Hi there, this is my first post on this forum so I apologize if I am posting in the wrong section or anything. I am here to spread some info which I found quite difficult to find myself.
The front speakers of the ST205 (non premium system) are 8 inch woofers.
Today I installed some Focal ISU200 speakers and they are a drop in replacement. Stock screws. Stock screw holes. No cutting required.
To wire them I unsoldered the stock wiring loom connector from the toyota speaker, and I soldered it to the included crossover cable provided in the ISU200 kit.
I stuck some waterproof closed cell foam into the door space behind the speaker. This should improve midbass a little.
I then installed the included gasket to the speaker housing and screwed the new woofer into place.
Above the connector for the main speaker is an additional connector which isn't plugged into anything. The wiring colours are the same as the ones for the main woofer. This is a perfect connection point for a tweeter (and probably it's intended use).
I chopped off the factory connector and soldered on the included crossover for the tweeters. I zip tied and ran this wire into the triangular panel by the wingmirrors. Note for those planning to use this kit: The tweeter crossover has 3 wires. Ground, Car and Display. The display wire is used when demoing these speakers in shops and can be chopped off. Use Car and Ground.
I screwed the tweeter housings to the triangular piece and drilled a small hole for the wires to go though. These are very easy to mount.
The result? This system sounds FANTASTIC. A deep and rich sound with crystal clear highs.
I haven't replaced the rear speakers yet as they are not crackling like the front ones were and honestly sound just fine.
I hope this can help someone! I have included several pictures.