I have a Kenwood 2-channel 60w rms amp and Polk DB651 (also 60w rms) ready to go in to power my front speakers off the stock non-JBL navi HU. My friend says the front speakers will be 2OHM as the dash speaker is in line with the door speaker. If this is true, this would put too much strain on the amp and overheat it. Ive read online that the way the Prius is that the front speakers act as components so are true 4 OHM even though they are wired in line with eachother. Will I be safe installing my amp? I will use the stock dash speakers for now and might upgrade later. The other option would be to disable them altogether
"Assuming" the 2015 and 2010 base stereo uses the same 6 speaker-set up they are 4 ohm. frodoz Stereo Upgrade | PriusChat
There is no really simple answer. The 2 speakers are in parallel. The dash speaker has a small capacitor in series with it, which will greatly increase the impedance at lower frequencies. I have no idea what the impedance vs frequency is for the 2 OEM speakers, nor have I seen any published numbers. Putting the dash and front door speakers in parallel is pretty common with toyota, as my 2002 camry does the same thing. When I upgraded my dash speakers, I replaced the small capacitor with a much bigger one to allow lower frequencies to be produced by the dash speaker. I also added a 2 ohm resistor in series with the dash speaker and the door speakers. This way, the lowest impedance load should be 3 ohms, rather than the worst case OEM impedance of 2 ohms. People thought I was nuts, but I didn't want to break the OEM head unit, and resistors are cheap. If you break the pioneer amp, at least it will be cheap and easy to replace compared to the OEM head unit. I suspect it won't break as the pioneer amp is likely much better designed and robust than the OEM head unit. If you replace the dash speakers (and you should as they really suck), you might want to put some 2 or 4 ohm resistors in series with them. It turns out that the dash speakers have a much more direct path to your ears, and need less power (all other things being equal) than the door speakers. With my setup, I have each speaker being driven separately by my JBM MS-8 8 channel amp. I removed the capacitors and resistors I was using with the head unit, and turned doen the dash speakers a few db, which resulted in a more balanced soundstage. You should also replace the OEM door speakers as they suck too. See weasel.com: 2012 Toyota Plug in Prius Stereo for lots of pictures of the OEM speakers and my stereo build.
They were 25w resistors, which were $1 each at my favorite electronics store. 5w would be large enough...
