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Installing a forward firing 12" IDMAX subwoofer behind seat

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Installing a forward firing 12" IDMAX subwoofer behind seat

Old 07-05-2017, 03:16 PM
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Default Installing a forward firing 12" IDMAX subwoofer behind seat

Looking to put a forward firing 12" IDMAX behind the seat. Mounting depth on it is 8.75 inches, cut out is 11 inches, outside diameter is 12.5 inches.

Already have an amp behind the driver seat, so this would go behind the passenger and replace the glovebox.

Not really seeing anyone who crowbarred something that big behind the seat yet. Consensus seems to be that forward firing in the cabin is the best route to avoid rattles and for best sound quality. Heard nothing but complaints about trunk installs and "magic box" up/down firing.

Sub is getting 1000 watts RMS at 2 ohm.

I'm using a Zenclosure and, after a certain SPL level, there simply isn't anything that can be done with the hatch rattles outside of filling the thing with cement.

Any advice on this would be helpful.
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Old 07-06-2017, 07:38 AM
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deaden your hatch floor , and the underside of the hatch

i did mine, and it still moves , but does not rattle
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Old 07-06-2017, 09:25 AM
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What are everyone you going to use to enclose a 12" behind the seat?
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Old 07-06-2017, 12:27 PM
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Originally Posted by BlueSQ View Post
Not really seeing anyone who crowbarred something that big behind the seat yet.
That is because it will not fit.

Getting a 10" forward firing that space is tricky, a 12" ain't happening without some major custom fiberglass work. The problem isn't diameter so much as the depth given the angle of glove box face. You'll need a shallow mount sub, no IDMAX.

If you want a 12" sub you have 2 choices: spare tire location or downfiring in the glove box. I did option 2 and it rattled like crazy... no thanks.

My experience in multiple hatchbacks is rear firing is the best. Any 12" with 1,000 watts is going to rattle, not much you can do about that. Why not two or three 10"s under the strut bar instead? It will move air then one 12".
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Old 07-06-2017, 01:51 PM
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Originally Posted by jdmfetish View Post
deaden your hatch floor , and the underside of the hatch

i did mine, and it still moves , but does not rattle
I did that. I think it's coming from under the interior sheet metal, but above the exhaust. Worst around the 60hz-80hz range.

The hatch resonates with whatever is in contact with it. Only leaning on the thing at the hinge by the roof fixes it.

Full tilt will shake anything but the buzzing/rattling happens pretty much across the volume range and it's all coming from the back.

I spent months working on this car, when I had everything wrapped I was pretty bummed out to find it's still pretty bad.
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Old 07-06-2017, 02:01 PM
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Some install pics of the sound deadening
Attached Thumbnails Installing a forward firing 12" IDMAX subwoofer behind seat-20160628_213047.jpg   Installing a forward firing 12" IDMAX subwoofer behind seat-20160628_233645.jpg   Installing a forward firing 12" IDMAX subwoofer behind seat-20160708_033155_lls.jpg   Installing a forward firing 12" IDMAX subwoofer behind seat-20160712_222224.jpg   Installing a forward firing 12" IDMAX subwoofer behind seat-20160714_010850_lls.jpg  

Installing a forward firing 12" IDMAX subwoofer behind seat-20160714_010911_lls.jpg   Installing a forward firing 12" IDMAX subwoofer behind seat-20160714_010926.jpg   Installing a forward firing 12" IDMAX subwoofer behind seat-20161101_212845.jpg   Installing a forward firing 12" IDMAX subwoofer behind seat-20161101_212853.jpg   Installing a forward firing 12" IDMAX subwoofer behind seat-20160713_014243.jpg  

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Old 07-06-2017, 02:03 PM
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Finished trunk / sub location
Attached Thumbnails Installing a forward firing 12" IDMAX subwoofer behind seat-20161027_211343.jpg   Installing a forward firing 12" IDMAX subwoofer behind seat-20161108_095851.jpg  
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Old 07-07-2017, 01:32 PM
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Originally Posted by BlueSQ View Post
The hatch resonates with whatever is in contact with it. Only leaning on the thing at the hinge by the roof fixes it.
Maybe new weather striping around the hatch?

Nice looking install!

...but as I said before: monster 12" monster + 1,000 watts is going shake things. Does you rear wiper bounce off the rear glass? The rear of the Z has lots of interlocking plastic bits that rub and rattle. Even my little 8" @ 300 watts causes rattles despite a good layer of Dynamat and some foam blocks I stuffed back there.

The Z is by far the loudest car I've owned interior wise. I should tear apart my wife's Infiniti Q60 and see what they did with it to quiet things down for that model. I did noticed the rear wheel wells are fully lined with some kind of foam mesh to reduce road noise.
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Old 07-10-2017, 07:39 PM
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Both of my spring lift assist springs are shot so I ordered a couple more to see if it does the trick. Maybe some more pressure against the whole hatch assembly will help.

