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View Full Version : Box for two DD 1508's - Got questions..



westman995
07-10-2009, 01:23 PM
Ok so im pretty sure im gona build a custom box for the rear of my 82 Trans Am. I got two DD 1508s on their way to me. So i am wondering what is the absolute best box size for the 1508? I want to get maximum output and really surprise some people with these little things. I should have more than enough room to go ported with these little subs, i would image. I think i got under 3 cubes to work with in my area, so should be enough i think.

Another question is, Is there any calculators or sometihng out there where i can easily change like the heighth of the box to make it the correct volume, or how do i got about figuring out exactly what height to make it to get the right volume?

This is kind of like what the box will look like to go in the rear "well" area thing.. I was planning to do this for two 12s but decided no way in hell i can get enough cubes in that area for the two 12s. It should be real similar to this minus the top being bigger than the bottom, and maybe not quite as high due to not needing as much space with the 8s. The box was not drawn to spec, its much deeper than it really can be, was just drawn to show idea of the shape it would have been.

http://i242.photobucket.com/albums/ff177/westman995/Audio%20Equipment/box5.jpg
http://i242.photobucket.com/albums/ff177/westman995/Audio%20Equipment/box4.jpg
http://i242.photobucket.com/albums/ff177/westman995/Audio%20Equipment/box3.jpg

So more than likely ill be trimming the height off that box, and the top wont be quite as big like i said, cuz that was to fit some 12s.

Can you recomend a box calculator that you can figure out what size to make it to get the right volume?

I read that .9 cubes ported some guy hit almost 150 with a single 8.. Now would that be .9 cubes before or after sub and port displacement?

I am also going to do slot ports im pretty sure.

One more question, since im doing two subs. Do i want to put a divider between the subs and put a port on each sub, or just build one big box with no divider and only one port? Im thinking with a divider is the way to go, but dono for sure.

loudmofo
07-10-2009, 01:26 PM
the box i built for both is 1.7cb ft and ported at 28hz i sould have mine sometime next week so ill let you know how it works out

westman995
07-10-2009, 01:31 PM
the box i built for both is 1.7cb ft and ported at 28hz i sould have mine sometime next week so ill let you know how it works out

Did you ever even use the subs i purchased from you? Sounds like you didnt. Ordered some more?

Is that without a divider then? I also read a bunch of times to tune it up to around 40 or so...

loudmofo
07-10-2009, 01:33 PM
looking at you design and being in a firebird i would do 1 big slot the long way behind both subs have both subs in one chamber.

loudmofo
07-10-2009, 01:38 PM
Did you ever even use the subs i purchased from you? Sounds like you didnt. Ordered some more?

Is that without a divider then? I also read a bunch of times to tune it up to around 40 or so...

i never used the subs i sold you i really wanted the platinum cones :D so when i got payment from you i called dd and orderd them thanks again .
dd always recommends 40hz but i have tuned dd subs lower and they sound great i mite try making a loading wall for mine out of 1/2in plexi will have to test and see how they like 28hz.

westman995
07-10-2009, 01:40 PM
If you think that will do best, ill prolly that way first. If i dont like it i would think it would be too hard to take the top piece off, add a divider and do two ports or something if i really wanted/needed to. So the slot in the very rear of the car?

I also read the 1508s need something to "load" off of? Which ive never really heard of before. But i guess it means it needs to have something to stop them from bottoming out. Do you think it will work fine in there? Or would i be better off trying to get them to "load" off of something. If i have to, my idea is something i read, to put plexi glass in front of it. It would give it a cool look and i wouldnt have to worry about anything falling on top of the subs while back there facing up.

westman995
07-10-2009, 01:42 PM
i never used the subs i sold you i really wanted the platinum cones :D so when i got payment from you i called dd and orderd them thanks again .
dd always recommends 40hz but i have tuned dd subs lower and they sound great i mite try making a loading wall for mine out of 1/2in plexi will have to test and see how they like 28hz.

