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Old 05-07-2013, 07:57 PM   #1
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What else with this amp?

I want to run this amp in line behind the stock Alpine amp to an aftermarket 8" sub.

Amazon.com: Rockford Fosgate PBR300X2 Punch 300 Watt 2-Ch Boosted Rail Amplifier: Electronics

Is there anything else that I need to pick up for the install?

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Old 05-07-2013, 08:27 PM   #2
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Power cable. 300W / 12V = 25A over no more than 10 feet means you need minimum 10awg cable.

Inline fuse and holder rated to the same gauge as your power cable.

Ground cable. Same rating as your power cable, short as possible and no more than three feet.

Be careful though, not too many 8" subs will handle as much power as that amp is capable of giving you.

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Old 05-07-2013, 08:31 PM   #3
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The sub I have says 350w max, 175 RMS. Is that too much amp? If so, is there a better option for something similar? (small, usable in line after the alpine unit)
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Old 05-07-2013, 08:35 PM   #4
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Old 05-07-2013, 08:59 PM   #5
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Assuming your sub is a single voice 4ohm unit, the first amp is more powerful than you need if you run it off the two channels bridged and it's underpowered if you run it off a single channel. It probably isn't an ideal choice.

The second one is just underpowered, and I'd prefer your first option - given the choice I would always rather have an overpowered amp for the speakers, you'll hear when you're overcooking it and you can bring it back within the safe zone.

Post the details of your sub and we can probably find you a more appropriate amp. Matching outputs is always best.
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Old 05-07-2013, 09:11 PM   #6
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Its a dual voice coil. It says 2x4 ohm, not sure what that means.
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Old 05-07-2013, 11:33 PM   #7
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Ah, that changes things slightly. Dual Voice Coil (DVC) means that you have a lot more wiring options. You can wire a 4ohm DVC sub to two 4ohm channels, or you can wire both coils in parallel to present a 2ohm load to a single channel. Essentially, with your sub both amps are significantly overpowered, but they're good amps. I'd be very happy taking the second one you list and using that to power your sub - it pushes 300W RMS @2ohms.

Wire it like this:

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Old 05-08-2013, 12:41 AM   #8
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Awesome, thanks! BTW, why couldn't you use the 4ch version of this amp in line behind the alpine to power the speakers? Here's how I saw that it was recommended to wire the amp to the sub:
"To hook up the amp in line behind the stock amp, you will need to use the 2 sub coil signals from the Brown wire clip into the high level input on the amp, and run the bridged amp signal back through 1 of the coil wires to the sub. The amp can be mounted to the existing amp case and mounted back up in the existing mount."

Sound right?

Could something similar not be done with the 4 channel version to the speakers?
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Old 05-08-2013, 09:06 AM   #9
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Quote:
Originally Posted by 01svtL View Post
Awesome, thanks! BTW, why couldn't you use the 4ch version of this amp in line behind the alpine to power the speakers? Here's how I saw that it was recommended to wire the amp to the sub:
"To hook up the amp in line behind the stock amp, you will need to use the 2 sub coil signals from the Brown wire clip into the high level input on the amp, and run the bridged amp signal back through 1 of the coil wires to the sub. The amp can be mounted to the existing amp case and mounted back up in the existing mount."

Sound right?

Could something similar not be done with the 4 channel version to the speakers?
I'm not sure I understand what you mean here. To drive your sub, your wiring options are:

- wire a separate 4 ohm channel to each coil (so two amp channels required)
- wire a single 2 ohm channel in parallel as per the diagram above
- bridge a pair of 4 ohm channels and wire your coils in series (8 ohm impedance)
- bridge a pair of 4 ohm channels and wire you coils in parallel (2 ohm impedance)

The multi-channel amp you listed (PBR300X2) doesn't support 2 ohms bridged, so the last option isn't viable unless you like the smell of stuff burning. If you want to go with the first amp, it will work nicely with the first wiring config; otherwise, look for a mono amp that will give you circa 200W RMS @ 2 ohms and go with the second option.
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Old 05-08-2013, 06:02 PM   #10
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OK you have me confused. The first amp I posted is the 2 channel. The second one was the mono-block.
The better choice is the monoblock wired the way that picture shows, yes?
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Old 05-08-2013, 06:51 PM   #11
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Quote:
Originally Posted by 01svtL View Post
OK you have me confused. The first amp I posted is the 2 channel. The second one was the mono-block.
The better choice is the monoblock wired the way that picture shows, yes?
Well, not really. It will work OK, but when I went back and looked at the spec again this morning I noticed that I was wrong - the monoblock puts out 150W RMS @ 2 ohms. I prefer to have an amp slightly overpower a speaker than the other way round - either way round you'll knacker the speaker if you run it at full chat for too long, but if you're overpowering the amp then you'll wreck that as well.

The two channel amp with a channel per coil will work fine, alternatively find yourself a nice deal on a mono amp that will push 200W+ RMS and 500W+ peak @ 2ohms and wire in parallel as per the previous post.
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Old 05-08-2013, 06:53 PM   #12
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Quote:
Originally Posted by 01svtL View Post
OK you have me confused. The first amp I posted is the 2 channel. The second one was the mono-block.
The better choice is the monoblock wired the way that picture shows, yes?
Well, not really. It will work OK, but when I went back and looked at the spec again this morning I noticed that I was wrong (blame hockey playoffs making me drink) - the monoblock puts out 150W RMS @ 2 ohms. I prefer to have an amp slightly overpower a speaker than the other way round - either way round you'll knacker the speaker if you run it at full chat for too long, but if you're overpowering the amp then you'll wreck that as well.

The two channel amp with a channel per coil will work fine, alternatively find yourself a nice deal on a mono amp that will push 200W+ RMS and 500W+ peak @ 2ohms and wire in parallel as per the previous post.

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