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Old 09-04-2012, 08:02 PM
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Please help with subs!!!

This weekend I'll be picking up two Rockford Fosgate P1S4 12" subs (no enclosure) and a Rockford Fosgate amp (I'll get model number tomorrow). I need the box to be shorter than 15.5". I want to go with a ported box. What will the interior volume need to be? Do you recommend building or buying a box?

Thanks in advance

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Old 09-04-2012, 09:36 PM   #2
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they are listed at 1.4 cubic inches each so you will need a 2.8 cubic in enclosure.

i suggest building your enclosure, go on caraudio.com's forum they have free box plans, find what fits best and go build an enclosure. the last one i made was 3.4 cubic feet enclosure out of 3/4" mdf and only took one 8x10 sheet of mdf. it isnt hard to do you just need the right tools to do the job.

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Old 09-05-2012, 08:25 AM
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So the amp is a Rockford Fosgate P300-1. Will this be enough to power both subs? If yes, how should I wire them?
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Old 09-05-2012, 01:00 PM   #4
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It's sufficient. Wire them in parallel:



Subs are a 4 ohm, 2 in parallel produce a 2 ohm load, amp is rated for 300 watts peak at 2 ohm, so you're all good.

As for a box, always build your own. Cheaper, easy to do, and if you're good with tools, you can make use of odd contours and such.
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Old 09-05-2012, 04:47 PM   #5
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all you need to build the enclosure is caulking, circular saw, power drill, sawz-all and a straight edge. depending on the design it should take about an hour to build, just take your time, measure twice and cut once.
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Old 09-05-2012, 05:37 PM
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Quote:
Originally Posted by Bronek
It's sufficient. Wire them in parallel:

Subs are a 4 ohm, 2 in parallel produce a 2 ohm load, amp is rated for 300 watts peak at 2 ohm, so you're all good.

As for a box, always build your own. Cheaper, easy to do, and if you're good with tools, you can make use of odd contours and such.
Sweet. Thanks for the diagram

Do I need to buy a special harness for my 730n nav?

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all you need to build the enclosure is caulking, circular saw, power drill, sawz-all and a straight edge. depending on the design it should take about an hour to build, just take your time, measure twice and cut once.
I got all those and I live by that motto
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Old 09-05-2012, 05:38 PM   #7
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And a some screws
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Old 09-05-2012, 05:49 PM   #8
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Quote:
Originally Posted by IP0VV3R View Post
Do I need to buy a special harness for my 730n nav?
What was your stock system? If your stock system had a sub, tap that for signal. If not, then you have two options: 1) Get an adapter and wire the whole setup that way. 2) Tap the rears for the signal near the amp by splicing into the line. This will remove any HU sub-control, so all your sub settings will need to be controlled from the amp.
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Old 09-05-2012, 05:56 PM
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Quote:
Originally Posted by Bronek

What was your stock system? If your stock system had a sub, tap that for signal. If not, then you have two options: 1) Get an adapter and wire the whole setup that way. 2) Tap the rears for the signal near the amp by splicing into the line. This will remove any HU sub-control, so all your sub settings will need to be controlled from the amp.
I have the stock Infinity system with sub
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Old 09-09-2012, 03:40 PM
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I just bought the subs, amp, and capacitor. My friend is telling me that the 300 watt amp and 1 farad capacitor won't power the subs enough. They have a rms of 150 watts. Is he right?
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Old 09-09-2012, 05:00 PM   #11
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capacitors are not needed, do"the big three", upgrade the battery ground cables with 0/1 gauge cables and change the alt to batt cable to a 0/1 gauge wire, it costs about $20-$30 to do and will have a better effect than a 2 farad cap. i am pushing over 2000watts just to my sub alone and "the big three" stopped all dimming of the lights and drain on the battery.
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Old 09-10-2012, 03:59 PM   #12
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Quote:
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I just bought the subs, amp, and capacitor. My friend is telling me that the 300 watt amp and 1 farad capacitor won't power the subs enough. They have a rms of 150 watts. Is he right?
The subs have an RMS of 150w. 150x2 = 300.
The amp has an RMS rating of 300w at 2ohm, which is what you are wiring them to.
300w = 300w

You're all good. You can't hurt a sub by underpowering it - that's the same as turning the volume down. You can hurt a sub by overpowering it.
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Old 09-12-2012, 06:35 PM   #13
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The subs have an RMS of 150w. 150x2 = 300.
The amp has an RMS rating of 300w at 2ohm, which is what you are wiring them to.
300w = 300w

You're all good. You can't hurt a sub by underpowering it - that's the same as turning the volume down. You can hurt a sub by overpowering it.
Actually, you can blow a sub with too little or too much power, even the exact right power could blow a sub. It's all in the distortion or clipped signal. Distortion can be introduced into any system with any amount of power, it happens when the signal source is maxed out or close to maxed; any stereo will put out a clipped signal at the higher volume levels. Amplifiers have gain settings for this reason... if you need to turn the source's volume all the way up to get the sound level you want, than the amp's gain should be turned up to enable you to achieve the same sound level at a lower source volume.

