Looking to install new amplifier and was told "DO NOT exceed a 30A current draw or 350W RMS"

In a more specific sense, that is true. There are too many variables in speaker design to take into account like speaker size, target frequency range, magnet material, speaker materials, distance from voice coil to maget etc..... But i was trying to speak in the general sense. I installed some 300+ watt component speakers for a friend and told him they simply wouldn't work well before i even installed them. They had huge magnets that barely fit in his doors. The head unit was just not enough to get bass out of them without major clipping. The bass sounded terrible, and IMO the factory speakers sounded better aside from the nice new tweeters. So the next week he bought a 150Wx4 amp and i hooked it up, all his speakers sounded great with plenty of bass, mids and highs. It was well rounded, just needed some dynamat but that's a different story. So in the general sense, i'm saying don't go out and buy some whopping big speakers with giant magnets and large power requirements. Buy speakers that are more reasonably matched to you power input, which was a head unit i spoke of earlier, and with the best efficiency.

I have some 4 foot long crimp tools, but now i just buy screw on terminals, they seem to work the best for me.


But back on topic of the OP, i had to replace a fuse today for my cigarette lighter and i noticed under the hood (retrieving fuse puller) that the DC-DC fuse is 125amps. That's actually really big considering that most economy cars don't even have 125 amp alternators. I would take a guess and say the wire to the battery is probably 2guage or 1/0 gauge. Someone would need to verify, if it is, then that's good news. Perhaps the prius can handle more than crutchfield is saying it can. But ultimately, someone needs to measure current of all factory 12 devices including lights, engines, radio etc.... so we can get a better idea.

 

No need to guess. I added a new ground wire to my battery. I have pictures from my 2012 prius. The factory wire looks to be about 10 gauge. Of course, it is a Japanese wire, and doesn't come in AWG size. Still, my 6 gauge wire was a whole lot thicker. Perhaps you should look at some pictures, like Lopgok's stereo upgrade - in many small parts | PriusChat before guessing about some mythical 2 or 0 gauge wire. It only takes a few minutes to expose the 12v battery and look to see what is on your car...

 

It's been raining for the past few days, including today. I'm a dad now so i have no interest in installing an aftermarket system because i keep the volume low most of the time anyways. So i'll hold off on checking.

But if you're saying it's 10guage in size(japanese use metric wire sizing, it's in mm), then that's your bottleneck. You really should never exceed an average current of 20amps. If it's 8 guage, then you should never exceed an average current of 30 amps, which is probably the reason for the crutchfield 30 amps rating. It's hard to say what your average current will be since it's different for ever install due to different volume and gain levels, as well as the music itself. So they have to recommend worst case scenario of 30 amps rms max ratings of your amp.

Heres a ampacity chart:
Amps and Wire Gauge - 12V Circuit

The only way to know for sure is to feel the wire, make sure it's not hot after playing for a while. And if you have an ammeter clamp, check the amperage. And if you have a voltmeter, make sure the voltage doesn't drop with your music, below 14v.

 

First things first. The absolutely biggest noticeable thing you can do is increase speaker efficiency. About the most efficient I've seen recently are around 94db. Sound pressure level doubles with an increase of around 6db in sensitivity and is very noticeable at 3db.

It also takes 10x the output in Watts do double SPL (percieved volume). I have a 6 watt vacuum tube (huge difference in sound quality than anything solid state) I drive a 12" JBL D130 speaker with a sensitivity of about 101db. If I ran 2 of the same setup (12 watts output and 2 JBL D130 speakers) full bore in the backseat of a Prius you would be scrambling to get out of the car.

FYI. There is no such thing as an RMS watt. RMS is a standard deviation measure of a sinusoidal waveform, current or voltage, a watt is basically a unit of heat that is a calculated measure. It can't even be physically measured. The terms and quotes of RMS, THD, comes from the "marketing department".

 

Pretty funny then that the power and electronics industry thinks that P=I*E, where the power is expressed in watts is a perfectly normal thing that they use every day.

RMS stands for Root Mean Square and is a mathematical constant that is applied to a pure sine wave to get it's equivalent DC voltage or current.

And finally, the output of any amplifier absolutely CAN be measured by putting IN a pure sine wave and using a standard AC watt meter to read the output, as long as the meter is calibrated for the frequency involved.

 

True, it is a huge difference in sound quality. More distortion, lower dampening factor, likely more noise. Also heavier and makes more heat than most solid state amps. Also pretty tough to find tubes...

If tubes were so good, there would be lots of instrument amps (not music instrument, but professional measurement instrument) using them.

Oh, I forgot, tube amps also have 'microphonics' where the sound of the speaker effects the tube amplification. The only tube amps being used today are very high power RF amps and travelling wave tube amplifiers for microwave RF.

Low frequencies can suck up hundreds of watts. I like pipe organ music. I have a 600w stereo amp for home use. My car subwoofer amp will be 75w x2, with 92db/watt woofers. Your 101db speakers are likely horn loaded and have tons of distortion.

