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Is the noise high frequency whine or low frequency rumble? Clicks? Pops? Static?
-high frequency only notice when the tweeters a connected
Does the frequency of the noise change with the engine RPM?
-It changes with rpm a little bit
Do you have a specific ground cable running from the head unit to the amps?
-no. Only the 2 after market amps that I installed are grounded. they aren’t individually grounded. I wired them to a distribution block and then to a chassis. Tomorrow morning I will shave it to bare metal.
Have you cleaned all the specific ground connections to the chassis down to bare metal?
-No but I will do this tomorrow
Do you have a dedicated ground wire coming from the battery to the amps?
- not from the battery. From amp > distribution block > chassis
Is the Bose amp and your aftermarket amps grounded at the same location?
- yes
Did you ground any of the shields on the balanced outputs from the head unit?
- no. How would I do that? If you could explain in simple terms if possible... just touch a wire to the shield on one end and the other end connect to a chassis ground or a amp ground?
Do you have a lot of lights and accessories on the car putting a further load on the alternator?
- no
If I understand you correctly, you are running an aftermarket amp along with the Bose amp? If correct, is there the same noise on the Bose amps?
- not on the bose amps. never made the noise before
No man, not thinking that at all. In fact, using the 4-channel in stereo bi-amp mode isn't even explained in the Skar manual so what you're doing is pretty advanced! As I said, I'm no expert so...
I think I understand now... Bose amp still in place, and in fact still running the rear door speakers?
If that's true, you would only need to tap off LF and RF signals from the head unit - at the Bose amp as you're doing - then use Y-cables to get into the 4-channel inputs...
Inputs 1 & 2 would be LF and RF, and you'd set the switches to "HPF" and 0 bass boost, then those outputs would drive new front door tweeters. The super tweeters fequency response curve starts at 2.2k so you can turn that "HPF" control on the amp all the way to 5k and the tweeters will handle anything above that.
Then inputs 3 & 4 would also be LF and RF and those outputs would drive your new door "mids" as you call them, though they're actually full range speakers. You may or may not want to use the "LP" switch on the amp for channels 3 & 4. In a true bi-amped setup you would kick that in and then adjust the crossovers so each speaker is only handling it's own part of the frequency spectrum. But I have the feeling this will sound great even if the new door speakers are running in "full" mode. Then in addition you have a choice of bass boost for those channels so you've got a LOT going on.
Tapping off the sub from B46 is the way to go - already summed and filtered. That polarity thing is no longer an issue although you still want to get it right for all the inputs and outputs to be running + as positive.
I guess you've already got it all working and now just chasing noise? This is where a real car audio guys would be more help than me. But I can further describe the balanced thing, as I understand it:
RCA connectors are traditionally "unbalanced" in that the "+" side of the signal is one center conductor and the "-" side is a shield woven around the outside. In a "balanced" cable like a microphone cable, there are two conductors, + and - , surrounded by a metal braided shield. That's why mic cable connectors have 3-pins. This is a better scheme for noise and interference rejection and clearly Bose thought it would be best to use this in our cars because that's how they ran from the head unit to the amp. That's why there is a +/- wire for each sound source AND a shield connection surrounding it all. I've never looked at the wiring harness so I don't know if each pair has it's own shield which is tied together at the end, or if there are multiple signal wires in one shield.
In any case, whining motor noise is always something that needs to be chased down in car audio as the power source has an alternator trying to supply constant DC voltage. So there are various line filters and things that the pro-installer guys know about, and maybe somebody can jump in here and make some better suggestions. But I'd start by experimenting with what should be grounded to what. Try grounding the Bose amp to the Skars, try grounding the cable shields, etc... You're almost there and it's gonna sound great.
yes that’s how I have it! I will do the splitters tomorrow for the LF and RF. Yes I’m still pretty much chasing the noise now and that’s it. For the balanced out put would I touch a wire to the shield and on the other end ground it to a chassis bolt or a ground amp? Or how would I do it? I think from what I noticed each +/- wire set is wrapped in the shield. EX: when I took off the electric tape and wrap around the wires to splice I noticed that on the brown (Rear RH+) and and yellow (Rear RH -)cables they were wrapped as one in a shield as they moved further away from the bose amp . Really appreciate the help!
Is the Bose amp and your aftermarket amps grounded at the same location?
