firing direction for subs

i have a 1997 mazda protege and im trying to figure out how im going to shove 4 12 inch subs into the trunk.

the space i have to work with is...

37 inches wide,16 inches tall,32 inches deep....

im thinking of maybe firing them all up im the trunk, theyde fit perfectly. but how would it sound?or how about all firing down?

or maybe curving the front inalmost like a U shape then they all could fit and fire forward.

do you guys have any suggestions? im so stuck on this and i need to get it done lol

any help would be appreciated, thanks guys

dump 2 of the subs....make a bigger box and give your subs more power.

Ill bet if ya put all 4 in the trunk, you won't be able to make the enclosures the optimum size.

If U used every sq. inch of the trunk space ....youd get 2.74 ft per sub. But thats not possible.

What kind of subs...and are ya lookin for sealed or vented ?

New and improved...

You've got plenty of cu. ft. to put in 4 subs, just limited on width to put 4 across.  But plenty of depth to work with at 32".  Here's a thought on splitting the subs into two enclosures, 2 in each box, a back row and a front row.  All are firing same direction, the subs in the back row are inverted, and you take advantage of the 32" depth you have to work with.  These subs can use 1.75 ft^3 or quite a bit less air volume.

The boxes can be of different shapes as long as the volume in each is the same (volume for inverted subs is less by the displacement of the driver plus some for the concave cone). 

Wiring would be separate from each box so you can reverse the phase of one of them.  4 ohms per pair and paralleled at the amp hookup for 2 ohm total.

It looks like a tight fit and not enough volume in the rough pic I made, but you have 37" of width to use so there's plenty of room for air volume.

 

-------------
Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

im only going to be running one amp though,a rockford fosgate 1000a2, so how would i phase only two of them?

i love that design though, it looks awsome, thanks man.

p.s. i know the subs only require a 1 cubic foot box each sealed. but i could go bigger and sound better right?

also with 2 rear inverted subs in the back, how would the SQ/SPL be affected?

1.  You just reverse + and - wires at the amp terminals.  You'll have a wire coming from each box, so when you connect the back box wire, switch polarity at the amp.  (You can put double wires on the amp terminals.)

2.  Glad you do, I would like to try this out myself.  It should look real cool when you see it with the trunk opened.  It will be calculations like mad to get the boxes designed, but it's a lot of fun IMO.  Should be very do-able.

3.  Yes, work on the math using your full working width and see how close to the max. 1.75 ft^3 you can get.  The larger enclosure space will give you more SPL per watt.  Smaller spaces take more power.  You'll be along the lines of 1 to 1.5ft^3 for each driver with this setup, though, in my estimation.

4.  There should be no decline in either when all is done properly.

I can link you to some help files on calculating angles and stuff.  There are good wedge enclosure calculators on this site, here.  For figuring interior space put a "0" in the thickness category.  And a lot of other good links:  copy and paste my sig.

...and here I was anticipating a question on Step 2: Figuring Volume and Measurements.......lol...but you are already setting up the saw for the build!  No, I know you wouldn't start cutting wood before its time...

For visual appeal, the design wants the face of each box to be the same angle.  Their bases also are the same height.  Now, since you (I hope) have already figured out volumes for each box, you know how much room (depth) to give the front one and how much for the back one.  To have figured angles for the back box, you will already know what the depth and height is, and the angle of the face.

Copy the same angle for the front box.  The highest point should be the same as the highest point of the rear box.  The depth is determined by the available space overall (still 32"?) minus the depth of the rear box.  That leaves one angle, the backside of the front box.  It is formed by drawing a line from the center top to the top of the base.  During a build, I would measure and fit angled baffles after the base and any other known baffles are cut and assembled.

This project takes careful consideration of driver fit.  I hope you have the subs so you can work up a virtual mockup before cutting MDF.  The inverted subs have to clear the front box while allowing the boxes to fit snug together.  And the front subs have to easily clear the floor of the box.

The pic I made is true to scale as far as depth and height.  The subs were drawn freehand, but I tried to approximate scale as close as my eye let me.  You can copy the pic to a picture program and print it "to fit page".  You'll then have a working paper model for figuring volumes.

Front box will have two right angle wedges and a rectangle.  Back box will have one right angle wedge and two rectangles.  Those rectangular air spaces will most likely be about 1" but that's valuable air volume.  For wedge calculation, use the formula 1/2 base X H X W, or use the wedge 1 calculator in this site using "0" for thickness.  You are just figuring interior volume.

