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Subwoofer box help

 

New member
Username: Mark8313

Saginaw, MI United States

Post Number: 1
Registered: May-12
I have two T1D412's (800 rms)Rockford Fosgate Subwoofers.
I have two T1500-bd Rockford Fosgate Amps.
I want a dual chamber box, with single chambers but the ports are on the outside of the subs not between the subs.
I have 2004 Ford Taurus SES with a big truck.
I am looking for a depth of around 19 inches. A height of 14.5 inches and a length of 36.50 to 38.50 inches. I really need some help with making a box that is perfect for my subs. My main issue is the I have all mac computers and the software for this is all windows. So if someone who is an expert could help me out.
I'd be truly greatful.
 

Gold Member
Username: Joe1234

Post Number: 1556
Registered: May-09
You would benefit of giving up more space, some calcs show you can only do their small reference design 1.75 cubes per sub with those dims.
 

New member
Username: Mark8313

Saginaw, MI United States

Post Number: 2
Registered: May-12
So what would it look like if I had a perfectly tunes box? Its t1d412's. I'm looking for loud deep bass
 

Gold Member
Username: Joe1234

Post Number: 1559
Registered: May-09
If you can go to 21 deep that will help.
 

New member
Username: Mark8313

Saginaw, MI United States

Post Number: 3
Registered: May-12
Okay I can do that. What other dimension should I have to have it tuned perfectly? And what would a sketch of this look like so I can have a visual?
 

New member
Username: Mark8313

Saginaw, MI United States

Post Number: 4
Registered: May-12
What Will 21 deep help me with exactly?!
 

Silver Member
Username: Lord_huggington

Ontario Canada

Post Number: 601
Registered: Oct-10
Double post.
 

Silver Member
Username: Lord_huggington

Ontario Canada

Post Number: 602
Registered: Oct-10
I am an expert.

21 deep will add space (obviously). It will allow for more porth depth, which will lower the tune

You should refrain from saying "about" 19 inches because then we'll use 19 inches. Go measure and tell us the exact dimensions you can use.

Using .75" MDF you have 2.54 NET each before port area & sub displacement with 38.5 x 21 x 14.5 (outside), with a 1.5" baffle (where the subs sit), which aren't counter-sunk and sit on 1.5"

2.06 cubes NET each after sub displacement when both ports are 2.5 x 13 x 19 depth, tuned to 42.35 Hz. This is fairly high port area.

It's unwise to use a narrow port (less than 2").

With a 2" port on each side it'd see 2.137 after sub displacement @ 37.385 Hz, with 12.16 inches of port area per cubic foot. I generally use 12-16. 10 or 20 is too low/high... most of the time.

Watch what happends when you use 38.5 x 21 x 14.5 with one port on one side with a dual chamber...

4.487 NET after sub displacements (.12 cubes each, unsure) @ 35.92 Hz. port 4 x 13 x 18.25 depth.

ALL calculations before box bracing.

4.33 cubic feet would be ideal to get 12" of port area per cubic foot.

4.487 minus 4.33 = .157.

It's a tiny space but I suggest adding the .157 to port depth lol.

You should get about 2.25 each @ about 35 Hz with 12" of port per cubic foot. Which sounds pretty good considering the recommendation on sonicelectronix is 1.75 ported. Not an ideal box but it will give good results.

If you have two 1500's @ 2 ohms for about 1500W than you'll want to upgrade your electrical. Big 3, battery, alternator.

Welcome to the money pitt.
 

New member
Username: Mark8313

Saginaw, MI United States

Post Number: 5
Registered: May-12
Thank you Lord_huggington. Im am glad to know I am getting advice from an expert and not some.....yeah know.

So heres the whole story basically.
36.5" x 14.5" x 19" are my dimensions I want to use. If it is really truly a huge difference with tuning and sound output, the biggest I can go is 38" x 15" x 21" and I am using .75" MDF with a 1.5 Thickness in the front of the box. I have a box somewhat laid out where I have the cuts made for the 36.5" 14.5" and 19" box. But I have one more sheet of 4x4 MDF that I can cut up to change the dimensions. If I can use the 36x19 sheets (top and bottom) and the 36x13 sheet for the back, in some way then I'll be 100% devoted to the bigger box. I just need some help big time with the template and the design. But I want each sub to have an individual chamber. I would truly appreciate your help.

My alternator is a 135 ampere I believe, and I do need a second battery very badly. Its like I have a light show in my car at night. The lights flash to the music. I have 1/0 awg in all of my car and I have a third amp coming tomorrow the T-400-4 and soon the T-1652-s speakers and tweeters.

The money pit is correct. I only buy Rockford Fosgate products too. beside the head unit and battery. So I know that part haha.
 

