Sound proofing rear quarters
01-28-2021, 06:12 PM
#31
While sound dampening material like rubber or asphalt or ceramic loaded vinyl works best being directly attached to the metal, MLV (mass loaded vinyl) is a noise blocker, not an absorber. It is least effective when applied directly to the metal. You need to either add a layer of foam or buy it with attached foam and apply it with the foam between the vinyl and the metal surface.
Last edited by Billu; 01-28-2021 at 08:17 PM.
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01-29-2021, 12:57 AM
#34
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Actually, just the opposite.
While sound dampening material like rubber or asphalt or ceramic loaded vinyl works best being directly attached to the metal, MLV (mass loaded vinyl) is a noise blocker, not an absorber. It is least effective when applied directly to the metal. You need to either add a layer of foam or buy it with attached foam and apply it with the foam between the vinyl and the metal surface.
While sound dampening material like rubber or asphalt or ceramic loaded vinyl works best being directly attached to the metal, MLV (mass loaded vinyl) is a noise blocker, not an absorber. It is least effective when applied directly to the metal. You need to either add a layer of foam or buy it with attached foam and apply it with the foam between the vinyl and the metal surface.
1) Stop it outside the car
2) Dampen panels
3) Decouple the remainder TO the chassis boundary.
4) Absorb from within the cabin
01-29-2021, 01:00 AM
#35
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nope, thats the only part of the interior trim i left in. Didnt want to damage the area around the sunroof. The material is stuffed up above the opening above the seat belt reel. ..used a small dowel rod to help wedge up as far as i could. Majority of it is down below the speaker hole.
chuck, i stuffed it in in “handfuls” and didnt use a bag....this is on the interior cavities. I will probably uses the same approach on the exterior cavities when in get to it....especially on the upper hollows of that pillar. The lower area may need a bag to either keep it dry or help keep the smaller chunks together, but i can tear it of in larger sections, it comes in long sheets.
just thumping the panel on the inside before and after has gotten rid of the “hollow” sound.
chuck, i stuffed it in in “handfuls” and didnt use a bag....this is on the interior cavities. I will probably uses the same approach on the exterior cavities when in get to it....especially on the upper hollows of that pillar. The lower area may need a bag to either keep it dry or help keep the smaller chunks together, but i can tear it of in larger sections, it comes in long sheets.
just thumping the panel on the inside before and after has gotten rid of the “hollow” sound.
There are significant wind noise entry points that you can manage up there...consider it.
03-02-2021, 10:41 PM
#36
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Add foam sound-absorbing materials on top of that. I've had a concern for being able to block the lower b-pillar cavity while avoiding any possible issues with moisture trapped up in there. My instinct says to blow a thin dry-cleaner's bag up in there (shop vac...), and follow with a mist of water and some expanding foam. The water mist "cures" the foam quickly, and prevents creep and bag explosion up top over time. Not an issue in most places, but in our very dry high-desert climate it solves a nagging issue. In a previous car in a similar climate, I had expanding foam bleeding out of lower cavities after I filled the rocker cavities. If you want to find every manufacturing gap in the tub, expanding foam will alert you with yellow streamers and blobs in the oddest places.
In wheel-well cavities, do the same with the plastic bag material or painters film, with edges secured with gaffers tape. Foam them, then sculpt with am electric kitchen carving knife. Close the bag, and you have a molded 'plug' held in by the tape. Removable if/when needed, zero clean-up back to original. getting spray foam off after it's cured to clean painted metal is too much work; use the bag.
did you fill it from the holes that secure the door sil plate. Im at the perfect time to do this. As far as i can tell that rocker is pretty well sealed with little or no chance of water getting in and is hollow along the entire door opening and then some.
did you use your run of the mill homedepot expanding foam in the can.... ?
10-06-2022, 09:12 AM
#37
Rennlist Member
Does anybody knows when Porsche will have original soundproof for 928? They have everything for 964 and I don't understand why they don't have anything for 928....
10-06-2022, 11:47 AM
#38
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I've been using lead sheeting, de-coupled with visco-elestic foam. It's more effective than mass loaded vinyl, by the pound, and thin. It conforms to shapes almost like foil. 1/8 or 1/64 inch rolls are available on amazon. I used a flooring underlayment as the foam "de-coupler" on the body side and 1/2 inch visco elastic (almost like memory foam...memory foam would work) on the interior side. I mentioned this before and i think some thought "HEAVY" but the net difference between an effective amount of dynamat, foam, butyl or some other approach is not significant. maybe 30 lbs difference if you do the entire car. I highly recommend it. Super effective...but it must be de-coupled, floating between layers of foam. Gluing to the body kills the ability of the lead to convert the sound waves to "wiggles"
10-06-2022, 03:34 PM
#39
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Here's a spreadsheet of all the factory part numbers for each sound insulation piece for a '79 and an '89 928. Pricing and availability are 2-3 years out of date.
