4 Rocksford Fosgate Subwoofers and Amp Problems!

kade12

Junior Member
Feb 22, 2019
19
0
11
First off, I just want to tell you what I have. I drive a 2004 Chevy Silverado 2500 HD. I have (4) Rocksford Fosgate P35 Punch compacted 4ohm 300W/ 600W (RMS/PEAK) subwoofers. I have these bridged and running to a Kicker 1200W 2 channel Class D Mono Amplifier. (Handles up to 600W RMS (continuous) @ 4 ohms or 1200W RMS @ 2 ohms). Also I have a Dual XPR540 4 channel amp running the kicker door speakers.

The Problem:
Everything sounds good and plays well at low volumes. This means barely anything from the subwoofers. Immediately when you turn volume up including bass, the bass will cut out or just turn the amp into protective mode. I used a multimeter to test the amp and it seems like every time the bass will hit hard it is dropping my voltage from 13v- 10-11v. I have done almost everything I have researched. The grounds are great! They are screwed to the frame with multiple self tapping screws and very snug. All connections are tight and nothing else seems wrong. Like I mentioned, the subs will bump at low volumes only. Now I have also installed a dual battery, yellow top deep cycle Optima battery and a bigger alternator with a smaller belt for more power. Those both did absolutely nothing. Another weird occurrence is when this bass hits hard, it will shut amp off, my odometer and instrument cluster, and the JVC head unit. But the weird thing is it is all like a reset. Everything will turn back on and begin working in about 5-10 seconds. Also when I am playing music at low with subs running, if I pull up on the window buttons (like I'm trying to roll two up at same time), the battery meter rapidly goes down and will also cut the subs out. Oh and I have a capacitor which seemed to do nothing either. Anyways I thought it could be the wiring of the subs (they were done at Best Buy like 3yrs ago by their Geek Squad) because they were {2 of them bridged (positive/negative together) then positive to positive, negative to negative, then ran to amp. So I've been running 4 bridged subs to this to channel amp. So I researched a little and the specs on the amp and it said not to bridge the subs. So then I researched what to do and a video told me to (parallel) them. So I did this to one sub,{ positive to positive, negative negative, then a positive and negative wire directly to the amp.} I tried it and the sub would concave in more and put out a little more bass, but still when bass hits hard, it will shut amp off, my odometer and instrument cluster, and the JVC head unit. I literally took it all apart and checked connections, grounds and everything and everything seems fine. Ill attach a picture of my set up so you all can see what it looks like. Any suggestions would be greatly appreciated. Ive been dealing with this for almost 3yrs trying to find a solution.

NOTE: The picture of system is after I re-wired the single sub, that is why the exposed speaker wire is not connected.
 

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NL5

Diamond Member
Apr 28, 2003
3,287
12
81
Are you running the two channel sub amp in Bridge mode?
 

LTC8K6

Lifer
Mar 10, 2004
28,520
1,575
126
Have you tried holding the engine at 2000rpm to see if that has any effect?

Most alternators have a pretty low output at idle.
 

Bartman39

Elite Member | For Sale/Trade
Jul 4, 2000
8,878
51
91
Ok have you tried it with just 2 of the subs...? If not then do so and try it with both pair (seperate) this will ensure 2 things 1 that your amp will run both pair of subs next is one of the speakers bad...? Let us know...
 

rstrohkirch

Platinum Member
May 31, 2005
2,434
367
126
You have a mono block amp that's rated down to 1ohm. If you're running 4 4ohm subs in parallel you're running that amp at 1ohm nominal load which should be fine. To test the amp, run 1 sub and then add a sub after you've determined that the amp is operating correctly. If you get to 3 subs fine and the 4th causes issues, then reverse the order of the subs you add and test again. If it happens again then you're amp is to blame. Come back after you've done this. Should take you less than 30 minutes.
 

NL5

Diamond Member
Apr 28, 2003
3,287
12
81
Yeah, I just read your description that it was a two channel amp, but I looked up the kicker cx 1200, and it looks like a monoblock as stated above. Everything I could find says it's only stable down to 2 ohms. So, you would need to wire two subs in series, and the other two in series, and then wire the two sets of subs in parallel. Which will leave you with a 4 ohm load unfortunately. If it is 1 ohm stable, then you can wire them all in parallel, and you'll be at 1 ohm. There is no way to get a 2 ohm load with those subs. You would need four 2 ohm subs.

I suspect that you may have a weak ground from the battery to the chassis as well. It's often overlooked when the electrical system is upgraded.
 

kade12

Junior Member
Feb 22, 2019
19
0
11
Okay so I wired two subs parallel and still at low volumes they work fine, if anything a little bit louder, but when a big bass drops, it still shuts everything off.
 