- yes
yes. but the bose amp I didn’t ground it anywhere . I only tapped into wires with rcas but never grounded anything. Only the after market amps are grounded to the chassis. They are all in the same location (trunk)
and also, what I did for the front speaker installation:
For mid ranges: Removed the stock 10 inch sub woofer from the doors and in that place out a 10 inch mid range woofer and wired that to the amp.
For the super tweeters: I put the super tweeters where the small mid ranges used to be and got rid of those stock ones and ran wires to the amp. And then I left the stock tweeters still connected. So the stock tweeters and the super tweeters both are puttting in work. Would this also cause noise? Should I unplug the stock tweeters?
I had forgotten there are 3 components in the front doors... And there are 2 stock speaker cables running to each door - one for the woofer and one shared by the midrange "squawker" and the tweeter. I guess the Bose amp might actually do an active crossover for this. I learn something everyday.
Did you run two additional speaker wires to each door or are you using the stock woofer wire? You say the stock tweets are still running so you must have disconnected the "squawkers" and left the tweets connected? And that means you left the inputs in the Bose amp connected and just spliced into those wires, right? I'm still sorting it all out in my mind.
OK, first thing - as per Absinthe's idea about grounding all the amps to the same spot, attached is a pic of where the Bose amp ground is. Apparently up in the left side C-pillar (marked B24). I'm not sure if that point is accessible from the trunk or if you have to pull away a bunch of the interior trim to reach it, but theoretically, to avoid ground loops it would be best to ground them all to the same point or at least as close as possible.
The other end of that ground wire terminates at pin-12 of B42 at the Bose amp, but I don't think you should just tap into it there with two extra amps because it may not be a large enough wire to handle all that power.
Also, I kinda don't think that your issue is caused by that particular ground situation - though I could easily be wrong. I think it's more likely where and how you tapped into the audio signals and linked to your 4-channel amp. It might have helped if the Skar amp had balanced inputs but it doesn't so you'll need to keep experimenting.
Something I would try would be to get a bit of balanced mic cable (like Belden 1503a), put RCA plugs on one end connecting the internal +/- wires but leaving the shield wire disconnected. Then use the shortest length of wire possible to reach the Bose amp, tie into 35/36-LF, 33/34-RF, AND connect the shields of these wires to pin 21. This way you are "extending" the original audio signal shield that extra couple of feet to where it attaches to the new amp. That might be worth a try.
Your super tweeter amp channels have their own level control too so you should be able to balance things out to sound good, once you get the noise out. You may not need them to be running at full power...
Is the noise high frequency whine or low frequency rumble? Clicks? Pops? Static? - high frequency only notice when the tweeters a connected
Does the frequency of the noise change with the engine RPM? - It changes with rpm a little bit
Do you have a specific ground cable running from the head unit to the amps? - No, only the 2 after market amps that I installed are grounded. they aren’t individually grounded. I wired them to a distribution block and then to a chassis. Tomorrow morning I will shave it to bare metal.
Have you cleaned all the specific ground connections to the chassis down to bare metal? - No but I will do this tomorrow
Do you have a dedicated ground wire coming from the battery to the amps? - Not from the battery. From amp > distribution block > chassis
Is the Bose amp and your aftermarket amps grounded at the same location? - yes
Did you ground any of the shields on the balanced outputs from the head unit? - no. How would I do that? If you could explain in simple terms if possible... just touch a wire to the shield on one end and the other end connect to a chassis ground or a amp ground?
Do you have a lot of lights and accessories on the car putting a further load on the alternator? - no
If I understand you correctly, you are running an aftermarket amp along with the Bose amp? If correct, is there the same noise on the Bose amps? - not on the Bose amps. never made the noise before
OK, the most curious thing about this is your comment on #2 above, the frequency changes with RMP a little bit. This leads me to believe the issue is in the various charge/discharge cycles occurring within the various ground loops you have created. If this was the result of a single loop or simple alternator whine, it would be an obvious audio tachometer. It would be obvious and blatant not vague and subtitle. To help explain this I need to give you a bit of theory on balanced outputs of an amplifier.
In a balanced output signal, the hot (+) and the cold (-) signals are inverses of each other. They are the (typically) the same waveform just 180 degrees out of phase. They are measured in reference to the signal ground which is a synthesized ground midway between the hot (+) max voltage and the cold (-) minimum voltage. Given the fact that car audio amplifiers exist in the DC world of the car electrical system, the signal ground will usually not be a chassis ground.
