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Discussion Starter #1 (Edited)
Ok, I got some questions about adding a better subwoofer and yes, I have searched a lot, but I can’t find the answers so here it goes.

I just got a 2008 IS250 with the sound system that uses 13 speakers and the small Pioneer Amp. I do not have the NAV System, only the Radio/6 CD Player. I am very pleased with the stock sound from each set of speakers on each door (Tweeters, Mids and Woofers) but I am not happy with subwoofer in the back.

What I want to do is simple: Add a Subwoofer with a dedicated Amp to the trunk.

Question 1: After reading many posts and looking at the wiring diagrams, I understand that the Stock Subwoofer has a Dual Coil setup rated at 2 Ohms/35Watts each. Is this correct?

Question 2: I understand that there is an Orange cable in the main harness for the Stock Amp that powers up when the car is turned ON. Is this the correct cable to tab to get the signal to turn ON the new Amp or should I look for a different cable? If so, which one? Is there a cable that power up when the sound system is turned ON only? That would be the ideal as long it has enough current to give the new Amp a signal to turn ON.

Question 3: I have a 4 channel Amp. Would it be wise to power up both my new subwoofer and the Stock Subwoofer too using this Amp, or should I disconnect the Stock Subwoofer and just use the new Subwoofer?

Question 4: If the answer for my previous question happens to be to disconnect the Stock Subwoofer, then should I remove it from the panel so the new Subwoofer can be heard better inside the cabin? Is the trunk insulation that good that I really need to do that?

My plan if possible: using the 4 channel Amp, tab into each Stock Subwoofer channel + & - and power up my Subwoofer with a bridge setup using two channels, and power up the Stock Amp using the other two channels also in bridge mode. I would have to bridge also the Stock Subwoofer coils so my Amp sees them as 4 ohm (my Amp can only work as 4 ohm).

Thanks in advance.
 

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Question 2: I understand that there is an Orange cable in the main harness for the Stock Amp that powers up when the car is turned ON. Is this the correct cable to tab to get the signal to turn ON the new Amp or should I look for a different cable? If so, which one? Is there a cable that power up when the sound system is turned ON only? That would be the ideal as long it has enough current to give the new Amp a signal to turn ON.
I forget if it is pink or orange. I may have said orange in another post but I am starting to believe its pink. I would verify it for you but I didn't drive my car today. I do remember that it is all the way at the edge. I just recently replied to a post so check on that as well.

Question 3: I have a 4 channel Amp. Would it be wise to power up both my new subwoofer and the Stock Subwoofer too using this Amp, or should I disconnect the Stock Subwoofer and just use the new Subwoofer?
Because the power rating on the subs are different, I would not attempt this install. I would get a mono amp with the same power rating as the aftermarket sub and run that by itself. It will sound better that way instead of running two subs with different power rating.

Question 4: If the answer for my previous question happens to be to disconnect the Stock Subwoofer, then should I remove it from the panel so the new Subwoofer can be heard better inside the cabin? Is the trunk insulation that good that I really need to do that?
Its not simple to remove it (in my experience). The insulation around the stock sub is good so there's no need to remove it. The insulation in the trunk is also good, which makes the sub sound great. I have it in a sealed box and it is perfect. My setup is Alpine Type-R 12in Dual Coil with Alpine M-450 amp. It is slightly under powered but it hits hard enough for my taste. One thing you do need to do is to dampen the vibration from the little plastic hole cover in the back seat. That's the only rattle I hear. Otherwise, its perfect.


Thanks in advance.
You're welcome.
 

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I Just Did Mine But I Have Navigation I Think Its The Middle Harnest When You Turn The Car In The On Possition It Comes On Use That As Your Remote Wire You Can Just Tap In And Wire A Suplike I Did It Will Take A Lil Time The Amp Im Sure You Know Is On The Passenger Side In The Trunk Under The Panel,you Can Cut Back The Wire Cover To Acess The Wires From Here You Can Addwhat Ever You Need To
 

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Discussion Starter #4
Thanks for the replies!

