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Discussion Starter · #1 ·
Hey everyone.

I have a 96 Supra NA and I'm in desperate need of some guidance / expertise in the audio area. Here are the details:
  • Bought the Supra in 2009 and it had an older double din head unit.
  • Within two months we replaced it with a Kenwood DDX-616. It was installed by a "professional" car audio business.
  • Still using the stock amp under the passenger seat
  • Either immediately after the install or shortly there after we noticed a loud popping noise whenever we turned on the head unit. It was annoying but not so much that we got it fixed. I know...tisk tisk.
  • We've had a lot of work done to the car to fix it up (its been a project car)
  • Now, when the head unit is turned on and set to anything other than "Standby" (no audio), we hear a loud popping noise when an audio mode is enabled, loud static out of the speakers and there doesn't seem to be a setting for low volume. Its either pretty freaking loud or really loud.
Looking for any recommendations here. I really want to get this fixed. Do I just get a new head unit and amp?

Videos:
-Popping noise (turn up your volume) - Pop and Static.MOV
-Volume problem 0 -> 1 - Volume Problem.MOV
 

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On the volume problem, will the volume increase over level 1 (as displayed on the screen) at all? Maybe play a quiet song and try to increase it higher than 1. What I'm getting at is two things: (1) trying to determine if the volume circuit functions at all, other than as an on/off switch; (2) I wonder if the speaker-level outputs of the head unit are wired into the signal-level inputs of the stock amp, which would be overdriving the amp even at the quietest volume.
 

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Installing a ground filter should help lower the volume and remove that pop sound.
 

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Discussion Starter · #4 ·
@bitshftr - The volume knob works just fine. The issue is that volume 1 is way too loud. It just gets louder from there (as it should with normal volume control). Interesting idea on the speaker-level wires. How would I test or confirm that?

@supradriver247 - I did notice that on the back of the head unit there is a dedicated wire, connected to the head unit housing, and going to a ground on the car. Is that the ground filter you were referring to?
 

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@bitshftr - The volume knob works just fine. The issue is that volume 1 is way too loud. It just gets louder from there (as it should with normal volume control). Interesting idea on the speaker-level wires. How would I test or confirm that?
You'll have to see what head unit wires are connected to the stock harness, or are wired to the amp. Does the head unit have RCA (signal-level/line-level) outputs? Are they connected to anything? What about its speaker output wires?
 

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Discussion Starter · #6 ·
Looking at the back of the head unit it does have RCA connectors but they aren't in use. Also, it looks like a "connector harness" was purchased as none of the wires coming off the head or from the car are coupled together. If it would help, I could rip apart the dash again and take some pictures of the rear head unit and harness setup.
 

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+1 for pictures. But I would say you are definitely using the speaker-level outputs from the head unit, since you said the RCA connectors aren't in use. Now the question is, did the previous owner install a speaker-level-to-line-level converter between the head unit and the amp?
 

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Issue with the volume is the new head unit's high power speaker level outputs are wired to the factory amps input. The voltage from these speaker level outputs are to high for the factory amps inputs. you need a LOC (Line Out Converter) to bring the voltage down to something the factory amp can use. Assuming your factory amp isnt already damaged due to this that should solve your volume issue.
 

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Discussion Starter · #11 ·
Awesome info everyone. Thank you.

I will work on getting a picture of the harness thats in use today. Should be able to get that within a couple hours. Also, @HiloDB1 you and others here have a great idea of whats going on. Thank you. One question though, I'm assuming that even the correct harness to connect Kenwood head unit to the factory harness wouldn't be enough to lower the speaker output correct? Should I look to buy one of those LOCs or should I remove the amp all together? Not sure which one is better for the car in the long run.

Also, there was an idea regarding the ground. Aside from the ground that is coming in to the head unit via the wiring harness (black port in lower right) there is another wire that connects in where the red arrow is that also connects to a ground.
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Discussion Starter · #12 ·
Ya know...another thought just popped in my head. When we had the Kenwood head unit installed (9 years ago) we didn't have this volume issue. The popping noise YES, but not the volume issue. It was only after I had my mechanic try and fix the popping noise that the volume problem reared its head. Does any of that make sense to you folks? What could he have touched or changed that could have caused this?
 

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What could he have touched or changed that could have caused this?
He could have removed a line-out converter, but you're going to have to ask him what he did, because his "fix" wasn't one. The need for a line-out converter is what I was headed for recommending, but it sounded like volume issue didn't always exist, which is why I was holding back that recommendation until we could see how you have the head unit wired up.

I'm assuming that even the correct harness to connect Kenwood head unit to the factory harness wouldn't be enough to lower the speaker output correct?
Correct, unless the harness that was used somehow bypassed the stock amp and went straight to the speakers, which is possible.

