Stock radio outputs?? Really?

[2012NismoCoupe]

So, I'm considering replace the rear deck speakers with some better aftermarket ones, and wanted to know what the Watt output was to the rear speakers, so I measured the Volts DC and the Resistance, then based on Ohm's law calculated the Watts and the Amps here's what i got:

Measured at the rear speaker connections:
16 milliVolts DC <-- Why?
12 Ohms
1.333 milliAmps
21.333 microWatts <-- Really?

has anyone else checked their outputs? I'm gonna have to have an amp just to drive anything other than stock. I mean 21 microWatt's? Really Japan?

Anyway, I'm just confused and looking for some answers... Any help is appreciated.

[2012NismoCoupe]

anyone?

[AppleBonker]

I need more details.

At what volume did you measure the voltage?
Where did you actually measure the line voltage (IE at the speaker terminals or on the back of the head unit)?
Was the speaker disconnected at the time of measurement?
Were all of the speakers disconnected?
Was the car running?

Is the stock speaker really 12 ohm? Not sure I ever paid attention. Also, I'd measure mine, but I sold the car. And it was the Bose system anyway.

[DJ_B_Easy]

I think 2 things are throwing you off here, assuming some or all of the questions AppleBonker asked above are answered "mid volume", "at the back of the head unit", "speaker was disconnected", "the car was running". So this is just intelligent guessing, but Id check your numbers again.

1) You had the voltmeter on the wrong calibration when you measured the voltage. Try giving a click or two to the left.
2) I highly doubt the stock speakers are 12ohm resistance. That would be an assbackward engineered design. Even if all 6 speakers in the car were wired in parallel you would get your load down to 2 ohms, and I imagine they are driven at 4. I doubt they are all wired in parallel anyway.

EDIT: I think I may have jumbled those numbers. Ill see if I can dig up my stock speakers and check out some specs for you when I get home.

[2012NismoCoupe]

I'm an electrician for a living. The DVM was set right and was getting nothing in the Volts setting and only when switched over to the millivolt setting did it read anything.

The stock speakers are rated at 4ohms if I remember correctly. They arre rated at 25 watts as well. I measured it connected and disconnected (at the speaker connection of couse not at the head unit, I don't want to rip my dash apart its a new car), I also measured it at a mid volume about 15, then at 20 and 22, it obviously gave the highest readings at the highest volume. I measured the battery volts and it read 12.6-ish, so the DVM is working....just unsure how the readings could be so low to the speakers??

[DJ_B_Easy]

I measured the battery volts and it read 24.6 ish

Either I am completely misunderstanding you, or you are doing something incorrectly. Car battery is 12 volts.

Regardless, if you already know that the stock speakers are rated at 25W and 4ohms, just match the resistance exactly and the wattage as close as possible shooting a little high if you have to. If you dont want to power the speakers with an aftermarket amp anyway then you are simply swapping one set of drivers for the other and you dont really need to worry about making sure your set-up is electrically sound because you arent changing anything but the driver. TBH, not really sure that is going to be worth it since most OEM drivers are engineered to work with OEM headunits and individual car acoustics.

[2012NismoCoupe]

sorry mis-typed that should be 12.6 not 24.6 my bad.

[2012NismoCoupe]

that's not entirely true, see everyone gets hung up on Wattage output and so on, but here's the thing (amplification aside) if you have stock speakers that are rated 25w 4ohm, and have a sensitivity of i'd guess around 81-85 dB, that means that those speakers with 1W at 1m are 81dB, where as the ones I'm putting in are Rockford Fosgates with a sensitivity of 91dB, so they are 91dB at 1m with 1W input, and therefore are so with the same input the aftermarket ones will by defualt produce a better SPL, and thereby a better cleaner sound, also louder, without amplification. So there is a difference, factory speakers are not designed with individual car acoustics in mind, they are designed with budget friendly-ness in mind, if it works and they can used it, then thats what goes in it.

But, here's the thing, just because the factory speakers are rated at 25w @ 4ohms doesn't mean that's what they are receiving, the resistance they receive is based on the length and gauge of wire used as well as what the headunit itself is transmitting through that wire. Also, on a stock speaker those specs would be more like max levels, the root mean square would be more along the lines of say 10w @ 4ohms. Theoretically that wire should have about 11.5V in it, with a resistance of about 6 to 8 ohms, that would give between 16 & 22 watts to the speakers, this from the factory aspect would ensure that even at maximum volume the speakers would be less liklely to blow out, providine them with less parts that could potentially require replacement. Anyway, I just wanted to verify what I thought it should be, but I was stunned with the numbers I measured and wanted to see what others had found....