Tmaung, I found your write up:

“Adding an amp and sub is really easy. I took the speaker level input that were going into the stock sub and then wired them into my speaker level connector adapter for my amp. If you don't have that, then use an LOC 2 channel and get it out to line level.
As for power cable, run it along the passenger side of the car. Easy to pop up the door sills and it is pretty easy to just poke a hole through the rubber thing at the firewall. There should be a hole in the backseat (near the right rear passenger's arm) that will go into the trunk.
The ground wire is just right by the spare tire.
The remote wire is supposed to be tapped into the stock amp that is located on the passenger side of the trunk. You just lift up the plastic piece. From the 4 harnesses in the back, it is the second harness closest to the front of the car. Look for a pink wire. You will need a 20-22 gauge (red) taps and that should get the signal to the amp.
Be sure to take the negative terminal off the battery before any installation. I blew 2 fuses during my amp + sub install and they were a pain in the butt to find at autozone. I had to go to the stealership where they charged me a butt load for each one. And just in case you blew the fuse while working on the stock amp, it is located by the battery under the hook (not the one by the steering wheel).”

So I guess it is the Pink Wire and not the Orange. I also found the Harness Schematics so I will be checking colors on the paper against the real thing when I take it apart.

About my idea of using one amp to power up both Subs, I forgot to mention that my Amp is a 4 Channel Amp that you can bridge two and two channels to make it a 2 channel, and that Channels 1-2 and Channel 3-4 have separate X-overs and Volume Levels so is like having two amps on one.

My idea is to power up my Sub with Channels 1-2 (bridged to make it Mono) and the Stock Sub with Channels 3-4 (bridged also). I will have to wire the 2 coils for the Stock Sub in Series so my Amp sees a total of 4 ohms as it can only work on 4 ohms when bridged. I plan to keep the volume for the stock Sub very low, just enough to move it but not to damage it, while I will blast all the way up the volume for my Sub.

I was afraid the insulation in the trunk would block the Sub from being heard, but for what you said, there is no problem. To avoid taking apart the deck on the back, I think I’m going to cut the four cables from the stock Amp to the Stock Sub at the Amp level, re-direct them to my Amp, do the “series” connection right there at the cutting point, and connect the amplified signal from my amp back to the harness to feed the stock Sub.

I won’t be doing this for a week or two as I have no time for now, so if you or anybody thinks my plan is a bad idea, please let me know so I can correct it before I get to work on it.

Again, thanks a lot!
 

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I actually only have one wire tapped in at the stock amp. What I did (without taking the top part of the back panel off) is to lift it up a little, unhook the harness from the stock sub and pop it down to the trunk (you need to take off one of the black clips from inside the trunk that is holding the cloth piece). If you have a flashlight, you can easy do that with one hand without TAKING APART the back panel. I also did not tap any of the wires for the sub. I inserted the speaker level wire into the holes and held them in (if the hole is on the top of the harness i had the speaker wire shaped like a hanger into the hole and taped them to the harness one wire at a time). I am not sure if you understand clearly. If you have any questions, PM me at any time.

I will try to get pictures soon. I am still cleaning up my car from my AVIC install and I just installed the intake last night. I am going to NYC this weekend so I won't have time until next week for a picture.

I still think having two subs is not a good idea. The lows will have different effect with the distance and air flow of the two subs. (I was just guessing that it would be hard to setup the gain/volume so its optimal for the front and the rear seats). Plus a four channel amp is not that powerful. Just get a nice decent mono amp. Because of the trunk insulation and the sealed box, my sub sounds really clear and precise in my case.
 

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Discussion Starter #6
I understand what you are saying about the frequencies. That is another problem I’m not sure how to address. I was thinking originally to remove the stock Sub all together and leave the opening so the sound can really travel to the cabin. But since you said it is not really necessary, and better yet, now you also said that to access the stock sub is relatively easy without taking apart the deck, I might just use my own Sub. I have another amp with me that is a two channel and that can be bridged to a Mono setup.

If I have time, I might test each setup; otherwise, I will have to decide before I start working which setup to go for.

I will try to take pics of whatever setup I make and post them with an explanation so others can also take ideas as well.

Thanks again. I’ll look forward seeing your pics once you finish yours.
 

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Ok so I did my install tonight.
Everything went great accept I have no signal coming from my LOC. I am going to try to connect it at the sub location not the amp harness tomorrow.
The blue, brown, green, and pink wires did nothing for me.
 

