jack (new style)

Subwoofer jack (new[er] style)

Around 2002-2005, Subaru added a new square, 8-pin connector on the backs of some of their stock radios.
On the radios in some models, this connector includes a speaker-level output for the subwoofer - there is a subwoofer amplifier built into the radio (65W or maybe really 20W). This amp is fed from a mix of the stereo audio signal (pre fader).

In some Foresters and Legacy wagons, the factory subwoofer itself is just a plain, unpowered speaker. It's built into the side or pillar in the rear cargo area (not under a seat). It is driven from the subwoofer pins on this new 8-pin connector.

Here's a pin-out diagram for the Forester (box labeled <CN702 8P CONNECTOR>):

(Diagram is from this thread on ScoobyMods: "Forester XT Head unit Pin outs")
Here's a portion of the 2005 Forester wiring diagram showing how the subwoofer is connected:
Note that the Subaru wiring diagram numbers the pins differently than on the ScoobyMods picture above - looking at the back of the radio they are:
4 3 2 1
8 7 6 5
Where I talk about pin numbers below, I'm referring to this numbering scheme. (The drawing for connector "i64" on the above wiring diagram is a mirror image view - in that drawing you're looking towards the contact pins of the car's connector).

On the Forester, the subwoofer connects to pins 4 and 8 ("Woofer +/-").

Other Subaru models have a radio with this new style subwoofer connector, but still use a powered subwoofer under one of the front seats (like in the previous post). The subwoofer harness is very similar to the "old style," except that the sub gets the left channel from the new 8-pin sub connector. The sub still taps the right channel, as well as +12V and ground from the 14-pin connector...

(Picture from this thread: "stock sub w/ aftermarket hu")
The T-harness has a short gray wire on the square 8-pin plug, looped between pins 1 and 5 ("Signal +" and "Signal -" on the above Forester diagram). UPDATED: On at least some of the OEM HUs, that enables the 5th-channel subwoofer output (so the HU's sub amplifier IC will be shut off in cars that don't have either the T-harness or a rear cargo speaker).

Using new-style sub harness with another HU

The factory under-seat powered sub and T-harness will work with any other 1995-2007 Subaru radio (except SVX), or even with an aftermarket HU (provided you don't cut the factory radio harness, and do use a wiring adapter for the install).

If your sub has the new-style T-harness (with the additional 8-pin plug) and your HU does not have a compatible 8-pin socket, you'll just need to jumper two pairs of wires on the T-harness. See this thread:
stock sub w/ aftermarket hu
post #18 for pictures, and posts 20 & 21 for instructions.
2005 and 2006 Legacy and Outback HUs have a similar jack that provides additional features...
Pin numbering on socket:
4 3 2 1
8 7 6 5
Here's the pin-out for 2005 & 2006 Legacies and Outbacks:
Pin  Function                               OEM sub harness wire color 
 1   Signal + (phone input)                 (NC)
 2   Tel On (phone input enable)            (NC)
 3   Satellite (steering wheel) switches +  Violet/White
 4   Subwoofer +                            Red

 5   Signal - (phone input)                 (NC)
 6   Subwoofer -                            White
 7   Satellite (steering wheel) switches -  Orange/White
 8   Body Integrated Unit (Illum. Control)  Green

NC = No connection - the factory harness has no wire at this pin position
Here's Subaru's 2005 Legacy/Outback wiring diagram:
Notice that the "superwoofer" connects to pins 4 and 6 (instead of 4 & 8 on the Forester).

Steering Wheel remote-control buttons

The "Satellite switch" pins (3 and 7) are for remote-control buttons on the steering wheel...

(Picture by phoenix96 in this thread: "How to Install Steering Wheel Radio Controls")
Illumination Control pin

Pin 8 connects to the car's "Body Integrated Unit." This wire is for Illumination Control ("Bright" mode). Normally, the radio's display (along with other parts of the instrument panel) are dimmed when you turn on the headlights. This wire cancels dimming of the radio's display when you press the BRIGHT button on the clock.

Cell Phone Audio input

"Signal +/-" (pins 1 and 5) are for a mono audio input into the radio for a cell phone car kit or OnStar-type device.

Connecting pin 3 to ground:
  • Mutes whatever source the radio was playing,
  • Displays "CALL" on the LCD, and
  • Sends the mono audio input to the radio's front speakers
Pin 3 will do this even if the radio was powered off.

See this thread on LegacyGT for more info:
AUX in on a Stock '05 Head Unit w/o Silent CD (The Project)
(before you get your hopes up, that aux-in "project" failed - that input/mode uses fixed tone settings that aren't so good for music).

Changes 2007 and later

Starting in 2007, Legacy/Outback factory HUs dropped the subwoofer output and phone input from this connector and added a real Aux input. See post #10, below.

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Last edited by SVXdc; 09-27-2013 at 11:20 PM.
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