Tutorials: Sound Deadening Your Vehicle
- Saturday 30th January, 2010
For this tutorial we have used a Lancer and sound deadened the doors, but you can use it as a guide to do the same to any part of your car….. the floor, quarter panels, roof etc.
Vehicle Used for Tutorial - 2000 Mitsubishi Lancer VRX
Before we commence we should point out that unless you feel 100% confident, have a specialist do it for you. It really isn't hard, but time and care needs to be taken when removing plastic trims and coverings or you can guarantee you will break something. And most importantly, before you go unplugging any wire harnesses, disconnect the negative terminal from your battery. Also, ENSURE YOU HAVE A FIRE EXTINGUISHER PRESENT AND WITHIN REACH. Safety First! In this procedure, you are using a highly flammable wax and grease remover, and a potential ignition source.... a heat gun.
- Wax & Grease Remover (K&H make good stuff, 4lt for $20)
- Sound Deadening
- Heat Gun
- Electrical Tape
- Duct Tape
- 3 or 6 mm MDF
- Some kind of paint
Sound deadening is arguably one of the most effective upgrades you can make to your car audio system. Great speakers installed poorly sound ... poor. Ensure you are getting the very best from your speakers, and going that extra step with sound deadening will ensure you are getting the best from your products.
If you follow this tutorial closely you will end up with some very solid doors. This brings many improvements to your car the most noticable of which being that the door no longer resonates in sympathy with the speaker. The deadening will also cut out a lot road noise, especially reflected noise from your tyres.
So first task, open your door and admire that stock look, give it a tap and shudder at how the sound is akin to an empty can of Coke!
Next you need to remove the door trim itself. This usually involves unscrewing pieces of trim like door pulls and handle surrounds, then the door trim itself is usually attached with a series of clips around the perimeter of the door trim. If you are unsure, take your time, as its better to go slow rather than break something.
Most vehicles have a plastic ‘vapor shield’ covering the whole door. Remove this (messy job due to the glue used) and strip the door of things that are covering metal such as door handles etc. You can temporarily remove any wire harnesses and replace them back over the sound deadened area after, just sure to make a mental note, or a photo, of where the clips attached to the door, as it can be a little time consuming to find them after they are covered with deadener.
At this stage, you door should be pretty much bare of extra things, just the panels left, so break out the Wax & Grease Remover and with a rag give all surfaces a good clean, otherwise the deadening sheet will lift from complex curves in 6-12 months. Clean every surface you intend to sound deaden. It is better to use Wax & Grease Remover rather than thinners or acetone because the latter two will take the paint with them as they clean! Not a good thing…
A part that often rattles in the door are the lock rods that open your door. To combat this, a simple solution to simply wrap them in electrical tape. This adds mass to them and so lowers there resonant frequency. Wind it around several times, but if its too thick it may foul the door skin, some experimentation on your part will be required here.
Before you start to apply the deadener, if it’s the sheet variety, stick it out in the sun for an hour or so to soften it up to make it easier to use.
Before you apply it, heat the sheet up with a heat gun before, as this just softens the material up much more, making it easier to apply. Additionally, many brands use a heat activated glue, so the heat actually helps the sheet to stick properly. If you heat the adhesive side rather than the ‘dead’ side it is most effective.
Do the inside of the door first, it will depend on your application as to the size of the sheet you can apply at once, but if you can only stick down a small amount before the sheet goes cold and hard, then cut the deadener into smaller pieces. You want the whole piece you are applying to still be pliable when you apply it. Aim for over 90% panel coverage with the deadener, any gaps you have will reduce the effectiveness of all this effort. If you can, overlap the pieces slightly to there are no gaps.
If you want to do more than 1 layer, clean the first layer down with wax and grease remover again as it will help the second layer to stick much better.
Now the inside of the door is done, time to turn our attention to the outer skin, where the speaker will commonly mount. This skin is often full of service holes to allow things such as power window motors and the like to be replaced should the fail etc. Unfortunately, these holes do not suit the needs of us car audio people. As we are trying to make the door an enclosure, having gaping holes which allow the back waves of the speaker to interfere with the front waves of the speaker and causing nasties such as cancellation is not what we want at all!. So we must seal all of these up so that the back waves of the speaker stay behind the speaker!.
To combat these holes, they should be covered up with thin MDF. 3mm or 6mm is perfectly fine. It doesn’t have to be super thick, as the door will never pressurise like a sub box, these panels are just to separate the speakers energy.
The first thing would be to make a template so that we can make the panels out of MDF later. To do this, grab a piece of cardboard and if you can, trace the hole from behind the door trim, by this I mean stick you arm in the door and hold a piece of cardboard over the hole and trace the outline of the hole from the inside, if you can reach and do this it saves a lot of time over doing it the conventional way. The conventional way would be to ‘eye ball’ the curves of the whole and try to replicate it by cutting with scissors. Both ways work fine, one is just a bit faster.
Your traced out template should look like this:
So cut this out, and check to see that it fits well.
Repeat this for all your gaps in the skin, just remember to leave space for your lock rods!
Once you have all the templates, trace them onto some 3 or 6mm MDF and cut out. When this is done give them a quick coat of paint. This is because MDF is a porous material and since doors are not waterproof, it’s a good idea to paint the MDF to give it some moisture protection.
The next step is to attach these to the gaps. There are various methods of doing this, but I feel this way is the easiest to remove should you ever need to have the innards of your door serviced.
Grab the roll of duct tape and apply *lots* of overlapping layers across the hole. This forms the base for the MDF to be stuck to. When you’re halfway done it will look like this:
The next task is to continue with the duct tape over the MDF panel and surrounding area. When this is done, it will sound ‘deadened’ by itself and should not move hardly when u push it with your finger. A quick tip is to not use Gaffer tape, but only duct tape as the adhesive backing on gaffer breaks down after a while, whereas duct tape will seal for years and years.
The final stage is to apply the deadener over the outer skin of the door. Apply it the same way as before, be sure that you push the deadener into all the little nooks & crannies of the door skin, this may require some more heating and the use of a small roller (saves getting burnt fingers). Just be careful not to cover up any clip holes with sheets as it will be hard to get the door back on otherwise!
But before you go crack a tinny or grab that after game entertainment, what about the door trim!
The door trim is a poor fella that is often over looked. They are most often a thin piece of injection molded ABS plastic just itching to start resonating and destroying that hard work!.
Solution? sound deaden that too! Prepare the trim and apply it the same as the door and you’re set. Before you put the door trim back on, go and get some adhesive closed cell foam strip , or even that Raven foam weather stripping and apply it along the line that your door skin attaches to the door, this just helps in that *extra* bit of sealing.