Ah, how much did those platinum ones run you? Well i heard alot of people say 40 or so just for the 1508s not really for any other subs, so i guess just have to do some testing/tuning to figure out how it really sounds best to your liking. Ill prolly be doing some testing of different hz too.

loudmofo
07-10-2009, 01:46 PM
fire the subs and port up same design you have now just do the port 1st the long way closest to the hatch and subs in front of it and if you do the loading plexi like i plan on dont cover the port with it only the subs hope you understand what im saying.

westman995
07-10-2009, 01:48 PM
Yep i understand what your saying im pretty sure. Fire sub and port up like i planned. Port all the way in the back of the car, and the long way. And dont cover the port with the plexi haha.. I think the plexi would be a great idea to protect the subs also. So i really want to do that.

Ive got lots of questions cuz the only boxes ive actually built before were just sealed boxes built to specs.. Nothing special there. Im fairly new to the building ported boxes.

loudmofo
07-10-2009, 01:52 PM
yes thats the idea the type of car you have works great with subs up and ports up the plexi does look good i seen it done a few times the best was lcrx with the box of 4 8s in the crx he has done alot of testing and used them the most i would pm him also.

westman995
07-10-2009, 01:55 PM
Ya i seen he had some before also. I will PM him about some specs and to see what he has liked best since he also used them in a hatch, not real similar car but its still a hatch.

westman995
07-10-2009, 02:07 PM
Ive read stuff about like "dead space" or whatever on some boxes, does that really happen? Is it possible to have problems with my design where its bigger on the top than the bottom?

I had another idea, depending how high i want to build the box, i may not even need to make the top of the box bigger than the bottom.. I could just make the top baffle big enough so it covers all around the rear to look nice. Ill do a little sketch up quick to show.. Depends how it looks in the rear with it being that high tho.

loudmofo
07-10-2009, 02:30 PM
Ive read stuff about like "dead space" or whatever on some boxes, does that really happen? Is it possible to have problems with my design where its bigger on the top than the bottom?

I had another idea, depending how high i want to build the box, i may not even need to make the top of the box bigger than the bottom.. I could just make the top baffle big enough so it covers all around the rear to look nice. Ill do a little sketch up quick to show.. Depends how it looks in the rear with it being that high tho.

thats what i would do also make the top like a trim panel no need to make this box super big i would start with 2.2cb before sub and port displacement.

westman995
07-10-2009, 02:54 PM
Ya that design above was to get max volume for some 12s at first. Should be quite a bit easier doing it for the 8s not having to squeeze as much as i can out of the space. Even tho you already know what i mean, here some pics.

Also, would the port work like this, or would i be better off doing the subs in center and port right behind? I kind of like the offset look having them both to one side.

But, one problem. I may not have quite enough room to make it the right size by doing it this way. It all depends on how high i want to, or can make the box. I dont want it sticking up real high. Idealy i would like to have the plexi be flush mount with the rear floor area.


http://i242.photobucket.com/albums/ff177/westman995/Trans%20Am/Trans%20Am%20Stereo%20System%20Install/Untitled4.jpg

Pics of the rear of my car.. To see where i want the plexi to be flush with. Yes i know its dirty, ive since cleaned up the wiring, its not a great car but its what i got right now.
http://i242.photobucket.com/albums/ff177/westman995/Trans%20Am/100_3764.jpg
http://i242.photobucket.com/albums/ff177/westman995/Trans%20Am/100_3766.jpg

loudmofo
07-10-2009, 02:58 PM
Ya that design above was to get max volume for some 12s at first. Should be quite a bit easier doing it for the 8s not having to squeeze as much as i can out of the space. Even tho you already know what i mean, here some pics.

Also, would the port work like this, or would i be better off doing the subs in center and port right behind? I kind of like the offset look having them both to one side.

But, one problem. I may not have quite enough room to make it the right size by doing it this way. It all depends on how high i want to, or can make the box. I dont want it sticking up real high. Idealy i would like to have the plexi be flush mount with the rear floor area.


http://i242.photobucket.com/albums/ff177/westman995/Trans%20Am/Trans%20Am%20Stereo%20System%20Install/Untitled4.jpg
http://i242.photobucket.com/albums/ff177/westman995/Trans%20Am/Trans%20Am%20Stereo%20System%20Install/Untitled.jpg

i wouldnt make the port like that i would do it on the length of the box the long way if you dont have the room just place it on the drivers side from top to bottom

loudmofo
07-10-2009, 03:02 PM
like this '
[QUOTE=Noobtastic14;6056172]http://i40.photobucket.com/albums/e216/saxwonder05/SDC10023.jpg

westman995
07-10-2009, 04:27 PM
Ya i understood what you meant to make it that way, i was just wondering if it would work fine like that. I just like the look of the subs on one side. So i should put the subs in center like your pic, or is it ok to do them both to the side, but put the port right behind the subs like yours?