But, then, you may have really gotten past all this already.  What is the volume for each chamber, and what is the displacement of the driver?  How much did you add for cone area for the inverted subs?  Do you have a divider baffle figured in to separate the subs and provide bracing support?  What thickness of MDF are you using?

im using 3/4 inch MDF....here are the subs im using.

https://www.shopping.com/xPF-Rockford_Fosgate_HE2_RFP4212

i came up with 2.532 cubic feet for the rear box on the rockford fosgate website

the bottom of the rear box i put as 16 inches though

That would leave you only 16" OD for the front box, and you won't get enough volume.  The ratio of front/rear is going to be approx. 3 to 2, as far as depth goes.  The front has to be larger because the subs will take up some of the volume.

Do you have specs for those subs that give the displacement?  Something from the manufacturer? 

Go over these posts in this thread again to pick up all the details gone over so far.  Get the measurements on paper.  Work the measurements of the two boxes, making changes where needed,  so you end up with the rear box approx. 0.25 ft^3 (check manufacturer specs) smaller than the front box interior air volume.  Once you get it looking right on paper, draw a true-to-life outline on a large piece of cardboard or paper similar to the drawing I posted.  Hold a sub in place and see if it fits. 

-------------
Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

Displacement - 141.70 cu in - but thats from a P3 which i guess is like the equivelant of the HE2 DVC....

heres all the have for the HE2 DVC

https://www.rockfordfosgate.com/ez2/ModelInfo/ModelInfo.asp?ItemKey=10062923&CategoryDesc=Speakers%20-%20Raw%20Drivers%20/%20Separates

i took a stab at the math for the bottom length for these(not good with math so bare with me lol)

front bottom=21"

rear bottom 11"

am i doing this all wrong or does this look right? lol

Those subs look like about .08 displacement, so count that as solid fill and add that much more volume to the front on each side.  Total .16 air space added to the front.  The rears will be actual air volume plus about .02 for each inverted sub, total .04 for the rear.  Figure the difference in air volume front to rear is 0.2 ft^3 (the front needs .2 ft more than the rear). 

Your OD numbers look like a good start.  If the front OD depth is 21" and there is 3/4" MDF on each end, subtract 1.5" to make depth 19.5". 

When doing a problem like this there is a lot of trial and error involved.  Becoming familiar with the math will happen for you because you will be doing the same math over and over.  Be sure to use the printed pic...

...or draw a pic, label all the sections (wedges and rectangles) I showed you above, make notes and lots of them.  I believe you should end up with about 1.5 ft^3 for the front for each sub and the equivalent for the rear, which would be 1.4 ft^3 for each sub chamber.

Good luck with it.  I believe you have info or links to all the tools you need along with the info I gave you.  You should be able to come up with a good working diagram and measurements.

Here's a good calculator for finding the length of the slanted side (hypotenuse) of a right triangle.  It will also give you the angle of the cuts at the ends.

https://www.1728.com/pythgorn.htm

For this project you want the faces of both boxes to be the same angle.  You can use this calculator to find the exact length of the angled side and the angles of the cuts you have to make.

Call the face of box front "wedge 1", and call the face of box rear "wedge 3".  In my current workup (which isn't complete), I have the rear box depth at 11.6".  The height at 11.5" (these are inside measurements).  Input those two numbers for "sides" and find hypotenuse.  It comes up as 16.33".

If you copy wedge 1 with the same sides 1 and 2 lengths as wedge 3, the angles and hypotenuse lengths will be identical.  The difference in the front box volume can then be made up in the wedge 2 space.

The angle of wedge 2 is not important other than that the inverted sub has to clear it, and you find its base by using the remaining available space after wedges 1 and 3 have been figured.  (Wedge 1 + 2 bases will equal the interior dimensions of depth for box front.)

(Add additional height (air volume) to both boxes by increasing the height of the rectangles on the bottoms.  It is here where you will get the most added air space.  Keep the same height on both boxes.  You are only limited by the available room in your car, and the inverted sub at its highest point will dictate how high you can go. 

