Problems with Rockford-Fosgate PMX-2

[sunedog]

I replaced the Kicker head unit on my 2017 23 RSB with a Rockford Fosgate PMX-2 and have some issues. I am not big on audio and know VERY little about amps and subwoofers but hope some of you can offer some guidance.

The boat originally had the Kicker KMC10 head unit, a kicker amp mounted under the helm and an unknown subwoofer under a port side seat. I didn't mess with the amp or sub when I replaced the head unit. I am pretty sure I wired it in the exact same way the Kicker was wired.

The issues are:
1) strangely, in order to increase the volume, I have to both turn the volume knob and hit the sub+ button a few times on the head unit. To decrease, have to do the reverse. If I turn just the volume button up, the sound is super weak and degrades the more you turn it up. With the sub punched up, turning the volume knob down doesn't reduce the volume much. So I have to use both controls simultaneously. The system sounds pretty good to me when I do turn it up, but this is annoying.

2) The balance and fader adjustments are completely inoperable. No matter what adjustment you make to either, all the speakers play equally.

I am not able to tell you much about the way everything is wired. Most wires from the head unit go through a connector then disappear into a spaghetti maze of tie wrapped bundles. I can get a pic of what enters the amp if that would help. The sub under the front seat is covered in carpet and is virtually unaccessible. I can barely see a couple of wires entering it and exiting, but that's about it. The boat is underskinned so I can't verify anything under there such as serial or parallel wiring to the speakers.

I've played with every setting in the PMX-2 menu and can't make any headway. Hope some of you audiophiles will recognize the problem.

 

[LaurencetheAdventurer]

Gemini says:
It sounds like you have a classic "signal routing" mismatch. When moving from a Kicker KMC10 to a Rockford Fosgate PMX-2, the wiring harness might look the same, but how the unit handles the outputs is likely the culprit—especially regarding your "sub volume" quirk and the dead fader.

Here is the likely breakdown of what is happening:

1. The Volume/Sub Knob Mystery​

The PMX-2 is designed with a dedicated Subwoofer Output (RCA) that is controlled independently of the main volume for fine-tuning bass on the fly.

• The Problem: It sounds like your main speakers (through the amp) are actually receiving their signal from the Sub Out RCAs or wires, rather than the Front/Rear Out.
• Why it behaves that way: If your amp is only "listening" to the sub channel, the main volume knob won't do much because it thinks it’s only controlling the (non-existent) main speakers. Meanwhile, the Sub + button acts as your primary volume because that’s the only signal the amp is getting.
• The "Degrading" Sound: When you turn the main volume up but not the sub, the head unit might be trying to apply a crossover (filtering out high frequencies), leaving you with a muddy, weak signal.

2. Inoperable Balance and Fader​

If moving the fader from Front to Rear (or Left to Right) does nothing, it almost guarantees that the installer (or the previous Kicker setup) "summed" the wires.

• The Likely Scenario: Your Kicker amp might be a 2-channel amp that is being fed by a single pair of RCA cables. If all your boat speakers are wired to that one amp, the head unit sees them as one single zone.
• The Fix: To get fader control back, you would need separate RCA cables running from the PMX-2 (Front and Rear outputs) to the amp, provided the amp has enough input channels to support it.

---

Recommended Next Steps​

Since you mentioned a "spaghetti maze" of wires, let’s simplify the troubleshooting:

• Check the RCA Plugs: Look at the back of the PMX-2. There are sets of RCA jacks (red and white plugs).
  
  • Ensure the cables going to your amp are plugged into FRONT or REAR, not the SUB jacks.
  • If you only have one set of RCAs plugged in, you will never have fader control.
• Factory Reset: A few Bennington owners have reported that the PMX-2 can occasionally "glitch" its internal routing. Try a factory reset in the settings menu just to clear the board.
• The "Punched Up" Setting: In the PMX-2 menu, check the Internal Amplifier setting. If you are using an external Kicker amp for all speakers, some people find better results by turning the internal amp "OFF" to reduce heat and signal noise, though this depends on how the speakers are physically wired.

