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Discussion Starter · #1 ·
I've got the standard audio package (not Infinity).

I was cleaning out my trunk the other day and noticed that there is a cut-out on the deck behind the back seats for a sub. I didn't have a ruler, but the hole looked to be almost 7 inches across. Most 6.5" subs use a cut-out just under 6 inches.

Anyone know what size sub is intended to be mounted here?

If I do add a sub, I'll most likely keep the stock head unit, so I'll either have to feed the amp speaker-level inputs or add a line level adapter behind the dash.

If anyone has done this, I'd appreciate any suggestions or tips.

Thanks!
 

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Discussion Starter · #2 · (Edited)
No advice? No thoughts?

Well, looking through the tech notes didn't help much. However, the illustrations did show a speaker grill on the rear deck over the sub. This is not present on my car as I don't have the stock Infinity system.

I'm still not sure on the size. At this point I'm thinking I'll probably go with an 8" sub. (In most cases it's actually cheaper than the 6.5, has a larger selection, and moves more air.) If the cage on the back of the speaker isn't small enough to drop through the stock hole, then I can always drill a few bolt holes in the deck and mount the speaker under the cutout from the bottom side of the deck. A strip of self adhesive weatherstrip around the rim of the speaker should make a nice rattle-proof air-tight seal once it's bolted in.

Don't know if I will cut the rear deck cover and install a grill over the sub, or just leave the bass to radiate through the deck unmodified. I'll probably try it uncut first. If it's too muted or rattles the deck cover, then I'll probably cut and install the grill that comes with the sub. (Although I'd rather not advertise the sub is even there if I can help it.)

I'm still undecided on the best way to hack the sound input though. From the Crutchfield site, I know that Blaupunkt has a line of amps that have a special wiring adapter to use the factory harness. Basically it's a small adapter that plugs in between the factory stereo and harness, and sends sound and on/off signals back to the amp. Only problem is that their amps are not bridgeable to mono when using this connector, and I won't need stereo.

Again, any suggestions are welcome. I want to think this through completely before I start dropping cash and modifying things.
 

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Discussion Starter · #3 ·
Quick update...

The Crutchfield site did not list a sub to fit in the cutout for the Inifinity system, so I called and spoke to a rep. He confirmed what I suspected: the factory system uses an odd size sub. Bigger than a 6.5" but not quite an 8" either. So, a bottom mounted 8" is probably the easiest solution. He also said he probably wouldn't cut the deck cover as the bass should come right through the back seats and deck cover without any trouble.

There is a mono Blaupunkt amp that uses the plug-n-play harness, but it's outa my price range. Looks like I'll have to tap a speaker to feed the amp.

I'm still considering replacing the stock deck as a possibility at some point. Having said that, it would probably be best to tap the speaker behind the dash and using an adapter to provide RCA outputs. This would give 2 benefits. First, I woulnd't have to dig into the doors to tap the speakers for input. Second, if I replace the deck later, I'll already have RCA cables running from the deck back to the sub amp to I won't have to re-wire. Just plug and play.

I'm still open to any thoughts or ideas as this project is still a little ways off. (Probably be doing window tint first.)
 

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I think you're on the right track with what you're planning so far. The only issue is the "how" you tap into the stock output and power the sub... I have the Infinity system, otherwise I'd be doing this right along with you!

-Gary
 

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Adding sub

You can get a new headunit that will fit the dash, I have done it to my car. The headunit has a built in crossover so I can send an output to an amp to drive the sub. I believe Crutchfield also has pieces that will take the speaker level in from your stock unit and give you an output to drive the sub.
 

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Installing Stereo components in Kia Optima (2006.5-2008)

