rockford sub and amp question
 

Looking at getting a sub for the 370, was wondering if the rockford fosgate R500×1D amp would efficiently push one 12" p3d2 sub. Just want to make sure if would power the sub enough before I purchase. Any input is appreciated, thanks!

Impedance of the amp and sub match (2 Ohm) and power ratings (500W amp, 600W sub) are close enough. 500W should be plenty in such a small listening environment. How do you plan on wiring the dual coils of the sub to the mono amp?

Would the p3d2 10" (1000watt) peak, or p2d2 12" (800) peak pair best with this amp?

That shows the coils in series - 4 ohm impedance. I didn't look real close at the specs so you may want to check and see what the amp output is at 4 ohms.

The main parameter is impedance. The impedance of the speaker should match the impedance of the amp. Speaker impedance can be higher, but you lose some volume. If speaker impedance is too low, you run the risk of damaging the amp. In this case, since the amp will handle loads down to 2 ohm, you will be OK.

As long as the speaker is rated for the same or more power as the amp, you are OK. Unless you plan on using a bigger amp later on, no need to buy a speaker with "excess" power handling capabilities. But it doesn't hurt anything either - assuming the speakers have the same efficiency (being from the same line from the same manufacturer, they should be close), they will all put out the same volume per watt.

The amp is 250 watt (rms) @ 4ohm. Do you think that will be okay?

Depends on how much bass you want. My rule of thumb is to get more amp than you think you will need. You can adjust to desired output level.

Okay, thanks for all your replies southark. I really appreciate it. I will look for a more powerful amp then

You're welcome. Keep in mind that it takes 10x the power to double the volume. Eg, if you start with a 100 W amp and want twice the sound, you need to step up to a 1000 W amp. I'm not sure how much bass you want, but 500 W ought to do it in a small car. You'll probably seldom want to use that much on average but it provides some headroom for the "thumps." Of course, if you like it really loud, the sky's the limit.

Ok so it will be safe for the sub to be underpowered a bit?

Underpowering can lead to clipping which is not good for the Amp or the Sub in the long run. That amp is a good selection due to it being Class D and will run cooler and more efficiently than your standard Class A/B amp. Considering the amp is 500w RMS @ 2ohms, you want to provide it with a 2ohm load to take full advantage of it's power output. I would use a 4ohm DVC sub(P3D4-12) and wire it for 2 ohms(unless you have purchased the sub already). Another way to maximize bass output is "corning loading". Placing the sub as far back in the Hatch area and in the corner will provide more output at a given frequency depending on the resonant freq of the sub/enclosure and vehicle acoustics. All in all, 500w RMS is plenty in a 370z.

http://img.techpowerup.org/140910/Capture084.jpg

^Roadster, I talked to JL audio AND RF about clipping because I bought the amp the OP is talking about to drive the shallow mount JL 13" and BOTH JL and RF said clipping is BS, it doesn't hurt the amp or sub, and both said peak output is complete BS too.

The one I got came with a paper saying that it was actually rated at 598Watts and peaked at... 2400 watts or something

Not exactly true, but in a roundabout way........ Underpowering will never harm your speaker. The harm comes when people increase the amplifier gains to get louder, and put the amp into clipping. When gains are set properly, clipping is not an issue, and any amplifier will suffice.

^This. I forgot what exactly they both said, and they said this exactly.

And most people set the gain way too high because it sounds louder.


RF sets the gain where it should be.

And that, My friend is complete snake oil. A clipping amp will most definitely cause mechanical failure of your subwoofer, just at an undetermined pace. They simply gave you a sales pitch.

There are 2 camps when it comes to clipping, so educate yourself and believe what you want. Fact is clipping creates distortion and I'm sure we all agree that we want clean output. Making sure that amp see's a 2ohm load is paramount in setting up the properly optimized system. Why pay for a 598w RMS amp if you only try to get 299w RMS out of it?

I know, I have done my research, and I'm not trying to be an asshole about it. Just stating what I was told by JL and RF.

And read what the other guy posted about the gain settings.

:iagree: to an extent. But As Southark stated earlier in the thread....Always a smart Idea to go big on amplifier power, that you can pull back on, which lessens the chance of clipping, and speaker destruction. As opposed to trying to get BIG off a small amp.
Steve Meade designs has an awesome piece out there called the DD-1.
It is used to set your amplifier gains correctly to match your head unit. It also detects distortion, which you can use to see exactly what volume setting your head unit starts to distort at. you hook this to your head unit, and it sees distortion at, say 35 out of 40 clicks, you KNOW to never turn that knob past 35. Simple.
It is 10 times easier to use than an o-scope, and 10 times less in price.
I recommend them to anyone who is serious about their systems. $150 for piece of mind, and a truly optimized setup.

Clipping is when you reach the output limit of the amp and it starts putting out DC (the top of the waveform is clipped off or flat). In addition to sounding bad, this can cause overheating of the driver coils, which can quickly destroy the small coils of a tweeter or mid-range (drivers aren't designed to handle DC). Since woofers typically have much more massive coils, overheating is not as big of a problem but clipping should still be avoided. As others have mentioned, if you set up the system properly, clipping will be minimized.

I ended up going with the p3d4 10, that way I could use the amps full potential. Thanks everyone for the input

You made a great choice. Just make sure you use the correct enclosure for the sub to capture all it's performance.:tup:

What are the preferred enclosures now days? Back in the day, a air tight (un-ported) enclosure as big as you could get was best. Now, after looking at rockfords website, it looks like ported is the preferred way to go.

I know both work, and maybe ported is better with some frequencies, but they need to be "tuned" last I remember.

As a rule-of-thumb, a ported enclosure will be more efficient and give better low-end response. But the enclosure has to be designed/built properly.

A Q&D web search turned up this: Subwoofer Design Theories

This is true. And building a ported enclosure yourself is a somewhat daunting task for a first timer for sure. there are many variables that will have an effect on your speakers performance and/or introduce unwanted noises.
Sealed boxes are more forgiving to the builder, and will play a flatter frequency response throughout its range, but lower frequencies may suffer. processing will help with that problem to an extent, and honestly, the untrained ear would never notice.
Remember that every sub will have its own design parameters, (box volume for sealed, ported ) and they must be followed for optimum performance. Some subs will only perform in one or the other.