SQ issues. Alternator whining noise in speakers.........

[Slammer 10+ year member]

I just did an install in my 2006 Lexus IS350 (non-Mark Levinson sound system), and now have a whining noise in my speakers which rises and falls with the engine's RPMs.

Install:

Car has a factory amp, and is VERY difficult to pull original HU. I installed an MTX RE-Q5 processor, splicing into the factory amp's output wires. From there, I have run JL Audio interconnects to a Memphis MCA200.4 amp. The amp's output wires are then spliced into the factory speaker wires, which run to Hertz Hi-Energy HSK165 6.5" component speakers.

Issue:

The Hertz speakers are rated at 100w rms (each woofer), and the tweets are another 50w. The amp that I am running is only rated at 50w rms x4 @ 4ohms. In order for the speakers to get loud, I had the amp gained at approximately 3/4s. With the car running and the volume on the HU turned all the way down, you can hear a buzzing from the speakers, which rises and falls with the engine speed.

I have found that the lower the gain on the Memphis amp, the less audible the buzzing noise is. With the gain set at 1/4, there is no buzzing, but I do not get much out of the speakers. My concern, is that there is an issue with the RE-Q5 processor, the amp, or even the signal that is coming from the factory HU and factory amp. I have the amp properly grounded, and even re-grounded the RE-Q5, running it's ground directly to the frame instead of splicing into the factory harness.

I have researched forums and articles, but nothing conclusive. If the signal from the HU is bad, I am screwed. I tried several grounding points, as many of the articles insist that this is a ground issue. I know that the Memphis 6ix processor has a ground loop isolator switch, which is incorporated into the processor, to help eliminate buzzing and whining, but the RE-Q5 does not. If that is the issue, how would I remedy it?

Sorry for the ridiculously long post, but it is a complicated issue and I am puzzled.

Thanks for any imput or advice you may have.

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[hip3 10+ year member]

I had this same problem for a while, tried everything and looked everywhere. Eventually I swapped the amp and it was gone. Put other one back in and problem was there again. Maybe your amp is causing the issue.

 

[Slammer 10+ year member]

I am with you, and have considered going with a better amp, but hate to do it and it not fix the issue. I do believe that if I had an amp which made more power, it would play louder without using so much gain. My estimate, is that the Memphis amp is probably putting out half of the RMS power that the speakers are capable of handling. What's holding me back, is that everything I read tells me that there is a ground, or ground loop issue causing the whining noise.

 

[helotaxi 5,000+ posts]

Its definitely a ground loop. The problem of course is finding the source. Some amps are very sensitive to source grounding and ground isolation. Leaving the factory amp in the signal chain is not helping you. Tap into the signal chain ahead of the factory amp.

 

[Phoenix Risen 10+ year member]

^^^ that,

also try grounding your rcas

 

[Slammer 10+ year member]

I am pretty sure that I have to run the processor after the factory amp. There are only two pair of input signals out of the HU. One is audio and the other is an ATX signal, which I understand to be a digital signal. The factory amp is 14 channel, and I am splicing into the output and use the processor to sum the signals. I have heard of grounding the RCAs, but have no idea how to go about it..........

 

[rumple4skin 10+ year member]

but you see by splicing into the output of the factory amp you are going to get its internal ground loop along with it. in this case if you MUST keep the factory amp you must go thro it one wire at a time ( after that one circuit at a time) and find the ground out and fix it. this is really time consuming and im betting more time consuming than replacing the factory hu. this prob gets really bad with cars like that 92 thro 99 taurus because they made the mistake of running a factory uh wiring kit for a cd changer in the trunk but only sold like 40k cars with the changer in it. this makes it easy to and grounding issues in all kinds of places not to mention making it hard to find a real wiring harness for the hu itself.

 

[Slammer 10+ year member]

Are you saying that I need to pull each negative speaker wire, one at a time, and ground it to the chassis, until I find the one that is causing the ground loop? Does anyone know how the ground loop isolator switch on the Memphis 6ix works? If that little switch would fix the problem I am having, I would ditch the RE-Q5 and go with the 6ix. Also need to know how to ground the RCAs. I did disconnect them, and didn't get the whine from the speakers. One thread said that if the whine persisted with the RCAs disconnected, the problem was in the speaker or the amp wiring. If no noise, the problem is before the amp. First step after that was to disconnect each component before the amp and test. My problem is that the only component before the amp is the RE-Q5, and if I disconnect it, I have no signal to the amp. I am sure their example was for someone running a crossover, or a processor that was not required for them to get signals to the amp.

 

[helotaxi 5,000+ posts]

Disconnect the inputs to the RE-Q5 with it still connected to the amp. If the noise persists, your RE-Q5 is the problem. If it is gone the factory amp is your problem.

 

[nateberrier 10+ year member]

:facepalm:

 

[Ineed$ 10+ year member]

I have this problem only when all 4 rca channels are plugged into the amp. If I disconnect 2 channels the whine goes away. I can move the rcas around and have no issue but as soon as all 4 channels are plugged in the whine comes right back. All grounds are solid and I know the rca cables are not the issue.

 

[Phoenix Risen 10+ year member]

it still sounds like you need to ground the rcas, take a piece of bare wire, wrap one end around the exposed metal of one rca and use one of the screws on the case of the hu to attach the wire to the case.

 

[helotaxi 5,000+ posts]

His RCAs don't go to his HU.

Sounds like a ground isolation problem with the RE-Q5.

 

[Slammer 10+ year member]

Hold up. The post about having the problem with all 4 channels at once wasn't me. I suppose someone else is having a similar issue, but didn't make it clear that they weren't the thread starter. I am going to pick up a cheap isolator at Best Buy this evening, but will try grounding the RCAs first. If neither of those work, I will have to assume it is in the RE-Q5. I have a JL CleanSweep, but didn't use it because I am told that they are a nightmare to set up. Also, I don't have the SSI for it, and wouldn't know until the install if I would need one or not. Not to mention, JLs training video states that some systems with multiple inputs could even require two SSIs. Perhaps if the grounding the RCAs and the isolator don't work, I could just get a basic hi-lo converter (for diagnostic purposes only), and see if the whine goes away. The problem with them is that I am summing 14 channels into the amp and cant do that with a regular converter. I will update progress late tonight or in the morning. Thanks for all the input.

 

[Slammer 10+ year member]

Grounding the RCAs was no good. I ran a jumper from the chassis to the shield of the front channel RCAs, but didn't make any difference. I picked up the isolator earlier, and will probably try it in the morning.