down firing for a 99+ silverado?

Vehicle specs: 1999 Chevrolet Silverado (newer body style) Extended cab. Pioneer P3100DVD head unit. 6.5" Infinities in the doors. Don't know what they are specifically, my dad put them in long before the truck became mine. Rockford Fosgate 200S amp bridged to power a Rockford Fosgate Z3410 (basic, 10" sub). I got the amp wired to two of these subs, and a standard car box. I bridged it and build my own box to fit underneath the driver's side of the rear seat in the truck. I came across two 10" Kickers with an amp for cheap and they are now sitting in your standard ProBass box in my closet. For one, that ProBass box will not fit in my cab if I want back seats, and secondly, those two subs provide way more bass than my simple extended cab truck will ever need......for now.... I'd like to do the same thing here, build a box for one to fit under the back seat, and power it off one amp. (Amp is another story, I might end up trading for something more suited for my needs). I've pretty much come to the conclusion that a down firing box would be my best bet. The seat bottom sags a bit with a heavy person in it, so the current box was built with a few inched of space above it to accommodate this, but as is, I don't let people sit there for fear of it sagging too much and jacking up the sub. With a down firing box, will I be able to just brace it well and have it up against the bottom of the seat? Does the box touch the floor on all 4 sides of the sub? Will this produce negative affects in my vehicle? I was planning on another sealed box, should I be thinking vented or this? I'm new to subs and boxes, but handy with building, and my dad is even better. I just need help designing the box, or getting a few questions answered. After that, I can plan and question you guys, and begin to build a prototype box. If I do the same as last time, I'll end up using the prototype box for a long while because I get to busy to build a better, prettier one... I did a bit of searching around before I joined, as well as before posting, but if I've missed a topic, by all means, let me know, and I apologize.I've got twenty years of education, sir. I graduated the tenth grade twice!

First off, you could take a look around this site to help you come up with ideas for your box:

http://www.soundoffaudio.com/items.cfm/cat1/SUBWOOFER%20BOXES/cat2/CHEVROLET

As for your other questions, I would say that you should be able to have the box right up against the seat if they are downf  firing. A little bracing would not hurt either. When subwoofer boxes are build correctly and with the correct material (mdf/partical board/ and some types of plywood) they are surprisingly strong (as they would need to be to contain all the internal pressure created from the woofers). Just make sure to use plenty of glue and the box should be fine even if a heavy person is sitting in the seat.

If I was constructing a down firing box, I would make good use of rubber stoppers (take a look at some of the boxes on the website above). Just place these around the subwoofer so there is room for the woofers excursion, so it is not hitting your floor.

There should not be any negative effects on your vehicle unless it is extremely rusted out, which I doubt that it is.

And finally, it is up to you on what type of enclousure to build. Sealed will prove to have slightly better clarity and response, while sacrificing efficiancy. Vented/Ported will give you more output, but is much harder to design and construct. It is up to you.

Hope this helped. Excuse my spelling.

-Andrew

I was also wondering about how much air needs to be able to move around under the box. http://www.soundoffaudio.com/item.cfm/id/741 I'm guessing that is ideal. I can make wooden or use rubber spacers to have just the 4 corners supported and all 4 sides of the bottom of the box open to the air. That was one of my main wonderings. Yet with this box (one of the first I came across while searching). http://subthump.com/product_info.php?cPath=1_71&products_id=28 There doesn't appear to be anywhere for air to move from under the box, to the rest of the cabin, I would think that is necessary...right? I has seriously not thought of using spacers yet (this is why I ask around). That will make the design much simpler, as I can flush mount the sub to the bottom of the box, not have to have the box around the sub extend downwards to rest on the floor. I've got twenty years of education, sir. I graduated the tenth grade twice!

I think my box will be most similar to this here. http://www.soundoffaudio.com/item.cfm/id/741 I'll use rubber/wood stoppers on each corner. I'll probably have the front/back of the box at 90* from the bottom, to make it simpler on me for the first box. Questions: 1. Would a rubber stopper suit my needs better? Keep the box from rattling at much or something? I would assume it would at least help.. 2. Should I put 4 slits in the carpet so the stoppers are resting on the steel floor of the pickup, not the 1/2" of carpet/padding? 3. Should I consider having the 4 corners actually bolted to the steel body of the truck? This wouldn't be too hard for me. I would assume I'd just run a long bolt through the bottom of the box, the middle of the rubber foot, and into the floor of the truck, with a nut underneath, correct? 4. I cannot seem to find the volume for my sub. Not the volume of the box, the volume of the sub so I can subtract that from the box volume to make sure I'm hitting at least the minimum requirements for the box. Thanks for any help guys!I've got twenty years of education, sir. I graduated the tenth grade twice!

The volume a sub takes from the box is called "displacement".   I am not seeing the need for rubber stoppers. As far as securing the box in, 2- "L"-brackets with tek screws - 2-"L" brackets held by 1/4" threaded anchor bolt / wing nut-- if you plan to remove it occasionally for any reason.This is what I do for FUN!

Oh, I re-read your posts about the stoppers. I wouldnt do it, looks #1, stability #2. If you cut the sides out the full size they can be first, then the bottom of your box, the baffle, is raised up 2"and screwed between both sides. Leave no less than 2 inches of floor clearance and 12" of width(minimum). From the side of the truck it should appear form fitted. Leave the gap in the front side of the box.This is what I do for FUN!

Had to re-read that second post, but I think I get it now. BEFORE CARPETING, looking from the side of the truck, you will see one large, shaped piece of MDF. Matching piece on the other side. Back plate. Bottom of box (w/sub attached) is screwed inbetween those three pieces. Front of box only comes down to the level of the sub, leaving only the front of the box open for the air underneath to escape. Thanks for displacement, I was having a brain fart there and remembered it's called that like a day after posting... Why do I want to use tek screws with two of the L-brackets? Why not drill 4 or 8 holes and use anchor bolts with wing nuts on all of them? Probably won't be removing the box often, unless I'm going to build another. Another question, if I'm going to be drilling holes, and using L brackets to secure the box to the floor, won't I need to remove the carpet/padding from the area as well? I don't mind I guess... I don't quite see how the box would move around if the sides are cut to fit, and the seat is pressing down on it from above. Although I could really shape the sides well, and get some extra volume without that corner being carpeted. If the carpet is coming out, I'm building the box for behind the driver's seat, since my truck is a 3 door. Also, would it be a good idea to utilize the seat mounts in the back of the truck? I can attach two L-brackets to the bolts that the back seats rests on, leaving me with only two L-brackets to drill holes for.I've got twenty years of education, sir. I graduated the tenth grade twice!