One side project that I decided to do was to see how good I could make the factory stereo sound before replacing the stock system with aftermarket parts.
I had bought the outboard knee pads from JPM Coachworks which required the door cards to be removed to install them so sealing and deadening the doors seemed to be a natural thing to do. On my Civic Si, this had a MAJOR improvement in the sound of my OEM stereo and then any aftermarket upgrades.
Goals:
1) Remove resonance from the panels and attempt to create a better airspace for the door speakers to operate in.
2) Add a noise barrier layer and take care of the back wave behind the speaker to clean up the sound.
3) I was going to add as little weight to the car as possible.
4) I was going to make sure that I maintained all functionality and didn't obstruct anything.
Materials useage:
- I had some left over Second Skin Damplifier from my previous car that I decided to utilize.
- I also bought a door pack of Damplifier to offset what I had.
- I bought two sheets of Overkill Pro closed cell foam.
- A set of Second Skin Speaker Tweakers.
- Some DAP Adhesive left over from installing my JPM Coachworks E-Brake Boot.
- Some plastic sign board to cover access panels. I've seen these done with thin wood, MDF and cardboard, but I prefer the plastic cardboard sign material because it's lightweight, and weatherproof.
- Duct Tape
There are enough DIY's on removing the door cards out there that I won't bother to go over this process. However a little trick that will help later is to take a crayon or something else non-permanent and trace the outline of the door card against the door itself. You will thank yourself later because this will give you the boundary of where the door cards cover.
However it wasn't easy to find a picture of what the door looks like under the door card, so here's one for those of you wanting to see what detail there is:
The first step is to remove the factory plastic sealant. Obviously this is the best time of the year to attempt this because typically there is a nasty bit of cleanup due to how messy this sealant is. But at this time of year, with the cooler temps, I was able to get this all off with a minimum of mess.
If you do make a mess, or live in a hotter climate, a lot of paper towels and Goof Off will be your best friend in getting the rest of the sealant off.
Something to note here... there are actually sound deadening on the outer door panels themselves from the factory. The white square you can see here behind the windows mechanism is one of the spots.
The other spot is behind the speaker.
With Damplifier, full coverage is NOT necessary to effectively deaden a panel, you are just trying to remove the peak area of resonance. Therefore instead of using large chunks, I was going to instead use small pieces, and use the technique of rapping on the panel with my knuckles to determine where there was a resonance or buzz to be dampened.
I probably still used too much, but after this, the door had a nice solid thunk noise with no ringing or vibrations. I also covered over any hole in the door that wasn't required for fasteners on the door car.
At this point, it's the easiest place to install the Second Skin Speaker Tweakers. They go behind the driver in the door and break up the back wave created by the speaker. They attach with super glue gel and there's a potential here to make a HUGE MESS and damage your paint... which I learned the hard way on my Si... Fortunately I didn't make the same mistakes as before but you literally have to put the whole tube of super glue gel on the back, then hold it into position while it bonds. I always try to have some Damplifer underneath of it to give it a good surface to bond to. They're flexible so I let the end fold at the door beam.
Once that was finished, then the next step was to construct panels to cover over the bigger gaps. My preference is to use the outdoor sign board material which is like a plastic cardboard but I've seen these panels done out of wood paneling, MDF, and regular cardboard but I wanted something that would be weatherproof.
To construct the panel, first you want to fit it to the area that you want to cover. I typically use a Sharpie to get a rough shape, and then keep test fitting and cutting away small pieces until it fits. you may have to put small slots into it to allow cables or wiring through.
Once you have your panel finished and fitted. You want to cover it with Damplifier to create a more solid/substantial piece that will not vibrate. You don't have to cover it exactly and use one piece, but I'll trace it out on the Damplifier and then cut it out.
The resulting panel can now be put into place and sealed with duct tape. Try to get all the edges but it doesn't have to be a perfect seal... there are still plenty of air gaps that air and water can escape from in the door, but you're just trying to minimize them. I admit this looks a little bit ghetto, but it makes the panels easily removable if you have to service the window parts. I've seen several methods of attaching these panels including using screws and sealant, and this is not only a less permanent way to close the gap, but you don't have to worry about accidentally damaging something by accidentally drilling or screwing into something.
Now we look at doing the noise barrier with the Overkill Pro. This stuff is thicker than the normal Overkill closed cell foam barrier and though it does make it a bit less easy to put the panels back on, it seems to be a much more effective noise barrier.