I have just purchased a 2008 Kia Optima LX (base model). To give others information on Installing an aftermarket component such as subs, amp, or speakers, here's what I have;
**NOTE: This is only for general information. Be sure to weigh your need for an aftermarket stereo compared to voiding any warranties. Installing Stereo’s is always a large liabilty. If you are unsure about what you are doing, Please find someone who does. I would hate to see a radio burn out because of crossed wires during installation.
The 2006.5-2008 Optima has six stock speakers. These include two tweeters near the front corner of the front doors. The four main speakers are located in the doors. Without Speakers located in the rear dash, it is a little tougher to install stereo components that others have explained.
I have found a website which requires a free registration, and is very helpful. It offers the schematics and wiring diagrams of every inch of the Optima. It is the shop companion of Kia mechanics. I will outline how to access and navigate this site at the bottom.
To Install Components to The Stock Stereo Head Unit: You will need a converter such as a Scosche FAI-3A. Mine is blue, and has input and output jacks where you tighten or loosen small screws. The website which I have outlined at the bottom will show you how to remove dash trim. You must remove the dash trim and pop the radio out. Disconnect the plug on the back, and begin to splice ONLY the Speaker wires. Again, the website will show you which wires these are. Using butt connectors or splice connectors (never twist wires together and cover with electrical tape, this is unsafe and unprofessional) strip the ends of the wires and add a length of speaker wire, making a "T" where the bottom of the T will be inserted into the converter. You must continue the wire from the dash to the plug, as the Scosche FAI-3A is NOT an inline converter. Connect the new wire to the converter, and try to hide it somewhere. It may not fit behind your radio, and may need to be hidden behind the center console. Either way, check the wire lengths and be sure you have enough to hide the converter.
You will now run your RCA cables to the output jacks on the converter (done before hiding box). An ignition wire will need to be run. this is the wire that sends the power signal to the radio when you start the car. This same signal wire needs to be run to the amplifier along with the RCA cables. I typically run these wires to the trunk underneath door sill trim, etc. You can be clever and make this look very clean. I would first find out which side of the car (under the hood) that the battery is on, and run these wires on the opposite side. If you run the battery cable on the opposite side of the car than the RCA and Ignition wire is on, you will have less interference or white noise when songs or radio stations are switched.
Reinstall the radio and dash trim. Hide all of your wires. You can now run your amplifier power cable. You will either need to find a hole in the firewall (under the dashboard) or behind the front fender. I know that some Hyundai’s and Kia’s do not have a hole in the firewall, and have wiring harnesses run behind the front driver’s side fender. You could drill a hole in the firewall, but think methodically-will it run into anything else or will it allow water into your vehicle. Be Extremely Careful with this. Run your power cable from the positive terminal of the battery to the location of the Amp. DO NOT CONNECT POWER TO THE AMP UNTIL IT IS GROUNDED! Ground out the amp by connecting an adequate-guage wire to the amp’s ground terminal. Find a spot in the trunk where metal is exposed. You will need to sand the metal with a fine grit of sandpaper. Drill a hole large enough to thread a screw which will secure the loop hook end of the ground wire. Crimp a loop end on the ground wire and secure to this bare-metal area. BE SURE to leave yourself enough ground wire length in case the sub enclosure slides around the trunk. I have had smaller sub boxes slide around the trunk so bad (I’m a pretty spirited driver) the they had ripped the ground wire off. Not Good!
You are now Ready to add power. Connect your power wire. Hop in the driver’s seat, and see how she sounds. Good luck!
Here's the site Kia Global Information System (KGIS) register and begin using the option column on the left side. Under “Technical Information” click “shop” Put in your Model and Year, leave the last tab saying “Control Unit” Click “GO.” On the left pick your vehicle based on engine, and Click It. Click “Body Electrical System” Click “Audio” Click “Audio Unit” Click “Components and Components Location.” This will give you all the diagrams you need to know for locating speaker and ignition wires. Good Luck!
 

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Adding Sub to Optima rear dash

Fastlerner- That's a good idea to add a sub to the rear dash pre-cut hole, but you will still need to add the amp as well as a wiring harness. Unless you are concerned with keeping more trunk space, I would just add a package. Granted your idea would look cleaner and offer more trunk space, it's probably more trouble to hide the wires and amp. The infinity amp that comes with the premium sound package is pretty small, so they can hide it easier. If you want thump in the trunk, I would recommend something larger than the 8 inch sub. Also, a sealed enclosure would help with the sound compared to one in the open. I should have bought the showroom Optima rather than the one that came right off the truck, for $3,000 price difference after rebates, the Showroom model had more chrome than a Cadillac, Leather, moonroof, 2.7 V6, automatic climate control and the premium sound with sub. But then again if I did that, I wouldn't be here trying to help others. Good luck with your idea, be sure to let us know how it turns out.
 

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Discussion Starter · #8 ·
Thanks for the input guys. What you outlined is pretty much what I had figured out after a bit of digging.

There are also line output converters out there that provide the power on signal for the amp.

I don't like the "package" all-in-one deals as they are certainly no easier to hide than an amp and take up more room. I'm trying to make it as unobtrusive and close to factory as possible. And installation is not really any less work as all the same leads and connections still have to be made. All it would save me is having to remove my back seats to get the deck exposed. (Already looked through the kiatechinfo site.)

A single GOOD 8" sub rated for free-air applications should be all I need. Anything bigger would overpower the stock system and sound too boomy. I could give a crap if the guy in the car next to me can hear my music, as long as it sounds like a concert hall INSIDE the car. :)
 

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I have a 12" JLWV3 in my 08 SX hatchback.

I put her in a sealed 1.25 cubic foot box and feed her around [email protected] ohms.

I'm happy.
 

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i got 2 tens in a box thats fits perfectly in the very back of trunk where the hole is and i still got plenty of space. i have a stock radio too, all u need is a line out converter to add the white and red plug into your factory deck.
 

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2018 Kia Optima S with a 2.4 engine
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I know for the 2018 Kia optima S
I was trying to hook up a aftermarket amp to a stock stereo using a loc but didn't know the wiring color coding and even after I found it out couldn't get it to sound right because of all the built-in crossovers and things like that throughout the car.. but then I talked with crutchfield and they walked me through the whole process there's two main clips on the back of your radio if it's a 7 in touch screen with six speakers (no stock car amplifier) the farthest clip to the left(the first clip) has one blue wire, that's your remote hook up, the next clip over (the second clip) has your speaker wires, on that clip the wires all the way to the right (they are the wires that are thicker than the rest of the wires) the speaker wires are set up kind of weird. because the speakers you want to use to tie into to add a LOC converter are the top 2 I think they are red and blue and then the bottom two can't reminder them colors... But with this car if you want your system to sound awesome and go through a hell of a lot less hassles with polarity issues, I would highly recommend you get what's called keyloc converter, what a huge difference from a regular loc!! I've been doing systems for 30 + years, so please take my advice on this one yes they are more expensive but with this you get what you paid for and with these new cars and all the hidden crossovers and things like that the only way your system's going to sound right in a new car adding an aftermarket system is with the keyloc !! It will save your car system and make it sound a 1000× better if you're adding an aftermarket amp / system trust me what I posted here will help you a lot if you have the same kind of car, or any newer cars... But I did a ton of research just to find out these few little things, but with that keyloc converter my system sounds way better than any other converters I've tried and it took away all the troubleshooting it's well worth it
 
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