Rep Power: 255

Hey I just bought 2 12" subs and an amp for them. I am hoping to build a sealed or ported box for my trunk(whichever is easiest). I have a 4x8 sheet of MDF board, screws, liquid nails, wood glue, and lots of silicone sealant. Could somebody either find a post or type me some instructions. I would like to have some quality sound coming from the box without using up ALL of my trunk. I can find lots of DIYs on how to make boxes but none with dimensions. Are there some dimensions that somebody could give me for my box to give quality sound with trunk space remaining, and yes I would like to make a box because I want to keep my spare tire.

 
Rep Power: 262

The dimensions depend on the type of subs and the size of the amp. You need to read or find the book that came with your subs and amp.

 
Rep Power: 379

you have to read the specs on the subwolfer. It will tell you the cubic inches of air space you need for a sealed or ported box. Sealed boxes are easier because you don't need to figure out port hole settings. Sealed=SPL Ported=SQ

 
Rep Power: 255

ok thanks for that. Also can I hook up my amp to the factory stereo or not? I really do not want to buy an all new HU, because I'm saving up for a bodykit, but the amp and subs were an amazing price on ebay.

Update: I checked the manual and it said the reccomended enclosure size is 1.25 cu. ft. Now how do I go a about building that. I have figured out that If I wanted to make a cube it would have to be 13 inches on all sides but I heard cubes suck for sound. Do I just kind of measure what I have to work with and go from there? Like measure the height from top of trunk to ground and width from seat to seat (I want to mount it behind back seats in 01 coupe) and then figure out what my depth should be so the entire enclosure has a volume of 2.5 cu. ft. (2 x 1.25 cu ft)?

 
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alright man.. to build this box you need to do some math.. unfortunitly i dont know what the equation is.. i will find out tomorrow at work and re post.. Now for the question about the stock deck.. you can power you amp with a stock deck with somthing called a line in converter... as you know amps have to have RCA's pluged into them to work and a factory deck doesnt have RCA outputs.. so what this does is takes the rear speaker outputs from your deck and converts them to RCAs..Now there are two down sides to this.. no rear speakers and no Voltage output "V".. you can solve the voltage thing by getting a line driver.. ebay has them http://cgi.ebay.ca/PHOENIX-GOLD-SLD4...QQcmdZViewItem . i should really look into that if you keep your stock deck or your amps wont be running to par.. and since you have two amps you should get a multy channle line driver.. to solve the rear speaker thing run them in series but they wont be getting much power.. Best thing to do man is just get a aftermarket deck..

 
Rep Power: 255

Ok so here is my next question if i get a new deck will I have to buy a console adapter to allow the new deck to fit in where the old one was because the old deck is really big like 4 inches and a custom one is half the size? Also my amplifier has a high input on it which is basically 4 wires that look just like speaker wires. Can I wire the inputs into these. ( let me describe it to you. Its like a little wiring harness the plugs into the amp and it has four inputs for it (L+, R+, L-, R-) Can I wire the corresponding outputs from factory radio to these?)

 
Rep Power: 0

Yes, I believe that is what the high outputs are for, for wiring the factory deck up to the amp.

As far as the box goes, if you need 1.25 cubic feet for each sub, then you will need 2.5 cubic feet total. If you would like the box to fit perfectly in the back of the trunk (that is, with a sloped front so the speakers face towards the front of the car, behind the rear seats) then you will need to make the front of the box sloped forward. To calculate volume, you will need to take the number if inches and divide them by 12 to get number of feet for each dimension of the box (length x width x heighth). Also, when calculating the cubic feet for a box with a sloped front, take the width of the box at the top and the width of the box at the bottom (eg. 10" at top and 16" at bottom, this is what I used) and subtract the top from the bottom. (this would be 6" here) now multiply 10" by (remember to change it to feet by dividing by twelve) the heighth and the length ( both also divided by 12). This will give you a "rectangle" for the rear half of the box. Now, to find the area for the front part that is sloped, take the 6" (or whatever number you use) and also multiply by length and height (divided by 12) and half this number. ( because only half of the rectangle is going to be box) Add this cubic foot number to the number for the back and you will have an approximate number.

As far as cubes sounding bad? I've never heard of this and don't know why they would. I had to 2 Kicker L5 tens in perfect cubic boxes and they sounded good to me. What's important is to get the amount of volume correct and seal the box well. Also, remember to predrill the holes for screws if using MDF and always allow the caulk to dry for 24 hours before putting the subs in the box (use a fan to air it out) as some types of caulk can release fumes that could damage the sub. I'd rather be safe than sorry.

 
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are you serious??

i've never heard a ported box sound cleaner than a sealed

 
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If your amp does have the speaker level input then you can wire your factory desk right in the amp.. but still get the line driver.. And if you do go with a aftermarket deck the you will need a dash kit and a wiring harness for it. They are like $40 CND for both..