 

While true, it's a matter of "if you can't beat em, then join em". Vrms x Irms = Power(watts). This is typically the way power is calculated for thermal dissapation and circuit loading purposes. It's the DC equivalent of power for an AC signal. However, it was actually the FTC(federal trade commission) that created "continuous power" because amplifier manufactures were constantly trying to outdo each other with ratings advertising. They were simply calculating instantaneous peak power levels and throwing it on the spec sheet. As long as they have some sort of justification for the number they could prove, they couldn't be sued for false advertisement. So the FTC created "continuous power", which simply played a set sine wave up until clipping at a certain THD level. This over time i think turned into "RMS Power".

 

Way too much technical BS. All I know is that my JL XD700/5 and other accessories still work with the Prius and it's been 6 months of playing it loud everyday. Just sayin..

 

The big battery just keeps feeding the 12v which feeds the amp/s. All bs aside, you can run 2000 watts with a digital amp if installed correctly, with no ill side affects. May piss off the neighbors though.

 

Not if the amp really consumes anywhere near 2000 watts you can't.
That would require 166 amps and exceeds the capacity of the ENTIRE 12 volt system by about 200%.

THAT is why RMS or "true" power ratings are important.
I think it is likely that the "2000 watt" rating of the system you are talking about is just
marketing hype (a downright lie).

 

In the last few years speakers are more and more being rated at program power to take out the confusion from lay people. Someone who went to the Univ. Of Google for their knowledge base might think a 120w speaker can actually be run at almost 170w. In school we were taught to consider voltage and current specs. Stated as RMS unless specifically said otherwise. In the real world it should be run at much less because speaker manufacturers tend to be way too optimistic with the ratings. Another reason to be conservative, especially with low frequency drivers, is that impedance is frequency dependent. At 20hz that 4ohm nom. sub is more like 1ohm, an 8ohm nom. mid range fluctuates between probably 1 and over 20ohms across the audio spectrum.

A "down and dirty" method of checking actual "average" output is to clip you meter leads on the speaker, crank up your system, using peak hold on the meter set to volts or just guess at the highest voltage reading you see, square that number and divide by the impedance stamped on the speaker frame (not the measured dc resistance). That is your (calculated) output in watts.

 

Easy Rider, isn't the amp's rating a rating of output power, not input power consumption? Amplifier gain takes low voltage input and creates higher voltage out dependent of the gain setting, the rating is the peak power attained after the gain achieved isn't it?

For example a 30 watt peak x 4 amp. It'll create 120 watts out but does it really consume the entire 10amps DC at the input, especially if the power supply is regulated? If it did, and many if us are running up to 500w peak, then none of our cars would work because we'd be overloading the electrical systems, hybrid or not. I'm only curious on the theory behind Input DC power requirements versus output ratings. I don't believe they're really the same but could be wrong.


iPhone ?

 

You can NOT push more power OUT than you have coming IN.

Therefore, the total power usage will always be MORE than the output power.
IF......all of the "power" measurements are made in the same units.

To say, for instance, that you can get 500 watts per channel output while only consuming 100 watts of power input is ridiculous.

There are industry standards for labeling the power consumption of electronic devices.
Look at the "name plate" of an amp and it should show the maximum power drain for the whole device.
Divide that by two and that's the absolute maximum power that you can get from each channel.......measured in "real" watts RMS.

 

Name a guitarist today and I guarantee you they are all using tube amps. Brad Paisley is endorsed by Groove Tubes and does their magazine ads.

Those 101db speakers are single 12 inch drivers. They were originally designed for hi if systems in the late 60's. Fender had JBL label the ones they used with an F designation (JBL D130F) back during the loudness wars of the 70's. They were specifically used for "loud and clean" with very low distortion.

 

Yes there is hype and marketing involved with amps, just like cars and everything else advertised out there. I also concede almost nobody cranks their system full tilt all the time either. So explain to me how my JL HD900/5 works without detriment to my car using the linked specs.

HD900/5 - Car Audio - Amplifiers - HD - JL Audio

frodoz Stereo Upgrade | PriusChat

 

Nothing in that "spec" shows what the max. power DRAIN actually is.
And like you said, a one thousand watt amp doesn't draw much when the volume control is set on "1".

 

k

You are absolutely right. I have repaired 100watt amps with 1.5 amp fuses on the input. Current draw that comes from a source is just what it takes for the power supply section which is completely separate from the audio section as far as the signal goes. The power supply provides all the bias voltages for the silicon stuff (op amps, transistors, etc). The comment below yours is also correct, you can't get out more than you can put in.

There are lots of conversions and feedback loops sucking up heat also. In a vacuum tube design you have to couple and match a high impedance output (high voltage and low current) to a low impedance speaker (low voltage and high current) through an output transformer. Since a transistor or op amp is a high impedance in with a low impedance out it isn't needed. You can just use a capacitor to couple it and block any DC at the same time. With modern solid state amps, by the time the signal gets processed by all the NFB (negative feedback) alone I'm surprised there's enough of an original left at the output.

An old saying from an audio engineer I know who used to work for the BBC. "everything comes from the first few watts, the rest are just along for the ride and to wear out speaker cones".

 

Hello stratman
Could we speak offline about a tube amp I'm trying to have installed in my 2007 Prius ? Thanks mike