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Old 03-24-2014, 10:31 PM
VerdiRiverRat's Avatar
VerdiRiverRat VerdiRiverRat is offline
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Boat: 1994 Mastercraft Maristar
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Subwoofer Issues - Bad Amp/Ground/Cables?

I don't have the specs for my setup since it came with the boat. This is what I do know.

- Kenwood KMR-550U deck.
- One amp running my tower
- Another amp powering the 12" sub

So the sub has always had issues since we got the boat late last summer. It would work intermittently, and when it did work, if I had the volume up past 32 the whole stereo would shut off. There was no clear pattern to determine when it worked and when it didnt.

Just got the boat ready for the water, getting it cleaned up and trying to tackle this stereo problem.

This is what I know:
  • When I took the boat out this weekend and turned the motor on, all the speakers whined and buzzed so bad I had to turn off the stereo.
  • At home testing I noticed the sub wasn't working at all so the first thing I did was run new RCA cables. (I also ran a Y splitter from one of the other preouts to rule out a specific issue with the pair originally used for the sub)
  • Without the motor running there is a constant hiss or static. If I disconnect the RCA cables, to the sub amp the hiss goes away.
  • When I turn the stereo on (no motor) and let it play with the new cables after a few seconds the subwoofer just pulses like a heartbeat. Even when the volume is all the way down.
  • I disconnected the RCAa and hooked my my iphone directly and it works fine, and no pulsing. Seems the pulsing only happens when its connected to the deck.
  • However, I thought it was odd that when playing it from my iphone I could hear the music coming from the tower. But the amp is only connected to the sub, the other amp is what runs the tower. This seems to be a red flag to me, but I dont know what it means! hahaha.

So I ruled out the RCA plugs, even though the new ones did seem to get the thing to produce sound at least. I would think if it was a bad ground or the amp was bad then I would have the same problems when I hooked it straight to my iphone.

I'm trying to track down the ground wires to check the connection but it looks like its happening behind a panel, and I don't know how to remove those yet.

Anyway, any leads would be great! Tomorrow I'll take some pics of the setup for a little more clarification.

Thanks!

Last edited by VerdiRiverRat; 03-24-2014 at 10:38 PM. Reason: To set subscription setting
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  #2  
Old 03-25-2014, 11:35 AM
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drschemel drschemel is offline
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I think I would run a ground cable directly from the battery to the stereo case and see how much that improves things. If it helps, you can hide it later. The shutting off certainly sounds like a bad ground issue. The back-feeding through your tower speakers could also be caused be insufficient ground. It a place to start anyway.
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Old 03-25-2014, 12:35 PM
bsloop bsloop is offline
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So much going on. Sounds like a typical multi addition hack job over the years.
Likely in the power wires/ground issues that would best be solved with eyes on the project.
I think you would be time and money ahead and seek a knowledgeable, local stereo person either at a shop or on the side.
Paying for an hour of them going though it will likely give you direction to solve the problems. Then decide if you can handle it or need professional help.

Or if you know enough about stereo to run wires and crimp, just redo it -
My guess and semi worst case scenario would be - there are separate power wires to both amps (sub amp wire is probably too small resulting in high resistance thus low voltage and shut down) plus the HU is running off the console power/ground.
Clean it up with a single run of 1/0 pos and neg to distribution blocks placed near the amps. Then proper gauge wire to the amps. Pull your HU switch power and ground from the distribution blocks also, not from the console power. The constant hot should be on the center jumper of the switch with only the blue "remote" wire actually on the switch.
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  #4  
Old 03-25-2014, 04:07 PM
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Kweisner Kweisner is offline
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Holy cow. Either what bsoop suggests OR tear it all down to scratch and rewire step by step. In other words, disconnect everything and the methodically wire back to proper spec. While it could be power issues, it could also be that speakers are miswired, and ot amps are wired to high level (speaker) inputs And RCA. Too much to diagnose from the symptoms--a few pix might help us rule some "could be" items out. Looking for connections to both amps as well a eqpt brand and models.
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Old 03-25-2014, 08:18 PM
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David Analog David Analog is offline
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With list of noise issues I would assume that you have problems with B+ supply and ground potentials being different from audio component to audio component. A single B+ point and a single ground point for ALL audio components usually will remedy this. But when I read about the signal from one zone showing up in another zone, my opinion quickly changed. You may have a 'Whack a Mole' with another gopher that keeps popping up as soon as you fix one. If the installation was done with a degree of logic you might have a shot at anticipating where all the landmines are buried. However, in this case I would gut the existing wiring, leaving no stone unturned, and start from scratch. That's the only way you will have a trouble free system all season long. IMO.
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Old 03-25-2014, 08:39 PM
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JimN JimN is offline
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Quote:
Originally Posted by VerdiRiverRat View Post
I don't have the specs for my setup since it came with the boat. This is what I do know.

