Need box design help (sealed volume calculation)

[POS carb]

Hello! I'm upgrading my old subs and I keep getting a wierd result from the online calculator I was reading
I have 2 15" subs, they should be in a sealed box if possible, and I want SQ and good low end extension ~20-25 HZ minimum
The subs are MB Quart RWE-352

Here are the T.S. parameters
RE - 3.2 OHMS
QMS - 5.52
QES - 0.481
QTS - 0.443
FS - 24 HZ
VAS - 210 LITERS

can I put these in a sealed box? I don't want to eat up all the trunk space

[3rdCoast]

well they r 15's they r gonna eat up the trunk space in our cars. A friend of mine had 2 earthquake 15's in his 3g at 1st and the box barely fit. Sealed boxes r smaller its gonna be hard i'd say to get a ported box for 15's to fit in our trunk nevermind still havin trunk space........

[LiTtLe xOx BitT]

With 2 15" subs there really isn't any way to avoid eating up trunk space. Bigger isn't always better, you can get 2 10's or 2 12's that will have the same effect as the 15's. With 2 15's with 2" on each end of the box and a 2" space between the subs is 3 feet wide. plus 2" space on the top and bottom is 19" high, plus your depth. That is going to take up a lot of space. I would go with some higher quality 10's or 12's.

[POS carb]

USING 0.707 Qtc
http://www.mhsoft.nl/spk_calc.asp#sealed
this calculates a 3.8 cubic foot box PER SUB with a F3 of 41.2 hz

http://www.carstereo.com/help/Articles.cfm?id=26
this calculates a 4.8 cubic foot box and 38.31 F3


USING 0.800 Qtc
http://www.mhsoft.nl/spk_calc.asp#sealed
this calculates a 2.6 cubic foot box PER SUB with a F3 of 47.1 hz

http://www.carstereo.com/help/Articles.cfm?id=26
this calculates a 3.28 cubic foot box and 38.88 F3

why am I getting 2 totally different results??

:pc:

[3rdCoast]

MB Quart doesnt give u a suggested size? A lot of manufactures do. Why not take those 2 different calculations and get an average from them or go with somethin inbetween both of them? Are u sure they all sealed calculations and not one ported and one sealed.....:dunno:

[Magny]

alright, found your dimensions, but the thing is, no sealed box can be tuned down to that level you are looking for.

your box needs to be around 1.50 cu.ft., closest i can get you is 1.500167 from calculations. anyways, the box size is (internally): 16"X16"X10 1/8".

only thing is the QTC number is at 1.08 and the F3 is at 44.57hz.

hope this helps you out.

[POS carb]

that's cool man, thanks! I found an article on Crutchfield.com that paired a Premium series 15 (practically identical speaker) inside a 1.5 cubic foot sealed Q-logic box so your calculations make sense...
Can you tell me what you used to arrive at that?

Also what if I do an oversized Isobaric enclosure? I can definately cut down on the volume like that and I bought the two of them to get a 2 ohm load for my amp. If I use only one I only get 500 watts vs 1000 out of my amp

I guess I'll buy a trailer and put the bass in there, a big honkin ported box :rockon:

[POS carb]

MB Quart doesnt give u a suggested size? A lot of manufactures do. Why not take those 2 different calculations and get an average from them or go with somethin inbetween both of them? Are u sure they all sealed calculations and not one ported and one sealed.....:dunno:

no they don't tell me the size.... you'd figure for paying all this $ they'd tell you how to put it in a box... instead they give me stupid drawings on how to mount it to the box :uh:

[Vanilla Sky]

you can use them in an isobaric alignment and have a MUCH smaller enclosure than the optimum for a single.

according to winISD, the optimum sealed enclosure is 5.187 cubic feet, whereas the optimum sealed enclosure for that sub in an isobaric alignment is 2.594 cibic feet. now, remember, that you have to include another 5.187 enclosure for the second sub, which you'd not have to do if you install them in an isobaric alignment. the problem you are going to have is reduced output. i'm sure you don't want to have essentially one sub when you have two installed.

an enclosure as "small" as what magny has suggested will be "peaky" at best. the 1.5-ish enclosure is about all the space you have, though. this is exactly the reason i purchase drivers to fit my space, not space to fit my drivers.

