Hey guys. New to the site. Been reading several threads for awhile now and just decided to become a member. I have a question. Currently I have 2 12w7s with 2 750/1 HD amps. All JL audio. My box is made out of 3/4 mdf wood with a 1 inch face like JL recommends. Box outside dimensions are 16 inches tall, 18inches deep, and 38 inches wide SEALED with a sealed divider between them. I want to go ported but keep the same box. What size ports do you all recommend? How long/deep into the box? How big around? (If I were to go with round)
Any help would be great. Thanks in advance!

 

Usually for the same sub, a ported box will require a bigger enclosure than a sealed one. Head on over to JL's website. There are some good tutorials there & you will also find information for your particular driver.

I myself prefer running a bigger enclosure than JL recommends. I've used 10W6's, 12W6's, and a 13W6....all these drivers sounded a lot better in a box that was bigger than the recommended enclosure. Much better low end extension, & overall sound. These subs were all used in a sealed setup.

These guys make good boxes.

OEM spec for a 12W7
http://www.lifeafterbass.com/laboejlaupom1.html

Another box they made for a 12W7. It's bigger and has a lower tuning frequency.
http://www.lifeafterbass.com/labsl2ftpomd8.html

Both of these boxes are bigger than the recommended sealed enclosure. You will need to get another box as yours won't work for what you want to do with it.

 

Thanks for the reply. Here's my deal though. I don't have anymore room for a bigger box. I could make one about 5 inches deeper than what it is. But then I would have to make it shorter in height to still be able to get it in the trunk. I made this sealed box a little deeper than and a bit wider than jl specs but couldn't make the height to specs because it would not have fit. I just really prefer ported boxes. I like the sound of them. What can i do? The first link you sent is almost perfect. Depth and height is perfect but the width would not work since I need 2 and only have 40 inches width to work with. Any suggestions? Thanks for the help

 

In that case the answer is simple....go ported with a single sub. That single sub, in the bigger & lower tuned box will sound better than two subs in a box that doesn't meet the proper air volume.

 

I was afraid of that answer lol I'm going to play around with this box and see what I end up with. I have a jl audio fiber glass box made for 2 w7s that is also sealed. So if I mess this one up to bad I can always go back to it. Thanks for the help.

 

Your welcome.

In my 7th gen, I'm running a Boston G5 sub with a tunable passive radiator. This set up is like having a ported box, but in a very small box. It sounds great too. It's too bad JL doesn't offer something similar. That way you could have that ported box sound but with much less room taken up.

 

I agree. Can you explain that set up? I have heard that before but honestly never really knew what it was.

 

This link will explain what it is. I have this exact model. Unfortunately, Boston Acoustics isn't making car audio products any longer.

http://www.crutchfield.com/p_065G510...+g510rs&tp=112

 

What frequency do you want your box tuned at?(30hz, 35hz, 40hz, etc) That will determine how long and how big of a port you will need.

 

Correct, but you also need the proper enclosure.

 

I'm wanting in tuned at jl audios recommendations which is like 36. Something. I found this box online. What are your opinions?

http://www.fatboxusa.com/products/12...udio-12w7.html

 

The only thing with JL's specs is that they are tuned on the higher side. I myself would go with a box that would have a lower tuning frequency, like the one I mentioned above. That's just my preference though.

If you have already listened to these subs in a factory spec box like this & you like it, go for it. It comes down to what you like. It will definately sound much better than just adding ports to a box that's too small. Report back on your impressions.

 

I really don't know. I have heard that the jl audio specs are tuned a little high like you mentioned. I do have room for the boxes you posted a link for I would just have 2 separate boxes with with the subs either facing up or towards each other. the boxes would be long ways instead of side by side. Hope that makes sense. But with that box I posted I would be able to have the subs firing directly to the back of the seats so when I folded the seats down, bam all you would see is the 2 subs from the inside. I'm open for all ideas. I just want to get the most out of these subs. I just want it to be stupid loud just because lol thanks for the help!

 

Take a look at the port length calculator on the12volt.com to give you a baseline to start to play with.

Using slot ports, and assuming your box is 3/4" MDF..........if you went with a typical 2" wide port, with a port height of 14.5"(16" box height, minus the two .75" pieces of MDF that are the top and bottom of the box), that would come out to you needing a 19" long port if you kept the same box size. You could make it an "L" shaped port to go down and make the turn towards the center of the box as you only have ~14.5 of depth after you take out the wood dimensions and 2" of port space needed at the back

Disclaimer: Those calculations are just using straight dimensions, and not taking into account the displacement of the woofers or the internal pieces of MDF that would essentially drop your internal box volume down a bit. While the differences are very minimal and I'm 99% sure you wouldn't hear the difference if you took the time to calculate the displacement that these elements take, some people want EXACT specs. When I am making a box for "daily" use listening to music, straight dimensions are good enough for me

 

That's an awesome site. Exactly what I was looking for. Thanks! Here's another question. Does the port have to come out of the front of the box?

 

See the first post, 3rd pic. That's basically what one side of your box will look like.

http://www.diymobileaudio.com/forum/...-wanted-2.html

 

Not necessarily, but having the port face the same direction of the sub CAN augment the output. You can also have the port fire into the cabin through the rear deck, but that'll require quite a bit more work.