Silver Member
Username: Lord_huggington

Ontario Canada

Post Number: 604
Registered: Oct-10
They don't need individual enclosures, infact it doesn't allow them to move in sync (as much). Not that you could tell a difference. It would help brace the box, though, but at the cost of space. Not that it'd need that much bracing lol.

Why two ports? This gives a bad port ratio. The more square/circular the port the better. This stops air from touching the walls and allows the box to breathe better.

It'd actually be worse if your lights weren't flickering.

135 amps is good for 1000W-1500W sub amp so you should be good.

Upgrade to 0 gauge wiring on everything you can, especially the "big 3", where you upgrade the batt, ground, amp wires ETC.

RF isn't that good :\. Sorry lol.

.75"
1.5" baffle
36.5 x 14.5 x 19 outside
dual chamber, separated by .75"
2 ports, each 2 x 13 x 17.25 depth (not physical but calculated, it's complicated lol)
~1.8 cubes per sub after sub displacement (not bracing) @ 42.6 Hz with 14.44" of port per cube. Can't go lower than 2" so you're kinda stuck with 1.8 @ 42.6, which is so NOT ideal for music.

Horrible.

.75"
1.5" baffle
dual chamber, separated by .75"
38 x 15 x 21 outside
2 ports, each 2 x 13.5 x 19.25 depth (calculated, not physical)
2.184 per sub after sub displacment (.12 per sub) (not bracing) @ 37.62 Hz, with 12.36" of oprt per cube.

After bracing (and maybe 45 degree corners which would help a heck of a lot) you'd be looking at about 2 @ 38 Hz with 12.5" of port per cube.

Your box isn't ideal but it'd work.

I did 2.25 @ 37 and it was pretty good but dropped off horribly.

You'll want atleast a 35 Hz tuning, 2 cubes per, and 12" of port per cubic foot, which you don't really have if you keep the port straight. If you did an L-shaped port, you probably could get it with the 38 x 15 x 21. Otherwise it wouldn't be worth doing.

I'd tell you to get a 15 but you can't fit it on the baffle as they're usually 15.625" outer width lol.

You might want to go with 10's if you want a lower tune from 30-35 Hz. 38 Hz isn't great for daily, around maximum 30-33 Hz is.

Lots of port is good for most decent sized subs and the port shouldn't be more than 25" or else the air flow is weak. This is why most people end up tuning in the high 30's and get loud. The more port you have the better low's youll get, even though the tune will be higher. If the subs are choked below the tune than they won't put up numbers. The suspension is what will control the subs below the port tune, not the power. Therefore if you let the box breathe more via high port area, even though the tune will be higher, they'll breath better and get as low as being tuned low but you wouldn't hit the higher notes *as well*.

If you aren't getting 10's than do the 38 x 15 x 21 with two 2" x 13.5" ports for about 2 @ 38 Hz w/12.5" of port per cube after sub displacement @ bracing.

It's not like you'll hear a difference between 2 Hz & .2 cubes but the subs would appreciate it.

I had a 1500W @ 1 ohm amp with a stock 90A alt with a stock battery, big 3 0 gauge wiring, 0 gauge on the amp and didnt see lights dimming. The amp & sub broke in 6 months. I did 2 cubes @ 37 Hz. It wasn't bad but I knew I should have tuned lower and had more space for such a beastly sub.

I can calculate these things in my sleep so if you change your mind...

If I were you I'd try to fit a single 15 with 1 port. That's what I was going to do but now I'm trying to do 2 18's walled with a 3500W amp, 270A alt and 2 batts.

Money. Freaking. Pitt.
 

New member
Username: Mark8313

Saginaw, MI United States

Post Number: 6
Registered: May-12
Alright, so think I'll start over with the box. My max dimensions are 38.5 x 15 x 21. And I'll make it anyway that will make it the best.

I've been with Rockford Fosate for a long time and I strongly disagree. Sorry...

I have 1/0 awg which is larger than 0 gauge. Is that bad?

So I am okay with the alternator but what battery do you recommend? And I want to keep my 2x 12's.

So with the box in all what would make it the best and loudest?
 

Gold Member
Username: Joe1234

Post Number: 1566
Registered: May-09
OP only your brains know what sounds best to you, and your dims are rather limited, anyways, here something to work with, dual chamber will take too much space so you can always gain match:

Enclosure Specifications:

Fb = 34.5 Hz
Vb = 3.7 ft^3

External Height = 14.5 in
External Width = 38 in
External Depth = 21 in

Port Width = 4 in

Cut Sheet List:

* All Dimensions in Inches.
* Wood Thickness is 3/4 for all Parts.

External Enclosure Parts:

2 x Front & Back (3 parts) = 38 x 14 1/2

Left & Right Sides = 18 3/4 x 13

Top & Bottom = 38 x 18 3/4

L Port Internal Assembly Parts:

Front to Back = 14 3/4 x 13
Extension = 3 x 13


Upload
 

New member
Username: Mark8313

Saginaw, MI United States

Post Number: 7
Registered: May-12
That box is bad a** man!
Thank you very much.
Now for the middle brace and the corner brace in the port, what should I do to make those?
 

