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Here's a list of some easy and affordable door treatments that I've found to greatly improve the clarity, as well as the total bass output and low end extension of your mid/bass. If you're using high quality drivers in the doors, proper treatment and install is a must.

First thing's first. Make sure to sound deaden your door. This will make the largest difference in reducing annoying rattles. Make sure to do both the inner panel and the outer panel. Use a good 2 or 3 layers. A heat gun or even a hair dryer can be used to soften the deadener up for making it more moldable and easier to apply. Find a good asphalt based mat that is cheap, easy to work with, sticks well under room temperature, and doesn't fall off in extreme heat. I use and recommend Raamat which you can find here: http://www.raamaudio.com/
60 sqft of deadener should be more than enough for 2 doors.

As for liquid sound deadeners, I don't use them for a simple reason. They take forever to apply! You would need to clean your door, then apply a single coat. Allow it to dry, then apply another coat. With thick coats and bad weather, it can sometimes take up to a full day to dry between layers. I'd save the liquid deadener for hard to reach places, or for areas where mat doesn't stick easily such as the roof of the cabin or trunk. In my experience, the effectiveness is about the same as a decently thick asphalt based deadener.

Also, you can sometimes reduce annoying door mechanism rattles by applying a bit of thick grease to the part.

The next thing I like to do is seal up any large holes in the door panel. Doing this very noticeably increases the bass output. I like to use plexiglass since it's somewhat cheap and weatherproof... and also looks nice. It's also much sturdier than trying to stretch sound deadener over a large hole. Cut out a piece that fits your hole, use a bit of silicon, liquid nails, or other thick adhesive/sealant and then slide it in. These panels can be easily removed with a screwdriver worked into the edges if maintenance on the door is needed.

Next, I glue a large sheet of egg carton foam behind the speaker location. These do hold water, so you may want to treat it to avoid mold growth. It won't rust your door however, since the foam sits on top of the sound deadener. If you live in a more humid climate, you could use a "Deflex" pad which is sold here: http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=268-242

You should notice a slight improvement to your midrange. For me, the egg carton foam was a bit more effective than the Deflex pad.

Last but not least, buy ~2lbs of non-hardening modelling clay and a small sheet of 3/4" or 1/2" mdf. Cut a ring or baffle for your speaker to sit on. Place about 5mm tall height of clay on both sides of the ring. Now mount the speaker to one side of the ring, and the ring to your door. Decoupling the speaker from the actual door itself will further reduce vibrations, and clean up your midrange and bass. As an added touch, I like to add a bit more clay around the baffle in order to add weight to the area and further dampen any vibrations.

3/4" mdf baffle with non-hardening modelling clay atop.


Seas Excel w18 with non-hardening modelling clay around the baffle.



Notice the plexiglass + liquid nails which was used to cover the hole in the door panel. Also, notice the 3 layers of deadener on the outside door panel through the glass.


Sheet of egg carton foam behind the speaker.



Deflex pad behind the speaker.


Shot of my trunk lid with asphalt based sound deadener applied.


Shot of my trunk with about a 4mm layer of liquid deadener applied.
 

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cool article.... i was just going to make a thread on eca about where to get modeling clay but i guess i'll ask here. why use non hardening as opposed to hardening?
 

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It does get soft and putty like when hot, but these pics you see have been in my car for over a year and a half. I couldn't imagine it getting hot enough to drip.

You can buy non-hardening clay at any arts and crafts store. I think the hardening kind gets dry and brittle which is why you want the non-hardening.
 

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modeling clay...

Once you scew the speaker down doesn't all the clay just squish out anyway??

I agree on the deflex pads...they made a huge difference in my doors. My doors get water in them so I decided not to go with the foam.
 

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npdang,

when you used expanding foam for your trunk, did you use hard-drying (cracks and holes) or soft-drying foam (window frame)..?
 

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The clay does squish out when you screw it down, that's why you don't screw it down all the way :) I like to leave 3-5mm of clay on each side of the mdf baffle.