And are you saying to make the port the whole length of the box?

loudmofo
07-10-2009, 04:31 PM
the subs should be close together for beter spl the port can be ethier way just not like on top like that pic

westman995
07-10-2009, 04:45 PM
Should the port be the full length of the box like your pic or should it be not as long? Either way, the port as long as the box looks kinda cool.

westman995
07-10-2009, 04:47 PM
I dont think its going to look quite so long when its drawn to specs tho, the drawing makes it look a little long.

http://i242.photobucket.com/albums/ff177/westman995/Trans%20Am/Trans%20Am%20Stereo%20System%20Install/Untitled5.jpg

westman995
07-10-2009, 05:01 PM
Well according to the slot port calculator on the12volt.com, i put my rough estimates in of the box to get about 1.8 cubes with the box being 25" long, 17" high, and 10" deep. But that is before displacement of the subs and the port. Not looking too good, I havent measured but i dont think i want to go any higher on the height of the box or the plexi wouldnt look or do much good i dont think..

And if i do a 24 inch long by 1 inch wide port on the rear, tuned to 37 (just a random number to try( the port needs to be 22 inches long.. So im not really sure how the hell im going to pull this off, unless i build the box like my original design which is going to **** do to all that extra cutting and **** that im not really that great at.


EDIT: Ok this is not looking real good. Even by doing my original design, i dont seem to be able to get very much volume out of it. The thing is i was at first measure 20 inches from bottom up total, but i just measured and realized i only have 15" from bottom to top to work with. So even with the top part being bigger, it looks like i only get about 1.8 cubes not even counting a port.. The port is going to take up quite a bit of volume, am i right?

loudmofo
07-10-2009, 06:09 PM
you will need to bend the port to make it work look up port bending

westman995
07-10-2009, 06:27 PM
But even besides the fact of the port, how is the less volume going to affect it? I dont want to go through all the trouble of building this box custom to the car, and then turn out to not be big enough and not be as loud as it can get.

westman995
07-10-2009, 06:34 PM
Ok so this is drawn much more closely to spec as i measured it on sketchup, its not dead on but real close. Now, is there a box calculator out there to find the volume of this shape? I cannot find anything. Or how would i do it on a regular calculator? The only thing i can think of is do the top part and bottom part seperate and add them, but it wont be exact volume then.

Specs are 25 wide by 10 deep on bottom, 15 from top to bottom, 40 wide on top piece, the middle pieces that stick out one side is 5 and other is 10.. I didnt know how to write on the pics so i had to type them out.

Where i the ideal location of the subs in a box of this shape? Im afraid of the shape being a problem. I dont really know, its just something i want to figure out before its built.

http://i242.photobucket.com/albums/ff177/westman995/Trans%20Am/Trans%20Am%20Stereo%20System%20Install/1508box2.jpg

westman995
07-10-2009, 06:44 PM
Would you suggest this design?

How about have the port like pictured, and have the subs right next to each other on one side of the box? Im just afraid of the shape something may not work right haha..

http://i242.photobucket.com/albums/ff177/westman995/Trans%20Am/Trans%20Am%20Stereo%20System%20Install/1508box5.jpg


Ok so if i make the port 18x1" it asks me to make it 14.8" so it would make it easier to make the port.. Does the width or height of the port really matter if its tuned correctly to what its saying? Or is the wider port going to be better?

westman995
07-11-2009, 07:52 PM
Ok so i threw the subs in a small slot ported box, a real piece of **** haha.. I tuned the port to 40hz, and wow i am very surprised already. And im only pushing 125 rms to each sub.. Cant wait to get them in a real box, and some real power to throw at them.