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I cannot say much about the LOC. My amp takes in speaker level input so it was easy for me. I have the pictures. I will try to upload them tonight if I remember.
 

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Speaker level inputs an a loc are basically the same thing they take the signal from the speakers an convert it into signal an amp or rca cables can understand.
 

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i know what the LOC is but what I meant was that I cannot guarantee that your LOC is working. Argghh I have the pictures but I haven't uploaded it to my comp yet. I have an exam tomorrow so I will do everything after the exam. I keep getting bogged down on school work.
 

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Ok so LOC's are complete garbage. I hacked up my RCA's and used the Hi level inputs. It sounds great.
 

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Discussion Starter #14
Ok, last weekend I did my install. I decided to change the setup from my original plans as I didn’t really feel like taking apart the Stock Subwoofer. I got it to work, but I have some problems. This is what I did:

Setup

I tab into the speaker lines for the Stock Subwoofer to get the signal. I didn’t cut the cables, just tab into them and ran both channels (as you should know, the Stock Sub has two 2 Ohms Channels for Dual Coil Setup):
Channel 1 = Brown (+) & Green (-)
Channel 2 = Pink (+) & Light Blue (-)

I used a 2 Channel Amp that I had (I have three more amps in my house but this one was the best for this case) and used the High Level Input the amp has to connect both channels. I used the Orange cable to get the Remote Signal from the Stock Amp.

I have the schematics for the harness and the Stock Amp and I confirmed each wire to be the correct one matching both color and code. I made sure each tab was good, and double checked the connections once they were all ready. I can say there is no problem on that side.

I used a 10” Sub and powered using the Bridge mode on my Amp.

Now I have the Stock Amp running the Stock Sub, and the new Amp running the new Sub.

I played with the new Amp settings to make the sound as good and loud as possible without having distortion or clipping from the new Sub. Adjusted the frequency and the gain to the best levels and left the x-over to the low option just to make sure we stay on the same note here (it shouldn’t make a difference as the original signal is already on the lows, but just in case).

The sound is actually very good. I am pushing 250 Watts from the new amp, and the Sub is rated at 300 Watts so is a perfect setup. I am happy with the sound quality, and it added just the right amount of extra power for the base that I was looking for.


Problems:

I have two problems. The first one, is the fact that a small amount of engine noise get through even when the head Unit is OFF.

The second one happens when I turn OFF the engine. I hear a small “puf” sound. I know this is coming from the new Sub.

Usually both problems are related to bad Ground, but I made sure the Ground is good. I used one of the screws inside the trunk where the Spare Tire is (as advised by most people).

I noticed that if I unplug the two channels from the Stock Amp to the New Amp, the engine noise is gone, so I think the problem is not Ground for the new Amp, but maybe for the Stock Channels. The New Amp has a ground wire for the High Level Input and I did connect it to the Ground, still the engine noise is there.


Solutions:

Nothing yet, but I am accepting comments, ideas, suggestions, anything from anybody that might have a clue on this. The engine noise is not noticeable at all but it is there and it means there is a problem. The “puf” sound is kinda annoying and worries me as it could damage the amp and Sub eventually.

Thank you in advance.
 

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Hey,

I have two suggestions for ya. You may want to move the ground connections from your aftermarket equipment to the same ground location as the factory amp. It is best to have the same reference point if possible. This is especially true for the high/low level converter. It sounds like you are inducing noise into this component since it changes when you disconnect the stock sub from the circuit.

Another thing. Please mind the phase of your new sub. The front surface of the stock subwoofer fires into the vehicle interior through the package tray. Hence the rear surface is firing into the trunk and is of the opposite phase. Since the new sub is firing into the truck, you might have some phase problems so I would experiment with the new sub with +/- phases to see how it sounds.

Also see if the sub thump changes with you disconnect the factory sub. This can tell where the thump is originating.
 

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Discussion Starter #16 (Edited)
Well, I tested disconnecting the High Level Input signals once more and not only the noise is gone, but also the “puf” sound is also gone when I turn OFF the engine. So all the noise is coming from the High Level Signal.