I also use the soft expanding foam in my trunk lid... I know the hard one can wrinkle your lid if you use too much. Either way, fill your trunk in small amounts at a time and let it fully dry before adding more... I learned the hard way and tried to dump 3-4 cans in at once and it took months to dry... all the while leaking the entire time.
 

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npdang said:
I also use the soft expanding foam in my trunk lid... I know the hard one can wrinkle your lid if you use too much. Either way, fill your trunk in small amounts at a time and let it fully dry before adding more... I learned the hard way and tried to dump 3-4 cans in at once and it took months to dry... all the while leaking the entire time.
lol..thats what it says on the instructions...

did you ever get that stuff off your paint?
 

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10K2HVN said:
npdang said:
I also use the soft expanding foam in my trunk lid... I know the hard one can wrinkle your lid if you use too much. Either way, fill your trunk in small amounts at a time and let it fully dry before adding more... I learned the hard way and tried to dump 3-4 cans in at once and it took months to dry... all the while leaking the entire time.
lol..thats what it says on the instructions...

did you ever get that stuff off your paint?
Lol... gonna have to repaint my bumper.
 

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Honestly, this thread is one of the finest car audio pieces I've ever read in terms of concrete and effective ways to improve the sound quality in ANY car. However, one question:

npdang said:
Next, I glue a large sheet of egg carton foam behind the speaker location. These do hold water, so you may want to treat it to avoid mold growth.
I'd never thought of doing that, but it would certainly be a much cheaper (and IMO no less effective) treatment than Black Hole 5 or Deflex. What kind of treatment would prevent mold without stiffening the foam unduly?
 

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DS-21 said:
I'd never thought of doing that, but it would certainly be a much cheaper (and IMO no less effective) treatment than Black Hole 5 or Deflex. What kind of treatment would prevent mold without stiffening the foam unduly?
I too would like to know what products can be used to avoid having the egg crate mold or hold too much water.
 

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how do you think this stuff (wit the peel & stick backing) would work? 1/8" thick, but is supposed to be great. granted, its really expensive. Seems like it could be great for doors or trunk lid to add mass and give some good soundproofing at the same time.
 

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My first post here guys:) Great site, I should of joined sooner!

Most excellent thread and thanks for the props, I do have a couple of comments for now though;)

1) Our product is now butyl based just like the big dogs, has been for some time now.

2) I use Ensolite foam behind the speakers instead of a Deflex pad or the egg crate stuff, it works rather well and costs practially nothing for such a small piece.

3) We, my son is now a part of what we do, are fellow enthusiasts first, business second, we love car audio and performance and will do all we can to help others achieve thier goals, wether or not you buy from us does not matter in the least, we are here to help:)

Thanks, have a great day!
Rick
 

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I purchased a roll of the mat 60 from Raam Audio and they were very responsive. Very quick shipment which is always a nice thing to see :)

I haven't received the roll for installation yet but it should be here by the end of the week.
 

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Instead of using regular sound deadening mat, would using non hardening clay to fill up the holes in the doors and layer the doors have the same effect as the mat? I figure the non hardening clay will do the same purpose of sealing up the door, adding mass, and reducing vibration. What do you guys think about this idea??
 

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Filling small holes and divots in your doors with clay sounds like a pretty darned good idea to me. If you just filled in the low spots with clay, applying your actual door treatment would be easier as you would have to conform to a lot less terrain.
 

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anyone have a favorite liquid deadner? I was thinking of picking up a 5 gal bucket of SS spectrum for $150 (seems like a good deal) to spray on my floor and in the trunk. Anyone know how effective this stuff is?
 

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Discussion Starter #20
Liquid is ok... it's about the same effectiveness as mat but it can be easier to apply in some areas (like the roof or floor). I generally don't recommend it because it can be a chore to have to paint one layer, let it dry for half a day, paint another layer, on and on... whereas mat you just slap it on and you're done.
 
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