Help building sub box

[87gnblackdemon]

I've decided to put my subs in the right size box and hand down my box to my sister. I've looked around and there aren't too many boxes big enough for what I need. Subzone has single 12" sub boxes that are 2.5 cu ft and they are perfect, but the advice I've been given is to try and build my own, so thats where I am.

I was told that 4x8 3/4" mdf would do me fine, and in order to get 2.5 cuft/chamber the box would have to be 36"wide, 17.5"high, bottom depth 18.5" and top depth 13.5 and all sides 3/4" thick. But when adding a port the measurements would be 17"widex17"widex20.5" deep, this would give me about 18" straight depth to extend a tube from front to back. Total dimensions for the entire box would be 17"hx33.25"wx20.5"d.

Right now I don't know if it would be better to split the box or have the subs share the air space, and if I'm going with one port or two. This is all for 2 12" vegas124dvc.

All these measurements were given to me, I did not do them.
Any different opinions on the measurements? Splitting the box? Or number of ports? Also what would you recommend I use to connect the mdf pieces so I don't hurt the cu ft space?

 

[Audiowizard]

Originally posted by 87gnblackdemon
Total dimensions for the entire box would be 17"hx33.25"wx20.5"d.

Is that the inner box dimensions?? If it is then it would calculate as follows: 17" x 33.25" x 20.5" = 11,587.62 cubic inches = 6.7 cubic feet which divided by 2 subs will = 3.35 cubes per sub.

If that is outer dimensions, then you would subtract 1.5" per measurement for the 3/4" MDF which will calculate as follows: 15.5" x 31.75" x 19" = 9,350.37 cubic inches = 5.4 cubic feet which divided by 2 subs will = 2.7 cubes per sub.

Right now I don't know if it would be better to split the box or have the subs share the air space, and if I'm going with one port or two. This is all for 2 12" vegas124dvc.

If you are running the subs both bridged mono to the 1 amp channel, then you can have them share the same space. If you
are going to have them run to a stereo channel (1 channel per sub or 2 mono amps, 1 for each sub) then you need to divide them so they arent fighting each other in the same box.

I personally wont run subs in the same air space because of choice.

All these measurements were given to me, I did not do them.
Any different opinions on the measurements? Splitting the box? Or number of ports? Also what would you recommend I use to connect the mdf pieces so I don't hurt the cu ft space?

The port size is critical so it needs to be the proper length and diameter for the air space. It can be calculated using a port tuning nomogram.

Depending on how you are going to power cabinet will determine if a divider is needed. A divider will never hurt the performance of subs so I would recomend using it (just my opinion)

I build my woofer cabinets one way and that is using dry wall screws and carpenters wood glue. The screws will help compress the joints and the glue will help hold and seal. For it to work you must pre-drill mounting surface and countersink for a nice clean finish. You can use an air nailer which is faster but using the screws will make the joints stronger.

Get someone to help you build this for better cuts and safety.

If you have any questions on building cabinet, let me know and I will help you through it.

 

[be_regal]

audiowizard or anybody do you know of any good links to help design a box, as far a measurements, what size port to use if chose, and just cabnet stuff. I think Im strangling my S12L7's in the box they are in now. I think the box I have now is way to small for them. I'm not getting anything close to the spl that I was getting with a set of Kicker C15's 4 olms. To power the 15's was a single ZR360. I was running them bridged mono to take the amp down to 2 olms. They hit hard. Now the S12L's are dual voice coil 8 olm subs, but with these I have bought another ZR360 to compensate powers. I choose the 8 olmer's because on the Kicker web site they claim the zr360's max out put is at 4 olms at like 400 and something watts. I'm not really sure right now of the cubes of the box but I'm guessing about 1 sq ft per sub internally not counting the displacement of the sub in the box. The 15's had I think a 2 cubes per sub. What do u think I need to do to get the spl back or more than I had before since I do have twice the power and twice the sub. What are your thoughts? Do you think its the olm load going into the amp, the box size, or what?

 

[87gnblackdemon]

The measurements given to me were the outer measurements. Those measurements are a little off when you broke it down for me. I'd like to have a dual 12" box with 2.5cu ft per chamber, with a port per speaker 4"x13", I'd want the ports in front instead of on top, thats the way they show it in the cerwin vega speaker manual. Sqaure box. Ya think you could calculate those measurements for me. And I was thinking with the amount of space in the GN trunk, that it would be better to make the box longer from side to side rather than wider front to back, ya know with the hump in the front of the trunk and the shelf in the back there isn't much room.

 

[Audiowizard]

Be Regal and Blackdemon,
E-mail me your the max height and width of your trunk where you want your box positioned and I will calculate both of you cabinets for both of your subs that you can build to spec. I also will add some air space for basket area so you will have near perfect specs for air space. You may have to give me a day or 2 to get everthing calculated. I will figure out the ports for your Cerwin Vega subs also, and please give me model #s of subs so I can get the right dimensions for both of your cabinets. Thanks.

 

[be_regal]

DUH!!!

I went out to check the internal volume of my box, its 1.6 cubic ft per chamber. Well I forgot to account for the displacement of the speaker when I built the box. After I did the calculations with the speaker displacement the box is .17 cubic feet. No wonder the don' hit like they should. Well I broke out the old TI-85, did some figuring and measurements now I'm ready to start construction all over again. This time the box is going to be 1.7 cubes per chamber after the speaker is put in. This is the best and worst part about doing things like this yourself. Audiowizard thanks for the offer. Im building a sealed box so it should be easy.

 

[Audiowizard]

You have it under control be_regal . Let us know how it turns out.

 

[87gnblackdemon]

AUDIOWIZARD: I sent ya an e-mail with my trunk specs, do you get it??

 

[Audiowizard]

Yes, I got your e-mail . I am still working on specs, I will let you know the dimensions of box size and port length.

 

[GNandTTA]

Because of the very loose spider on Cerwin Vega subs you need to make sure the box size and port size are right on the money. I would look on thier home page to get exact dimmensions. I had a pair of CV 12's in my GN a long time ago. Back then they needed exactly 2 ft3 and 1 3" port (don't remember the length) per woofer. I can honestly say they were the loudest I've had - except maybe for my current dual 10" bandpass w/ports facing the trunk. You may want to get a subsonic filter also to help protect the CV's. Ported enclosures unload (loose control) below the port tuning frequency.

 

[Audiowizard]

Hey blackdemon,
Let me know what the woofer basket area is so I can add that to the enclosure area, thanks.

 

[87gnblackdemon]

Only thing I can find is the mounting depth, I think this is what your asking for , if not let me know.

5.625 (142.9mm)

 

[Audiowizard]

Originally posted by 87gnblackdemon
Only thing I can find is the mounting depth, I think this is what your asking for , if not let me know.

5.625 (142.9mm)

I need the area of the basket with magnet. I.E. .60 cubic foot. What ever the area of the magnet and basket displaces inside box, I need to add that to the area of cabinet to make up for area it displaces. The mounting depth that you gave me is the actual measurement of the depth of basket and magnet once mounted to cabinet.

Look for a spec of the DV12 and see if it has a (VF)* It stands for volume of frame. It should be in cubic inches I.E.....100.0 cu. in.

 

[87gnblackdemon]

I've got two sets of measurements, not sure which one is right.

Volume Displacement: 0.13ft3

Enclosure Volume: vbox=2.00ft3(net)+0.13ft3
(driver displacement) + port displacement.