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hey guys, i just read some posts about someone complaining about trunk rattle, and it reminded me of something. i hear lots of people say that a sub wont sound good if you face it towards the cabin unless you build a wall. anyway, i have had several differnt high quality subs in my car including and L7 and a JL 13W6 (current sub) and all of them only sound good when facing the cabin. if i turn them to face the trunk.... they sound terrible. almost like its not even on.... just boomy trunk rattle is all i hear. trunk lid is dynamtted. anyway i dont have a wall built and it sounds pretty good when facing the cabin. maybe this is because every one of the boxes has been ported? idk. the new box im getting will have a wall and will be sealed... cant wait till its done and ill post pics.... within the next week or so. anyway what are your guys thoughts on this? why does my car sound crappy when the sub faces the trunk? just curious.
-Dustin
 

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not to sure but i bet it has something to do with sounds waves having to bounce off 3 walls to get into the cabin..."well" sounds good to me anyway..lol...but heres a pic of my 2 10w7s this is how a wall should be built for best sound..be sure to post some pics...
 

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yep, you have to seal the front from the back if you face it forward.
 

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I have 1 12W7 facing the trunk and it sound great to me. With the proper install, a sub facing in the cabin or in the trunk will sound great IMO. Good Luck....
 

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i have two 15" solobaric L7s and i have them faceing the trunk and i got 3 layers of dynomat and it sounds like king kong beating the crap outa the inside of my trunk... i hate it... the box that i got is ported and i was wondering if i turned them around would it make a difference?
 

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I'm facing my 2 JL Audio 12W6's foward into cabin in a sealed box. They sound great. MILAN, it's worth a shot turning the subs around. You really have nothing to lose and the sound can only improve, just my opinion.
 

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I have 2 10" L7's in a sealed box facing forward and it sounds great to me. It's all in the box design.







 

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as far as i know, the difference is mostly separating the front and back of the subs. If they face forward, they either need to be sealed or ported to the rear. or facing rear, sealed or ported to the cabin. This way the subs aren't bouncing around in their own air. so...yes, it's in the construction.
 

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I'm facing my 2 JL Audio 12W6's foward into cabin in a sealed box. They sound great. MILAN, it's worth a shot turning the subs around. You really have nothing to lose and the sound can only improve, just my opinion.
i turn the box around and faced it toward the cabin at first it sounded like crap but then wen i puled em all the way back againt trunk lid leavin no room for air space it sounds great... no rattle... doesnt realy matter now cuz she wont even turn on now!!! err.. i think the ignition fuse is blown or something... i turn the key and it just clicks...anybody have this problem?
 

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i have mine firing forward. more bass in the car but when the seat is up the trunk rattles. i got an idea from another member "bighitter" to cut 4" holes into the back of the seat. that and dynamat should eliminate my rattle. here's some pics:



 

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K boy here it is... I used to do installs so yes I know my Sh!T, LOL.
The trunk rattle is caused by back pressure from created by the speaker.
Just like the BP from the exhaust in a car kills your HP gains, This back back pressure in your sound system causes sound cancellation.

manufacturers try to get the queitest interiors possible. to do this they design the car to send the noise picked up from the rear tires and wheel into the cab area to cancell out the noise from the front tires and wheels.

the worst part comes in tht Bass, has the same frequency as a lot of this "noise".
So if you face the speaker to the trunk, the 1st sound wave created by the speaker is sent into the trunk, and then back into the cab (causing trunk rattle).

(think of the sound waves used by radars) when the sound is reflected, the waves cancel each other out, so you bass is reproduced in a crappy muffle or a sloppy rumble rather than crisp sound.
A lot of you might notice a huge difference when you have the trunk open or closed, it's not just a matter of having th trunk in the way or not (kinda is but not entirely) It's the same reason why your radio sounds different when you open your windows as when you have them closed.

The stereo is actually designed to work (better) with the windows up and to give the driver a better listening position called the "sweet spot."

If sit in the driver seat and ever had to lean over the seat to pick something off the passenger side floor board you notice a big difference in sound, even though your face may be closer to the speaker in the door the stereo hi-fonics have changed.

K, o back to the box issue... When you face the speakers to the back/trunk
and dyno mat (or sound proof by other means) the trunk you might eliminate the rattle (because the matting now "eats" or absorbs the sound wave but you are also blocking out your own bass (not all of it but you loose more than you think)

To get rid of your shaky trunk you do have to make sure that there are no sound waves entering the trunk. So yes, building a "wall" (sealing off the trunk) from your Sub set up and the rest of the trunk is what you need to do.

Doesn't mean you have to use a sealed box, you can use a ported box (into the rear deck lid or into the cabin) but the rear wall (innner most to the trunk area) MUST COMPLETELY SEAL THE TRUNK FROM THE SUBS.

it may be a little forgiving but, still seal it up as best you can to eliminate the rattles...

Hope it helps... Cynthia.
 

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Actually,

it's not cancellation that causes rattling. It's rattling that indicates
cancellation.

If you have a sympathetic vibration, you are loosing sound, so it
makes perfect sense to use some type of sound deadening in
the car to ameliorate the rattling.

As far as bass waves, let's take 100hz for example. The wavelength
of 100hz is approximately 11 feet long. Are our trunks 11 feet in length?
No, then that's not how bass gets canceled.

We do, however, have to be careful of half and quarter wavelength.

11 feet is 1/2 the wavelength of 50 hz, while it is 1/4 the wavelength
of 25 hz.

THIS is where we will experience some cancelation. AND IT IS THE
ONLY REASON YOU MUST SEALED THE TRUNK FROM THE FRONT OF
THE SUB ENCLOSURE WHEN FACING FORWARD. This explains
why milan1228 had good results when the box was at the very
rear of the trunk facing forward (NO REFLECTION AT ALL).

There is less of an issue facing the rear because, unless, from my
previous example of 100hz, you have about 5 1/2 feet between the
sub and the rear of the car for the bass waves to hit and reflect.

The 11 ft example from above is based on the speed of sound at
sea level.

Sorry for this long post, but maybe this helps someone in deciding
how to design their sub system.
 

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And to follow up:

This car has to be the most prone to rattle that I have come across in
at least 20 years!!!!

But I still love it.
 

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Some of this is a little confusing to me. I have a 12" JL sub in an enclosed box. Right now I have it facing rear, about 1 foot from the inside back trunk wall. I have the trunk dynamatted.

I haven't even tried facing it forward. yet, no rattle. Now I will experiment.
 

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Some of this is a little confusing to me. I have a 12" JL sub in an enclosed box. Right now I have it facing rear, about 1 foot from the inside back trunk wall. I have the trunk dynamatted.

I haven't even tried facing it forward. yet, no rattle. Now I will experiment.
I think you are ok with the way you are facing it. It may not
sound better facing the front for the reasons explained by
both T8STY1 and myself.


BTW, did you ever post pics for your install?
 

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Ok.... I Have To Tell All Of You How To Fix The Rattle For Good. I Spent All Winter Messing Around With Ideas Dynamatting My Car And Everything. There Are Two Black Rubber Screws That Are Very Large In Size. One On Each Side Of The Trunk Lid When You Open It. Bring Them Out A Lot Farther And Put Some Dynamat On The Surface Where It Meets The Base Of The Trunk. I Guarantee That Will Fix It.
 
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