The reason why balanced outputs are preferred is because of how they handle noise. Per above, the hot and cold signals are the same (including the noise components) but 180 degrees out of phase (Notice the noise is in phase as it occurs outside the amplifier). Therefore, when fed into a differential amplifier, the signals 180 degrees out of phase are amplified while the signals in phase are attenuated (minimized). Although this topography makes the amplifier more complex and fussy to work with, the effect is has on noise is worth the price. This is why grounding the braid on the balanced head unit output may not be a good idea. Doing so will introduce instability in the amplifier output since the signal ground is being forced to chassis ground and is no longer actually creating a symmetrical center point between the hot and cold signals. Although there will likely be no ill electrical effects, any noise on the system will be brought front and center.
In your case I think the problem a bit more complex as you have a floating shield on top of dirty or missing ground on the amplifiers. You have:
One loop from the battery to the head unit,
One loop from the Bose amp to the battery
One loop from the head unit to the Bose amp
One loop from your aftermarket amps to the battery
One loop from the aftermarket amps to the Bose amp
One loop from the aftermarket amps to the stock head unit
1 -3 are minimal given the connection is via balanced signal. 4-6 are likely where the problem lies. If this were my ride, I would do the following in order:
Do the big three - This upgrades the three key electrical cables in the system with 1/0 or 4 gauge wires: the battery ground to chassis wire, the chassis to engine block wire, and the alternator plus to battery plus wire. This solidifies the ground plane in your car and maximizes the transfer of clean power. It also cleans up the chassis ground points
Run a dedicated ground wire from the battery to the ground distribution block in the rear of the car. The Infiniti is an easy car to do this to since there are pre-made channels on either side of the chassis that will easily accept 1/0 cables. There are lots of posts on this forum and on others that show this. Don't skimp on the cable size. The price difference between AWG 4 and AWG 1/0 is not that great and again, while your this deep in the car, do it once and be done
Every place where a component is grounded to the chassis should be done through shiny un-pitted and clean metal to metal contact. If you have a 1" ring terminal for your ground lug, every square millimeter of that ring terminal should be in direct contact with a clean shiny point on the chassis
If you intend to keep the Bose amp long term, make sure there is a ground lead from this amp to the other two. Probably overkill but better to do it now then figure this out after you put everything back together again.
Once you've done this take stock of where your at. Is the noise still present? Does it react more directly in line with engine RPM or is it still vague? Try disconnecting the inputs to the aftermarket amps, is the noise still present? Did it go away? Did it change amplitude? Focus on the basics you challenge the balanced head unit to amp questions
Something I would try would be to get a bit of balanced mic cable (like Belden 1503a), put RCA plugs on one end connecting the internal +/- wires but leaving the shield wire disconnected. Then use the shortest length of wire possible to reach the Bose amp, tie into 35/36-LF, 33/34-RF, AND connect the shields of these wires to pin 21. This way you are "extending" the original audio signal shield that extra couple of feet to where it attaches to the new amp. That might be worth a try.
Your super tweeter amp channels have their own level control too so you should be able to balance things out to sound good, once you get the noise out. You may not need them to be running at full power...
A good experiment. Can't predict the outcomes here as I avoided the whole issue by using a DPS that used balanced inputs
A good experiment. Can't predict the outcomes here as I avoided the whole issue by using a DPS that used balanced inputs
thank you to the both of you I will try this tomorrow at my shop. I do wraps for a living but nothing car audio! If for whatever reason what I try doesn’t work What if I just get something like an equalizer like the Skar SKA7EQ | 7 Band 1/2 Din car audio Pre-Amp equalizer? Would that do anything? Would U recommend something like this general and for what purpose exactly? If not I should just get a balanced amp?
You're getting it. But I'm confused... are you planning to use the 4-channel in "bi-amp" mode? Like, 2 channels for tweeters and 2 for woofers? Are you running additional speaker wires to the tweets? Are you sure you don't want to just use the stock speaker wires and run passive x-overs with the new the door speakers? And are you planning to leave the Bose amp installed too? Just trying to understand your plan.
What you describe with the sub is definitely a phase issue, one of the tapped off pairs that you are sending to the mono block must be reversed. Here's how I read the wires carrying signal from the head unit to the Bose amp via connector B43. Mind the +/- and be sure +'s all go to the "center pins" of the RCAs...