[Magny]

that's cool man, thanks! I found an article on Crutchfield.com that paired a Premium series 15 (practically identical speaker) inside a 1.5 cubic foot sealed Q-logic box so your calculations make sense...
Can you tell me what you used to arrive at that?
Also what if I do an oversized Isobaric enclosure? I can definately cut down on the volume like that and I bought the two of them to get a 2 ohm load for my amp. If I use only one I only get 500 watts vs 1000 out of my amp
I guess I'll buy a trailer and put the bass in there, a big honkin ported box :rockon:
First I searched the web like mad trying to find a recommended box size for it and came across a german website that has the size: BigDogAudio.de (http://www.bigdogaudio.de/pd1196718910.htm)
Then when I had a recommended spec size, I used one of the sites you used: http://www.mhsoft.nl/spk_calc.asp#sealed, and put the specs u have given in the slots it goes to. then i played around with the QTC until I got the Vb to 32.458 liters, which in turn, when converted to cubic foot in volume its 1.5 cubic foot(used a conversion table from OnlineConversion.com (onlineconversion.com/volume.htm)). Once i verified it, then I took the volume and put it to a box calculator which gives me size calculations of each side to get the internal volume to specs.:Defpoms Sub Box Calculator (http://www.radiomods.co.nz/speakerboxcalc.html). So now you know, but also to let you know, I didn't fully explain everything to you here, just gave a quick rundown. Trust me, if I gave it detailed, I would be typing for hours lol.

[Vanilla Sky]

hehe, i prefer to just type it all into winISD and figure the box dimensions on my own. it's not exactly hard. pick the measurement for length and height, then let the required volume determine depth. a little simple math goes a long way.

[Magny]

Well the clculators are what I used to design my box that I will be putting into my 88 Ford Bronco with a working 4x4 system, that I had recently purchased. Gonna sit 4 15" subs with 2 1400.1 amps and 2 3 farad cap, one per amp. The subs are gonna be in a ported box, around 2.7 cu.ft.. already drew out plans for it, more or less on a paint program, but the layout is pretty self explanitory once u see it.
This is what it looks like from the top:
http://img.photobucket.com/albums/v216/Magny/Sublayout1.jpg
this is internal with the ports shown in red:
http://img.photobucket.com/albums/v216/Magny/Sublayout2.jpg
this is with the braces that are gonna support the inside and sidewalls. It is said that if any one side is longer than 12" to use some kind of brace or support:
http://img.photobucket.com/albums/v216/Magny/Sublayout3.jpg
The last 2 pictures are more or less looking at the box from the bottom so you know which way it is really facing. I am gonna have these firing upwards towards the roof. I may do a second box and stand them both up and go to the extreme, but not until I get some major bank to reinforce the cab the right way for that much crap lol. So for right now, my plan is just for one box.

[gp02a0083]

my kicker box with 2 12" s takes up the whole trunk 15's in our cars is really big

[Magny]

my kicker box with 2 12" s takes up the whole trunk 15's in our cars is really big

only way we can get 15's to fit in our cars is to do an infinite baffle system. mine is already made for 2 12's and i still have space to change it for 15's, but i can only do it once lol. but anyways, its really not hard to make another backer board for the subs to sit on.

here is a pic when they were in progress:

http://img.photobucket.com/albums/v216/Magny/2004_0617Image0001.jpg

i have a pic of it with the cutouts, but I can't seem to find it, so ill take anouther pic of it when i get up, way too late to do it now.