Anyways, knowing that box theyre in now is too small and theyre already somewhat loud, i am just going to build the box to whatever size looks best in there, in the end after port displacment i think it should be a nice size and do pretty well. Only time will tell tho to see how it really sounds.

Now, one of my main questions i need to know is.. Does the height or width of the port matter as long as i make it the right length to the hz im tuning it to?? I mean do i really gotta build the port from one side the other? Seems really long.

So, can i get away with doing the port like the last pic i posted?

Fuknmovin
07-11-2009, 09:11 PM
You need to have the proper port area for your subs, I am not familiar with DD's specs but typically you can take the volume of the box after displacements and mulitply it by 16 to get the desired port area for good output. take the height times the width to get total port area. You need this AND the right length to get it performing its best. You have nice subs they deserve the right box, do your homework and it will turn out nice!

westman995
07-11-2009, 09:35 PM
The DD site says 15 sq in. port area, and 19 inches long. Do i really have to go with 19" long, or do i do the length according to my box?

So i would want to get a total of 30 sq in port area for the two subs, or not?


EDIT: Ok i came across this on the DD site

1.50^ft (2) 8" or (1) 10" 24.0 sq" vent x 22" long
1.75^ft (2) 8" or (1) 12" 28.0 sq" vent x 21.5" long
2.00^ft (2) 8" or (1) 12" 32.0 sq" vent x 21" long

So, im prolly going to be doing the 2x8" witha about 1.5 cubes after displacement.

Im also PMing another member thats helping me out, he told me it needed to be 22" long, which i did not know what that meant at first. But now i understand better. I never knew about the having to have so much port area. I just thought it was tune it to whatever and that was it.

So lets say i got 1.5 cubes after displacement. And the port is 22" long, how do i find out how deep and wide to make it to get the right port area?

EDIT 2: Ok once again this it not looking to great, seeing as how it says to use a 22" long port, i dono how in the hell i can fit that on my box with the way its shaped. I could try to do it in the middle of the top of the box, but the subs are going to be in the way. If i put the port on one side of the box, i cannot make the port real long due to the shape of the box?? And i dont see how bending the port in any way could help or be beneficial...?

Fuknmovin
07-11-2009, 10:09 PM
just do the math, if you need 28sq" of vent then you need to play with it until you get what you need like this..14" wideX2" tall = 28" of port area, then make it as long as you need to to get the tuning you need, a website called (the12volt.com) has a calculator for the length...

Fuknmovin
07-11-2009, 10:25 PM
Sometimes you will find a certain tuning frequency or box shape just flat can't be done, so you need to try something else. You can bend the port around the back of the box sometimes to help. Try messing with this calculator to learn more about how it works...

http://reaudio.com/speaker_box/LPort_Box_Calc.html

westman995
07-11-2009, 10:27 PM
Ive been using the calculators on the12volt, theyre pretty handy. Ok so after that.. I have one big problem. There is NOWHERE on the box at all that i can do a 22" long port. When DD says on their site to do 22" long i am only assuming that that means how long it is on the outside of the box, not the lenght going inside the box, is that correct?

My only idea so far is, to build the box as shown in my previous pics, except on the drivers side not have the big hump sticking out, and just go straight from top to bottom on that side, allowing me to do a longer port, but even then my box is only going to be 16 max inches tall.

So, i am really stumped on what to do right now. Knowing im supposed to do a 22" long port really messes stuff up, as i cannot fit that anywhere. So i may have to sacrifice something to go with a different size/lenght port or whatever.

westman995
07-11-2009, 10:28 PM
Sometimes you will find a certain tuning frequency or box shape just flat can't be done, so you need to try something else. You can bend the port around the back of the box sometimes to help. Try messing with this calculator to learn more about how it works...

http://reaudio.com/speaker_box/LPort_Box_Calc.html

The only problem is i cant really fit the subs anywhere else. I think im gona have to go wtih the plan and just do it, but make the port a little different than is recomended by DD. Even if i dont put the subs in that spot, there is no other palce that has more room than that.

I cant really see any of these calculators helping me at all due to my box shape, either that or im just too stupid to figure it out. If i were building a normal shaped box i would have this **** down already.. This is really confusing me.

