Will my voltage be ok?

[TheUnderFighter 10+ year member]

800w will push the subs fine, but 1200 would be louder, yea.

I have OEM 70a alt, and oem battery, and a big 3. I run 1200w on the sub stage, and 300w on my front-stage. I experience very little voltage drop, but that is only my experience. Even pushing it hard, with headlights on and the heater, I may drop to 13.4. If you're going below 13 I'd be wary, and obviously the less drop the better. But usually cruising around during the day, even with the volume cranked I'll sit at about 13.9v. So you're using less than me, with a much better electrical. I'd say give it a shot and see how low you drop, if at all. You could be just fine.

 

[Moble Enclosurs 10+ year member]

Precisely. You will only get about 60-70 efficiency from the amplifier in most cases on musical power. You will see the 1200 on your peaks. Just because your rms says 1200 on the amp, does not mean it will always push 1200 continuously. Voltage varies upon frequency as well as current and resistance, so the average will be around 800 watts, yes. This will be a more accurate figure to use. Technically, you can get it to 1200 easy on a 90amp or 100 amp alt. But the amp is not the only thing using the alternator seperate from charging, such as lights, ac, etc. You will get about 60% of the alternator for aftermarket use. And your looking at a 54A peak from this alt, if 90A alt is used, as an average. That can supply up to over 2kW of power ideally. Because the amplifier will not be 100% efficient, is why you will not always get the entire power rating of it. And even the manufacturer rating may be off. So, the efficiency of the amplifier is commonly reduced to 70% efficiency as well.

So, 60% efficiency from the alternator, and 70% from the amplifier will give you an idea of how much it will pull. In this case, 60% of 90 is 54A. And say resistance is solid at 1ohm. The alt will supply about 2900watts@1ohm. Not everything will be on the same resistance level as the subwoofer amplifier, so this may be best case scenerio. Now, the amp states 1200@1. That is best case as well, so you can figure for 70% efficiency which is at 840watts safely. So, your amp asks for 840watts, and the alt can supply enough for the amp to operate efficiently. The subamp will ask for a draw of about 29A and you can supply it with 54A. Now, if this were all at 1ohm, that would be the case. This may vary upon the load, but that is why percentages are used, to try to compensate for draw.

Now, regarding 800watts not being enough, that can be based on efficiency as well as sensitivity of the drivers, since we are now dealing with dB levels as an output figure for the word "enough". You will be surprised at what low power can achieve if the sensitivity is good on the drivers as well as high efficiency of the enclosure. But, since this is a relative field of output, it can be very possible that it may not be enough as well. Like ram said, best to just test it all out. All we can do is take partially accurate guesses at this stage. But should be acceptable answers given here.

 

[BNolan12 10+ year member]

800w will push the subs fine, but 1200 would be louder, yea.I have OEM 70a alt, and oem battery, and a big 3. I run 1200w on the sub stage, and 300w on my front-stage. I experience very little voltage drop, but that is only my experience. Even pushing it hard, with headlights on and the heater, I may drop to 13.4. If you're going below 13 I'd be wary, and obviously the less drop the better. But usually cruising around during the day, even with the volume cranked I'll sit at about 13.9v. So you're using less than me, with a much better electrical. I'd say give it a shot and see how low you drop, if at all. You could be just fine.

Ok thanks. I will see at first how i am and if need be i will throw a nicer battery under the hood.