Stock FR-S amp
 

So I was playing around yesterday and found out some information I didnt see posted anywhere. In my trunk there is a stock amp for the radio how ever it only does the front door speakers and the 3.5" in the dash, if you unplug it, the tweeters in the dash and the ones in the back still play

I am going to find out what rms it pushes as soon as I get a little more time

do share :)

actually while you're investigating this you should come up with a full stereo schematic of the car. list all speakers, what they are powered from, and how much power they are receiving.

it would be great info for anyone looking to upgrade.

There is already such info everywhere , if I recall correctly its a 2 channel 300w amp

Can it be used to drive anything? Say a small subwoofer?

i highly doubt its 300w rms. you would also have to find what kind of ohm load it can handle to power other stuff with it.

I agree it prolly does 25x2

I doubt you can run a any kind of sub off of it. and im sure its not a 2 channel 300 watt amp either , if the whole system is 300 watts and its only powering 4 out of the 8 speakers. my quesss its probobly like a 100-200w. I am going to be tied up this weekend but I will get some info on it as soon a I have the chance

Did i say RMS? Its a peak value.. every amp advertises their peak value.. I dont know the RMS, I would guess 75 watts per channel RMS? Maybe 70?
Ofcourse you can power a Sub.. but will you will be supplying enough power with it.. HELL NO.
I will let you know tomorrow when I get my car, I will measure the value for you with a DMM

See here:
http://www.ft86club.com/forums/showthread.php?t=5280

Page 4, standard audio system -- 140w(peak) 2ch amp.

sweet thanks

Most aftermarket manufacturers list the inflated max or peak power at 14.4V at an ugly THD at a 2ohm load. This generally accepted marketing practice is quite dubious in my opinion since this condition isn't the expected real world conditions the amp will see. Since this is a 2 ch amp the max watt/ch is 70. Let's drop 20% for 12.5V operating range and it goes from 70w to 56w. Now half that to get your rms which is 28w, calculate for a load of 4ohm, which most audio speakers are spec'd at, and you're down to maybe 17w rms if you're lucky. I won't speculate what the real wattage is at a THD of <1% but it'll be less than 17w rms.

Now considering that the stock in dash and rear speakers have a power handling of 15w RMS it would make sense that the amp would only have 17w rms at 4ohm at <1%thd.

The head unit is 160w max divided by 4 ch gives you 40w max or 20wrms at 14.4v, or 16wrms at 12.5v assuming it was already rated at 4ohm at <1%THD. This puts it in line with the 2 channel amp in the back and in line with the 15w power rating of the speakers.

So I'm looking to just add a powered subwoofer to my FR-S while leaving the rest stock. Does it make sense to have it connect via the head unit or extend off the wires going to the stock amp somehow? Below are two frontrunners.

[ame="http://www.amazon.com/Kicker-Hideaway-Compact-Powered-Sub/dp/B007LQWSYC"]Amazon.com: Kicker Hideaway Compact Powered Sub: Car Electronics[/ame]
[ame="http://www.amazon.com/gp/product/B004HW6F9M"]Amazon.com: Pioneer TS-SWX251 10" Flat Subwoofer with Enclosure 800 Watts: Car Electronics[/ame] with amp

I just want a little extra low end but be able to pull it out easily or keep most of my trunk space.

Infinity basslink should fit your needs with out having to get an amp or do crazy wiring.

Can I just piggyback off the power and audio cables going to the stock amp in back or do I need to run the new cables all the way up the length of the car to the head unit/battery?