Fuknmovin
07-11-2009, 10:53 PM
I hear ya, I am dealing with an odd shape right no as well, can be a pain to get right sometimes, try doing a fiberglass box and still getting it to sound good! LOL!

westman995
07-11-2009, 11:12 PM
Ok, i hope i am right when i say the 22" wide wont make a ton of difference as long as i have port area the right size?

Ok so 16x1.5=24 which is what i need, 24" port area. Then it says i would need to make it 18" long. I would have the bend the port at the bottom, but i should be able to, just going to take some extra time and work.

No thanks on the fiberglass, too much work for me haha..

DNick454
07-12-2009, 12:08 AM
Transmission-line box I designed for two 8" drivers...


http://i94.photobucket.com/albums/l87/DNick454/transline4.jpg


:D

Line is 7.7 feet long with port area = two 8" cones and tuned to 36.5Hz

Shame you don't have more room to work with :(

Fuknmovin
07-12-2009, 11:03 AM
Ok, i hope i am right when i say the 22" wide wont make a ton of difference as long as i have port area the right size?

Ok so 16x1.5=24 which is what i need, 24" port area. Then it says i would need to make it 18" long. I would have the bend the port at the bottom, but i should be able to, just going to take some extra time and work.

No thanks on the fiberglass, too much work for me haha..

Yeah, the port can (within reason) be any shape as long as there is the proper area, as for the bend, you just do it like the ones you have seen, like the one above. Remember to draw a line in the center of the port to measure the length as its not as simple as it looks to measure them in the bend. I like to draw a diagonal line from the inside corner of the bend to the outside corner, then trace a line in the center of the port from beginning to end and then measure that line for total port length.

westman995
07-12-2009, 12:43 PM
Nice box dnick, wish i did have some more room. But if i were going with a bigger car or more room, i would prolly go with some bigger subs even tho these subs pound for their size. I havent gotten to see what they can really do yet either tho.

This is going to get quite confusing, as im already pretty confused on what i should really do. I have two ideas. Not sure i really like either of them tho. Here they are.

First is to take off the left side of the box and make it straight top to bottom, and port out to the side. Which i would want to do, as far as output since im told its better to go out the side. And ive tried it with port to the side and it seemed fairly louder. But im not sure i like the look of that. The port would only be 13.5 inches high and i think 1.75 wide to get about 24" port area.
http://i242.photobucket.com/albums/ff177/westman995/Audio%20Equipment/1508box41.jpg
http://i242.photobucket.com/albums/ff177/westman995/Audio%20Equipment/1508box42.jpg

And if i for some reason needed to make the port too long where it would hit the subs, i could possibly do this. Where it has the angle in the front as my car has that shape. Just not sure how much, if any it will help. Due to the subs having a huge magnet, im not sure the magnet will clear the box. I will have to check into that.
http://i242.photobucket.com/albums/ff177/westman995/Audio%20Equipment/1508box43.jpg

And the last one, assuming the subs will clear if i slant the front and move the subs forward a little.. I can get a 22" long port this way.
http://i242.photobucket.com/albums/ff177/westman995/Audio%20Equipment/1508box44.jpg

mmouse57
07-12-2009, 02:16 PM
west if your in florida and need help making a box lke that id love to build it for you just pay the $30 for sheet of mdf wood screws and some glue 'tips excepted if you like the final results :)

im talking http://i242.photobucket.com/albums/ff177/westman995/Audio%20Equipment/1508box44.jpg

like this :) i build so many boxes but i rarely get to build a box like that and my $10k worth of tools in the garage just scream to be used right :)

westman995
07-12-2009, 02:23 PM
Florida? Says your in st cloud? Haha im in southern Minnesota. And there is a town in minnesota a few hours away called st cloud, unless you used to live here??

By the way, i dont have the wood yet and i was wondering what size they come in? I dono how much im going to need. Maybe more than one sheet?? And how much do they generally cost?

