[Melvivio]

Coool. this is now one of the first modification to the car! I wonder if I can buy the stuff in holland [img]style_emoticons/<#EMO_DIR#>/smile.gif[/img] , ah well, lets focus on getting a 968 first before thinking of all the modifications [img]style_emoticons/<#EMO_DIR#>/smile.gif[/img]

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[Johannvb]

A shop around the corner of my house sells it. http://www.johnfreriks.nl/

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[rxter]

I got a pack of dynamat extreme in. I had expected a closed cell foam product, but instead the stuff looks like a huge sheet of butyl tape. And it weighs a ton. Anyone know how this stuff works? Seems like a pretty unsophisticated solution. I'm pretty sure that I don't want to add 40 pounds back into the car. Has anyone tried dynaliner instead of dynamat? They say that dynaliner goes on top of dynamat.

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[flash]

the stuff WORKS



as an audio engineer, i can tell you for certain that the only way to kill sound penetration is to add mass and/or deaden vibration by means of isolating vibrating membranes. fluff and padding only dampen internal resonance, and do NOTHING to prevent penetration.

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[ds968]

[quote name='rxter' timestamp='1330750466' post='122674']I got a pack of dynamat extreme in. I had expected a closed cell foam product, but instead the stuff looks like a huge sheet of butyl tape. And it weighs a ton. Anyone know how this stuff works? Seems like a pretty unsophisticated solution. I'm pretty sure that I don't want to add 40 pounds back into the car. Has anyone tried dynaliner instead of dynamat? They say that dynaliner goes on top of dynamat.[/quote]



See my post (#22) in the " sound deadening material placement in doors.." thread on the following page.



worth the added weight IMO ..but then again, with spacers and steel bolts on all my wheels I had already added about 40+lbs ( rotating mass equivalent ) to my car, so the additional 15 or 20 lbs or whatever the dynamat xtr weighed was just one more compromise in favor of sight and sound, at the expense of performance.

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[rxter]

Look ma, no blood - well minimal blood.



I found that installing in smaller sections was easier to maneuver through the little door holes.



   



The roller, while very effective, is not all that useful as there are not a lot of places where you can use it. Mostly pressing hard by hand.



I got the alu tape for seams. Is that really important? I suppose it will keep the dust out of the seams but I don't ever plan to go in here again so do I really care?

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[Cloud9...68]

Wait'll you put those panels back on. Maybe you'll have better luck that I did, but I had a heckuva time getting everything lined up. I'll rebuild a rear suspension or an engine, but for me, working on door panels is something we should sentence those who have committed crimes against the state to.



Are you doing the whole car? The worst of the droning comes from the back, so I would think putting dynamat under the cargo floor, inside the rear wheel well, and around the spare tire and such, would offer the most benefit against noise. This is definitely something I would do to any street 968, particularly a coupe. Yes, it adds some weight, but if you're worried about it, especially in a moderate climate such as SoCal, you could always install a lightweight battery and offset most of it.

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[rxter]

I may do the trunk. I'd like to do the area where the rear speakers go as that is in the pass compartment, but the seat belts and top mechanism is in there with precious little room to maneuver.



I will most definately not be messing with the carpeting. It's in good shape and way to hard to pull from what I've read.

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[Cloud9...68]

Ah, I forgot that you have a cab. It's probably not that important to do the back area then. That big hatch window in the coupes really reflects the road noise inside the car, creating a very annoying and tiresome drone. If I every buy another 968 for the street, I'm going to pack about a hundred pounds of dynamat back there. I rode in a 2000 M Coupe a couple of years ago, and it had the exact same noise, so I'm sure it's the configuration of the rear hatch area, which is similar between the two cars.

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[MB968]

[quote name='rxter' timestamp='1330750466' post='122674']

I got a pack of dynamat extreme in. I had expected a closed cell foam product, but instead the stuff looks like a huge sheet of butyl tape. And it weighs a ton. Anyone know how this stuff works? Seems like a pretty unsophisticated solution. I'm pretty sure that I don't want to add 40 pounds back into the car. Has anyone tried dynaliner instead of dynamat? They say that dynaliner goes on top of dynamat.

[/quote]



What you are looking at is not an unsophisticated solution. You expected closed cell foam, because foam is commonly used to absorb sound waves. But, the small holes in foam only work on higher frequencies. In order to absorb frequencies below 100 Hz, our anechoic chamber had foam pyramids that stuck out from the walls and ceiling about 30 inches.



But if you know what components are turning the energy into noise (i.e. constitute the speakers), then it is better to dampen them. I'm not familiar with dynamat, when I worked in this field we used a lot of EAR products. As I see Dynamat in these pictures, it looks to me like an unconstrained layer damping application. It appears to be foil backed, but would need to have a much thicker metal layer to be an effective constrained layer damping application. As I recall, butyl is a decent viscoelastic material with reasonable damping properties in the temp range of interest. We often added products that came with the layer of damping material, with foam attached to it. If you put the dynaliner on top of the dynamat you'd have a similar product. It serves to dampen, as well as to absorb.



