Your right with the 120v stuff but you got to remember that ohms law is constant, and all cars run on 12v ( actually closer to 14.4 with a alternator ) so when you only have 1/10th the voltage you need 10x the amperage. Most car amplifiers are classified as high amperage setups....

 

I read from someone else in here that the stock alternator is 75 amps. If I did the math correctly 1200 watts / 75% /14.4V = 111.11 amps to run at full power. If you were pushing heavy bass for long periods of time using 40% of that total you are still pulling 44.4 amps which I imagine would suck some major juice from the battery at idle. What you need to do is drive your car at 4K rpms and above all the time to keep that alternator spinning I'm sure at idle it's not putting out anywhere near 75 amps. They make caps that have amp meters built into them, they are the bigger 5 farad and above deals. You can get a Kole 20 farad cap on ebay for 99 bux and it will tell you right on it how much current you are pulling. I will probably get one just for that reason, I don't need more then 1 farad but for 99 bux wtf not right?

 

I've gone through this a few times I'll go through it again but more simplified.

-Music is a dynamic load with 10-25% duty cycle depending on the type of music.

- To gain 3 Decibels of sound you must Double the power.

- 3 decibels is what it takes for the human ear to clearly perceive a sound as being louder.

- 10 decibels is what we perceive as "twice as loud"

- a 1200Wrms class D amp is on average 80% efficient.

- A Class a/b amp (speakers 4ch, 2ch) is around 60-65% efficient

so if we have a 1200 watt class D mono amp and a 4x75Wrms Class a/b amp and we're listening to music at maximum potential power it will be pulling.

1200/13.8/4X1.2=26 amps of draw. MAXIMUM with music.

4x75=300
300/13.8/4X1.4=7.6amps

so 33.6amps draw with some heavy music(Metal, rediculously bassy rap.)
Less with more dynamic music.

Now make that half as loud (not half max volume on the knob, but have as loud audibly) and it's 10X less draw. so about 4amps if it wre a constant load. Plus each amplifier pulls an extra 1-3 amps for it's circuitry and whatnot. so about 8 amps. roughly with more than enough power to damage your hearing.

This figure comes as wha it would be if it wrre a constant uninterrupted load. However music is Dynamic and you get alot of peaks and valleys. So current draw a half power can shoot over 60 amps momentarily at the peak of a bass hit or a good guitar solo.
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Now getting into advanced stuff here which is the most common problem.

People drive their amps nto heavy distortion all the time. Why. Improperly set gains, or more commonly not enough signal voltage and peoples love to use the head units EQ at +6 bass +6 Treble.

Most amps do alot better with a higher voltage input from the head unit. (4Vrms+) a head uit only puts out that 4Vrms with a CD and with the volume knob at full minus one or 2 clicks.

With Most japanese head units like Clarion, Pioneer and Eclipse than means alot of knob turning tog et them to 60. People don't like doing that, they like it really loud at 17-25 or so. At that setting the hed unit isn't even sending 1 volt down the RCA's so gains on the amps are cranked.

what this causes is "clipping" either overzelous use of the EQ or badly set gains will cause "clipped" waves. Also maxing the amplifier past it's potential will do this but that is FAR more rare that distorted signals.

When a signal is "clipped" the sound wav does not appear nice and round, it gets very square at the peaks. This causes a huge loss in dynamics that I spoke of earlier. So distorted music can actually be a 50-80% load even if the amp isn't making full power. It's forced to hold it's peak loads for alot longer. This bth hurts your ears and greatly increaes the chance to damage your speakers.

That's enough rambling for now

 

Injundon: What is your preferred technique for setting gains by ear (ie without a bunch of fancy equipment?)

 

depends on the person. With MP3's being ripped at different reference levels it's gotten trucky o find the hapy median. Since most FM tuners, and aux inputs only give off 2.2V and 4V with a CD it's wonky. If it's a hardcore audiophine we break out the fancy stuff. if it's the average joe who uses their ipod alot or sat radio and MP3's just a cheapo DB meter to balance subs and speakers and set by ear.

 

I have the Pioneer Premier DEH-P980BT with the 5V preouts. What I want to know is, if I set my kicker amp to 5V (it goes to 8V) is that all I need to do to ensure that the pioneer doesn't send a clipped signal to the amp, and the amp wont sent a clipped signal to the speakers? I have the advantage of having an oscilliscope (sp?) handy that I can use to measure the sine wave at high volume but I'd really rather not have to break that out unless you recommend it. I had some Kicker 700 watt RMS amps before and even at max gain they did not clip at high volume. It was quite impressive really. My main concern though is the deck sending a clipped signal to the amp at this point. My friend says that past 3/4 volume a lot of decks will start sending clipped signals which aint cool with me!

