Car stereo's

[Markk]

I'm a total noob to this. Hell, I wouldn't even call myself a noob cuz I'm not into this stuff. but lately a friend beens telling me that he wants a 300 watt speaker in his car.

I was wondering, can you really get 300 watts in a car which has a voltage battery of 12 volts? And would you be able to get this wattage in RMS?

Is there some kind of fine print I don't know about?

[MikeS]

1) I can't say for certain without specs, but that's an overrated amplifier. It might put out 300 watts peak at a ridiculously low impedance.

2) Let's assume it actually does what they say it does... 300 watts RMS translates to 20.8 amps (assuming most alternators run at ~14.4V). Many car alternators can handle that with minimal dimming of lights at night. The weakest link is typically the car's electrical wiring, namely grounds. It's too common to see a large power wire coming off the battery to the amp, a large ground from amp to chassis, and the stock ground wires from battery to ground and alternator to ground.

In short, it depends on the car's electrical system. If you experience dimming of the lights, start with upgrading the hots and grounds at the battery and alternator (the alternator ground is typically through the block to the starter then to chassis).

FWIW... I'm running over 600 watts RMS in my truck with an 80 amp alternator and larger than stock underhood electrical wiring. My 600 watt system is small by today's aftermarket standards.

[JacksonMIA]

It's not too uncommon to find cars with 500W (or more) factory stereos, but I think, as Mike said, it's probably overrated. My two amps are rated at a total of about 1200W, but it's probably not using nearly that much power even at peak.

[ArtieToo]

Car stereo has gone crazy, but yes, you can get that kind of power out of a car stereo - but not out of 12 volts. All high power car amps have a built-in switching power supply that converts the 12 to 48 or more. Its like having one of those RV 12-to-120AC adaptors built into the amp.

My own son has a 1000 WRMS amp in his S-10 pickup. Yes, you heard that right. 1000 watts in a space the size of a phone booth. (Against my better wishes.)

[34029324079]

I killed my alternator with just 1x12" sub...if headlights dim, watch out! you can get additional alternators and power equipment to avoid this. I dont recommend subs in general since they screw with my ears...maybe Im too old...to each his own.

[Sludgenutz]

Is there some kind of fine print I don't know about?

Musical instrument amplification gear, and home hifi are generally rated in RMS (root mean square) Watts. This figure is the most conservative (realistic).

An identical amplifier may be given a Peak Power rating, which could be double the RMS rating.

IPP (instantaneous peak power) is a junk rating that could be four times that of an RMS rating. Cheapo car stereo gear manufacturers are the most likely to use this rating system. Of course, lots of these wattage ratings are simply lies, and have no basis in reality.

100 Watts RMS = 200 watts Peak Power = 400 Instantaneous Peak Power. So few devices are actually measured by the end user. Buying well known quality brands will usually insure they are less likely to do shady things with the numbers.

[Markk]

Well, I know about peak to peak and whatnot because I was out for buying a home theatre system but I had no idea what goes on in cars. 1000 watts in one car, sweet mother of mercy.

Are those wattages even used for the driver to listen to the music or is it like a "scare the other gang with you're stereo system" tactic?

[MikeS]

Well, I know about peak to peak and whatnot because I was out for buying a home theatre system but I had no idea what goes on in cars. 1000 watts in one car, sweet mother of mercy.

Are those wattages even used for the driver to listen to the music or is it like a "scare the other gang with you're stereo system" tactic?

hehe... it's not uncommon to see SPL guys with 2000+ wrms per woofer. Take a competition 15" or 18", consider that some run multiple woofers, and you've got the potential for even higher wattage requirements.

In retail car audio wattages are used to "one up" the competition, and most are sorely overrated. Chances are good that if a manufacturer tells you an amp's rating without specifying RMS or peak that the rating given is peak power at the lowest impedance the amp can run at.

Also remember that just because an amplifier can output 300 watts doesn't mean it's going to do it continuously, especially with subwoofers because they tend to require power in short burps.