unregulated car amplifiers

haemphyst wrote: haemphyst wrote: 3dB louder requires twice the power, conversely, half the power will require half the power. What this means is if your PA makes 1000 watts, and your PPI makes 600 watts, that is less than half the power difference, so the PPI will not be noticeably quieter. What the hell was I thinking?? What I meant to say was this: Conversely, 3dB quieter will require half the power. DYohn wrote: KPierson wrote: 37.8 I was going to guess 42. Hitchhiker's Guide to the Galaxy. However... as I said, you cannot answer that with a solid number. First, you DON'T GET WATTS PER VOLT! You get watts per amp. I already said that. Then, I see that you are asking what an amp is? Dude... For one amplifier rated for X watts, you might (AS ONLY AN EXAMPLE) get 12 watts per volt, but on another amplifer, rated for 4 times the output power, you will get 24 watts per volt. Another amplifier, rated the same power as the second example might get 20 watts per volt, based on the topology of the amplifier, i.e. Class A vs. Class A/B vs. Class D. You are asking about, and looking at, it the wrong way. Think about it... No matter WHAT the amplifier's output is rated, the input voltage is ALWAYS 12 volts, right? Which part of the equation must change? The input current, right? Additionally, the current input demands will go up if you put a lower impedance on any given amplifier, right?

Oh, this is GOOD stuff right here!!!!

power = voltage x current current is the same as amps (amperage not the actual amplifier) just like fuses have an amp rating, this is the point at which they blow because of too much current. now with that said, lets say you have an amp that is rated 400 watts at 12 volts. and that amp has 2 20 amp fuses in it. you can take the total fuse rating which is 40 (2x20) and multiply that by your voltage which is 12, remember, power = voltage x current, and you get 480 watts. now you wonder why the amp was only rated at 400 watts. this is because that 480 was made under the assumption that amplifiers are 100% efficient, meaning that every bit of input current is being transformed into raw power. but, this is the real world and nothing is 100% efficient in electronics. energy gets lost to heat and other things that go on inside amplifiers. so lets say that that amplifier is a class D amp which is at the top of its efficiency which is about 85% efficient, meaning only 85% of the input current is being turned into power and 15% is being lost to heat. take that original 480 that we got from our equation and multiply that by 85% and you get............408 watts. but, even then, we are assuming that the amp is being ran at 1 ohm. so you can see that it really depends on the individual system specs.

soundnsecurity wrote: but, even then, we are assuming that the amp is being ran at 1 ohm. so you can see that it really depends on the individual system specs.

Not necessarily... If the amp is rated at 400 watts into 4 ohms, the manufacturer can certainly fuse at 40A. 400 watts out @ 85% efficiency = 480 watts in no matter HOW you slice it, or what load it is attached to. If the amp's internal DC-DC power supply is CAPABLE of driving a 1 ohm load, by providing adequate current to maintain the voltage across such a low impedance, then a respectable manufacturer would provide for such an increase in input current requirements, by beefing the fuse complement. They would just say 400W @ 4 ohms, 750W @ 2 ohms, 1050W @ 1 ohm (or whatever the power output would be...) and fuse accordingly. The fuses would just never be in any danger of blowing while running the 4 ohm load. By your assumption, you are guessing that every manufacturer out there builds every power amplifier to be run at 1 ohm.It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."