Sound Deaden the subwoofers and surrounding rear trim panel

fmorelli

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[This is a rescue thread from the UK z4-forum. Much like the Photobucket debacle, postimage.org made a change that killed all the links to its repository. After repeated requests by several z4-forum members to get this fixed, the author nor anyone else seem to address it. Thankfully I had the information and have recreated the thread here, to protect availability of the content. It was originally created by billy_beemer, who as of this posting, had not logged in to the z4-forum for two years.]
 

fmorelli

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I have the 11 speaker setup, to start with I thought one of the subs was blown, but mainly the farting noise of the stock subs comes from the surrounding trim (at least on my car it did)...

As I couldn't really find any concrete documents on the wattage and resistance of the subs (which I know at least are 2 ohm and probably 30-40watts RMS) I felt it best just to have a go at applying some good old Dynamat to try and resolve the problem..... and it seems to have worked quite well, more punch to the subs and less farty noise.... almost no farty noise in fact..... not bad for an afternoons work... as I couldn't find a guide, here's how:

Wind deflector off, prise off the little caps to reveal some screws, pop those out...
IMG_5215.jpg



Prise apart the rollbar cover...
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IMG_5214.jpg


Unscrew.....
IMG_5216.jpg


IMG_5217.jpg


Pull out the weather trim...
IMG_5218.jpg


Pull up to remove the kick plate guard, you'll need to remove the rivets and slide them back in to put it back on later...
IMG_5219.jpg


IMG_5220.jpg


You need to unscrew and remove the speaker before doing this part, and make sure you have a small precision flat head to remove the wire connections for the rear courtesy light and the speaker - remember extra care must be taken when using screw drivers near speakers...
IMG_5221.jpg


Wasn't 100% sure whether these rivets should be removed but I wiggled this around until it came free
IMG_5223.jpg


Remove cheeky bolt (you need to remove the trim nearer to the front of the car to reveal this)
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Pop this off...
IMG_5225.jpg


Take a tea break and ponder on whether this is worth while..... of course it is - you're a man, man up....
My pondering took me to a time when I owned an MX-5 and I thought.. the BOSE on the cheap mazda didn't rattle......
IMG_5227.jpg


Open the roof half way, remove cheeky rivets - there's one hidden at each end too.
\
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Now the panel can slide free to reveal some bolts, pop those out...
IMG_5232.jpg


Cheeky bolts hidden behind the little plastic cover that just kinda wiggles free
IMG_5233.jpg


Remove remaining top bolts and you'll find the whole trim panel starts to wiggle free - its held in around the centre console and removing this was a faff, you have to peel back the side covers slightly and work it free - a 2nd pair of hands or even a 3rd would have been a bonus but I managed to do it - you have to be weary as the plastic going into the centre console is dead sharp and will mark the soft leather arm rest...


IMG_5234.jpg


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Subs! Unbolt, unclip and take inside.....
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4 screws hold in the sub, once removed it took a fair bit of prising to get it out but with care and force (forceful care?) out it will come.
IMG_5241.jpg


Now go to town with the Dynamat, I coated the inside of the box, the back of the box, inside the metal enclosure on the car and parts of the bulkhead trim before slinging it all back together.
IMG_5242.jpg


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Now play some dance music with the BASS up and hope you haven't caused any new rattles in doing all this.

I lost a couple of rivets putting it back together so some spares would come in handy........
 
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fmorelli

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On my car, exactly. 0.7 lbs per sq ft - I used Noico 80 mil sound deadening. My car has about 10 lbs of that material. It's extensively deadened. I made the decision to do this in part moving to a complete ball joint and spherical bearing suspension, motor and trans mounts, and exhaust, and already being a two seat convertible (not quiet to begin with). My goal is to get to a 600whp track capable car that I can still take a 90 minute drive with my wife and have her not hate it. So had to lower NVH.

Filippo
 
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Lurcher

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While I understand the deadening of the outside of the enclosure and the car itself - placing any dampening inside the sub chamber just takes away required airspace and adjust the perceived "Q" of the sub (adjusting performance and frequency levels). If anything - some poly batting inside the enclosure "may" help the sub think there is more airspace and counter any standing waves, but as these subs were built for this small of an environment, I'd doubt it.

Of course - this is all theory. Anyone doing this and have a RTA handy? I'm still not convinced this car can be adequately sealed to make a noticeable difference with the top up. This is just adjusting the resonate frequency of the tin can to a different point :grin:

With the top down - who cares....
 
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carabuser

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On my car, exactly. 0.7 lbs per sq ft - I used Noico 80 mil sound deadening. My car has about 10 lbs of that material. It's extensively deadened. I made the decision to do this in part moving to a complete ball joint and spherical bearing suspension, motor and trans mounts, and exhaust, and already being a two seat convertible (not quiet to begin with). My goal is to get to a 600whp track capable car that I can still take a 90 minute drive with my wife and have her not hate it. So had to lower NVH.