[AppleBonker]

that's not entirely true, see everyone gets hung up on Wattage

Some do. But not all of us.

factory speakers are not designed with individual car acoustics in mind, they are designed with budget friendly-ness in mind, if it works and they can used it, then thats what goes in it.

And I don't think DJ was saying it might not be worth it to upgrade the driver because the stock ones are better. Rather he was pointing out that a lot of factory stereos have tuning built in to compensate for the deficiencies of stereo components. I know the Bose system in the Altima does; I'm not sure about the base system. Put it this way: if you have a driver that does not have a flat frequency response curve, you can tune the amp to exaggerate frequencies where the driver under performs. Now, if you swap that driver for one with a flat (or flatter, anyway) curve, you will now start to hear frequency spikes where the amp is tuned for them (and you wouldn't have heard that with the stock speakers). I believe this was the point of his comment. ANY aftermarket driver will be better than the POS paper ones used stock. But the driver being better does not necessarily make the system better as a whole.

But, here's the thing, just because the factory speakers are rated at 25w @ 4ohms doesn't mean that's what they are receiving, the resistance they receive is based on the length and gauge of wire used as well as what the headunit itself is transmitting through that wire.

Well, technically the speakers don't "receive" a resistance. But I get what you're saying. A speaker being rated for that doesn't mean it will get anywhere close. And you are completely right about the stock wiring. There is quite a bit of power that will be dissipated as heat through the wires. That's why I was asking if you were measuring at the back of the head unit or at the speaker. It makes a pretty large difference.

Also, on a stock speaker those specs would be more like max levels

Absolutely.

the root mean square would be more along the lines of say 10w @ 4ohms

I'd actually suspect it would be less.

Theoretically that wire should have about 11.5V in it, with a resistance of about 6 to 8 ohms, that would give between 16 & 22 watts to the speakers, this from the factory aspect would ensure that even at maximum volume the speakers would be less liklely to blow out

Actually, given this logic you should expect the speakers to be woefully under-driven. You can't blow a speaker by under powering it. The engineers have to design the car for what some people will do with it: turn the stereo up to a level way past what it even sounds like, and boost the hell out of the "bass". Without a good-sized safety factor in there, they will be blowing speakers.

Finally, you've pretty much said you expect the stock amp to be crap. And you know the stock wiring is crap. It certainly is possible that the stock system is that pitiful; I've honestly never measured. I just know that stock systems are completely worthless and my goal is always to swap everything out as soon as possible. When I get to the point of installing my setup in my truck, I'll see if I can measure the power output before it is completely removed. You definitely piqued my interest.

[DJ_B_Easy]

But the driver being better does not necessarily make the system better as a whole.

^This.

I just know that stock systems are completely worthless and my goal is always to swap everything out as soon as possible.

^And this.

I guess I didnt put my reply together all that well, but IMO simply replacing the factory driver with an aftermarket driver is not going to give you the overall results you are expecting. You might find that your favorite hip hop song that sounded terrible on the OEM system now sounds great, but your copy of Pink Floyd that was clear as day has now gone completely flat (just random unfounded examples). At least add an aftermarket head unit as well to give you some more control over the soundscape (in fact, I would recommend doing this BEFORE swapping drivers). A small, inexpensive amp will go a long way as well. If you are on a budget, swap the drivers and see how you like it. If after a few months you arent happy, add the head unit. A few months later, small amp.

[2012NismoCoupe]

by the numbers swapping drivers will provide a better sound, but everyone has their own opinions and I respect that . I do understand what you are saying to some respect though about how a factory speaker (at an appropiate level) usually yeilds better Mid and High range frequency recreation, usually because the average factory speaker has a low end limit of about 80Hz on a good day, while adding a aftermarket will give you as low as 30Hz, which (at loud volumes) can be felt but not heard. The RF that I have are I think 50Hz to 22kHz, so they are of good range and would benifit highly from an equilizer, such as those in an aftermarket head unit. So I get what you are saying, but I think the route I will go, is those speakers and the 2 channel amp I have for now, I'll use the High Level input, so I can just run all but the power wire & remote wire in the rear of the car, and that will give me 50w RMS x 2 @ 4 ohms to 2 Rockford 6x9's rated at 150w peak and 60w or 75w (can't remember the exact number as they are at home and i'm at work) RMS @ 4 ohms, should sound pretty good, might consider a equilizer as well, to fine tune the rear speakers...

[AppleBonker]

Wait, you're planning on replacing and amping just the rears? That's going to severely jack your soundstage by moving the bulk of it to the rear...

Edit: I just realized you posted that in the OP. Had I caught that I probably would've said something earlier about that maybe not being the best idea.