Nut Hair Trick
07-12-2009, 02:27 PM
What's wrong with building the box the same width, for as deep as it goes? Do you really have to build out at the top? I would have one uniform width, run the port the whole width of the box, (w-1.5) would be your port length. Then just make the port as wide as you have to, to get your desired port area. For cosmetics, you could put make the top baffle flared out to cover the holes on each side of the box. If the box calls for a longer port than you have depth, then just bend it at the bottom.

westman995
07-12-2009, 02:30 PM
What's wrong with building the box the same width, for as deep as it goes? Do you really have to build out at the top? I would have one uniform width, run the port the whole width of the box, (w-1.5) would be your port length. Then just make the port as wide as you have to, to get your desired port area. For cosmetics, you could put make the top baffle flared out to cover the holes on each side of the box. If the box calls cor a longer port than you have depth, then just bend it at the bottom.

Well that WAS the plan at one point, at the beginning of the thread. But it turns out i do not think that its going to be enough volume with it being that small, thus the reason im trying to build it to get the max volume right now. Otherwise that would be the easiest way to go.

Volume before port and sub displacement would only be about 1.5.. Which is what i need after the port displacement.

How can i figure out just how much area the port takes up? Cuz the calcs i use i enter outside dimensions with the wood size but i dont think taht would work right for the port, would it?

westman995
07-12-2009, 06:47 PM
Ok guys, i had them in this smaller box which i thought was too small. But i built a (******) box, it was the T shape with the one side cut off, subs firing up and port to passenger side. I did it to right about 24" port area, tuned it to 40hz. Now mind the box was a pretty big piece of ****, old wood, leaked alot of air. I only built it to see what it would do and see how it would fit. Not only did it sound like **** it didnt fit near as good as i was hoping.. Well i threw the subs back into the smaller box, and they pound pretty hard in there. So, i think im going to make my design to be much more similar to that box. This box is also pretty crappy, old used wood from another box, but it is sealed up atleast. I had built that box for some other subs just to see how loud i could make them, just wanted to play with making a slot ported box to get better and not waste good wood.

So, the box i have them in is as follows

28" wide, 11.5" high, 12.5" deep..
Brings me to 1.6 cubes according to the calc on the12volt.com

Port is 1.5" wide, 11" high, and 13" long inside the box. That was said to be 40 hz. And then, thats only like what 16" port area? When it was to have about 24".. That going to be much of a problem?

But now, i have some questions on this. I know it pounds pretty hard in this box. But the placement of the woofers is what im concered about, regarding the port and stuff. I have on sub right on the side of the port, and the other is right on the other side of the port.. Well here is a pic to know what i am talking about cuz i cannot explain it. I would think it shouldnt really matter, but i just want to make sure im not going to mess anything up. This is what the current box looks like. Is there any problems with that design, mostly the placement of the port and subs. Cuz they pound pretty good in it, with only 125 rms to each off a rockford 2 channel..
http://i242.photobucket.com/albums/ff177/westman995/DD1508box1.jpg
http://i242.photobucket.com/albums/ff177/westman995/DD1508box23.jpg
http://i242.photobucket.com/albums/ff177/westman995/DD1508box3.jpg

westman995
07-12-2009, 06:57 PM
By the way, the real box is going to be very slightly different specs i think. Im gona built it just slightly less deep, and a little bit higher instead. And maybe around an inch off lenght only to make it fit in there better. And then ill do the top baffle to also be a trim piece like my original plan. So it sounds like this will work pretty good.

Im not really sure why in the hell the box design before was giving me not that much space, yet this box right here seems to be plenty.. Maybe ive been doing something wrong, but ive done the calculations many times and nothing has changed much.

EDIT: The box i am planning to make is going to be roughly 26x15x10 bringing me again to 1.6 cubes.. The port in that box would now be 13.5 high and 1.5 wide. That will be more like 20" port area vs the 16. Should that make much difference and help? Seeing as how DD wants to have 24" port area. The port would need to be 17" long to be 40hz which i think i want it tuned to, its loud like that to me. May change it up and test later but 40hz is starting point.

The main thing i want to run by you guys is the placement of the subs. The circle on the pics below are about the outside of the subs, you can see it will be close to the port but shouldnt matter. The thing im only asking about is one sub being placed right in front of where the air goes out, and the other behind the port where it doesnt escape. Here is a pic of what the box i want to build will look more like
http://i242.photobucket.com/albums/ff177/westman995/finalbox1.jpg
http://i242.photobucket.com/albums/ff177/westman995/finalbox2.jpg