Oh BTW, when the seat goes up, none of the back of the seat hits it, has plenty of space, even with my bar there.(knew this before my car got jacked cause my system worked for about a few minutes, mabey more, then it shutdown. had some kind of problem with the amp that I couldn't figure out. but oh well since it got stolen, don't have to worry about it again lol.) Oh and if anyone was to ask how it sounded being an infinite baffle system...........get lots of sounddeadner lol, you could hear rattles like crazy. I finally go rid of all of my rattles and squeaks, once I did that, the bass was hitting hard. and to say in my experiences of all my systems that I have ever owned, it was louder than them all. bass was kinda wobbly but it still was loud. It was only wobbly cause I didn't tune it right, plus couldnt tune it until i figured out what was wrong with the amp and adjust it again. but oh well, I know the infinite baffle i have set up works. while my head was buzzing from the bass, i checked all over for leaks and haven't found one, so knowing that, i know it was compleatly sealed of.

[Vanilla Sky]

my kicker box with 2 12" s takes up the whole trunk 15's in our cars is really big


nope, not always. i've seen 15" drivers that needed a box smaller than thier displacement. how would you like to have a 1 cubic foot box for a 15"?

[Magny]

nope, not always. i've seen 15" drivers that needed a box smaller than thier displacement. how would you like to have a 1 cubic foot box for a 15"?


Some of the 15's need at least a 1.25 cu.ft. box or more, haven't seen one at or around 1 cu.ft.. They usually average out to around 1.75-3.5, but thats most of them I seen.

[POS carb]

ok the owners manual that came with the subs had the 1.5 ft3 each requirement on the T-S sheet, for some reason that was cut off on the internet version. There are no response curves included.
I'm just cutting my 12's box to make 2 smaller boxes. These are perfect...

[Magny]

Well, this sucks...........I was doing alot of research and found out that internal bracing such as the ones I showed in my diagram earlier are not reccomended. Why you ask. Well from what I found out is that the sound waves get distorted by the extra walls inside the box, and not only that, it has mixed waves entering the port causing it to cancel itself out. So now I am working on how to brace it externally, which in this case, found it to be better to do a band-like bracing on the outside. Two bands to be exact, one about 1/3 down and the other an equal distance down. So in a way making it look like a crate with bands on it but wooden planks instead. It will be screwed on from the inside so it can be supported, also to prevent a flapping effect between the boards on the outside.

[89T]

as an ex installer did you think of just using thicker partical,or hard board?
in my truck(back in the day) i used 1" partical board for 2 boxes with 3 12"s in each. the box was also mono or no seperate chambers. there is no need if the subs are getting the same signal.1 amp per box bridged mono.
in the honda i am running 4 10" orions in a mono box.1 amp bridged.
using 3/4 inch partical board.
i hope this helped alittle.

[Vanilla Sky]

just a recommendation, stay far away from particle board. use MDF. it's a much stronger product and will not require as much bracing to keep from breaking under pressure.

[Magny]

Well I aint gonna use particle board, gonna try and see if I can get some HDF boards. It will be a step up from MDF but it will be a harder board. If I run out of luck on the HDF gonna end up using the MDF so I'm pretty much prepared for it. Plus gonna still build it as one complete box, not individual, and run 2 subs to 1 amp. Thinkin of goin 1 amp to 1 sub, but as far as db drag rules, I will still be within the class I am aiming for. But then again, have 2 classes to decide from. Might do Super Street 3-4 cause it give me the ability to use 2 alts and unlimited capacitors, whereas the Street Max 3-4 only allows me to use only the stock alt and up to 2 farads of cap. storage.



Oh and I was just speaking freely, not really knowing if the 2 last post I have seen after my last one were directed to me or not. If it was cool, if not, oh well, no biggie. Like I said, I was speaking freely if it wasn't.

[Vanilla Sky]

nah, my last post was just a post in general. if you have access to HDF, that's even better.

[POS carb]

I built 2 boxes totalling a hair under 1.51 cubic ft of internal volume, the subs drop dirty style! They hit hard too but are noticably lower at anything over 120 hz
I used 3/4" MDF, 2 seperate boxes, Liquid nails and drywall screws