Should I look to buy one of those LOCs or should I remove the amp all together? Not sure which one is better for the car in the long run.
In the long run, the best "sound" answer is to remove the stock amp, don't use LOCs, send the RCA line-level outputs of the head unit to a modern amp, and send that new amp's outputs to your speakers.

Also, there was an idea regarding the ground. Aside from the ground that is coming in to the head unit via the wiring harness (black port in lower right) there is another wire that connects in where the red arrow is that also connects to a ground.
You typically won't need the chassis ground (where your red arrow is pointing). But it also shouldn't hurt.
 

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Discussion Starter · #14 ·
OK, so I pulled some pictures and videos of the mess that is behind the Kenwood. For starters, I believe I was wrong. No simple Toyota -> Kenwood harness was used as you can see from all the tube connectors. Take a look and let me know if your assumptions are correct. I'm wondering if getting an official harness would help. Seems like this was just thrown together.

Video - Kenwood Wiring.MOV

More pictures
 

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Discussion Starter · #15 ·
So looking at a bunch of videos on Youtube AND looking into buying a different harness I see that most offerings for the Supra have two plugs that go into the car. One harness is for the front speakers and power and the other for the rear speakers. Why does mine only have one? This is getting more confusing. lol
 

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No simple Toyota -> Kenwood harness was used as you can see from all the tube connectors. Take a look and let me know if your assumptions are correct. I'm wondering if getting an official harness would help.
The video helps a lot. There is no such thing, that I'm aware of, as a "simple Toyota -> Kenwood harness". They way yours is done is typical...Kenwood harness connected to Metra (made for Toyota) harness via butt connectors. I could be a lot neater, and could be soldered and heat-shrinked, but like I said: typical.

There are 3 stationary connectors at the lower far right of the dash cavity, all next to each other. Your Metra harness connects to the stock radio wiring for one of them. Where does the wiring for the other 2 go? (can't see from the video)

I need to check the wiring diagram to refresh my memory of what wires are in each of those 3 connectors. IIRC, at least 2 of them are used for stereo wiring.
 

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Discussion Starter · #17 ·
Thanks @bitshftr. I took another video with more detail this time. The more I dig into this the more screwed up stuff I find. I'll tell you this though, if you can help me get to the bottom of it I'll send ya a bottle of liquor or a pack of beer.

I did find the 3 white wire bundles in the lower right (just as you said). However, those aren't plugged into the head unit in anyway. There is another group of wires coming up in that same area and those go to the head unit. Check out the video. If its blurry its because Google Drive is buffering. Just give it a little time.

Another fun video - Wiring Fun.MOV
 

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I put an alpine amp in my 87T, with the factory head unit, but running new door speakers and subs with the factory wires. The amp does the speaker power step down, and everything sounds pretty good.

The key 1st thing I think for your situation is to have the schematic for your cars sound system so you can see exactly what was there factory, what color those wires are, and then ID them on your harness.

Once you can do that, then see if the conversion harness they used, if the wires are labeled, are actually matched up correctly.

The popping sound you refer to sounds to me like incorrect wiring, a ground issue, mismatched impedance on speakers or amp (2, 4, 8).

Do you know if the speakers were changed? if so, they could have reversed something along the way which would mean a correctly wired stereo harness still might be reversed in some way.

Start with the car first and identify the 4 sets of speaker wire colors, and then the main radio wires from the car harness.

The second antenna wire would be there if you have the diversified antennas (pole and inside your rear window)
 

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Discussion Starter · #19 ·
Thanks @Dumeinao. I actually have the complete Supra manual (its like 1000 pages) so I'll take a look through that and see if I can find the speaker wiring diagrams. As for the speakers themselves, the front two were changed when the Kenwood head unit was put in. The remaining speakers are stock. One question there actually, I see spots for tweakers on the side pillars. Are those just for show? I ask because in all the audio overhaul videos I've seen and the explanations of the stock audio wiring harness it talks about 4 speakers and the sub...nothing about the smaller tweeters.

Part of me wants to buy a new Metra harness and a new Kenwood harness and rewire those connections the right way. I also think I should find all the speakers wires and make sure those wires end up where they are suppose to. Additionally, I'm concerned the factory amp is just shot but I don't know how to check.
 

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One question there actually, I see spots for tweakers on the side pillars. Are those just for show? I ask because in all the audio overhaul videos I've seen and the explanations of the stock audio wiring harness it talks about 4 speakers and the sub...nothing about the smaller tweeters.
No tweeters in the "A" pillars from the factory. If yours has these, they were added/modified by a previous owner. The stock tweeters are in the top corners of the dashboard. And yes, IIRC, they are not mentioned in the wiring manual at all.

I'll take a look at your new video here shortly.
 
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