The noise floor isn't the issue. Normal volume conversations are possible at freeway speeds since I deadened it. It's just the resonation that comes from the back. With only the sub playing it's very obvious but the resonations are only there with the trunk closed. With the stereo gear back there it's impossible to crawl back and see what's up.
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Old 07-11-2017, 08:09 AM
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I am not getting the rattling your getting, and I am running 3 x the power your using. My box is tuned to 30 hertz, and my car is deadened much more than yours is. I have the Road Kill from 6" up the firewall , straight back to 6" up the rear wall where the licence plate is, than from left door sill , to right door sill, and finally 6" up the hatchback side walls, including the package tray shelf. The hatch area has 3 layers, the cabin floor 1 layer.

I would opt to not use the forward facing behind the seat location personally.

Forward facing works really well in a trunk cars when the trunk can be completely sealed off from the cabin.

Try isolating and finding the particular point of rattling while parked, with radio on full tilt , and try holding that panel or panels with your hands to see if you can get it , than layer up deadner there.

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Old 07-11-2017, 08:44 PM
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Originally Posted by jdmfetish View Post
I am not getting the rattling your getting
Trying to isolate it is tough because it's compounded when the hatch is down since there's more pressure in there when it's closed.

It sounds like it's coming from the rear drivers side, around where the foam spacers go next to the rear fender.

Inside the cabin is silent, I pretty much followed the procedures at sounddeadenershowdown.com to a T, (decoupled MLV up the firewall, 3M Thinsulate and all) but that hatch is still a resonance trap right now.

I did find something that might help other users: I had a very nasty rattle outside of the car. I found out it was the plastic rear wheel well panel that had broken a few push-rivets. Replaced the rivets with some from my $6.99 100 pack. That pretty much eliminated all rattles from outside and it was loud enough to make a difference inside.

The heat shield above the exhaust was also rattling all to hell, I shoved some folded MLV up there and it did the trick.

The fact that I could hear exterior parts resonate from inside the cabin tells me there might be something else loose back there.
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Old 07-11-2017, 08:50 PM
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Originally Posted by jdmfetish View Post




I'm curious, where'd you get the delete button for the dead pedal? I like it, it looks clean.

Also, did SimplicityinSound do your kick panels by chance?
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Old 07-12-2017, 08:01 AM
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Yes, Bing did my kick Panels , and my A-pillars .

When the Dead Pedal is removed you simply have 2 Bolts sticking up thru the carpet.

I had a few of these laying around and simply got lucky.

http://www.rockler.com/screw-cap-cov...quare-x-screws
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Old 07-13-2017, 04:24 PM
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Originally Posted by jdmfetish View Post
Yes, Bing did my kick Panels , and my A-pillars .
Are you me?

Originally Posted by jdmfetish View Post

I had a few of these laying around and simply got lucky.

http://www.rockler.com/screw-cap-cov...quare-x-screws
Thanks!
Attached Thumbnails Installing a forward firing 12" IDMAX subwoofer behind seat-20160924_213415_lls.jpg   Installing a forward firing 12" IDMAX subwoofer behind seat-20160924_170742.jpg   Installing a forward firing 12" IDMAX subwoofer behind seat-3.jpg  

Last edited by BlueSQ; 07-13-2017 at 04:32 PM.
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Old 07-14-2017, 07:24 AM
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How can I be you , when you are clearly me !
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Old 07-14-2017, 07:26 AM
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what front stage are you running , rainbow ?
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Old 07-14-2017, 10:44 AM
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Originally Posted by jdmfetish View Post
what front stage are you running , rainbow ?
Seas Lotus Reference 165/1 mids, Illusion Audio C3CX in the pillars.
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Old 07-14-2017, 11:04 AM
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Unbelievable...

After trying everything short of ripping the system apart, I thought about having reverse pressure on the hatch to tighten things up. I was going to go with the penny trick until I inspected my drivers side truck release spring. It was bent. Replaced it and I just about shat myself. No resonance, no rattle, nothing. It was muddying up the sub stage so bad that I thought about pulling the sub box and inspecting it for leaks. There's still a few little rattles by the rear view mirror and tail light interior panel but they're easily located and fixable.

So, if your trunk is rattling all to hell, check out your trunk release springs!
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Old 07-14-2017, 12:12 PM
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those Seas are dreamy

lucky you

glad you resolved your issue , SWEET !!!!
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Old 04-30-2018, 08:24 PM
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An update to this and what was rattling in back. It's a combination of things.

1: 3rd brake light - I had to unscrew it and reseat it with a decoupler sandwiched between the clear plastic fixture and the metal.

2: 3rd brake light panel - it kinda floats in air and I had to put a felt pad on the corners so it wouldn't smack the glass as the sub hit

3: The release springs. One was bent as I posted a pic of.

4: The one way air pressure equalizing vents in the trunk corners. These are still an issue. The problem when the sub hits certain frequencies it causes the rubber on the vents to flap around. Inside it's annoying because it's very select frequencies, so everything sounds fine then *bam*, the muddy sound of the vent flaps going nuts. You can hear it more on the outside than inside. I have a separate thread discussing ideas on quieting this down. I'm not going to totally seal them up because they have a safety function for cabin equalization during airbag deployment and also for air circulation.

I'd still like that IDMAX up front to bring the substage forward but at this point I'm shying away from pulling it all apart.
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