- Kenwood KMR-550U deck.
- One amp running my tower
- Another amp powering the 12" sub

So the sub has always had issues since we got the boat late last summer. It would work intermittently, and when it did work, if I had the volume up past 32 the whole stereo would shut off. There was no clear pattern to determine when it worked and when it didnt.

Just got the boat ready for the water, getting it cleaned up and trying to tackle this stereo problem.

This is what I know:
  • When I took the boat out this weekend and turned the motor on, all the speakers whined and buzzed so bad I had to turn off the stereo.
  • At home testing I noticed the sub wasn't working at all so the first thing I did was run new RCA cables. (I also ran a Y splitter from one of the other preouts to rule out a specific issue with the pair originally used for the sub)
  • Without the motor running there is a constant hiss or static. If I disconnect the RCA cables, to the sub amp the hiss goes away.
  • When I turn the stereo on (no motor) and let it play with the new cables after a few seconds the subwoofer just pulses like a heartbeat. Even when the volume is all the way down.
  • I disconnected the RCAa and hooked my my iphone directly and it works fine, and no pulsing. Seems the pulsing only happens when its connected to the deck.
  • However, I thought it was odd that when playing it from my iphone I could hear the music coming from the tower. But the amp is only connected to the sub, the other amp is what runs the tower. This seems to be a red flag to me, but I dont know what it means! hahaha.

So I ruled out the RCA plugs, even though the new ones did seem to get the thing to produce sound at least. I would think if it was a bad ground or the amp was bad then I would have the same problems when I hooked it straight to my iphone.

I'm trying to track down the ground wires to check the connection but it looks like its happening behind a panel, and I don't know how to remove those yet.

Anyway, any leads would be great! Tomorrow I'll take some pics of the setup for a little more clarification.

Thanks!
Ironically, when an audio system makes intermittent thumping sounds, it's often called 'motorboating'.

If you connected the phone to the amp for the sub and heard ANYTHING from the tower speakers, you have a short. Could be from speaker wire to speaker wire, speaker wire to tower or something else, but you need to disconnect the speaker wires from all amps and check for continuity between all wires and any other. If you see any crossed wiring, replace it. I would bet that they aren't protected where the tower folds, where they come out of the deck or maybe they were pinched/skewered by a screw when the panel was installed. I wouldn't remove the screw when the amp is powered up, though. Once that panel comes out, I almost guarantee that you'll see things that make you scream like a girl. It's a good way to hide ugly.
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  #7  
Old 03-25-2014, 10:40 PM
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VerdiRiverRat VerdiRiverRat is offline
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Boat: 1994 Mastercraft Maristar
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Wow thanks for all the tips guys! I was able to spend some time on it this evening and found a disconnected speaker wire coming from the deck. I believe this may have fixed the pulsating and other intermittent issues as I haven't been able to reproduce that since fixing that connection. Previously I could fuss with the wires from the deck and it would cause all sorts of horrendous noises.

However, now I have a constant hiss or static sound coming from all speakers (regardless of volume). If I disconnect the sub amp, I still hear static in the tower, though it is not as loud. As I've been thinking about it, I'm wondering if this might be do to some Y connects I was using for the preouts for my troubleshooting. I'll disconnect those and see if anything happens. I also may need to adjust the gains and what not on the amps...havent even checked those yet.

After I connected the loose wire I wasnt able to test the iphone set up again to see if anything had changed with that amp playing through the tower as well. I'll try that out tomorrow.

