Mmmm.... Hushmat on the door.

[Syonyk]

I've been making slow but steady progress in my "Luxury Loyale" quest. The muffler that didn't have holes pointed at the body was a good start. The new stereo head unit is nice, and beats the pants off the stock unit (plus has a proper aux in). And the new speakers are, surprise, better than the old factory ones.

 

After reading some threads on Dynamat/etc, I decided to give it a shot. I picked up a "door kit" of Hush Mat from the local car audio store. It's very similar to dynamat, except you don't have to heat up the door to apply it. After looking at how the door access is (very limited), I decided this was going to be a lot easier than trying to use a roller inside the door and heating the dynamat. Plus, I like to support local business, and I've harassed these guys a lot with questions.

 

So, I pulled everything off the door, and started applying the stuff. It goes on fairly easy, though it's STICKY - getting it into position is difficult for some of the farther points. Also, I was only able to get 85-90% of the door - I flat out couldn't reach the rest of the areas.

 

I covered most of the outside sheet metal, and wrapped a bit around the side bar (not sure if that makes a huge difference or not, but I couldn't get much down behind it, so I covered it to help dampen any vibration getting through to it. I didn't do anything on the inside panel, because it seemed the power window mechanism used most of that.

 

It took 4.5 sq ft to do the driver's side door, if anyone was wondering. With smaller hands, I could get almost everything with 5 sq ft, or maybe 5.5.

 

Results so far:

1. The door thuds shut. It's noticeably heavier (not much, but enough to feel when opening/closing it), and the sound it makes when closing is a much more "expensive" sound. No reverb, just a solid "thud" and it's done.

 

2. The driver's side is quieter. Running down the road, I couldn't *hear* a huge difference, but I had that feeling of my left ear being semi-deaf. It was only when I was moving, though - at a stop, my ears were fine. I assume this is my subconcious going, "Uhm... this should be louder. Something's wrong." However, there was less road noise from that side.

 

3. I can't hear the driver's side lock mechanism anymore. I have power locks, and even over the clanging of the rest of the locks, I could previously hear the driver's door lock snap open/shut. Not now. I locked the door after I put it back together to test it, and my first reaction was, "****. I managed to jam the lock mechanism with the hushmat. How'd I do that?" Then I realized that it may have just silenced the lock mechanism. The lock works fine, but there's a definite difference.

 

I'm going to do the passenger's door tomorrow. That will use up most of the rest of the hushmat I have. I'll probably do the rear doors next month, and then the rear quarter panels & hatch in another month or two. I may eventually do the roof, though that'll just be annoyingly expensive (I paid $90 for the 10 sq ft that will do both doors).

 

I'll post more thoughts after I get more done, but so far, I'm excited. It's definitely a major improvement over the bare metal doors.

 

-=Russ=-

[daeron]

how much did the stuff you already got (enough to do both front doors, 90 bucks you said) weigh? and how much of that weight goes away as it cures, any idea? also, does this stuff act as heat insulation too? i would imagine it may be a bit expensive to use on the floors.. but it would CERTAINLY help eliminate road noise.. i mean, the doors already serve as a three layer baffle against road noise as it is, and the floor is just a single (albeit multi-ply) layer between you and the road... just a thought, because if its good insulation too.. keep unwanted heat/cold out. Maybe it just occurs to me because i live in south florida and have had too many cars without AC...

[Syonyk]

how much did the stuff you already got (enough to do both front doors, 90 bucks you said) weigh? and how much of that weight goes away as it cures, any idea? also, does this stuff act as heat insulation too? i would imagine it may be a bit expensive to use on the floors.. but it would CERTAINLY help eliminate road noise.. i mean, the doors already serve as a three layer baffle against road noise as it is, and the floor is just a single (albeit multi-ply) layer between you and the road... just a thought, because if its good insulation too.. keep unwanted heat/cold out. Maybe it just occurs to me because i live in south florida and have had too many cars without AC...

 

The box is 10-15 lbs. It's not that heavy, but I don't think any of the weight goes away as it cures.

 

I would assume it will help with insulation, though I don't know for sure. Doing the floor/roof would be really expensive, though.

 

I may eventually do the floor/firewall. I'll see. That'd be a while down the road, though.

 

-=Russ=-

[daeron]

i didnt think it would wiegh too much. I worked at a veterinarian for many years, and at one point one of our main suppliers started using these insulated bags for cold shipments.. they have a mylar outer layer, and inside it seems like bubble wrap, but a good bit stronger. I managed to snag about ten or twelve of them, and theyre about 10x18, 10x36 if i clit them into a sheet...and Im gonna use that underneath the carpeting on my Datsun, mylar side down as insulation/sound dampening.. it might not have a HUGE effect, but its gonna be super lightweight...and i could even do two layers if i had to. i cant wait to see what it works like.

[DasWaff]

In a nut shell, There are two parts to noise reduction... First, anything that forms an air tight barrier, and traps a bit of air (or better yet vacuum) will reduce noise, even if it is as thin as mylar. It inhibits the direct air motion which transmits sound waves. The practical application for cars is "sealing holes reduces noise".