 
Rep Power: 255

ok so lemme get this rite. I dont care if the subwoofers face the front i wanted them to face the back so when I put the trunk up then they face outwards. I just want to make a basic rectangular box since this is my first one. I bought a 4 x 8 sheet of mdf so i should have lots if i want to change it later on. So here is my idea i measured that the height from floor to top of trunk in the wheel wells is 17 inches so im gonna have a height of 16 inches. Then its about 46 inches accross the back so i figure my width should be about 30 or 33. Here is my question does having more depth on the subwoofer affect the sound. Cuz i want to have some trunk space left over but i also want some quality sound. Next i figured out that 2.5 cu. ft is 4320 can somebody verify this. Here is my logic (12x12x12x2.5=4320) So if i go with width of 30 and height of 16 and multiply those two together i get 480. So that means I have 480 to work with do i just divide 4320 by 480. Wen i do that i get 9. So that means my enclosure should be 30x16x9. Does this seem like a logical size?
thanks so much for the help. Also about which way the speakers face should i want them to face forward and fit flush with the back seat. I just figured that when I was carrying passengers I would have them face outwards and when i didnt have any passengers i would drop the back seat and flip it around. Also do i really need the line driver. It sounds like its a good idea but not 100% necessary and its expensive. If i was going to spend 100+ s/h i'd rather buy a cheap aftermarket from ebay and the mounting hardware and all that crap.

 
Rep Power: 281

Do you have any idea how heavy a dual sub box with subs in it is? Not to mention the wires and stuff that are gonna be back there. Its less trouble to leave it in one position, and a lot safer too. I don't think you want a sub box tossing around in your trunk when you take turns.

As for your dimensions, make sure you leave anough room for the trunk hinges to close properly.

 
Rep Power: 360

Sealed is the best for SQ
Ported is good all around
Bandpass is the best for SPL

 
Rep Power: 281

Thats IF you can get it to hit the frequency its designed for, other than that bandpass is useless.

 
Rep Power: 360

If the boxes are engineered correctly, then what I posted is the general rule.

 
Rep Power: 281

Taken from Cruthfield Advisor:

Bandpass boxes: Maximum slam!
Bandpass boxes are a special type of ported box designed for maximum slam. The woofer is mounted inside a dual-chambered box (one chamber sealed, the other ported), with the sound waves emerging from the ported side. The sound that comes out of the port is extra loud within a narrow frequency range.

Because bandpass boxes are super efficient within that range, they tend to boom. Their aggressive sound is great for rap, reggae, and hard rock. Not all subwoofers work well in bandpass boxes, though; consult our product information or call a Product Advisor to be sure.



Also, check here http://forum.ecoustics.com/bbs/messages/4/8374.html for additional information.

 
Rep Power: 255

thanks for all the help but im gonna go with a basic sealed box now and since mdf board is only $20 i can always make a new box later on, or convert mine to ported. I need an honest opinion here tho should the woofers face the back of the car or the front of the car. I was thinking that the back would be better cuz then the sound would "bounce" off of the trunk and it would seem louder. Also if I am just going to run 2 12s off of a 360 watt amp do i need a capacitor?

 
Rep Power: 337

you dont need a cap. no worries.
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this will explain why (in your case!) rearfiring is definitely the way to go:
http://www.installer.com/tech/aiming.html
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You dont need a line driver. they are useful, but I dont think they provide any benefit at all in this case. Certainly not enough to justify the cost, no matter how small.
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you will need an adapter for your dash. we call them "dashkits", and you can get one at any best buy, circuit city, or custom shop. Itll cost you $15 and be a drop in solution. cake.
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if you use an aftermarket radio, youll use RCA cables to transmit signals between the radio and amp. they will plug into the line level outputs, and work great.

if you decide to keep your stock radio, you'll use the speaker level outs to tap into the speaker level inputs on the amp. And itll work great.
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best advice for the box is to follow manufacturer spec. if they say 2 cubic feet, run with two cubic feet. if they say one, go with one.

keep in mind that their spec doesnt account for volume taken up by the subwoofer, wood, etc. thats extra you add to calculate the TOTAL internal volume.

and never forget there is a difference between internal and external dimension!

you have one cubic foot at 12x12x12 inches internal dimension. that means your box external will be 13.5x13.5x13.5! this can kill you if you have a critical dimension!

finally, when you design your actual dimensions, keep in mind it may be more inportant HOW you get the box into the car, rather than "will it fit". if you make the box too tall, it may not fit through the trunk hatch! maybe it will. youve got to measure, maybe make some test cuts to verify.

as far as what panels overlap what for construction, it doesnt matter at all. take your pick.

if there are any more questions, feel free to ask here or email me.

-Steve

 
Rep Power: 247

most subwoofers in a sealed box sound different when they are facing you. you get cleaner bass when they are towards the opening of the trunk.

 
Rep Power: 255

Can you please explain to me a little bit more about these dashkits?

 
Rep Power: 337

sure. its a panel made from ABS plastic. the three big companies that make them are american international, scoche, and metra. I am sure there are others, too.

each makes theirs mecahnically a little different, but all are effectively the same (so there isnt really a "best" one).

the face of this trim EXACTLY fits your dash hole. zero gap. it drops right in, no problem. in the middle of this panel will be a cutout that is perfectly DIN sized, so any aftermarket radio will pop right in.

The dash kit also comes with trim rings so that you can finish the look of the radio inside the car. ultimately looks as integrated as is physically possible.

any dash kit anywhere will cost you $15.