I wanted to share my experiences of upgrading my 6 speakers without changing the head unit or the wiring at all. I have the face lifted Gen 5 Subaru Outback 2.5 l petrol. The audio is now much clearer and more satisfying. I can easily hear voices at low volumes and there is much more punch, pop and grandeur to the sound. I would class this as an improvement from basic to middle quality audio and well worth it. Anything more than this would require a new head unit, new wiring, and a sub which I was not interested in doing. It works as a job you can do and is fairly simple to do. We did it on the pavement on-road over three one-hour sessions. The car has no damage whatsoever and looks the same as before in all respects.
In preparation, I did about 4 hours of forum reading and ordering of parts online, and 90 minutes of cutting and crimping to sort out the dash speakers before installing them. I would advise two people working together on the front driver's door. I have no prior experience of taking bits off cars and putting them back together, but I have a basic experience with home hi-fi and a limited experience of pro hi-fi. For instructions on the door trim, check the US forums and YouTube. You might break something but I did not. The windows have plenty of space with these slim Kicker speakers.
I replaced all 6 speakers - the 2 dash tweeters and the 4 door speakers
Dash midrange/tweeters (1 pair): Kicker KA47KSC2704, KS 2.75" (70 mm)
An alternative would be Subaru tweeter speaker upgrade kit (H631SFJ101), but I went with midrange/tweeters instead of tweeters because the original speakers in the dash were midrange/tweeters. The dash speakers required detaching from and reusing the old wiring harness. I used a basic Amazon crimping set to wire the dash Kicker speakers to the old wiring harness and I used the included capacitor (crossover / base blocker) on the positive (red) side of the circuit. I used two 5x25 mm steel washers to get the dash tweeters to fit into their second screw hole. When fitting the tweeters, remove the grey A-pillar trim before removing the dash speaker grilles. (The central grille was empty.) This is easy with the trim removal tools. Do not use a screwdriver to remove any trim. No harness is currently available for the dash speakers. The alternative option of the Subaru tweeter upgrade (H631SFJ101) includes the wiring harness built in.
Door speakers, coaxial (2 pairs): Kicker KA47KSC6504, KS 6.5" (160 mm)
For the rear door speaker brackets, I used the included Kicker mounting brackets. For the front door speaker brackets, I used the Connects 2 aftermarket speaker bracket (CT25SU02) for Subaru Forester 2013 which fit the Outback 2018 well. Speaker harness for the 4 doors (wires that plug straight into the car door speaker wire): 2 pairs of Metra 72-8104 Speaker Connector for Select Toyota Vehicles. No rewiring or crimping was required for the door speakers because of the harness.
I used speaker gasket tape on both sides of each bracket and shorter screws to fit the door speakers to the brackets (matched to the Kicker screws for head and shank diameter at a local hardware store). The included Kicker screws were too long.
4 x 6.5" foam speaker rings with foam backers.
Sound deadening: Dynamat squares for car doors (DYN10415) applied with a roller to the inner and outer door panels.
I broke only one door trim clip in the installation. I would suggest having a couple of door trim clips ready in case one breaks. They are available online like everything else for the installation. Also, watch the little rubber washers on each door panel clip and put them back on when they fall off.
Pleased with the results of the project.