https://webfiles.uci.edu/redwards/pu...2010-6-22.xlsx
https://webfiles.uci.edu/redwards/pu...2010-6-22.xlsx
10-06-2022, 03:41 PM
#40
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Thread Starter
Here's a spreadsheet of all the factory part numbers for each sound insulation piece for a '79 and an '89 928. Pricing and availability are 2-3 years out of date.
https://webfiles.uci.edu/redwards/pu...2010-6-22.xlsx
https://webfiles.uci.edu/redwards/pu...2010-6-22.xlsx
05-17-2023, 11:03 PM
#41
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You gotta look into stuffing Roxul up into the pillar ahead of the rear wheels, I did.
The door latch panel is _right_ there, and its a huge area of resonant road noise.
Also used this behind the front tires, in the washer bottle and cruise control cavities.
_huge_ gains there.
Yes, working to block noise already in the cabin in useful, but 10x harder than keeping from coming into the cabin in the first place.
The door latch panel is _right_ there, and its a huge area of resonant road noise.
Also used this behind the front tires, in the washer bottle and cruise control cavities.
_huge_ gains there.
Yes, working to block noise already in the cabin in useful, but 10x harder than keeping from coming into the cabin in the first place.
There was also a black angle-cut tube exiting at the bottom of the (left) driver's side behind the front wheel, so I didn't want to block that (don't know what it is from).
Last edited by hernanca; 05-17-2023 at 11:04 PM. Reason: Added picture.
05-17-2023, 11:57 PM
#42
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Thank you, Gentlemen. I did this today for the outside cavities only (behind front wheels & in front of rear wheels). Notice I only used a small amount of the big $75 bag (guessing 5'x1.5'x2.5') available at the local Home Depot when filling just the exterior cavities. I tore off as big of chunks as I could, but some crevices required fistfuls. My 86.5 rockers are aftermarket, so there are small open gaps at the bottom at both locations, and I didn't have anything to close that gap, so I stopped above the gaps with large pieces wedged against bracketing found near the bottom of the cavities. I will have to check it to see if any Rockwool migrates down before I eventually close the gap and finish the job.
There was also a black angle-cut tube exiting at the bottom of the (left) driver's side behind the front wheel, so I didn't want to block that (don't know what it is from).
There was also a black angle-cut tube exiting at the bottom of the (left) driver's side behind the front wheel, so I didn't want to block that (don't know what it is from).
Thats it.
I dont recall the product, but they have some new stuff I found there last trip doing Vans car...came in...much smaller clear bags, white material.
That tube is the sunroof drain.
05-18-2023, 08:40 AM
#43
Rennlist Member
I could do without the potential fiberglass itchiness property, though. I had read up on that and wore a long sleeve shirt and gloves to work with it and can't tell if I have any "above baseline" itchiness. Rockwell themselves responded to a posted question about the itchiness and said it will be less than fiberglass but both are fibrous materials, so it does have that property and had recommended the proper attire.
Thank you!! It did seem large-ish (2x larger than vacuum tubing, for reference). That implies I should have seen one on the passenger side, but I did not notice one so I will need to look for it. Also tells me I could easily extend it lower, now that I know what it is.
05-18-2023, 09:05 AM
#44
Having used this stuff when we built my dad's house 1) if you're sweating at all or working in Florida humidity you will get itchy, 2) his house is very quiet. Probably more to do with the interior door woodworking budget $ than what's beneath the sheetrock, but I do remember the day we put it all in being impressed.
05-18-2023, 09:07 PM
#45
Rennlist Member
Smaller bags would be great!! As long as it had all the same good properties of the Rockwool: water resistant, mold & mildew resistant.
I could do without the potential fiberglass itchiness property, though. I had read up on that and wore a long sleeve shirt and gloves to work with it and can't tell if I have any "above baseline" itchiness. Rockwell themselves responded to a posted question about the itchiness and said it will be less than fiberglass but both are fibrous materials, so it does have that property and had recommended the proper attire.
Thank you!! It did seem large-ish (2x larger than vacuum tubing, for reference). That implies I should have seen one on the passenger side, but I did not notice one so I will need to look for it. Also tells me I could easily extend it lower, now that I know what it is.
I could do without the potential fiberglass itchiness property, though. I had read up on that and wore a long sleeve shirt and gloves to work with it and can't tell if I have any "above baseline" itchiness. Rockwell themselves responded to a posted question about the itchiness and said it will be less than fiberglass but both are fibrous materials, so it does have that property and had recommended the proper attire.
Thank you!! It did seem large-ish (2x larger than vacuum tubing, for reference). That implies I should have seen one on the passenger side, but I did not notice one so I will need to look for it. Also tells me I could easily extend it lower, now that I know what it is.
