Sub boxing helps and tips?

[ChevyK1500]

About a month or so ago I had a 12 inch sub and a 10 inch sub chilling on my back seat taking up space and the 10 inch just stopped pumping so now im starting in on building a pretty much full sub woofer build (building a forward firing sub box from scratch, running larger gauged wire to amp, two new twelve inch subs, sub covers, custom lighting on box) this will be the first sub box im ever making myself, and the reason im choosing on building one myself is for three main reasons
1) I want a forward firing sub box and cant really find them anywhere
2) I needed a project for woods class so I decided on making a new box
3) I try to build any part I can for my truck so I can take more pride in it, "Built not Bought" is kinda its theme.

there are a couple things I would like to get to know a little better and some opinions.
1) Has anyone here made a forward firing box for 2 12's and have dimensions I could rob?
2) What would the best way of going about knowing im building the box right?
3) How would i go about getting the right air space in the box? (1.25ft^3 recommended, could I go more or less to get a deeper hit?)
4) Any little tips to help in building the box to make it easier for me?
5) What kind of sub grill/cover should I get? / is there a possible way to build my own? (i dont want a waffle or mesh one)
6) Ever hear of a sub spacer? would it be possible to cut a little groove into it to lay some LED's for lights?


Extra Info:
I have 2 new Hifonics HFX12D4 that are planned to go in the box (400RMS 800peak)
I will be using a Pyramid Arctic Series pb717x 1000 watt 2 Channel amp
planning on a 4 gauge power and ground wire
im trying to keep this on a really tight budget because Im only in High School and funds are very limited.

When I start building the box I plan on making a thread for it, and any help now would be greatly appreciated so I run into as few bumps along the way as possible. Thanks for helping out.

 

[Mean Green]

Alright, I'll try to help answer most of your questions for you to give you a better understanding! Before you start deciding on how you want your sub placement, you need to decide if you want a Sealed Enclosure or a Ported Enclosure. The reason you have to choose which route first, is because it is crucial to the box design.

1. The reason you don't see many pre-fab forward firing enclosures, is because they do not fit under the back seat. Even with a 10" sub, you basically have to almost lay it down and sacrifice most all of the rear leg room in the back seat. However, if you where to raise the backseat up a few inches, it would greatly aid you. Your going to have a really tough time making a forward firing enclosure for two 12's with the back seat in stock location if this is your first build. Up Firing or Down Firing is a much better route to go for simplicity sake.

2. Ported vs Sealed Enclosures. As a general rule of thumb; a sealed enclosure is best for sound quality and a Ported enclosure is best for SPL (sound pressure levels) aka loudness. I personally prefer sealed enclosures, because i'm a SQ guy. Also, sealed enclosures are generally easier to build then ported enclosures.

3. How do you know your building it right? You are going to want to use 3/4" MDF for the enclosures, MDF is ideal for subwoofer enclosures. If your building a sealed enclosure, it has to be SEALED. As in air tight. You are also going to want to build trusses every 8" or so inside the enclosure. To make these, just cut some 3"X3" squares out of scrap MDF and then cut them in half diagonally. So your left with 2 triangles from the one square. This helps add strenght the the walls of the enclosure. Secondly, every joint needs to be glued and screwed. Screws should be pre-drilled with a small diameter drill bit, every 4"-5". Also before installing the top or bottom of the enclosure, caulk every seem a few times inside the enclosure. Again, air tight is key. Also if you are planning on running 2 sub woofers, it is better most of the time to have two separate chambers inside the enclosure for each subwoofer. If you where wanting to go ported, most of the above applies to that as well. However box design is much different.

4. To do dual subs, your going to have to remove the jack under the PS rear seat to gain space. Even with that, it is going to be near impossible to to get 1.25^3 of air volume for each sub. It may not sound like that much room, but it there really isn't much room under the rear seat. You would be better off running two 10" or 8" sub woofers then running two 12" sub woofers. You could also try and find a subwoofer that doesn't require as much air volume. Regardless, if you are don't have quite enough of the recommended air volume, you can fill the box about 50% full with poly fill. This is a good thing to do regardless IMO.

5. For a grille or cover for the sub, you'll have to look at universal ones or grilles that are made for your sub. With that being said, you could absolutely fabricate one up as well!


I hope this helps answer a few of your questions, I'll be more then happy to try and help answer any more you may have!

 

[ChevyK1500]

Thanks for your help, i know for sure that im wanting to do a sealed box because i think it would be a little bit more simple for me.

I know the 12 inch sub would not fit standing vertically so im going to be building out in front of the seat a little bit to create an angle and have a little more room to fit the subs and more air space and I dont passengers often in the back seat.

My truck doesnt have a jack in it anymore because when i bought the truck i ripped it out cause it was broken.

on the trusses do i set those up vertically as a brace or place them in the corners?

what exactly is poly fill and how does it work?

what could i make a cover out of? or where could i find a nice looking cover for 10-15 dollars a piece?

 

[Mean Green]

Do you know the depth of your subwoofers? What I meant by laying them down, is bringing the bottom edge of the enclosure out quite a ways to enough face on the enclosure to mount the subwoofer. Try taking a straight edge and laying it from the bottom edge of the seat, to the floor. You are going to need at LEAST 14" of flat surface on the face of the enclosure to mount safely mount the subs.

The trusses you are going to want to set them up vertically every 6"-8", and then double them up in the corners. Again, glue and caulking are KEY on every joint as well as screwing it or you can also use nails. Personally I prefer screws and countersink them.

The poly-fil is the same material that you find inside the cheap pillows (Not feather pillows). It helps a bit with leveling out response, and somewhat tricks the subwoofer into thinking it is in a bigger enclosure.

Also, you didn't mention anything about this but I will throw this in here for future reference for you. Do not run the RCA cable from the headunit to the amp as you do the power wire from the battery to the amp. (Eg. Run the power wire and signal wire down the passenger side, and the RCA cable down the drivers side to the back seat.

As for grilles, you can try to look for something on eBay or Amazon etc!

 

[ChevyK1500]

thank you for the great amount of help, i'll remember to brace it good and try to figure out the angles needed to get 14+ inches of mounting height/angle and enough mounting depth at the same time. thanks for the help.

 

[Mean Green]

Not a problem! If you have any more questions, I'll be happy to help!