Finally, since I was cleaning this part yesterday, has anyone noticed that the sheetmetal clutch access cover is made from two layers of steel. I'd bet that there is some sort of viscolastic material in between the two sheetmetal plates. Looks like a typical constrained layer damping application to me.

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[flash]

again, the primary function is to dampen OUTSIDE proliferation and penetration, not inside resonance. while it does do a good job of helping reflection and resonance on the inside, it is more help from the outside. is is an elastic membrane that lowers the amount of energy transmitted to the sheet metal. it is surprisingly effective. the old school way of doing this was to add sheets of lead.



you can't apply reflection killing methods to absorbing energy in penetration. behind those big foam cones in that chamber, the walls were thick, heavy, and probably walls within walls. that's how every such chamber i worded in was built. pretty much the same thing when building a recording studio too.



killing what is inside a room is nothing like killing things from entering the room. very different methods.



the clutch access cover on my car is cast aluminum

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[lbpesq]

Best way to deal with the "drone"? Put on some music you love and TURN IT UP!!!! The Grateful Dead station on my XM radio does the job quite nicely! Of course I suspect the dynamat lining in my doors helps. <img src="/forum/images/smilies/968/rock.gif" class="smilie" alt="" />



Bill

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[MB968]

Flash, don't know how to respond to your inputs above. I am pleased that there has been some experimentation and success among members on this site improving the noise quality in our cars. I plan to take advantage of this knowledge at some point. None of my comments were aimed at changing the methods that I've seen on this site. I was responding to the unsophisticated comment.



Technically I can't completely agree with all your comments, some I do. For instance its not really true that it "lowers the amount of energy transmitted to the sheet metal". The sheet metal and the applied material act together. They are still subjected to the same amount of energy. But viscoelastic materials have the unique quality that they can absorb a lot of energy (usually as the long chain molecules microscopically slide back and forth over one another). Since the viscoelastic mat'l absorbs a lot of energy the total amount of vibration amplitude of the sandwich assembly is greatly reduced. An applied "elastic" material will not be very effective. And the way that lead worked was moreso for its mass to change natural frequencies of the sheetmetal. It was not really applied for it's ability to absorb energy, although it is much better than steel, but still not in the same class as polymers that have good viscoelastic properties.



If it seemed like it, I was not suggesting adding the foam to the back of the dynamat. Doing that inside the door would likely do very to absorb the noise that is already being transmitted to the interior of the car via many other sources. The soft materials in the car help some with that.



And finally, I was not referring to the cast aluminum access cover that we use to change the clutch. Although this cover also has what looks to me to be an applied nonconstrained layer damping material on the outside, and uses foam on the inside for apparent absorbtion of noise from inside the bell housing.



I was referring to the sheet metal cover that fits in front of the bell housing. It is part #29 on the parts list and is listed as "protective plate". Check it out. I don't often see applications of constrained layer damping, but this looks to be an example.

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[flash]

it lowers the amount of energy transmitted THROUGH the sheet metal. again we are trying to stop EXTERNAL noise from entering. we are not trying to quiet down internal resonance. however, it does a pretty decent job of doing some of that as well. softer materials inside the car would do better, but who wants to put big blocks of fiberglass in their car?



my engine is apart at the moment. i'll look at that cover. never gave that one a second thought.

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[Rap]

I'm sort of lost here. I can make no knowledgeable claims to the info posted. What I do know is that with the catback that RS installed, outside sound was increased. This sound as you go up or down in gears or speed sounds pretty good to me. Partly because of laziness I have not put a new stereo in and partly because I like the sound of the car. The one time I drove with buds in listening to music I felt somewhat disconnected to the car and the drive. Don't get me wrong, I love music and just installed it up and down in the garage but what's wrong with listening to the growl of a 968? Just an opinion I suppose! Lol

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[flash]

lol - not a danged thing!



however, if you were one to like to listen to your stereo, or just didn't like the constant drone of road noise, this is what to do to help that.



i still hear the exhaust just fine, but now it's only coming from the back of the car. what i don't hear as much of is the other extraneous noise from all around. as a result, the speakers don't have to work as hard to overcome that noise, and i can have the overall SPL lower. my ears don't get nearly as tired

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[Rap]

I do understand that. Your ears get tired? Is there some sort of exercise to strengthen your ears so that wouldn't happen!!! Lol

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[flash]

lol - absolutely they get tired. most people don't know that. ears are like anything else though. constant exposure to noise decreases their sensitivity. i can't count the number of shows i've gone to where my ears went into compression half way through. it doesn't take much though to have an effect. a concert may be 110db, and so would assume that it would create a problem. what many don't know though is that the inside of a car can easily be 95db. because it is lower it takes longer, but the effects can be the same. having a single frequency sustained for a period increases the likelihood of an effect.



that's why there things like noise canceling devices now. some cars actually come with them built into the stereo.

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[ds968]

[quote name='Rap' timestamp='1330878701' post='122713']I do understand that. Your ears get tired? Is there some sort of exercise to strengthen your ears so that wouldn't happen!!! Lol[/quote]



Yes, Thighs .

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[Rap]

From the nether regions?

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