So I have installed an uncalled4 custom fiberglass enclosure with 12" type r sub, currently powered by the mrp-m500 alpine mono amp in 2ohm output through Sound Acoustics capacitor for power.
Im also running the uncalled4 pnp rockford fosgate amp for the 4 channels instead of my oem amp. Output for the alpine mono amp comes straight from the stereo unit right by where oem amp was connected through fixed line stereo rca output converter. Power (+) and rca wires are ran on different sides of the car.
My issue: When the car is off everything works perfect, when I start the car and start driving I get a rpm rev noise from the sub from about 800-2500 rpms than it goes away after 2500 rpm. Its not a static noise but more of a actual bass, sounds like I have an exhaust

I tried different ground, different positive wire, swapping out rca wires, running rca ground filter, nothing works...
Also I found out that when I am in that range of rpms upon opening any door than the noise stops.
Does anyone know what this possibly could be? Our door trigger wires get a (-) upon opened door, so Im thinking its some kind of interference.
By unplugging the rca fixed line converter and trying to connect the output for mono amp straight on it only makes it louder.
I also tried plugging my iPhone as sound source using aux to rca y splitter right in front where rca would normally connect to the rca fixed converter, no noise was present, that tells me amp and rca wires are good. So it leaves me with the signal that is coming form the stereo unit to the rca inputs on the fixed line converter.
Im stuck

 

1. What are your gains and LP filter set at? Pics would be best

2. Are you wired into the LOC using the pre-amp or post-amp signal?

3. Have you disabled the noise cancellation mic in your car??

 

I also had this for a long time. Replacing the sub amp fixed it. It sounded just like the exhaust normally sounds but louder.

In the process of replacing the sub amp I might have created a better ground or it could have been the better RCAs I used not picking up noise. I never figured out exactly why I had it or why it went away.

If I did the math right, it would give a 30hz tone at 600rpm and a 50hz tone at 1,000rpm. So I'm guessing the noise disappears somewhere after 1,000rpm when it gets into a frequency where your low pass filter on the sub gets rid of it.

 

I think this is attributed to the noise cancellation mic in the car like trunk monkey suggested. I came across this in my friend's Type-S the other day and this is the same exact problem and disabling the mic fixed it.

 

Could be but mine doesn't have ANC and it had this problem. The way the OP described it, it sounded more like the problem I had. Instead of a random weird noise through the sub, it sounds like you car has loud exhaust and varies with RPM.

Easy way to tell, open the door and see if it goes away.

 

1. My gain is set to 100% since its only 500rms amp, the LP filter is about 85.
2. Not sure what you mean by pre-amp or post amp signal.
My LOC is wired in the passenger kick panel getting signal from stereo connection, and sending it to the rca wires that are ran on the right side of the car, the LOC is also grounded to the frame.
3. I will be disabling the whole system today, Ive read about it just now and it tells me to completely remove the system module under the center channel speaker.



This is the problem Im talking about. It sounds like exhaust but lower and louder. I always thougt its the amp, but with running different sound inputs through my rca the noise is not present. The rev noise is present when I send the sound signal from my oem stereo through LOC.

Will disable the rear mic first if still present, I will try to remove the whole module under center speaker!

 

the noise does go away when I open any door... i have tested with all 4 doors...

 

Easy fix, the others were right, it's the ANC.

 

will get that module out today, hope it works im tired of hearing that noise while i drive

 

You're gain might be up WAY to high, also factoring in possible noise. The gain knob is NOTa volume knob. It's to match the voltage of your signal. You need to figure out whether you're using the pre-amp signal or the post-amp signal. It will be simple to find out as it's just a matter of finding out which wire colors your wired into at the factory amp. Take a picture or tell us which colors you used.

Pre-amp will give you a flatter signal and will NOT be crossed. This way you can cross it at 100hz, 80hz, 60hz, 63hz, etc etc. Whatever you please. The voltage on this signal is around .2-.5v though, which is very low.

Post-amp isn't the cleanest way to go about it, but might be the best in your situation. It's a higher rated voltage at (don't quote me on this but..) I think it 3v-4v. Again..I'm not sure on that voltage so a little digging around will pull up the answer. This signal will already be crossed over so you'd need to put the crossover on your amp all the way clockwise (200hz).

 

oh gotch ya!! it def the pre-amp signal, since I have the PnP rockford fosgate amp instead of my oem amp. Im taking the pre-amp signal sending it to grounded LOC and than to the rca wires. my mono amp is set at 85hz

 

ANC is easily tested in Honda vehicles as it goes inactive when a door is opened.