Got This Done Right Before Labor Day Weekend...

Your sub looks great! It looks really fierce next to your pillow emojis

If you have the non-JBL system (you can tell if there's no center speaker behind the center dash screen), upgrading the factory headunit will yield improved sound, especially for your sub. The stock head unit rolls off the bass below 60 or 70 Hz or so. This is great for keeping the midrange door speakers from distorting, but as you're tapping the rear speaker output (I assume) for your sub, it's keeping the sub from hitting those low notes that it's specifically designed for. However the door speakers don't do well with that really low bass sent to them at high volume, as you'd get if you just wired them straight to an aftermarket headunit. In my system which still uses the stock speakers, I installed some 220uf Electrolytic Non-Polarized Crossover Capacitors in series with all 4 speakers when I added an aftermarket headunit, which rolls off the bass below 90Hz. Then I set my subwoofer crossover frequency to 80Hz. If your headunit can apply a highpass filter to your speakers, crossover capacitors wouldn't be needed.

If you have the JBL system, generally you'll need to replace both your headunit and speakers at the same time. The JBL system has 2 ohm speakers and uses active (built into the amplifier) crossovers, so generally the whole thing (speakers, amps, etc.) has to be pulled out (As 99% of headunits only have 4 speaker outputs, and are only stable to 4 ohms). Lots of details about it here: Prius JBL Audio system response, specs, and photos.

You have two options for the headunit: either replace the CD player completely, or install a single DIN below it in a "stealth" configuration where there's currently a storage tray. I did a stealth install as I've twice previously had systems stolen out of my cars. As my car is now, when the covering "door" is closed, it looks like my sound system is completely stock. There's a great thread on doing this, and how to wire up the Prius here: Stealth install an aftermarket stereo in Prius | PriusChat. There's a ton of info in that thread, so I recommend looking through it even if you don't end up planning a stealth install.

Hope these thoughts help,
-K

 

I'm getting ready to replace the head unit in my 08 JBL system, I'm getting the wiring kit that ties into the existing amp, do you think i have to replace the speakers as well or could I just stick with what i have? I'm happy with the sound so far, I just wanted the convenience of a Double Din stereo.

If i plan to get new speakers down the road, my thinking is that I could just run new speaker wire from the door directly to the aftermarket radio.
Any thoughts appreciated. Thanks.

 

Yes, like I said, some of JBL system speakers are 2 ohms. Most headunits only work down to 4 ohms, so you'll damage your headunit if you try to run them from it. Also the tweeters don't have a crossover (crossover in JBL system is built into amplifier), so you would need to design your own passive crossover (if you try to run the tweeters without, you'll blow them from the low frequencies in the full range signal). The only way to make the JBL speakers work with a normal headunit is to add 2 ohm resistors to the woofers, and then install your own crossovers. For this reason, everyone I've seen replace the JBL headunit also replaced the speakers.

The speakers are wired from the amp underneath the front passenger seat. You can tap into the wires there and then run wire into your dash to your headunit on the passenger side of the car.

 

Ok thanks for letting me know, what speakers would you recommend that would keep the same quality as the JBL? Thanks!

 

I just picked up some Rockford Fosgate speakers on Amazon for pretty cheap they have quite a selection of low price quality speakers.