PDA

View Full Version : Ported Enclosure for 3 8s, Your Thoughts?



The_Grimy_One
03-31-2012, 10:53 PM
Ok, so I am by no means a pro at this. I am just looking for some input, and want to verify this box will work for my 3 Cadence CVL 8s. They will be wired at 1.34 on my RE 35.1.

The overall size is 28 x 16 x 14... Port is 12.5 x 2.5 @ 31" long tuned to 30Hz. The volume before all displacements is 2.78 cubes. I was guessing that each sub is .1 cubes each. I know Cadence says 1 cube each, but I am hoping since I have the power that I could run a little smaller than that.

*The only real issue is I want to make sure the subs will fit on the front of the box. On the mock up I used the accurate dimensions, but maybe someone can double check that for me.

http://img252.imageshack.us/img252/8800/screenshot20120320at732.png (http://imageshack.us/photo/my-images/252/screenshot20120320at732.png/)


http://img696.imageshack.us/img696/9635/screenshot20120331at741.png (http://imageshack.us/photo/my-images/696/screenshot20120331at741.png/)

RAM_Designs
03-31-2012, 10:58 PM
Do not build that enclosure.

When you're figuring the port length, you have to use the net volume after all displacements. That means you have to take into consideration the port displacement before you know the exact port displacement. Then you can kinda mess with some dimensions and get to the right specs once you know exactly how much volume the port will take up with the given net volume and tuning you're wanting to have. The box you're describing right now is going to be ~1.6ft^3 with an upper 30's tuning because you found the port length based on the gross volume and not the net volume.

Moble Enclosurs
04-01-2012, 12:53 AM
With those dimensions, you are actually looking at about 1.78 cubes if the displacement is around .1 cubes each driver. The tuning will be around the mid 30s. But the issue is not that. The issue lies in the excursion and placement of the port. If you were to use these dimensions, it would be best to place the port on the side. BUT, even so, with a calculated 3k@1.33Ohms (which would be all parallel), then you would be above the max excursion of these drivers between 40-60Hz and below tuning at the obvious -3dB point of around the low 30s. BUT, that was based on max power ratings. If you use rms values, then you will be ok down to about 30Hz. But below that will cause issues, so the SSF should be set above the mid 30s, which a lot of people are not ok with doing because you lose a lot of low end output that way if you like it low. SO, the box is ok, but not optimal by all means. Just good.
Without cabin gain, you would also lose output around 53Hz and above as well. The actual usable response of these drivers is 11-53hz! Which means you can actually tune that box in the high 20s for a more musical response and it will be better with the port the way it is now.
With all three drivers, though they do have a low compression compliance, they require about 3.87 cubes to work best in (total for all three), and around 42V max output, which you would be around 44V anyway if you were to be at RMS :D Hope that helps.

The_Grimy_One
04-01-2012, 01:01 AM
Wow, that was a ton to read through. And yes I am basing it off of RMS ratings. So what would you guys recommend for tuning? I did not realize that I had to subtract the port displacement before I actually did the frequency calculation. I can probably go an inch wider, and 2 inches deeper. Would like to keep the height down if possible tho.

RAM_Designs
04-01-2012, 01:05 AM
With those dimensions, you are actually looking at about 1.78 cubes if the displacement is around .1 cubes each driver.

Indeed, I was using 28x14x14 for some reason.

The_Grimy_One
04-01-2012, 01:06 AM
Indeed, I was using 28x14x14 for some reason.

I can go maximum 29x18x14

The_Grimy_One
04-01-2012, 01:24 AM
Im so lost, I cant even replicate the enclosure they recommend. I must be doing something really wrong on the calculator. I may just have to pay one of you to design it.

duanebro
04-01-2012, 08:29 AM
Often the recommended enclosure is way off. If you want to diy, then figure out the displacement of the port + subs. (this will be a guess as you can't figure out the actual port size before the box) then subtract that from your max box volume. This is what you have to work with, plug it in to the calculator and play with tuning and box size til you get what you want. Post it back here for advice. Repeat until happy.

RangerDangerV2
04-01-2012, 09:00 AM
I would add a little more port....

The_Grimy_One
04-01-2012, 09:23 PM
Im working on the new design right now. I figured out what I was doing wrong. Does anyone know what the displacement is of these 8s?

Moble Enclosurs
04-02-2012, 12:30 AM
I am calculating for around .044 cubic ft right now. This is an estimation, but if you figure for the given cylindrical volume, it comes up to about .13 cubes, and half of that is .065 cubes, and the sub takes up just under half the cylindrical volume based on the exterior dimensions.

The_Grimy_One
04-02-2012, 12:54 AM
I am calculating for around .044 cubic ft right now. This is an estimation, but if you figure for the given cylindrical volume, it comes up to about .13 cubes, and half of that is .065 cubes, and the sub takes up just under half the cylindrical volume based on the exterior dimensions.

OK. Thanks. I will use something close to that. I am very close to finishing the box now.

The_Grimy_One
04-03-2012, 06:18 PM
Ok guys... I figured out what I wasdoing wrong, and now have a new box design, same concept tho.
Dimensions --> 28.5" wide x 14.25" high x 18.5" deep
Port --> 2.5" wide x 12.75" high x 34.5" long
Port Freq --> 29Hz
Sub Displacement --> .05 cubes each (1.5 total)

---------- Post added at 03:18 PM ---------- Previous post was at 03:18 PM ----------

Ok guys... I figured out what I wasdoing wrong, and now have a new box design, same concept tho.
Dimensions --> 28.5" wide x 14.25" high x 18.5" deep
Port --> 2.5" wide x 12.75" high x 34.5" long
Port Freq --> 29Hz
Sub Displacement --> .05 cubes each (1.5 total)

Moble Enclosurs
04-04-2012, 12:08 AM
sounds like a plan! Let us know how you make out! :D