Here are the results.  I figured out volumes and measurements for this project (may do this some day myself...) and I will outline it here.  All dimensions here are OD (outside dimensions).  The two boxes have the same common height at 15", the same common width at 36", and have a common base height of 3 3/4".  The face angle of each is 45 degrees, and saw angle cuts are listed here for the angles.  The face angle cuts are 45 degrees, but the angle on the rear of the front box has angle cuts of 16 and 74 degrees.  The lengths of the hypotenuses are 14 7/8" for each face and 10 7/8" for the backward angle.  There is a center top flat depth of 2 3/4" on the front box (I figured the air space directly below it at 1 1/2", so let the final size be determined when you assemble the angled sides), and a rear top flat depth of 3 1/4" on the rear box.  The depth of the front box is 16 1/2"; the depth of the rear box is 14 1/2".  The two boxes combined make 31" depth.

Volumes were determined using 3/4" MDF.  A solid 3/4" MDF center baffle is placed dead center of each box to separate the subs.  I figured subwoofer displacement ( or lack of, in the rear box) with these measurements.  Each sub will have 1.2 cubic feet of air space (displacement already figured in).  Build the boxes exactly to these specs and you will be good to go...(but check for fit in your car first).  Just an inch different somewhere will throw the balance off....and in your case where you are powering all subs with one amp channel, we want the volumes to be the same for each sub.

In this new pic, the subs have been resized to be truer to scale and the base has been raised.  But I didn't redraw the boxes entirely, so the rear will actually extend forward a bit more than is shown, and the front will be somewhat compacted.

Using the same side view, the interior space is divided into rectangles and wedges and calculated to get total volume for each box.  Measurements below the pic are interior, and the results are listed below.

                   1.0766                                           1.0766

                     .307                                                .5127

                     .307                                                .76

              ___.879___                                    _________

                  2.569   ft^3                                     2.35   ft^3

         -   ___.16___  sub displacement  +__.04___   cone area

                  2.41  ft^3                                          2.39  ft^3

The middle divider and all sides have already been deducted, so you just divide these box volume totals by two to get 1.2 ft^3 per sub.

Calculators used:

https://www.the12volt.com/caraudio/boxcalcs.asp#wed

https://www.the12volt.com/caraudio/boxcalcs.asp#rec

https://www.1728.com/pythgorn.htm

Enjoy the build and do a damn fine job on it.  I have a lot of hours in on this project!   lol

Rob, lol  I scratched my head for awhile on that one...and then it finally dawned on me how much you admire Bose...audio engineering with a twist!

And thanks for the nod, DYohn.  I know you aren't a fan of inverted sub setups, and neither am I....this one evolved from a challenge in the first post "How can I cram 4 subs into a space 37 x 16 x 32?"  Instead of a don't-do-it reaction, I thought why not, if he's going to do it anyway with them all facing up (blehhh!), let's see if we can make something workable.  So I threw an idea in there.  Then I eventually needed to find out if it would really work, and that involves real figuring instead of guessing....

This project was extra difficult because of the two-box design and the fact that one would have inverted subs... and that all subs would have to have the same air volume after displacement.  But once figured out, it's a very versatile system.  Just one of the enclosures could be used, for example, or the volume in either could be easily adapted to different subs by changing base heght without having to change the angles.  They are easier to load into the car than one bigger box would be.  And the setup is adaptable to further customization like putting a neon on the backside of the front box to light up the inverted bling factor.

Anyway, I hope someone who is just starting and wants to build his own setup sees this and uses it.  One could pretty much just use the post above and have all the details he needs to put it all together.  And of course he'll be on this forum for any other questions, too!  If it gets built, post up some pics.

ill be starting the building some time this week, my fiancee is in the hospitol right now, her cervix is 3 cm dialated already and shes only 33 weeks so far. so theyr holding her in there till prolly wednesday and then deliver it because then shell be 34 weeks. so things been kinda hectic here lately lol

but ill be definately posting up pics throughout the build and then of finish product :D thanks for all the help stevdart.

heres some other boxes ive built.....

Keep in mind that the outside measurements include the thickness of the wood.  If you start with a 16 1/2" base, you would then add a front and back 3" wall to make the total base height 3 3/4".  If you then cut a 14 7/8" front (slant) baffle and cut the edges at 45 degree angles....the box dimensions are done.  It would just be a matter of fitting a back slant with the angled edges cut as I showed, and then filling in the top space.  And then attaching the side walls.  (Don't forget to put in the center baffle.)

But, on the other hand, if the front and rear 3 3/4" walls are made to extend to the floor, the bottom piece will indeed be about 15" because it will fit in between the walls.

As long as both boxes have the same size/angle front baffle and the same base height as well as same total height, you can make up differences anywhere else.  And of course the volumes should be close to correct.  If you end up with harmony in the overall pair of boxes and the subs have the same net volume of air....it will be good.