 

ok... i would send your alt to ohio generator (ohiogen.com) they will put more windings in it to increase your amps. i have a 200 amp alt. the only bad thing is that you cant drive without an alt cause you have to send yours in. a battery cap would also help. and probably a couple batteries. if you mount the battery in a box and the cables are ran properly then you shouldnt have a problem. the 0 gauge wire is good. run it in place of ALL your power wires. to alt, starter, cap, amps, and fuse blocks. otherwise the wires will get hot and fry. also ground wires. what good is a power wire if it doesnt have the same gound. the old ground wire could be added resistance.

 

"10 decibels is what we perceive as "twice as loud"
- a 1200Wrms class D amp is on average 80% efficient.
- A Class a/b amp (speakers 4ch, 2ch) is around 60-65% efficient
so if we have a 1200 watt class D mono amp and a 4x75Wrms Class a/b amp and we're listening to music at maximum potential power it will be pulling.
1200/13.8/4X1.2=26 amps of draw. MAXIMUM with music.
4x75=300
300/13.8/4X1.4=7.6amps
so 33.6amps draw with some heavy music(Metal, rediculously bassy rap.)
Less with more dynamic music."

Seems like some people read a lot more than actually execute building systems.
Jiggaman, Use an oscilloscope if it's available.
I can't remember if Ohio can use the existing case or if they build a new one from scratch. I do now that the car's computer COMPLETELY limits the alternators output to help Honda eek out their EPA mileage ratings. The alternator they built for me is 160amps but at about 3,000 RPMS, I believe it tops out at 100amps. The stock alternator is something like 30 amps. Honda is notorious for wimpy alternator applications. Because this added electrical work load starts to hamper gas mileage.

Add grounds under the hood all over the place with at least 4 ga wire. Every which way you can think of.

You can isolate two batteries utilizing a Stinger 200 amp relay - SR200.
Stinger Electronics :: Where It's Loud

Use a larger second battery in the back of the car, not under a seat.
The alternator is the only thing charging the batteries. If you have a heavy draw and only the stock alternator, once the batteries are low, they won't fill up on their own unless you top them off with a battery charger. Next day, it'll happen again. The extra batteries give you reserve capacity or playing time for lack of a better term.

Cadence amplifiers as well as most amplifiers aren't even close to the efficiency ratings given in this thread. Any manufacturer can rate just their power supply in the amplifier, but by the time it hits the terminals, forget it. Plan for the worse. It's true about music being dynamic and your amp draw not being as constant, but it's a hell of a lot more than what was stated. Keep in mind that Fluke meters that measure voltage are typically measuring average peaks, not dynamic dips which is something to keep in mind. Dynamic dips typically are 1.5 volt lower. Example: If you measure 13.8v, it's can easily be 12.3 when your pounding.

 

Been installing and done many tests over the years, the above info is all pretty accurate. The overdraws that really crap out the amps efficiencies are 80% of the time caused by a clipped signal.

For Jiggaman setting the amp gain at 5V will never get your syste to maximum potential volume. It will only do it with a CD receorded at 0DB reference, As soon you thrown in an MP3 disc your down to 2.2Volts. same with radio or the aux input. Where I work we have most of the tech manuals for Pioneer and Alpine with all the little specs they don't provide you in the pamphlet you get with the head unit.

Best way to tune is with an Oscilloscope and an RTA but that's ony great if all you listen to is CD's. My beetle is tuned entirely for use of the IASCA and USACi CD's and whn I listen to other CD's it's usually way to quiet same with radio and I'm running 160Wrms per side and over 600 to the sub. With my gains set how they are I'm getting maybe 20% of that with most CD's or sat radio. So I cheated a little and used my DQT to u everything 6DB's to sort of help out with it. (I love having 8 EQ presets)

 

Injundon, your mecp certified??? where did you go to school or did you just sign up for the test and take it?? my brother went to mobile dynamics in az. he said it was cool.

 

I went to mobile dynamics in Toronto in 2001. my MECP certification is installer first class but expired last year or 2 years ago and I haven't re-taken the test. Where I live in the Montreal area they have their own required certification and don't recognize the MECP becuase they can't collect dues.. So I am currently just a CPA certified Tecnicien d'installaions 12v mobile.

 

Both happon to me

 

bump up an old thread. i was wondering at about how many wrms one has to push before any electrical components have to be changed/ added? ie, battery, wiring, alt etc.

im planning to run 2 components with a total of 450wrms. BUT then im thinking of putting in 2 x 600wrms subs with a total of 1650wrms.

anyone help me here?

 

I have near 2000watts RMS (1500w class D, 400w a/b) but as someone has already stated music is dynamic so the current draw will be up and down as the music plays. I have upgraded all my wiring under the hood to 0AWG including a 0AWG from the alternator to the battery and with a 0AWG ground to the block of the motor and one to the sheet metal of the car. Then 0AWG running all the way to the amps in back, along with a Shuriken BT35 battery under the hood. I have NO dimming issues period, and I feel no one has a need for a second battery unless you are well over 2500W RMS I wouldn't even consider it a good investment unless you will be competing with the car off.

Proper grounding alone can sometimes fix light dimming, but doing the big 3 under the hood definitely helps.

 

Find a local shop and see if they will rewind your alternator. Lots of places near me do it.