Fiberglassing a horizontal surface

I also have the PITA mercedes. I have an E320 2000. I want to help you as much as I possibly can. I finally found the solution to getting very decent bass in these cars after tons of trial and error. I have built and rebuilt this thins so many times its rediculous. I would do one of these

1. this is what I had to do but it works awesome. First off you need to completely seal the box off from the trunk. I mean completely....with no holes whatsoever. I had to cut 2 big holes on the rear shelp but you may not have to depending on the output  and size of your subs. ( I have 2- 13w7's sealed)... now I built a box in the shape of a trapezoid. put the enclosure in then sealed it up to the deck with walls attached to the box. I did the sides first then the front. I guess you may need a picture to underttand what I mean. http://home.comcast.net/~martinjammin/wsb/media/809484/site1025.jpg

heres the link to all my struggles with this car 

this one has the final fix and it is something else..... http://www.carsound.com/cgi-bin/UBB_CGI/ultimatebb.cgi?ubb=get_topic&f=4&t=006872 

http://www.carsound.com/UBB/ultimatebb.php?ubb=get_topic;f=2;t=004509

http://www.carsound.com/cgi-bin/UBB_CGI/ultimatebb.cgi?ubb=get_topic&f=1&t=023689

http://www.carsound.com/UBB/ultimatebb.php?ubb=get_topic;f=4;t=006711

You have to seal the box to the rear deck. I did it with Dynamatt but there are other ways....I highly recommend you do this one....but I wouldnt cut the holes as big...It is very loud though...I mean its sick to where the rear window looks like it will break the seal and the roof flexes like crazy....this hits really hard( force to your back type feel) and  its really detailed.  Its like a half slot loaded enclosure that is corner loaded off the rear window.

the other way is to space a baffle that will butt up to the face of your sub box and has holes in it to fit the entire sub face through it. Space ti as much as you have too away from the bottom of the shelf so it clears the dips and curves and will have enough room for sub excursion.. So essentially you will have a regular sub enclosure...and a box that will fit on the face but it has an oval or something cutout for the subs.  well seal that small baffle with the holes up the rear deck with dynamat fiberglass, sprayfoam or anything that you can. I will say you need to make sure the wood needs to be either glassed permanently or give it a gasket of some sorts so the metal and wood dont touch. It will cause a nasty squeeky/rattling sound when bass hits.   But once that smaller box it attached to the rear deck all you have to do is put the box in and lift it up to the baffle with the subs through the holes and get it affixed so that it will stay there....like wedge it up so it wont break the seal.  Heres kindof and example of that smaller box http://www.imagedynamicsusa.com/gallery/main.php?g2_view=core.ShowItem&g2_itemId=6593&g2_page=2 look how they do the IB setup. Now imagine its not IB and you had a sealed box butted against that baffle and sealed with the subs in the box but firing up through the holes

trust me these two methods will work and blow your mind depending on the sub...even if you build a ported box...please still seal them off from the trunk.COMPLETELY!!

or you can do IB( infinite baffle) like they do there but you will still have lots of trank rattle.

Well I guess I have to stop here because its getting kinda long. but if you have any questions let me know ...

Thanks man, I really appreciate that.  I have actually installed this before in my car.  I kept it in my original configuration for about a year, but I didn't like the way it was situated.  I basically just build a square box and cut a round hole in the metal dash.  Then I built an amp rack that fit directly under the sub box.  It wedged the box up against the underside of the dash and was simply held there by pressure.  The foam baffling around the subwoofer was pushed up against the back dash.  Eventually, that foam baffle on the sub got too compressed over time and the whole enclosure started to move around slightly.  Also, when the sub hit hard enough, it would hit the metal dash and sound terrible.

So here's my ultimate plan.  I'm not going to use fiberglass for the enclosure at all.  This will make it easier for me since I have a lot of woodworking tools already and no fiberglass experience.  It will start by cutting the hole in my dash into a square hole.  Then, I'll make a mounting plate for my sub that will fit on top of the dash (i.e. inside of the car).  It will be square with a round hole the middle.  I will seal the subwoofer to the mounting plate, and have the sub inside the car under the medkit door (that I will rebuild out of MDF so it doesn't rattle). I will dynamat (well, I'm using damplifier pro) the rear dash, and begin building the enclosure in the trunk.

I will start with the MDF piece that will butt up against the underside of the dash. I'll cut it to size and cut the hole for the sub, then I'll buy some 1-2" thick foam material from the fabric store, cut it to fit the MDF piece I make and glue it on.  This will make it so that there are no vibration problems between the metal dash and the MDF.  Then I will build the rest of the enclosure out of MDF.  I will build it such that it goes all the way to the floor of the trunk and is again held in place by pressure, like my old enclosure. The main difference will just be that my sub will be inside the cabin rather than butting up against the underside of the dash.  I'll probably get some L-brackets and some self-tapping metal screws and secure it further to the underside of the rear dash.  Somewhere in the whole mess, I'll mount my amplifier and Audiocontrol EQS 6-channel EQ...

Thanks much for your help, I appriciate it.  Any more advice?

I had a reallyinformative post that I wrote and wouldnt you know I accidentally closed the screen before sending.

basically do a round hole not square

try my setup because it is a PITA to keep the box up in the air and so it stays

this way it just sits on the floor and you can bolt it down...plus you can use plexi to display the subs front or rear

my setup has characteristics of rear firing as far as loudness but the accuracy of a forward fired enclosure.  It eliminates most mechanical sounds that you get from subs faced right at you and strenghtens the lows and tightens things up....Trust me on this...its nasty in your back.. this speakerworks s class uses the same thing  This link has more pics http://usdaudio.com/sw/cars/mb/but here is what I'm talking about

its almost just like being in a bandpass box but without the BP sound...you get efficiency and volume but it sounds natural and has some nasty impact.

either way you go let me know so as I am putting together a tutorial for fellow Benz owners...These cars are really meant for people that dont want to modify...Well that aint me...

well Im tired of typing fro now...you should have seen the post I deleted...Ill try to get the info to you later that I lost and left out here.

cool, thanks man.  You're right, it is pretty tough to get it to stay in place.  That will also help me avoid the problem of trying to get the sub to seal (the mounting plate would somehow have to seal to the enclosure in the trunk with screws and non-hardening rope caulk.  I think I'm going to follow your advice.  Here's a link to a thread I have started on www.bnzsport.com.  My plan is to update it as I go.  You can read everything I have thought of doing for this thing in more detail that I can imagine you'd ever want!

http://www.bnzsport.com/forums/index.php?showtopic=17043&hl=pete's+audio