A quick request for that photo:

If you can get a clear picture of the back of the PMX-2 (where the plugs go in) and the input side of the Kicker amp, I can tell you exactly which "spaghetti" strand is in the wrong spot. Look for labels on the amp like "Input Hi/Lo" or "CH 1/2."

 

[sunedog]

Thank you so much. That is exactly the information I was looking for. Here are some pics.

You didn't ask for these, but maybe they are helpful.

 

[sunedog]

Here is a shot of the whole back of the PMX-2. I added the big labels when I did the swap. The manufacturer provided the small labels parallel to the wires.


Aux input from the head unit connect to red and white RCA cables. Those RCA cables disappear into the spaghetti bundle.


Front Line Out and Rear/Sub Line out connect to RCA cables that go to the amp.

 

[sunedog]

Here are the amp pics. It's a Kicker KX M 800.5. Here you can see the entire top panel in one shot.


This is the left third (from the orientation it is mounted)


The middle third. I see the input level hi/lo button.


And the right third

 

[sunedog]

And I now see there is a fader on/off push button. Heading back to the boat now to see selecting "on" solves the fader issue.

EDIT TO ADD RESULT:
On the amp fader button, I selected "on." When I tune the fader 100% forward, there is no change. Music comes out of all 6 speakers. When I tune the fader 100% to the rear, the front two speakers are silent but the two midship and two in the Swingback still play.

 

[LD50]

I'm not 100% sure, but it looks like your Hi/Lo level input is set to Hi. Generally, high level input is us used when you are running speaker wire from an already amplified source (the speaker wires from your head unit) to give the amplifier its input signal. Lo level settings are used when you are running the sound source from a non-amplified source (the RCA cables from your head unit). From your first picture, I can't tell if you're running your high level source to the amplifier or if that harness is just a pigtail that was included with the head unit and the other end of the wires are open. It looks like that's not the case because I can't see any speaker wire running to the amp other than the outputs.

Is there anything wired into the PMX speaker harness?

 

[sunedog]

Thank you, as well, LD50. You guys are great.

I switched the Hi/Lo input level switch to Lo and the volume control now works as it should! The volume knob now allows me to crank the volume without adjusting the sub. Even if we don't accomplish anything else, that is a huge win. And maybe I'm imagining this, but the whole system sounded better after the change.

Regarding the wiring...The green, white, gray and purple pairs coming out of the connector under the head unit are unterminated. The only inputs from the head unit to the amp are the RCA cables.



The fader works as before --> 100% front setting and all six speakers play. 100% back setting and the front two speakers are silent and the midship and rear speakers play. I'm guessing that is because there are only four pairs of speaker wires leaving the amp and there are six speakers. The front speakers probably get two pair and the midship and rear speakers probably have to share the other two pair.

Honestly, fader and balance are not my primary concern. Just getting the volume issue resolved is great. Thanks again to both of you!

 

[LD50]

I'm glad that helped. Your fader situation is a little more confusing. The only reason I can think of that it would behave that way is because the rear RCA outs for your head unit are for rear speakers OR the subwoofer output. It could be that when you fade to the front speakers, it's still sending a signal through the rear RCA because of the subwoofer output. I would think that if you dial your subwoofer down to 0 on the head unit, it should then fade as expected. Thats my best guess without being hands-on.

Using your balance function should give you some insight as to which pairs of your swingback speakers are wired together. If I had to guess, I'd bet that the front SB speakers are wired in parallel to the right channel and rears to the left (or vice versa), due to the locations of the speakers relative to each other making the wiring easier.

Also, I'd make sure you tape or cap off those unused high level outs on your PMX ensure that the internal amp is always set to off in the settings. Over time, that could it could result in a short to your head unit.