Silver Member
Username: Lord_huggington

Ontario Canada

Post Number: 606
Registered: Oct-10
For the 45's in the corners, if that box is 14.5 outside, it'd be 13" height, and it would go to half the port width so that the 45 starts & ends directly in a 45 degree angle from where ... this is confusing me now. too tired to think. some people even get plastic and bend it and then fiberglass it so it's literally a smooth corner. to calculate cubic feet you to l x w x h divided by 1728. you'd calculate it as a square and then just divide it by two. I suggest using 2x4's because they're cheap/strong but those wooden dowells take up almost zero space, quite a perk with a small box.

It doesn't need a middle brace, if you couldn't see it, there is a middle brace that is a 3/4" dowell (circular wooden rod). If you did see it, it would take up .75 / 2 = .375 * .375 * 3.14 * height of the rod / 1728 = cubic feet. IE by "height" it's 13 or 13.5 depending on the external box height of 14.5 or 15. 13" height... it takes up .003 cubic feet. Which seriously isn't enough to give a hoot about lol.

great stuff joe.

do that box. low tune, enough space, good port size. You could go external height 15" though... more space, yada yada.

Did you calculate the inner cut-outs for how much space those add? They are 1.5" thick.... which comes to about .17 cubes total ;).
 

Silver Member
Username: Lord_huggington

Ontario Canada

Post Number: 607
Registered: Oct-10
too many batts to list. as long as it says deep cycle and goes along with your amps voltages IE some batteries are made for amps that produce power at 12volts, 14.4 volts, 16 volts, 18 volts etc. if your amp hovers around 14.4v than youll want a battery that is rated to handle 14.4v.

xs (on top right now)
optima
kinetic
dekka
 

Gold Member
Username: Joe1234

Post Number: 1573
Registered: May-09
OP my take is if you can't cut the 45 just don't do it at all, just round or slant the inner side of the turn, if you do it, make it in a way that no point in the duct is narrower than 4" wide, the wooden dowel rod can be had at home depot (the sheets too), 1" will be enough and I recommend it even if the box won't crumble without it.

The other thing you should take care of is making sure you can fit the box in it's way in, if not you will have to build inside.
 

New member
Username: Mark8313

Saginaw, MI United States

Post Number: 8
Registered: May-12
Oh crap......36.5" is my max to fitting into my trunk. Thank you for saying something. You saved me joe. So what could I do with the 36 .5" to get a tunes box just take off 1.5 inches to the whole thing or something different?
I could build it in the back but that be hard haha.

When I said middle brace I meant dowel. I'm a noob haha.

Any ways with the space of the port, in the part of the bend, it has to always be more than 4" correct? (It should all be the same width).
 

Silver Member
Username: Lord_huggington

Ontario Canada

Post Number: 608
Registered: Oct-10
Yes. Meaning on the inside of the port at the bend, directly when it has at a 45 degree angle to the other side of the inner port wall, where it would otherwise connect at a 90 degree angle. This has to maintain 4" at the 45 degree points. This also helps lower the tuning.
 

Gold Member
Username: Joe1234

Post Number: 1574
Registered: May-09
OP if your box barely fits Id suggest to build a cardboard dummy box and keep changing sizes until it does, Being the right width doesn't mean it's going to fit, if the resulting box is too small then you should build inside the trunk.
 

Silver Member
Username: Lord_huggington

Ontario Canada

Post Number: 612
Registered: Oct-10
I would do an IB with 2 15's.... RF even.
 

New member
Username: Mark8313

Saginaw, MI United States

Post Number: 9
Registered: May-12
I'll build it from in the trunk. It won't be to hard
 

New member
Username: Mark8313

Saginaw, MI United States

Post Number: 10
Registered: May-12
So far so good wit the building. Now when cutting out cicles for the
Subs, what do you recommend to use ?
 

Silver Member
Username: Lord_huggington

Ontario Canada

Post Number: 621
Registered: Oct-10
Something that rotates while cutting. I forget what it's called, rotozip?
 

Bronze Member
Username: Mark8313

Saginaw, MI United States

Post Number: 11
Registered: May-12
So I had to go to 36."5 x 14.5" x 19" for my dimensions because my box didn't fit. With that in mind I don't know how big to make the port and the L port extension now. Any help would be greatly appreciated.
 

Gold Member
Username: Joe1234

Post Number: 1608
Registered: May-09
You are off spec on those dims for a slot port, would take too much space, the next best option is one of these:

http://www.parts-express.com/pe/showdetl.cfm?partnumber=268-354

Cut for an effective length of 13" and placed between the subs.
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