OK I have already done an exhaustive search on Deja for other people's posts.
Most of them are concerned with road noise and vibration. However, I have a
slightly different problem.

My setup is like this. 6.5" oversize Peerless CSX series drivers in the doors
of a 97 Nissan Maxima. MB Quart tweeters, being pushed by a Rockford A500II
amp. Before that is a AudioControl EQX series II. The fronts are filtered at
90 Hz, 24 db/octave slope. I don't have a problem with lack of bass or rattles
from the front speakers since they are filtered this high with this much of a
slope. My EQX (for those who are familiar) does a pretty good job of
flattening the response out, but I'm getting sharp peaks around 300-400 Hz
(apparently this affects alot of cars with speakers in the doors). The EQ is
1/2 octave in the midbass on up. I have a 1/3 octave RTA so I can see what my
response is. I just cannot tune it out without seriously altering the sound.
The peaks arent too noticable at most times, but on certain passages,
particularly female vocals, it will husky up the sound with that imfamous muddy
mid bass sound.

I am concerned about the sound from the back of the speaker reflecting in that
metal cavity. I think this has alot to do with my peak. I know there is alot
of sound that comes through, because I can hear alot of midrange if I stand
outside of the car with all the doors/windows shut.
I went to home depot today to investigate the possibility of fiberglass or a
fiber fill material, much like what speakers are stuffed with. The fiberglass
should do an excellent job of damping the rear reflections, but my concern is
moisture. Apparently this stuff will become a sponge when it rains. I dont
need to accelerate any rust. On the other hand, I hear fiberglass won't be too
bad in absorbing the moisture and will dry out relatively quickly. My
speakers are already in sort of a pod (thanks Bose OEM) so I need not worry
about water coming in from above.

So I bought
http://www.partsexpress.com/pe/showd...&St=2409&St2=-
35991693&St3=89257490&DS_ID=3&Product_ID=5688&DID= 7 from parts express. I got
it in the mail and that stuff is just a sheet of foam, which looks like 3/8"
packing material. I think it would do little effect on the speaker's rear
waves. Its also very expensive for a sheet of packing foam.

I also think a 1/3 octave EQ will help by giving finer control in tuning out
the resonance, but I simply do not have the money for this at the moment, and I
want to explore a cheaper route. I will probably try out what fiberglass will
have with my car in the garage, just to see if it is even worth doing.

Advice on how to bust resonance? What about the fiberglass in the door idea?
Anybody do this, and have trouble with it staying wet?

 

I bought an eggcrate style foam mattress pad at Wal-mart. I cut it down and use it in the doors. But your problem may be more associated with the rear wave of the driver not being seperated from the front wave. For this you need to seal the door with something. The favorites are Raam mat version two, Peel and Seal, and Cascade audio VB2DHD. But there are several others. Another way to seal it is to use fiberglass and resin, but most people don't want to get that involved.

 

 

yeah, i think you should try deadening the door. both the door panel and the door itself, moreso the panel. go to lowes and check out the "peel and seal" stuff. it can be found in the rofing section and comes in rolls. i'd put a couple layers down.

 

Hmm thanks for the suggestions guys. Guess i got a project ahead of me. I was doing some toying with my system today, and sure enough theres a resonance in the doors. Not only if I pound on the door, it gongs like a drum, I played some tracks with different variations in the door scheme. First I used no door panel. now that just sounded like crap. Then I put on the door panel, and noticed alot of honky honkness coming out of the holes where the door handle is. Definate resonance here. Theres almost zero clearance bhind the speaker pod for anything when the window is rolled down. I wonder what I'm gonna do. Home Depot did not have the peel n seal stuff, so I gotta drive to Lowes then. Then somehow put all of it in my doors.

 

Ya, its a project, but its a fun one. I've done mine , my ex wifes's car, my girlfriends car, my brothers car, and built custom speaker pods for two Org. members. I promise you, its not very hard to do, and you'll notice a big dif once your done. ( Just make sure to snap some pics )

 

only lowes carries the "peel and seal" stuff. home depot supposedly carries another type ice something, but i can't find it in my HD.

 

I think I saw it at True Value Hardware. At the beach in NC a couple weeks ago. They were selling it by the foot.

 

hmm, we don't have too many true value stores around here. so that's cool. the ones at lowes is sold in 25ft x 6 inch rolls.

