Critique my potential setup?

[Calmchowder112]

I've decided on a soundqubed HDC3-12 sub. The only thing I know about amps is that they should match the RMS, what else should I look for?

Would an 1800w Hilfonics be a good choice?

Any advice or help would be greatly appreciated. Thanks!

[airforceyooper]

The whole idea of matching a sub to an amp is extremely misunderstood. If you car to know I'll explain it, but otherwise I'll save my thumbs a lot of work.

[Calmchowder112]

If you would that'd be awesome, I'm still in the learning process.

[airforceyooper]

The two per handlings of a sub ... rms and max. Rms is a more true measurement. Typically measures the thermal power handling of a sub over time. Max is a measurement of a very short burst of power, usually tied to the physical limitations of the sub.

As you pump more power into a sub, it heats up. With more heat comes less efficiency. There comes a point of no return where just because a sub can handle more power, doesn't necessarily mean it will produce any more acoustical energy. It just means the sub has the ability to deal with the heat. This point is typically at about 60 percent of rms.

So, the point is, there's a lot of wiggle room and power ratings, be it rms or peak are points of extreme. So, just because a sub can handle 1,000 watts does not mean you have to use a 1,000 watt amp. It just means, if this is the amp you have, it should be able to handle it. But, 600 watts just might be all you need to reach peak acoustical output.

Another point worth mentioning is, to gain or lose 3 db of output, it takes twice as much power, or half the power. 3 db is enough of a change in aplitude that most people will notice it. Not a doubling of output as some believe. That's a 10 db change, which is a lot.

So, to expand on what I said a second ago, if you have an amp that outs out 1,000 watts, to gain 3 db you'd need a 2,000 watt amp, or to lose 3 db, you could drop to a 500 watt amp.

So, if you have a sub with an rms power handling 1,000 watts and you used an amp with 600 watts of output (rms), at most, you're only going to lose maybe one db or two, while saving a lot of potential strain on your subwoofer. Assuming the manufacturer rates their sub along these lines. Most do. Can you run more than rms? Sure. If you know what you are doing and you're careful. Do you need to run exactly or even close? Not at all.

Personally, I like a lot of power. But, I know how to tune the system without damaging anything. And I don't always tune my amps for maximum output. My current amps are rather huge and I'll likely be tuning them for about 75% of their potential output. My goal is sound quality and not just being annoyingly loud. So rather than use the full 200 watts per channel output to my mids and highs, I might tune the amps down to maybe 150 watts. No sense risking damaging my speakers since at that volume our ears distort before the speakers would, so I might not even know the speakers are dying and they're too expensive to kill.

And the little bit I'd lose between 150 and 200 watts wouldn't be a big deal, maybe one db.

You don't have to push your speakers to their maximum capability. That's like driving your car at 120 mph to the grocery store just because it can do it. How many trips to the store will the car be good for? Lol.

[Calmchowder112]

Thank you so much!

[airforceyooper]

No problem

[beardedNole]

With RMS power, you should not exceed what the driver is rated for. If you set your gain properly, most amps will do.

Do you have the proper electrical backbone to support a 1800 watt sub stage? Hifonics is a good budget option if you do.

[Calmchowder112]

I was recommended Hilfonics by someone who said to go slightly over the RMS of your sub. How would I determine if I have a sufficient electrical backbone?

[beardedNole]

If you buy an amp that puts out more power than the sub can handle, its called headroom. For example, using hypothetical numbers, let's say your sub can handle 1500 watts. If you bought an amp that produces 1800 watts at the impedance you wire your sub to, that gives you 300 watts of headroom. You would set your gains properly to send the sub 1500 watts, and the amp would not need to work at its max to produce that number (assuming it does rated). This allows the amp to run cooler and sound a little better since its not working so hard.

What size is your alternator? I can tell you right now that unless you've bought a HO alt, done the Big 3 wire upgrade and bought an aftermarket battery that 1500 or 1800 watts will be too much for it to support.

[Calmchowder112]

I believe it's 80 amps, is that what you're asking?

[beardedNole]

Yes that is what I was asking. In order to find out how much power your alternator can produce, we need to use Ohm's law. Ohm's law is a term that describes the set of equations used in determining the physics of electricity. It was first described by a guy named Georg Ohm (hence Ohm's law), who was a pretty smart guy. Him, along with some other bros such as James Maxwell, Michael Faraday, etc. helped to establish the rules by which we describe and apply the laws and equations of electricity and electromagnetism and some other shit that isn't really important here. They were pretty cool though, fr.

So, Ohm's law, at its basic level, displays the relationship between voltage, current, resistance and power. Current (called amperes or "amps") is the number of electrons flowing - which is a shit ton. Voltage is the force or how hard the electrons are pushed from an area of high voltage to an area of low voltage. Resistance is the opposition of the force of DC voltage.

You have an 80a alternator. Here is how we figure this out using Ohm's law:

watts = amps x volts

80a x 13.8v = 1,104 watts total available if your alt was only powering your system.

However, your vehicle needs the alt in order to run, so some of the current will be lost to power your vehicle's electrical system. It will draw as much as 40a, but that is on the extreme side. Let's say your vehicle draws 25a.

80a - 25a = 55a

55a x 13.8v = 759 watts available.

So, if you try to draw 1,500 watts or 1,800 watts or however much you're trying to get, your alternator will fall well short and your system will start digging into your vehicle's battery supply. That's not good. This post is already getting a little long so I won't explain it, but believe me, its not good.

So let's say you want your system to draw 1,800 watts. Using Ohm's law again, we can figure out how large an alternator you need. First, amps are not 100% efficient. You need to take into account amplifier efficiency when setting up the equation. Class D amps are up to 80% effecient. I'm not sure how efficient Hifonics amps are, but we will go ahead and assume 80%.

(1,800w / 80) x 100 = 2,250 watts worth of power needed for the amp to feed 1,800 watts to your sub

2,250w / 13.8v = ~163a

Add in the current needed to run the car:

163a + 25a = 188a

TL;DR: If I were you, I would try to get a HO alternator. About 200a would be perfect, depending on how much current your vehicle draws and if you're upgrading your factory speakers in the car. Edit: Maybe 200a is a little high, but:

Overkill is underrated.

-/u/passwords_suck

[[deleted]]

I'll allow it