Upgrading Audio System W/O Changing Head Unit

In my opinion, your system is overkill and will sound minimally better than stock. Your system can only sound as good as your worse component. In this case, it's the stock head unit.

Maybe they exist, but I'm not aware of quality line out converters. By definition, they all sound bad.

You don't have an equalizer to control the subwoofer. My friend and I both had a simple systems using stock head units with line out converters tapped to rear speakers, amp and a sub. We specifically kept it simple because it will never sound good without changing out the deck. There were built in levels on the amp but in the end we still had to constantly adjust the fade for front and rear speakers to get the appropriate bass. Since it was tied to the rear speakers, it was rarely optimal. It's sitting in my garage right now. I moved it from the Integra to the Civic but I'm not going to bother on the Prius.

Another buddy had a system set up similar to your description plus an equalizer in an Acura Legend. It sounded marginally better than stock. He eventually swapped out the deck.

If I were you, I'd start with the bass amp and subwoofer and see how it sounds to you. You might find it adequate as my friend and I did. No need for a second battery or anything fancy. You can always add the remaining components as you listed later on.

 

There are harnesses that will retain steering wheel function to most head units.

Steering Wheel Audio Control Adapters at Crutchfield.com

There are few YouTube DIY's that show this on a Prius.

 

I think you are spending much more money than necessary.

The speakers sound fine, except for the 12" subwoofer. That is a very large sub, and I think you will need to do a lot of work to keep it from causing a lot of vibration in your car. Sonically, an 8" sub will drive down to very low frequencies already, without needing as large a baffle. And there is no baffle on a Prius large enough to contain a 12" woofer. An 8", in turn, will produce better sound without making your car sound like a rattling can... unless that's the effect you're going for. How are you going to mount that sub? You need to factor that in. Are you going to completely give up having a hatch area in order to install a subwoofer? Will you remove the cargo tray and the spare tire beneath it?

Secondly, I think that all of your hand-wringing over power is completely unnecessary. The Prius has a small 12V battery. This battery is continually recharged by the 200-600 Volt DC traction battery. Keeping this battery charged up is trivial. It is also very easy to run thick power cables to this 12V battery, because it's in the rear hatch area. I doubt that you will run into difficulty with the Prius 12V battery. The Prius 12V battery is rated for 30A. Your amp, by the way, is equipped with 30A fuses, so of course you can't exceed the battery's power output. You could consider a different battery. The Optima is rated at 38A instead of 30A. It may make a little difference. But probably not. When car stereo installers talk about second batteries and capacitors and stuff, it's mostly made up, and partly to regulate the effect of the car's alternator. But Prius does not have an alternator.

The power consumption of your stereo is very unlikely to affect fuel consumption.

Your speakers all look nice, although you can fit 6x9's in the front doors and get better bass. I think you ought to start with the six speakers powered by the Sony amp, and then see if you need all this other stuff. But if you install a sub after the six speakers, you should consider carefully whether 12" is really going to help the music you listen to. Personally, I think it will sound awful, but I know that some people are into that sort of artificially heavy thump-thump-rattle-thump sound.

The solar panel won't do Jack.

 

A PriusChat member mgb4tim has created a Fiberglas sub enclosure for Prius. Have a look. It holds a 10" sub.

Small Sub for 2010 Prius IV with JBL and Nav? | PriusChat

 

The head amp is pretty bad, but the usb input generally works as long as you don't care about fast forward, rewind, and remembering the position in a track when you switch away form the usb input.

The idea of needing a 2nd battery is a bit odd. You shouldn't need one unless you have well over 500w. And there is no reason to need more than 100-200w total in a small car.

Line converters are just resistor dividers. Nothing high or low quality about them.
Most amps will accept 'high level' inputs, which means speaker level voltages.

I kept the head amp, but replaced everything else. I suspect my stereo sounds as good as anyone's, and it was under $1000 except for my labor.

Either do it yourself, or find someone trustwirthy. If you find someone, ask to see their wire crimper. If it is not a ratcheting crimper, you are dealing with a loser. Use reasonably efficient speakers. Use thick power wires. Don't use 2ohm speakers.

weasel.com: 2012 Toyota Plug in Prius Stereo

 

My wire crimper is a soldering iron!

No disrespect intended, though. I agree with all your advice. Once you replace the speakers, the amp is next. At that point, the problem is the quality of today's audio. Sirius XM and streaming audio services use poor compression which lowers quality. And musicians master their music to compensate.

 

stock head unit is fine, in fact the dac and preamp are likely identical to those in aftermarket head units.

 

I have a 2012 and I have the head unit completely stock. I work for Hertz and Audison and I did my whole car plug and play. With todays technology you never need to change your radio. In fact I'm streaming fiber optically into my amp/processor over wifi in my car. With that being said, I get 24/48 steaming of any file I want over apple airplay using an apple tv with a power inverter. Im running our Hertz Mille Pro components up front, fully active and our Hertz Mille Pro coax in my rear doors. Im using our Prima OEM integration amps with our plug and play harness for the toyota cars so you never have to cut anything to integrate your amps into the car. With the amp i have a full built in processor and DSP tuning i can modify and play with to my liking. If you look hard enough, there are tons of products to help you integrate into your stock radio, more then just a Hi to Lo converter.

 

Since fiber optic cable is a wire, I don't understand what you're saying at all.

You have an AppleTV in the car, running from an inverter, which is cool. I assume you mean it's connected to your head unit using a TOSLINK cable, which is cool.

So you stream from your phone to the AppleTV via WiFi? That should be ok.

The only chink in this which I see, which is pretty small, is that Apple Music overall isn't the best quality music, but it's better than most MP3's and I think it's better than SiriusXM.

If you want to hear a funny story... I have a fairly expensive home theater system in my living room, with very nice Definitive Technology speakers. But I went into a tiny little shop in Berkeley called Berkeley Stereo -- and, the guy means "stereo." He sells reconditioned turntables (he fixes them himself) matched with tiny, $250, 40-watt tube amps and small, vintage bookshelf speakers. Not fancy or expensive -- but the sound is just amazing!

 

Ok, so using airplay, I can stream wifi into my apple tv, which then sends the audio signals up to 24/48 out via the fiber optic output into my amp. My amp has optical and analog inputs. I don't use that to send iTunes info out. I use a hi-res streaming service.

 

So you stream compressed from your phone to the AppleTV, right? It should sound pretty good. I think that will sound much better than streaming from the phone to the head unit via Bluetooth, because Bluetooth audio compression is awful. Not sure if it will sound better than transmitting from a USB stick attached to the head unit, but that might not give you the selection you want, or Siri control. Your solution "sounds" pretty good to me.

 

Yeah it sounds great, but it is not compressed since I'm going over wifi. I pay for Tidal's hi-res service so it streams 24/48 hi-res out over wifi. There are very very few items today that can handle bluetooth Hi-res streaming. Sony's new RSXGS9 is the only car audio piece that can stream hi-res bluetooth.