Filippo
Thanks for archiving this, I was searching for it over on z4 forum as I knew I'd seen a thread about this.

I'm looking to reduce the road noise in my car a little. It's pretty much all coming from behind the seats around the small rear window area. Did you notice a reduction in noise from that location?
 

fmorelli

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@carabuser, I performed all my sound deadening at once, so it is difficult to say what specifically may have helped in certain ways. Other things such as quality and condition of your tires can also play a factor.

I would definitely sound deaden the doors, which are like two large drums. You have to make the decision of whether to pull apart the rear bulkhead, which is certainly a pain in the neck.

Filippo
 

carabuser

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@carabuser, I performed all my sound deadening at once, so it is difficult to say what specifically may have helped in certain ways. Other things such as quality and condition of your tires can also play a factor.

I would definitely sound deaden the doors, which are like two large drums. You have to make the decision of whether to pull apart the rear bulkhead, which is certainly a pain in the neck.

Filippo

Tyres are just over half worn and 2 years old. I do have wider rear tyres which obviously doesn't help.

I was considering putting some sound deadening on the outside of the wheel arch, underneath the liner. Is it a bad idea to put it externally?
 

Lurcher

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I've done the doors, but.... With downpipes (even with a stock exhaust) if your worried about noise this is not the car for you. I'm not saying don't do it, just don't try to make the car something it's not - you will always be disappointed. I drive with the top down 95% of the time, and the hearing is going ever so slightly :cool:

I would NOT put any external to the cabin though.
 

fmorelli

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Depends on what you are doing. In my case there is not a single pieces of rubber left in the suspension, so the idea was to mute the car as much as possible. Not to mention the drivetrain is held more stiffly than stock. When you are headed to 600whp and that kind of suspension, one is as you say "making the car something it's not ;-)
 

carabuser

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I've done the doors, but.... With downpipes (even with a stock exhaust) if your worried about noise this is not the car for you. I'm not saying don't do it, just don't try to make the car something it's not - you will always be disappointed. I drive with the top down 95% of the time, and the hearing is going ever so slightly :cool:

I would NOT put any external to the cabin though.

It's just the noise coming from the rear speaker area near the seatbelt that's the problem. It's a common complaint and something that I think may be fixable with a small change.

If you lay a towel over that area the noise almost completely vanishes, it's something that other E89 owners have mentioned before but nobody has ever put effort into sorting out.
 

fmorelli

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@carabuser sorry I'm being dense. Can you shoot a photo of where you place the towel? Or do you have a reference link (you note other E89 owners discussing) ... I'm not really understanding exactly where the issue is.
 

carabuser

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@carabuser sorry I'm being dense. Can you shoot a photo of where you place the towel? Or do you have a reference link (you note other E89 owners discussing) ... I'm not really understanding exactly where the issue is.
Just from here, where he's poking the speaker grill:
img_5217-jpg.12782


I can't find the thread where others mention it.
 

fmorelli

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Wow ... ok ... that's weird ... there really isn't much there. I've attached a large photo which shows everything bare. Is this noise more with the top down (wondering if it is some kind of air tunnel)?

I have many photos of the car apart. Maybe this one helps...

Filippo

IMG_20180403_150730.jpg
 
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carabuser

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It's road noise, mainly tyre noise but it just seems to be really loud in that exact area, right behind my ear. It's certainly normal noise making its way in an abnormal way if that makes sense.

Maybe it's coming from the window or the seals around the roof. I'll check all the seals. There's no water ingress at all which is why I've not suspected seals earlier.
 

fmorelli

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The type of sound would make it clear. So remember, (I know this is dumb) but your ears being on the side of your head is going to bias where the sound comes from.

If it is road noise, then sticking a towel there is the same as sticking the towel on the left ear. What tires are on your car, how old are they, and how many miles?

One of the reasons I did work to dampen the bulkhead, and put the sound deadener all in the rear is that rear wheels often create a fair bit of noise in what is basically a drum (the rear hatch area). Notice how hatchbacks tend to be loud? In my case, I was going to the TTX Öhlins setup which was pushing us to a spherical bearing on the top mount - that wasn't going to help noise!

Word of wisdom - on rear upper shock mounts stick with a factory rubber mount. No value to putting anything else there, except if you like to increase the noise in your car :).

Filippo
 

carabuser

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Tyres are Michelin PS4S, 2yrs old and about 8k miles on them at the moment.

I'll certainly put some deadening on the rear bulkhead if that helps a lot. It's pretty easy to get to the bare metal around where the Combox sits, would that be a good place to start?