Many would argue that underpowering a speaker is actually worse than overpowering - a clipped signal is more likely in a lower power setup because the user will often compensate for the lower power with volume, thus introducing distortion. This is why you are less likely to blow a speaker at it's rated power with amp gains set properly; you can achieve higher sound levels with less volume from your signal source. I have my stereo and amps set up so that I never need to turn the volume past 25, even though the radio goes to 35. It's plenty loud at 25, and most would say that no one would need it to be louder; this means I never allow a clipped signal to be fed into my amps.

To get back on topic, yes, the amp you have will work well for the subs you have.
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Old 09-12-2012, 07:23 PM
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My friend offered me his pioneer gm-5500t. It's 820 watts. Too much? If I buy it off of him for $70-80, I could actually make money buy selling the amp I currently have
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Old 09-12-2012, 11:02 PM   #15
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Quote:
Originally Posted by eboven View Post
Actually, you can blow a sub with too little or too much power, even the exact right power could blow a sub. It's all in the distortion or clipped signal. Distortion can be introduced into any system with any amount of power, it happens when the signal source is maxed out or close to maxed; any stereo will put out a clipped signal at the higher volume levels. Amplifiers have gain settings for this reason... if you need to turn the source's volume all the way up to get the sound level you want, than the amp's gain should be turned up to enable you to achieve the same sound level at a lower source volume.

Many would argue that underpowering a speaker is actually worse than overpowering - a clipped signal is more likely in a lower power setup because the user will often compensate for the lower power with volume, thus introducing distortion. This is why you are less likely to blow a speaker at it's rated power with amp gains set properly; you can achieve higher sound levels with less volume from your signal source. I have my stereo and amps set up so that I never need to turn the volume past 25, even though the radio goes to 35. It's plenty loud at 25, and most would say that no one would need it to be louder; this means I never allow a clipped signal to be fed into my amps.

To get back on topic, yes, the amp you have will work well for the subs you have.
If you're cranking your speakers and they're not loud enough for you, you need better or more speakers and a better or more amps. Yes, clipping occurs, but that's only when people are pushing the system beyond its true maximum handling power.

I'd skip Pioneer everything.
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Old 09-13-2012, 09:35 AM   #16
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If you're cranking your speakers and they're not loud enough for you, you need better or more speakers and a better or more amps. Yes, clipping occurs, but that's only when people are pushing the system beyond its true maximum handling power.

I'd skip Pioneer everything.

I am really not sure what you are trying to get at here...

I am a Mobile Electronics Certified Professional at the Advanced level... I have studied autosound and audio signal, etc. as part of my job for over 7 years. What you are saying is simply not true.

Simply put - wattage is NOT what blows speakers, distorted signals blow speakers. You can have a distorted signal at ANY power range with ANY speaker or ANY amp. If you turn your radio up to 30 and it clips and distorts, simply adding better speakers and amps WILL NOT change the fact that your radio is clipping at 30. If you give your speakers 30 watts RMS when they are meant to handle 80, the lack of proper power is not what blows them, it's the fact that you turned your radio to 30 and gave them a distorted signal. On the other hand, if you give your 80 watt RMS rated speakers 150 watts RMS, you will get distortion because the speaker cannot handle that amount of power. The distortion isn't coming from the source in this case, but from the actual speaker trying to "handle" the extra wattage. This will also blow your speaker.
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Old 09-14-2012, 12:34 AM   #17
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Your argument went from being underpowering will blow them to bad signal will blow them... Bad signal, yes, of course that will. You're right that the distortion will cause them to damage and break. However, underpowering will NEVER blow a speaker or sub independently. Ever. Ever ever ever. Won't happen. You run a clear signal to any speaker or sub, and give it half the wattage it is rated for, that speaker or sub is not going to blow. Add another factor like the aforementioned distortion, and it's a whole new ball game.
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Old 09-14-2012, 09:20 AM   #18
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This is turning into a silly argument - I was simply correcting the false information you put out there that "you can't hurt a sub by underpowering it"

Obviously, it is not the lack of power that blows the sub in a underpowered situation, so I guess you were technically right, though the way you said it was very misleading. How many people out there would have taken your advice that they can't damage a sub if they underpower it? How many of those people would know that the actual power rating is somewhat irrelevant, and that distortion is actually more likely when in an underpowered situation? If you were a salesman at a car audio shop telling your customers what you told the forums, you would not keep your job for very long. You would have countless customers who return their underpowered subs and speakers that you told them would be fine.

My argument is simple, and I was never contradicting myself: If you underpower a speaker, you are more likely to introduce distortion into your system, and therefore blow your speaker. Distortion is also likely in an overpowered or even perfectly powered situation. As I said in my above post, the wattage DOES NOT MATTER. You saying that underpowering a speaker can't hurt it is not true though, though the wattage itself isn't what technically blew the speaker, but the lack of wattage is what drives someone to crank the volume and allow distortion into the system.

This makes your argument that wattage doesn't blow a speaker irrelevant, because wattage and distortion go hand in hand. You and I may know that in an underpowered situation distortion is more likely, but the average reader out there does not.

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