[cdicorpo]

Could you post the pin out of the HK amp connectors. I'm trying to add a DSP, 5ch amp, and sub to my HK stereo

If you're adding all that, why not just remove the HK amp all together? You could just take the signal from the head unit into your DSP.

 

[cdicorpo]

I am assuming that the volume control is being done by the HK amp. This is how previous HK headunits/amps have worked. You need to take the speaker level signal in order to retain volume control.

If thats not the case i'd be happy to eliminate the HK amplifier.

This is a good assumption, as lots of newer cars use CAN bus signals between head units and amps. The audio is sent at a fixed amplitude (usually stereo signal) to the amp, and the volume adjustment is done in the amp, along with the DSP, panning, fading, and other features.

HOWEVER, I doin't believe our systems are setup like this. Someone please feel free to prove me wrong, but here is what I've gathered. The head unit's amplifier section is the same for all cars, regardless of 6.5" / 8" / Nav / Harman Kardon / Rockford Fosgate Upgrade. It outputs four channels of amplified audio in various pins in the 10 & 6 pin plugs. Pin-outs can be found in the linked thread as well as from websites like Crutchfield, or on the package of an adapter harness like the ones from Metra (70-1761 & 71-1761, standard Toyota / Harman plugs).

As far as I Know, the head unit does not communicate with either the HK or RF amp via CAN bus. It controls audio routing, volume, pan, fade, 3-band EQ, and high volume bass rolloff regardless of the trim level and amp setup. Each of the optional amps then converts to digital, adds its own DSP adjustments for the corresponding speakers, converts back to analog and amplifies it again.

TLDR; you can remove the amp and take the signal from the output on the factory head unit.

P.S. - What the factory head unit does use CAN bus for, is adjusting vehicle settings through the menus, which can still be accessed through the steering wheel controls and the LCD screen in the gauge cluster, even without the head unit.

Here's the linked thread with pin-outs:
https://www.impreza5.com/forum/26-electronics-audio-lighting/8833-headunit-replacement-master-thread.html

 

[cdicorpo]

It wont be that much difference in wiring. From the crutch field diagram, all 6 amplified speaker outs are on the 30 pin connector on the HK amp. I was planning on adding my own spade connectors to hijack those outputs to send to my DSP (not ideal, but not the end of the world). Then DSP to Amp, then amp speaker outs back to the the 60 pin (other side of the splice). I'm going to amplify the front doors and dash and let the HK amp the rear doors.

If you're right... the other connect must be the speaker ins for the HK amp from the HU. But that can be phase 2. It would make sense from a production standpoint that the HU controls everything to minimize unique SKUs.

I just remembered something that slipped my mind, and that is, you are correct. The HK equipped cars have a different wiring harness than the non HK cars, that allows the tweeters to be amped as a pair, rather than in parallel with the door speakers and having a crossover (like the non-amped and RF upgraded cars). In this case, yes there will be 6 outputs from the HK amp. This makes wiring a 5-channel amp tricky.

To your most recent point, if you're adding DSP and an amp only for the front channels, then the HK amp will still be using it's own DSP on the rear channels, and that could present a tuning headache. There would be no way to highpass the rear channels when you add a sub. Unless you just don't care how the rear channels sound. As far as I know, OP did not highpass anything since they simply added a sub to the factory HK system.

What I would do, is purchase component speakers with a built-in crossover (highpass) on the tweeters, and wire the front channels in parallel so you can use all four channels on the amp, and the fifth for the sub. Unless of course you wanted to delay the tweeters different amounts than the front door woofers. Then you'd need 7-channels of amplification. When I installed my DSP and amp, I didn't use any delay because I believe my headhunt is delaying the speakers from the source, and the soundstage sounded fine as is. Not sure if the HK equipped cars delay in the head unit also, or in the amp.

 

[cdicorpo]

No volume control by tapping into the HK amp's front speaker inputs?? Maybe OP tapped into the amp outputs instead?? If the HK unit does volume control via CAN bus, I will be a little bit surprised, but glad to know definitively nonetheless. The way I understood it, is usually CAN bus controlled amps receive their signal digitally, which isn't impossible through the harness, but more so unlikely since there are four individual channels going into it, rather than a fixed-volume digital stereo signal. Might be worth contacting someone at Harman to actually figure out for sure how these systems are setup, since even Crutchfield doesn't quite know LOL.