The easiest way to trace out what you need is to put the door card down on it and trace out the shape with a Sharpie. Then cut it out with some scissors.
The next thing to do is to hang it on the door using a bit of duct tape and drape it over everything.
From here, you want to make slits so that any harnesses or cables can be passed through. You also want to locate and punch through holes so that the door card can be re-attached.
Once you have located everything and have made sure that the panel is going to sit flat, cut a hole through for the speaker. The next step is to put some tape on the sides of the Overkill in a spot which will allow you to fold down the top part and fold up the bottom, so approximately where you fed the door cables and the harness through.
Now this is where you need to be careful. Fold down the top of your sheet of Overkill and take your spray adhesive and slowly and carefully spray the door and the exposed Overkill with adhesive, for maximum adhesion it wants to be on both surfaces. This can be a serious B**** to clean up so go slowly... it needs time to "tack up" before it will adhere anyways.
When you're finished then slowly work the overkill up against the door and press until it holds on it's own. When you have the upper half stuck in place then fold up the lower half, it helps if you use a little tape and put the adhesive on the door and the other half of the foam, again, for maximum adhesion, both surfaces need to have the adhesive applied. Be very careful around the hole you cut for the speaker and some of the other holes, the adhesive will go through these and make a mess.
When you're finished, fold down the bottom and press everything together... you will be much happier if you make sure you keep your holes lined up correctly.
The result is a somewhat form fitting layer of noise barrier on the door.
You may need to clean up your trimming a little, but reinstall the speaker, make sure that you left enough Overkill around it so that it acts as a gasket for the speaker.
Before you put the door back together... We want to address the plastic in the door card which can also vibrate.... significantly. All of those odd shaped pieces of Damplifier left over from making your panels work well here.
Again, you don't need total coverage with this stuff... just enough to dampen the vibration. The tap test isn't as effective here so a bit of guesswork won't hurt.
Of course, don't forget that the main goal was to install these beautiful JPM Coachworks Outer Knee Pads.
From here... you just need to reassemble the door. If you have a BRZ Limited then the lights in the door are a bit of a PITA to get plugged back in, and it does take a bit of force to get the fasteners back in and compress the Overkill. Oh... and make sure you have all of those rubber washer things that go on the fasteners in place. This is now redundant but they were originally there so that the fasteners didn't rattle while in the door.
When you've finished both doors, it's time to figure out if all the work was worth it. I tend to work very slowly and deliberately and take my time doing this, and it basically took two 4-5 hour evenings to do this. If I'd just gone for full coverage I could've gone much quicker.
So did it make a difference.
OH HELL YES!!!!
I'd listened to a few choice tracks before, after I'd done the first door and after I'd done both doors. The difference is amazing. My test track was "Satellite 15...The Final Frontier" from Iron Maiden's "The Final Frontier" which I picked because the intro "Satellite 15..." features a staccato chaotic mixture of drums, bass and guitars that are hard to pick out and certain points caused massive buzzing in the panels when the bass note is plucked and allowed to ring out. The bass is distorted through the intro, which makes it hard to pick out if it's speaker distortion or the recording (it's the recording, but will distort a speaker pretty easily). From there "The Final Frontier" starts with a staccato snare hit and goes into clean tone bass, harmonized chord progressions and features a lot of wide open spaces for the vocals and the various melodies to ring out.
I hated listening to this song in the BRZ before... because everything muddied together in the intro and it's a long intro... the song is 8:40 in total. This is one song I used to listen to a lot in my Si and so I could barely stand to hear in the BRZ. Once the doors were sealed, the panel rattling was gone, and you could pick out each individual instrument... it was a night and day difference and the song now has the sound it deserves.
I probably drove around for another couple of hours after that I picking several other songs for dynamics including Rush's "2112", some of my Initial D techno and several Pink Floyd Albums. I still need a sub, but this mod definitely gives those door drivers a punch and a depth that they sorely needed, and when the bass gets busy it remains clear and distinct and doesn't just muddle together.
The next step... we're currently working on the rear seat sub woofer box/storage box/amp rack setup since the back seats in this car are useless anyways, and once I get the Sub ready to go, then that will be the next addition with some more sound deadening.
Oh... and since Damplifier is .35 lbs per square foot, used 8 2 square ft sheets total, plus the Overkill Pro and the Speaker Tweakers, I don't think that I added much more than 7 lbs to the car, which is a perfect result!