LF + #35 Pink
LF - #36 Blue
RF + #33 Red
RF - #34 Green
LR + #24 Purple
LR - #23 Sky Blue
RR + 26 Brown
RR - 25 Yellow
Now about the noise... These wires from the head unit are balanced, two conductors in a shield. That shield is connected to pin 21 of B43. So if you are wiring RCA pigtails to these connections, they should probably be balanced too with the shield connecting at least on the Bose amp side where you are tapping in. You may also want to ground that shield at the far end where your 4-channel amp is, but try with and without. That might make things quieter.
I'm not a car audio guy, just know a bit about audio so don't count on my ideas...
happy Saturday. Wanted to ask something else. I was reading that tapping straight into the bose amp with rca cables and then Connecting to the amp is not good for the amp if that amp doesn’t support high level input? I think skar amps only support low level if I’m not mistaken. What would be the Benefits/trade offs of using a LOC vs a rca/splice method?
thank you to the both of you I will try this tomorrow at my shop. I do wraps for a living but nothing car audio! If for whatever reason what I try doesn’t work What if I just get something like an equalizer like the Skar SKA7EQ | 7 Band 1/2 Din car audio Pre-Amp equalizer? Would that do anything? Would U recommend something like this general and for what purpose exactly? If not I should just get a balanced amp?
A good quality equalizer is going to be essential to contour the sound to your individual tastes and the interior of your ride however, unless it has balanced/unbalanced conversion functions or a line isolator it won't do a thing for the noise except filter it out. The problem i have with this method is I loose a lot of high end in the filter process.
I did some reading the past week and it seems that the most common method for translating a balanced output to an unbalanced input is to pull the audio signal from the hot (+) line and the shield. Some leave the (-) line float, others ground it. From the input to your amp, it really doesn't matter.
happy Saturday. Wanted to ask something else. I was reading that tapping straight into the bose amp with rca cables and then Connecting to the amp is not good for the amp if that amp doesn’t support high level input? I think skar amps only support low level if I’m not mistaken. What would be the Benefits/trade offs of using a LOC vs a rca/splice method?
If you mean pulling a high level signal from the output of the Bose amp and trying to feed it into your Skar amp you will likely overload the inputs to your aftermarket amps. Not necessarily damaging to the amp but essentially will output a square wave to your speakers which is a sure fire way to burn the drivers out quickly. In its simplest form, an LOC is essentially a voltage divider designed to translate high level signals (30V peak to peak or so) to low level (<5V peak to peak). The balanced signal from the head unit is line level and I believe most everyone pulls the audio signal here prior to the Bose amp. Also consider that the Bose amp has its typical proprietary Bose equalization which is only going to sound reasonable when used with its proprietary amps and drivers. Its designed as a system which is why its difficult to get OEM car audio to play nicely with aftermarket components. Therefore, I would not pull any signals from the output of the Bose amp except for the subs which are pass-through on the Bose amp (at least they were in 2008)
I bought an lc7i yesterday. Do you think installing this would make the noise go away? I’m also going to try and do the balanced output to imbalanced input thing today now that I understand how to wire it more. If this small thing should fix my issue and lc7i is not necessary I would just keep the lc7i in the garage til i really need it
Hmmm... I'm not sure about running the Bose amp speaker outputs through the ic7i, then into your new 4-channel. The blurb on that piece with all its BS on "AccuBASS" makes me wary. Also, running the output of an amp into a "power soak" then into another amp seems redundant and likely to add more noise and potentially twist up the overall EQ in weird ways.
But who knows? It might just make your system stop whining because speaker outputs don't need to deal with shielding. Or you may still have a ground loop with that routing.
I think you should try the other suggestions above first - either mine which was to try to extend and float the shield, or Absinthe's idea of floating or grounding the "-" side of the balanced signal. If neither of those work, then why not try the ic7i...?
For for skylines explanations just so I clear it up on my end, I ordered 1503a cable on Amazon it should get here tomorrow or Monday. So once it arrives on side A (side going to the Skar 4 channel amp) splice in some rcas but leave the shields disconnected on 1503a cable? And then side B (side going to bose amp) splice in 33/34 &35/36 and then for the shields on that side connect them to connector 21? I included a pic of how I should wire it.
And for absinthe’s explanation I’m not too sure what that means. Sorry still trying to understand as I’m a newbie and over thinking everything. I start to understand much better if I know what side of each cable both ends should go to and what to leave disconnected etc.
If these methods don’t work I will just buy some amps that support differential balanced inputs , I just like to learn so still tryin to do your guys’s methods 🙏🏼
🙏🏼
Sorry where it says “rcas spliced into here.” I meant the red cable spliced into the center pin of an rca and the black into the outer pin. Same for other side
