Box for Vibe Space CBR12

[MG's VH Wag]

Ok guys i have my final dimensions all sorted out. Is there a way i can figure out the size and length of the port i need to have? Also I was thinking of getting two 16mm mdf boards and fixing them together to make it 32mm thick, is this too thick or what?

The total volume of the box is 2.63ft.

 

[MG's VH Wag]

I found a site that helps calculate port lenghts etc. I will make a port out of 90mm pvc pipe and flare both ends so the air can flow past without much noise. What hertz should i tune the box/sub to? Here is a list of some port lenghts-

90mm port- 50hrtz= 1.53inchs
45hrtz= 2.51inchs
40hrtz= 3.88inchs
35hrtz= 5.88inchs
30hrtz= 8.95inchs
25hrtz= 14.05inchs
20hrtz= 23.44inchs

I can always make different port lenghts as i'm a plumber so i can get 90mm pvc for free/ dirt cheap.

Cheers!

 

[Philthy]

One port mate, simplicity is king.

Your gear is with me now, shipping it soon. You are going to LOVE the box the sub comes in.

Anything like the box my vibe gear came in?

 

[AutoSlick]

Nope, ahaha. The Space range comes in its own custom packaging.

 

[VSPantha]

If you want to get a proper port rather than use pvc pipe, jaycar sell them... and they're not expensive
Check them out on jaycars website... under browse products, select 'Speakers & Audio', then 'Speaker Ports' on the sub category. They're in different size diameters and are adjustable.
eg: Speaker Box Port - Dia 110mm x 160-280mm Long - Jaycar Electronics

 

[holdenboy]

Why are you going with a "triangle" shaped box? Personally i would go with a rectangle shaped box with a round port.
I dont think 1 x 90mm port will be enough port area for your box. It will sound fine, but you'll get louder by going with a 4" port.....6" would be even better but im guessing you dont want maximum SPL, more SQ. So in this case the port suggested by VSPantha will be ideal.

Dont worry too much about getting the length exactly right, but what i would do is extend the port out as long as it goes - 28cm (equals to approx. 33hz tuning) and leave it like that for a few days, then adjust it down to say 25cm (approx 34hz tuning) and left it for another couple of days, then take it down to 20 odd cm (approx 37hz tuning) and make a decision on what depth, and therefore tuning freq. is the best. If its still getting better at 20cm depth, by all means keep making it shorter untill you get down to 16cm (minimum depth).

Also remember that the sub will "loosen up" within a couple of days and sound better, so it might be an idea to re-lengthen the port to make sure a lower tuning frequency isnt better.

 

[MG's VH Wag]

So your thinking a box something like this? (see pic)

I would get some of those ports but my local jaycar just closed down which sucks. Do you have some sort of table that shows like what lenght equals what frequency? Also how thick should the wood be that i use on the box?

 

[holdenboy]

Yeah, a box like that would be better, just make sure it dosent extend the whole width of the boot (in between the struts), as you want the bass to be able to get into the cabin......i assume you want the sub / port to face the tailights?

You dont have to get that exact port, if you can get your hands on some 110mm PVC pipe that will work the same. Definately flare the ends to reduce port noise and increase output. Theres no real "table" which tells you what length equals what tuning freq. It depends on box size and port diameter etc.
A good tool that i use is this site,
Basic Car Audio Electronics

Scroll down the left menu untill you get to "Basic Enclosure Calculations", which is underneath "full version of this site". Scroll down to the calculator for ported enclosures, it will require the measurements to be in inches so a conversion program is good too (unless youre good with that stuff).
Anyway, put in the dimensions of the box along with the wood thickness, speaker displacement, port diameter and desired tuning frequency. Leave the port Ration at 1:1 and hit "calculate". This program takes into consideration the volume taken up by the port and re-calculates the length to compensate for this.
I realise theres probably a few other programs out there that do the same but i just use this one.

As far as box thickness goes, 18mm MDF will be fine....but if you want you could go with 25mm MDF or if you can only get 16mm (like me, stupid Nelson Bay) then either 16mm or if you want it extremely strong then yeah, 2 sheets of 16mm. Although recently i made up a 16mm box and pushed over 4kw into 2 x 15s through it, did 149db for about 2 weeks before the joins started to break apart, lol.
So yeah, its not a huge box so 16mm will work OK.....you may get a small amount of flex but you probably wont hear the difference between 16 and 32mm, you'll only see it on a SPL meter. Also make sure all your joins are sealed on the inside, once youve done one join run a line of glue down the inside of the join and with a wet rag push the glue into the join, this just ensures you have a properly sealed box and have no leaks.....very important in a ported enclosure as the pressure is actually greater at the tuning frequency than a sealed box.

Hope this helps you.....good luck

 

[MG's VH Wag]

Yeah mate i have made it 75cm long so there is about 20cm room each side from the struts.

I have only made the box 30cm deep so hopefully the sub won't need that much mounting room. I havn't actually made the box yet just drawn it out. The port won't need to be longer than 30cm will it?

I could only get my hands on 16mm MDF to so i have gone for two sheets of it to make it 32mm. Nice and heavy too lol.

 

[holdenboy]

30cm internal or external depth? If its external then you may have to make it a little deeper, or use a right angled elbow for the port. As a general rule you need to keep more than the ports diameter in distance away from the box wall, so this means in your case if you use a 110mm port then you need to have alteast 110mm of free distance in between the end of the port and the back of the wall.....basically, you'll only have room to go with a maximum depth of 190mm, this equals a tuning freq. of approx. 38hz tuning, not bad......but if youre after lower bass you'll need to use an elbow or make a deeper box