Our 2015 Prius V doesn't have a bad audio system but the bass is pretty muddy and the rear speakers appear to be nearly silent. The recommended update is new rear speakers and an amplifier. I don't like cutting into wiring so I am trying to avoid adding the amplifier. I looked for the most efficient speakers to raise the rear sound level without an amplifier. I purchased some Infinity Reference 6 1/2" speakers from Crutchfield. The sensitivity (sound output for power input) of these speakers is 93 db which is the highest of the speakers that they sell. They came with adapter harness for Toyota and adapter rings to replace the Toyota adapter rings. I also ordered the Hushmat. Installation was pretty easy, there is a youtube video on how to remove the rear door panels. Just two screws and pop out about 8 plastic clips holding the door panel on. Disconnect the two cables for door opening and locks plus the plug for the speaker wiring and the panel is free. I unplugged the speaker connector. I drilled out the three rivets holding the standard speaker adapter rings and removed them. Once I had access to the speaker opening, I could install the Hushmat. If you are not familiar with Hushmat it is about a 1 foot square piece of 1/2" thick peel and stick sound absorbing material. The Hushmat is supposed to be stuck to the outer door skin behind the speaker. The problem is there is a round door beam right in the center of that area. I positioned the Hushmat where it should be located and marked where the beam crossed that area. I cut the Hushmat into three pieces. One for the area above the beam, one for the area below the beam and an 1 1/2" strip to attach to the beam. I peeled off the adhesive back and stuck the pieces in place. I plugged the adapter cable provided in the kit to the speaker terminals. There is one narrow and one wide lug on the speaker and the same for the adapter cable so you can't get the wire polarity reversed. The other end of that adapter cable has a connector that plugs into the original speaker harness so you don't have to modify any vehicle wiring. The old speakers wires connected on the outside of the inner door panel and the new speaker wires attach to the back of the speaker which is inside the inner door panel. I cut a slit in the clear plastic sheet covering the inner door panel at an existing one inch diameter hole near the speaker opening and slipped the harness through it. The old speakers extended out from the inner door frame about an inch because of the original adapter ring. The new adapter ring does the same thing but has mounting holes for the new speakers. Three pop rivets secured the new adapter ring to the inner door frame. I had to elongate two of the holes on the new adapter rings so that all three holes lined up with the existing holes in the door. I replaced the door panels and was ready to check out the sound. The fader still needs to be shifted from neutral toward the rear speakers but not as much as with the original speakers. I selected some music with a lot of bass and put my hand on the outside of the door skin opposite the rear speakers and the vibration appears to be somewhat reduced on the rear doors compared to the front. The bass is cleaner and I am not sure how much is Hushmat and how much is the new speakers. I would have to say that time will tell whether the improvement was worth the cost, $100 and the effort.
I find the rear bass is a function of the source more than anything. Some of the best bass comes from HD FM radio stations. There is no doubt the mid and high frequencies in the rear are muted on this system, probably by design through audio filters.
I didn't get much benefit from just upgrading the rear speakers. While the bass is cleaner with the new speakers, I am not sure that the improvement was worth the time and $100. I was trying to avoid cutting into the wiring and adding an amplifier but it seems that is what is really needed. After driving the Prius for a while now I noticed that the road noise at freeway speed is considerably higher than our Odyssey EXL. The Odyssey is a large empty box with a lot of glass but it does a better job of keeping out road noise at freeway speeds. Honda must have realized that Odyssey's spend a lot of time on the freeway and they put an effort into containing road noise. There are different boxes to check when you are building a touring vehicle as opposed to building an economy car. Aware of the Prius road noise, I wasn't too surprised that there is no soundproofing on the inside of the door skins just bare painted metal. Any bass from the speakers causes the door skins to vibrate. You can feel it when you put your hand on the outside of the door while playing music with a lot of bass. Ideal speaker enclosures are rigid. An undeadened sheet metal car body is not ideal for sound reproduction but then it is not a concert hall, it is an economy car which is what it does best.
There is little doubt in my mind that Toyota has a crossover circuit in the head unit which is pushing only bass to the rear speakers. Plus the radio does not have a traditional bass boast feature that most American car radios always had. That effectively makes the front dash and door speakers the primary drivers for 90% of the frequency range. Given the integral amp is not very powerful and the factory rear speakers are muffled by low placement between the seats, an amp is probably the only real solution if you want to keep the head unit and all of its integral car functions. Its true that road noise sound deadening is almost non-existent in favor of lower weight and fuel economy. Some have reported good results with an aux amp with speaker level inputs along with sound deadening in the floor of the hatch area.
Actually, you stated that the speakers you installed were 93 dB, but.... Infinity cheats, and expresses their speakers' sensitivity in @2.83V. If you have 8 ohm speakers, that is the same as @1W/1M, or SPL. But car speakers have 4 ohm impedence (and the Infinities are even 3 ohms), and at 4 ohm 93 dB @2.83V works out at 90 dB SPL. The difference between 90 dB SPL and 93 dB SPL may not seem much, but 3 dB is actually double the sound level. I'm installing Hertz 170.3 speakers in the back door of my Prius v soon. They are rated at 93 dB SPL. To be honest, I have no idea what to expect. But it's worth a shot. I'll post the results here when I'm done.
After installing the Infinity speakers, I have to agree with rjparker that you don't get the full spectrum of sound at the rear speakers. I was able to adjust the front/rear balance control more toward the neutral position with the new speakers. You may experience a little more bass and it may be a little cleaner. Was it worth the effort? Only you can decide. It is, after all, an economy car. It has virtually no soundproofing. It transmits a lot of road noise into the cabin so it is never going to be a concert hall. I like my Prius V and have learned to appreciate the Prius for what it is and I am willing to live with what it is not.
I completed the speaker upgrade yesterday. My first impression is fairly positive. I have set the fade to 60% rear now, it used to be 80%. The advantage of that is that, if you set the fade way back, the tweeters in the dash stop producing sound. So everything that helps being able to set the fade more forward, improves the sound overall as well. I might even go to 40% rear, but I'll see what the kids find of it first. I think one big advantage of the new speakers is they produce a lot clearer sound, and they do also produce way more lows and highs as the factory speakers. That also enhances the feeling in the back that you can actually hear music, not just some indistinguishable muffled noise. So, for a $ 65,- upgrade, I am not unsatisfied. It was quite a bit of work though. I decided to cut some new 1/4" MDF frames to hold the new speakers, and getting everything to fit nicely took quite some time. Some notes on the video's showing how to remove the rear door panels: Some video's tell you to remove the window controls first. That's not necessary and only increases the chance of damaging the interior Some video's show removing the door panel by inserting a tool between the plastic panel and the door at the side. That is completely unnecessary and only increases the chance of damaging the panel. There is a large cavity at the bottom of the door panel in which you can easily get your hand and then you by gradually working your way outward you can gently get the panel of.