If anybody knows of a better ground to use instead of the bolts next to the spare tire, please let me know. I wouldn’t mind trying to use the same ground as the Stock Amp but I have no clue where it is. I was thinking to maybe just tab into the ground cable for the Stock Amp but to use it only for the High Level Input ground, not the for the new Amp Main ground.

About the phase, I didn’t realize that I am firing opposite phases into the trunk. It is obvious, but I did not think of it. I don’t want to switch the Positive and the Negative on my Sub as it could cause more problems since the Stock Sub and Amp are mounted directly to the car frame, so they see it as Negative Ground (-). Mixing could cause a short or a very bad sound result.

I was thinking to just eliminate altogether the Stock Sub but this means I either have to get to it under the rear deck, or just cut the two channels I tab into at the Stock Amp level. I don’t really want to do that.

If anybody have any ideas on this, or if anybody knows how to get to the Stock Sub without taking apart half of the car interior, please let me know (tmaung: I didn't understand very well what you said, but I PM you).

Thanks in advance, and thank you Gaugster for your comments and suggestions.
 

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It is best to have the ground cables to be as short as possible and physically attached to the same 'reference' point for the stock equipment. It is not an exact science so I would encourage you to experiment with moving the grould the the high/low converter as a first step. Then you could think about moving the ground for the aftermarket amp if need be.

Regarding the sub-woofer '+' and '-' speaker inputs, these inputs are an AC signal and have no direct relationship with the DC ground of the amplifier. So the speaker wires can be experimented with too.

NOTE - I am not suggesting to ever reverse the 12V positive/negative cables as that would be very very bad.:(

Basically you sit in you car and listen to the bass output then try to reverse the polairty of the speaker wires and see if the bass output gets louder or sounds better. Again, it is not an exact science. Typically the two subs will interfear with each other in some way. It just depends on what you think sounds best. If you aftermarket sub is super loud the output can stress the factory sub even if it is unpowered.
 

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Discussion Starter #18
All done.

Last night I did a lot of things. To start with, I realized that my passenger side Head Light has condensation inside and got me real mad. I posted the story about it on the Insight & Out section. I’m still trying to get the humidity out, if anybody has suggestions, please got to my post.

Now, about the sound system. I took apart the rear seat and took a look at the Stock Sub. To my surprise, the Stock Sub is actually upside down. This means the coils are on the top and the speaker itself points down into the trunk.

Since the cables that get to it are very tight, I decided not to touch it and leave it as it is. The theory about opposite phases doesn’t apply here because both Stock and New Subs are pushing into the trunk, so the phases are the same for the most part.

Based on that, I went back to check the ground connections. I did some testing, and also to my surprise, the High Level Input Ground was actually not working correctly. For some reason, even when it was attached to the same ground as my Amp, it wasn’t grounding 100%. I changed the cable, pealed it for about an inch, and rolled it on the bolt where I have the ground. It now has virtually no noise, and the sound quality is actually better.

I still hear a little “puf” when I turn OFF the engine, but I don’t think I can eliminate that, but I don’t mind it either. So I can say the problem with the sound is fixed.

Thanks a lot!

PS. Any help with the condensation would be appreciated!
 

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Glad to here that you got everything figured out. Your understanding about the phase of the sub woofers is not correct but if you like how it sounds than that is okay.

The direction of the stock sub doesn't matter as it will be wired so that all the stock speaker (Sub, Door woofers, etc...) are the same phase when firing into the interior. Just an FYI.
 

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Discussion Starter #20
I understand the phase problem, but as you said, I don’t like the idea of switching polarity, and that would be in this case the only way to alter the phase (correct me if I’m wrong). Of course I could try to figure out the phase for the stock sound, and then build a custom box that adapts the phase of the new Sub to match the stock phase, but now we are entering into complicated math… lol

On the other hand, we haven’t taken in consideration the frequencies. I don’t remember the exact numbers, but I think my Sub pretty much starts just to get “happy” where the Stock Sub is about to die (frequency wise). So even if I am out of phase, I think the waves won’t cancel each other as the frequencies are different. In practice, I think is happening this way as I don’t hear a loss of sound on any song I listen to (bass wise), or at least, I don’t feel it, so as you said, I’m happy with the sound :)

Thanks for your help!
 
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