 

3 layers of Raam mat on the outer metal skin, two layers on the middle skin, 1 layer capret padding on the middle skin, deflex pad in the door directly behind speaker, 2" thick mdf baffle, door completely sealed with Raam mat = ONE DEAD DOOR!
My speakers sounded incredible in there. Imagine a speaker trying to play inside of a tin can. Well, that's what it's like inside your door.

 

I'm not disagreeing with anyone's post, just sharing with you what I've done in the past and had excellent results with.

This is a very time consuming project but should not be too awfully expensive. Don't try it unless you have lots of patience and are willing to take your time and be meticulous. Any of the following things can be done by themselves, but together they will provide you with the next best thing to a sealed enclosure in your doors.

Take off the door panels, take off any plasic sheeting in there and clean off everything with some sort of heavy-duty cleaner, including the inside door cavity. The cleaner the metal the better.

Buy some high-temp mastic sheets from Mcmaster.com. They are practially identical to Dynamat for about 1/4 the cost. Put two layers of the sheets on the outer door cavity wall. Cover as much as you can by feeding the largest-sized sheets you can through the access holes in the door panelling. You really need a heat gun to do this (a hair dryer takes WAY too long and doesn't really get hot enough) and some sort of roller to press the sheets down. I found that a linoleum roller works well for this because it's small enough to get into the door cavity via the access holes. It's easiest to get the sheets into the cavity by rolling them up after you heat them (leave the plastic on the back so it doesn't stick to itself), putting them through the access holes and then unrolling it into place and then peeling the backing off & pressing it by hand where you want it. Then use the roller to press it down. The hotter you get the sheets with the heat gun the better they stick. The hotter the weather the better, too. If it's too cold then the sheets cool off too quickly. Expect to be sore and get some cuts or scrapes on your arms and hands when you do this correctly!!

Use two cans of Noisekiller grey in each door cavity. It's a spray can version of "rubber" that coats everything with a think layer of anti-resonating goop that rubberizes once it dries. Cover every moving or critical part with aluminum foil so the spray doesn't get on those parts. Spray that stuff everywhere you can in the door cavity being careful not to get it on anything you don't want immobilized. That's what the foil is for, so don't miss anything. Once it dries (overnight) take the aluminum foil off.

Then put one layer of the mastic sheets on the inside metal area of the door. Use the largest sheets you can and cover everything. As you go along cut away at the sheets with a knife for access holes, protruding nuts & bolts, wire harnesses, holes for the door panel snaps, etc. The more you cover the better. Then use smaller sections of sheets to cover the larger access holes. The reason for this is if you need to get into your door cavity later you can just peel away the smaller sections of the sheets rather than ruin the integrity of the large ones that cover the whole door. Then apply clear silicone to anything not covered by the sheets that may rattle. After you do this you should have a pretty dead door that not only will not rattle or resonate, but it should be as close to a sealed enclosure as you can get.

Then apply a layer of sheets to as much surface area as you can to the inside skin of the plastic door panel itself. Also use silicone wherever you can on this too, to stiffen everything up. Be careful not to use too much of anything so the door panel will still properly fit onto the door and snap securely into place.

I did the above procedure on my Explorer and I'm planning on doing the same to my Max when the weather gets nicer this year. In the Explorer I had 8-inch Dynaudio mid-woofers in the front doors. Each woofer had its own dedicated amp-channel with tons of power. Let me tell you, this was almost like having a sealed enclosure in your doors. It sounded like I put home speakers in them. There was absolutely NO discoloration by vibrations, resonances, and the like. It was pure music without any sort of distraction caused by the door.

Obviously, there are other products out their besides Noisekiller Grey and the mastic sheets that do the same or similar things and can be used just as easily. Whatever you do, don't plan on doing all these things in just one day. Plan on this project taking at least 16 hours, not including drying time for the spray and silicone. I usually did 4 hours a day after work and on days off and let the spray and silicone dry overnight as I went along.

Anyway, I'm posting from memory and I hope I didn't forget anything. I hope this helps everyone out there.

Oh...also. EQs are great, but you should do everything else you can do to get the music the way you want before you start EQ-ing. Sound damping, proper aiming and mounting of speakers, x-over points, and the like. A good EQ should be used to tweak, not totally correct problem areas such as peaks and dips in the audio range. Of course, you can correct these things with an EQ, but sometimes, if the problem is a large one, you may be asking more from your speakers than they can provide due to the above-mentioned problem areas. Likewise, if you cut frequencies too far back to prevent buzzes and resonations for example, you will be missing out on the music for that particular band you've just reduced.

Tony