Second, dampening material (like hush mat) inhibits the transmission of sound waves through a rigid membrane, like door steel, by absorbing energy. For calculating the effectiveness of dampening material the key is density (it also needs to be elastic). It takes more energy to make dense stuff vibrate, so much of the energy of sounds is absorbed. Structures like car doors are natural resonators, certain pitches (frequencies) will pass through them without losing almost any energy, this depends upon the shape, sizes, construction and air volume of the door. This is where stuff like Hush mat excels, it really cuts back on the resonance of the enclosure.

 

The less dense the absorbing material the smaller the range of frequencies it will absorb, and the higher the frequencies absorbed will be. In other words lighter material does not absorb low frequencies (bass) well. To make a less dense material more effective you have to use a greater thickness.

 

Since heat energy can move in a number of ways (radiation, convection, and conduction) not all sound absorber will serve as good insulators for heat energy. But in general they do help.

 

DW

[daeron]

DW: Yah.

 

noise reduction was a side benefit to me, the big thing was HEAT.. have you ever ridden in or driven a datsun 240/260/280Z?? the seventies style? them things get toasty.. also noxious sometimes with exhaust, but thats another matter.. :- )

 

but that was exactly what i thought. primarily heat insulation (likely two layers on the tranny tunnel, especially on exhaust side) and a minimal side benefit in putting another layer to dampen sound. that air-filled multilayer honeycomb behind the mylar should baffle SOME more sound than its mass might lead one to believe..and its a side benefit anyhow. good thoughts though.

[Virrdog]

(I paid $90 for the 10 sq ft that will do both doors).

:-\ $9 a square foot? Wow, that's a lot. I think you paid off whatever debt you had to the audio shop.

 

http://www.raamaudio.com/cgi-bin/index.cgi?p=pr

 

This place sells some of the best stuff you can get and is ran by a really great guy. He also supports the Subaru community and is now a Subie owner.

[DasWaff]

have you ever ridden in or driven a datsun 240/260/280Z?? ...that air-filled multilayer honeycomb behind the mylar should baffle SOME more sound than its mass might lead one to believe..

Actually, yes, a '73 260 I think... Same people roasting problem in some UK cars too (I remember a '59 MGA ride that left me medium to medium rare). You're right about the mylar bubble stuff. Since it combines both the sealed dead air and the absorbtion it will reduce noise more than one would expect from its density alone. I'll be very interested to hear what the results are, good luck, DW

[Prospeeder]

you realize you can get the same stuff, peal and stick, from places like Home depot and lowes for dirt cheap for HUGE rolls of it that work just as good.

[Virrdog]

you realize you can get the same stuff, peal and stick, from places like Home depot and lowes for dirt cheap for HUGE rolls of it that work just as good.

There are asphalt based deadeners and there are butyl rubber based deadeners and some are a composite of the two.

 

Butyl rubber deadeners are the best and highest quality. They are always the "top of the line" product for the different brands. Asphalt ones can be easily replaced with peel & seal stuff found at Lowes, etc... But you might end up with a sticky mess on a hot day, not to mention some smells. I would use the really cheap stuff on floors and something with a good adhesive on walls and ceilings.

 

I have been researching sound deadening like mad because I am about to do it in my wagon.

 

http://www.sounddeadenershowdown.com is another really great site. Very informative for learning how and what to buy.

[daeron]

you realize you can get the same stuff, peal and stick, from places like Home depot and lowes for dirt cheap for HUGE rolls of it that work just as good.

 

were you talking to me, about my mylar stuff?? because mine was free, that was the best part :- )

[Prospeeder]

oh i dunno, I wasnt talkin to anyone, lol, just saying you could get it cheaper elsewhere, but i guess if u live in a HOT HOT place it would be a good idea to get the exspensive stuff.

[subie94]

luckly the previous owner did almost every thing for me..

behind the speakers are the dynamat baskets..

 

 

he also did the tail gate.not sure about the back doors,haven't taken the panels off yet.

 

Syonyk,did you get any pics of while you were doing the install? are you planning on adding any subs or just keeping with the small speakers?

[daeron]

oh i dunno, I wasnt talkin to anyone, lol, just saying you could get it cheaper elsewhere, but i guess if u live in a HOT HOT place it would be a good idea to get the exspensive stuff.

 

heh, i was wondering... because id love to be able to find this stuff im talking about on a roll at home depot for 1.50/yd or something... ive seen products that sound similar (no knowing if my insulated bags are any less effective than their sound and insulating mat) for EXHORBITANT prices, ie about the same price per sqaure foot coverage as the dynamat and the curing goo hushmat stuff..but that was like, in jeg's or something...so it would be as pricey as they can get away with

[Syonyk]

Syonyk,did you get any pics of while you were doing the install? are you planning on adding any subs or just keeping with the small speakers?

 

I've only done one door. I was planning to get pics while doing the other door(s). Also, I did mine on the outside panel, not just covering the inside of the door like your Dynamat is.

 

I have a 12" sub & box that I'm going to wire up, but it's going to be removable - I don't want to eliminate the ability to haul a lot of stuff, and even with just two decent 5.25" speakers, it sounds decent.

 

-=Russ=-