Replacing rear speakers and conclusions...

It is fairly ridiculous how hard it is to get decent sound to come out of the rear speakers. I went ahead and replaced them this weekend, and here are my thoughts.

DIY replacement was not so bad. Pretty easy, and you want to keep the factory brackets on to easily mount the largest speakers you can fit back there, which is 6.5". Poke a hole through the paper cone and peel off the front surround suspension. Then take a hacksaw blade to the three arms holding the basket in place. Pull out the speaker assembly and marvel at how cheap it really is. Cut off the wires so you can reuse the factory wiring harness female plug, the Metra brand harness won't fit in place of the factory harness. Solder new wires and quick connect terminals to the factory plug. Drill out holes in the remaining factory mount to screw the new replacement speaker in place, if your speakers didn't come with screws some stainless steel 6x3/8" screws will do the trick. Mount the speaker, close up the door.

Yes the new speakers sound better. Much better response across the audible spectrum, and handles high volumes more cleanly.

The real problem is that the head unit still doesn't play the rears at an audible volume until you set the front/rear fade to more than 3/4 back. My conclusion is that the head unit is designed to create a frontal soundstage most of the time, and enforces this by almost always putting more volume to the fronts than the rears.

While this is an interesting idea, I find that the cabin of the Prius v is so full of road noise on the highway that the back seats can't hear the front speakers until they're cranked way too high for the comfort of the driver. In this case you just want to power the front and rear speakers evenly, and forget about trying to create a frontal soundstage.

There are two things you can do to fix this. Either install sound dampening to your cabin, or install an amp and rebalance the signal coming from the head unit. Installing replacement speakers alone will not be adequate to overcome the frontal calibration of the factory head unit. I suppose you could as a third option replace the head unit, but I don't know if replacement HUs can duplicate the hybrid engine and gas efficiency readouts.

In my case, I don't yet know if I want to install an amp. And for the time being my young family has a baby who falls asleep fairly easily in the car, in part due to all the white noise that the Prius v allows into the cabin while driving. I don't want to jeopardize being able to rely on that for some peace and quiet!

As a caveat, there is maybe one notch on the head unit front/rear fade that outputs equal volume from the front and rear speakers, but at this setting neither set of speakers are getting full power. So you really have to crank the volume on the head unit, which increases the distortion in its output. Not an ideal solution.

So that's my weekend speaker replacement adventure. I'll post some pictures of the install in a comment below.

 

I'd make sure to amp the line out from the head unit itself, I don't trust the speaker level outs to be clean enough to amplify.

The new speakers are JBL GTO638's which have the among the highest sensitivity ratings I could find. I was hoping that would be enough, and they are a tiny bit louder and definitely more clear than the factory rears. I would NOT recommend them because the tweeters stick out too far and the plastic door panel is slightly protruding in the speaker grille region because of it. The door panel is secure and the speakers are fine with the pressure but it's not ideal.