I was able to pop the panel off and see what exactly was going on. I've attached a wiring diagram I made as a result.

With all the potential bad ground talk, I was wondering if those ground connection points might be an issue? Is it normal for the ground wire to run through a fuse box?? And then right before it goes to the battery the ground gets connected to a smaller gauge wire. Wondering if I should just run the sub amp ground down the left side and have it connect directly to the battery and the tower amp just run down the right side and connect.

Thanks again guys!! Very helpful advice!
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  #8  
Old 03-26-2014, 10:54 AM
bsloop bsloop is offline
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Need to get more specific on wire sizes, part descriptions and equipment.
Negative fuse box, I think the panel and 10ga wire; BAD. Also the ground choke down point sounds like another example of a hack install that ran out of wire or was trying to scrimp by.

I commend you on the line drawing but I really think spending an hour with a professional will give you a much better understanding of what you have, where it is going and what needs fixed.
Be up front they are getting paid to evaluate the system, draw up a game plan. Fixing a minor gremlin can be 3rd. Let them know they can bid the work but you are interested in DIY and paying for inspection and direction. You will learn a lot.

If you are still trying to go cheap (which will just cost you more time and $$ in the long run) you might fill out your sig with a clearer location and ask for help. LakePirates.com is another forum focused on your region and might find someone local help. Be fore warned, you get what you pay for (but sometimes don't get what you paid for too).
I had a home builder friend that was interested in bumping up his stereo, asked equipment questions and was proudly showing off his new system the next spring. It looked and sounded good til he turned it up, then didn't and cut out. A quick inspection, he had used 10ga house wire for power and joined with wire nuts! He was dropping 2+ volts due to resistance from battery to amps.
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  #9  
Old 03-26-2014, 11:31 AM
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VerdiRiverRat VerdiRiverRat is offline
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Bsloop...I think you're right in the end. If I want it done right I need to get professional eyes on it. I never really thought about having them give it a once over and essentially pay them for a DIY plan.

I was trying to avoid ripping everything out, but it looks quite inevitable. The amps have no clear markings on what they are, from what I can tell at least. Oh well, it'll be good practice.

Thanks!
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  #10  
Old 03-26-2014, 02:10 PM
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JimN JimN is offline
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Quote:
Originally Posted by VerdiRiverRat View Post
Bsloop...I think you're right in the end. If I want it done right I need to get professional eyes on it. I never really thought about having them give it a once over and essentially pay them for a DIY plan.

I was trying to avoid ripping everything out, but it looks quite inevitable. The amps have no clear markings on what they are, from what I can tell at least. Oh well, it'll be good practice.

Thanks!
The make/model of the amps may be on the bottom or end cap.

I see several problems-

1) Two amplifier grounds changing to a smaller gauge before connecting to the battery. This causes voltage drop and not only does it limit the amp's output power (both amps), it causes the current to find a better path to the battery negative and this can be on the turn-on lead (blue), the audio cables (this almost ALWAYS causes noise) or any other common wiring.

2) The fuse box inline for the grounds- while it's a good way to avoid problems caused by cable polarity reversal, it's best to not have any breaks in the power or ground wires before they reach the amps. The one deviation that works is a distribution block, as long as its holes are sized appropriately for the cables.

3) it would be best if the power wires for both amps were the same length- during high current situations, the difference in resistance due to the extra length can cause ground loop and it becomes hard to replicate the noise when you need to demonstrate it.

4) It would be best to loop the radio's ground wire to the stud on the rear of the head unit and connect a heavier ground wire to the same stud, terminating the other end at the same distribution block used for the amplifiers. Abandon the ground wire from the dash.

I'll assume the "other wire" is yellow or orange- if it's yellow, it's the main power wire for the head unit (they used to use this for the memory and it used to carry low current but now, it's the main power lead and it probably carries 15A. If you have noise after fixing the ground wiring, this is where I would look. While you're running the new head unit ground to the distribution block, send a new power wire of heavier gauge. That way, the head unit and amps don't have different voltage/current sources. Abandon the yellow wire from the dash by cutting it, bending it over and using shrink n seal to cap it.
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