Help setting gain on amp equation?

Four 4 ohm subs in series is a 1 ohm load... Unless they are dual voice coil.

Voltage is calculated with the resistance that the amp sees. Which in your case is .5 ohm.

Four 4 ohm subs in series is a 1 ohm load... Unless they are dual voice coil.Voltage is calculated with the resistance that the amp sees. Which in your case is .5 ohm.

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Wrong. 4 x 4-ohm *single* voicecoil subs wired in *parallel* will be 1-ohm. 4 x 4ohm *single* voicecoil subs in *series* is 16-ohms.

BUT

The OP's sub is *DUAL* voicecoil. 4-ohms per VC. If he wires all the VCs in parallel he will have .5 ohm load. Let's just assume he has .5 ohms and answer his question.

Since each sub is wired to 2-ohms (2 x 4-ohm VCs in parallel), you are either putting 600 watts RMS into 2 ohms, or putting 2400RMS into .5 ohms.

So sqrt(600 x 2) = 34.64v, OR sqrt(2400 x 0.5) = 34.64v (same answer either way - which is a good thing)

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You could also assume you are putting 300W into each 4-ohm VC and calc sqrt(300 x 4) = 34.64v

****, that was a good explanation. So he's using or needs 34.64 volts? How does that work when I thought the vehicle is pushing like 14? I'm still new to auto electrical so forgive me and OP, sorry for cluttering your thread.

Wrong. 4 x 4-ohm *single* voicecoil subs wired in *parallel* will be 1-ohm. 4 x 4ohm *single* voicecoil subs in *series* is 16-ohms.
BUT

The OP's sub is *DUAL* voicecoil. 4-ohms per VC. If he wires all the VCs in parallel he will have .5 ohm load. Let's just assume he has .5 ohms and answer his question.

Since each sub is wired to 2-ohms (2 x 4-ohm VCs in parallel), you are either putting 600 watts RMS into 2 ohms, or putting 2400RMS into .5 ohms.

So sqrt(600 x 2) = 34.64v, OR sqrt(2400 x 0.5) = 34.64v (same answer either way - which is a good thing)

---

You could also assume you are putting 300W into each 4-ohm VC and calc sqrt(300 x 4) = 34.64v

Click to expand...

****, that was a good explanation. So he's using or needs 34.64 volts? How does that work when I thought the vehicle is pushing like 14? I'm still new to auto electrical so forgive me and OP, sorry for cluttering your thread.

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That's what amplifiers do and why they require so much current. Vehicles make low voltage with high amperage, the amp will convert that into a variable music signal that is higher in voltage usually but lower in amperage. Volts*Amps=Watts. 14v at 100 amps is 1400 watts, and 100v and 14 amps is also 1400 watts. Another reason his voltage is so high is because it is a **** ton of power that will take over 200 amps from the vehicle to produce...

Wrong. 4 x 4-ohm *single* voicecoil subs wired in *parallel* will be 1-ohm. 4 x 4ohm *single* voicecoil subs in *series* is 16-ohms.
BUT

The OP's sub is *DUAL* voicecoil. 4-ohms per VC. If he wires all the VCs in parallel he will have .5 ohm load. Let's just assume he has .5 ohms and answer his question.

Since each sub is wired to 2-ohms (2 x 4-ohm VCs in parallel), you are either putting 600 watts RMS into 2 ohms, or putting 2400RMS into .5 ohms.

So sqrt(600 x 2) = 34.64v, OR sqrt(2400 x 0.5) = 34.64v (same answer either way - which is a good thing)

---

You could also assume you are putting 300W into each 4-ohm VC and calc sqrt(300 x 4) = 34.64v

Click to expand...

Good explanation. I always get those two mixed up.

Ok thanks. So is that figure the voltage the amp is producing and not the alternator?

That's what amplifiers do and why they require so much current. Vehicles make low voltage with high amperage, the amp will convert that into a variable music signal that is higher in voltage usually but lower in amperage. Volts*Amps=Watts. 14v at 100 amps is 1400 watts, and 100v and 14 amps is also 1400 watts. Another reason his voltage is so high is because it is a **** ton of power that will take over 200 amps from the vehicle to produce...


Good explanation. I always get those two mixed up.

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Ok thanks. So is that figure the voltage the amp is producing and not the alternator?

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Yes that is the what the amplifier is producing. But indirectly it's also what the alternator is producing since it's fueling the amplifier.

Whoops

You're the man thanks. Now, will that voltage hurt your alternator or is the amps being drawn that hurts your alternator?

Yes that is the what the amplifier is producing. But indirectly it's also what the alternator is producing since it's fueling the amplifier.

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You're the man thanks. Now, will that voltage hurt your alternator or is the amps being drawn that hurts your alternator?

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Not spontaneously, but it will shorten it's lifespan and it's hard on the electrical systems in the car. Producing that voltage draws huge current from alternator. They are cause and effect.

I really appreciate your help. I don't like asking all the questions I have or that come up because there are alot of smart *** people on this site that will answer the question and make you feel like a d-bag for asking it. Thanks again.

Not spontaneously, but it will shorten it's lifespan and it's hard on the electrical systems in the car. Producing that voltage draws huge current from alternator. They are cause and effect.

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You guys have the concept *generally* correct, but your terminology is a little off. Don't confuse *voltage* with *power* (watts).

If the amplifier was perfect then it could put convert all the *power* available from the alternator into *power* into the speaker.

Under this simple assumption if you are putting 2400 Watts of power into the speaker, then you are pulling at least 2400 Watts from the alternator.

Since the charging system runs at 12 volts (approximately), your alternator needs to be able to produce 2400w/12v = 200amps (rms)

You will need a high output alternator to produce 200 amps rms at 12v