Bartman39

Elite Member | For Sale/Trade
Jul 4, 2000
8,878
51
91
Ok then I would guess you have a bad amp...? Now this is with only 2 of the subs NOT 4 correct...?

But did you try it with the other pair also...?
 

rstrohkirch

Platinum Member
May 31, 2005
2,434
367
126
The individual above is correct. The cx1200.1 the OP has is rated to do 1200w@2ohm. I looked up 2019 model and assumed it was the same but they changed it and the newest model now does 1200w@1ohm instead.

Based off that, OP you need to test with only 1 4ohm sub which would give a rated 600wrms. Your vehicle shouldn't have any issues with this. If the amp cuts out with just 1 sub then you can try a couple of things. First would be to switch over the inputs from the 4 channel to the monoblock. Make sure there isn't any issue with the input voltage. Next would be to run a ground from the amp straight to the battery running only 1 sub.
 

kade12

Junior Member
Feb 22, 2019
19
0
11
I really appreciate all of your help. So I need to test one of the subs, wired parallel and see if it works? Because right now, 2 subs are parallel running to one of the channels in the amp(the other two are disconnected).
 

kade12

Junior Member
Feb 22, 2019
19
0
11
I wired all 4 subs parallel and once again, they play good at low volumes, but when subs hit hard, it will turn amp into protect mode(and reset) and head unit will so the same! ;(
 

NL5

Diamond Member
Apr 28, 2003
3,287
12
81
I wired all 4 subs parallel and once again, they play good at low volumes, but when subs hit hard, it will turn amp into protect mode(and reset) and head unit will so the same! ;(

You can't wire them all in parallel. You're at 1ohm at that point, and it will put it into protect mode. Read everything above again. You have either a ground problem, or your amp is toast. I would put my money on the ground. If you fix that, you still need to wire the subs the way I said, so you have a 4 ohm load. You have the wrong impedance subs to run all 4 at full power.
 

Tim_Derr

Senior member
Mar 23, 2011
382
1,082
136
You can't wire them all in parallel. You're at 1ohm at that point, and it will put it into protect mode. Read everything above again. You have either a ground problem, or your amp is toast. I would put my money on the ground. If you fix that, you still need to wire the subs the way I said, so you have a 4 ohm load. You have the wrong impedance subs to run all 4 at full power.


It looks like he's running 2subs per channel so that would be a 2ohm load. If he was running all 4 bridged it would be a 1ohm load. Personally, I think it's a battery or (and) alternator issue.
 

rstrohkirch

Platinum Member
May 31, 2005
2,434
367
126
His sub amp is a mono block and only has 1 actual channel. It has 2 sets of speaker terminals on it for wiring convenience only.
 

Tim_Derr

Senior member
Mar 23, 2011
382
1,082
136
His sub amp is a mono block and only has 1 actual channel. It has 2 sets of speaker terminals on it for wiring convenience only.


I read it as "Kicker 1200W 2 channel Class D Mono Amplifier" and disregarded the mono as a typo so the 1ohm thing won't work
 

kade12

Junior Member
Feb 22, 2019
19
0
11
Could you explain more on the wiring of the subs. 2 in a series, 2 in a series and then all parallel. Not really sure on how to do that. I have tried to look up videos and diagrams but still not sure if that is the correct way to do so.

But I also see that you said it would be a 4ohm load. So really the only way to get them right would be to buy another amp for these subs. Any recommendations for that?

Thanks again for the help.
 
Last edited:

rstrohkirch

Platinum Member
May 31, 2005
2,434
367
126
You really want to trouble shoot the issue you have at hand to get a better determination on what's wrong. Generically, it sounds like an issue with the amp but it may be something else. RF has a nice little config tool that shows you visually the wiring to help you: https://rockfordfosgate.com/support/wiring-wizard/

In regards to what amp to properally drive the subs, you want a sub amp that does full power at a 1ohm load and has a decent brand name. Something like a R1200-1D would be a good place to start.
 

kade12

Junior Member
Feb 22, 2019
19
0
11
Wiring Diagram #2




Shouldn't this be fine if I use this since my amp is 1200W RMS @ 2 ohms
 

NL5

Diamond Member
Apr 28, 2003
3,287
12
81
Yes, P3SD4-10 Punch P3S 10-inch 4-Ohm DVC.

OK. Then your diagram is correct. You essentially have 8 subs. That diagram has each sub wired in series, then those wired in parallel. That would leave each sub at 8 ohms, and a total load at 2 ohms.

Did you ever check your ground from the battery to the chassis?
 
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