3 15 l7s box build please help

[TnTahoe]

the displacement for each sub is 0.16 cubic feet so times 3 and you got a total sub displacement of 0.48 cubic feet. And to calculate for bracing basically visualize how you want your box to look and find where it could use some support, my last box I used a couple of vertical braces and 4 horizontal braces. The horizontal ones were used to stop the side walls and front and back walls from flexing, and the two vertical ones were used to help support the weight of the subs. I used 2x2s as my bracing so to get that volume you have 2"x2"x(however long it needs to be) and divide that by 1728 to convert to cubic feet. So once you have an estimate of the bracing + sub displacement, you will want to include these into your volume. Example: you want your enclosure to be 14cft, and your sub disp. is 0.48 cft and your bracing is 0.32 cft, well you will need an internal volume of 14.80 cft to accomodate those subs, BUT you also have to plan for the port volume as well. So you basically just have to keep playing around with it until you get it right. Another note to consider is what type of port you will be using and the placement of the port or ports.

 

[abladeafficionado]

It's basically a matter of playing with the numbers until you find what works. I'm going to assume a 16 ft^3 box tuned to 32Hz for this example, with the subs and port both firing up.

Let's decide on a height and width, I'm going to assume 48" wide, by 24" tall based on your measurements, those will remain constant throughout our calculations. Don't forget that those are external dimensions, not internal. Assuming you use 3/4" MDF, internally, it's 46.5" wide by 22.5" tall.

Let's assume that there's 0.5 ft^3 of sub (like there is), and allow 0.2 ft^3 of bracing (round numbers for ease of calculations). Let's assume the port will be an L-port, running the width of the box, so 46.5" wide (internal dimensions), and let's make the port 5" wide, giving you 232.5 in^2 of port area.

For a 16 ft^3 box, to get a tuning frequency of 32.5Hz (I made a design change mid calculation so the tuning changed from 32Hz to 32.5Hz), with that port area, you need a 24.5" long port (taken from 12v's site). (46.5" x 5" x 24.5")/(12 x 12 x 12) gives us a port volume of 3.3 ft^3. Add that to the 0.7 ft^3 we allowed for sub displacement and bracing volume, and that gives us 4 ft^3 of volume that we must account for.

4 ft^3 of sub/bracing/port + 16 ft^3 of box = 20 ft^3 of airspace that must be factored into the box. Let's solve for the length of the box: 20 ft^3 = (22.5" x 46.5" x "X")/(12 x 12 x 12). "X" = 33" long (internally), so 34.5" externally + 0.75" for the thickness of the port wall on the inside = 35.25" long. Add 1.5" to the internal dimensions, and you get a box that's 48" wide, 24" tall, and 35.25" long.

So you external dimensions are 48" wide by 24" tall and 35.25" long, with a port that's 46.5" by 5", and 24.5" long. I haven't double checked the math or anything, but that gives you an idea of where to go with the design. You can go and double check the math if you want and use that design.

WARNING: I haven't double checked any math, or checked measurements with anything other than 12v's site, so don't use that design without going over the math and making sure it's all correct. I'm not responsible if that design isn't right. I'm not a box designer by trade, just a hobbyist. It takes a lot of time to do it right, and this was a quick design I generated, not a complete design that I've modelled up in sketchup and double checked like I usually do.

 

[BeaverGod]

download WinISD.

30 hz is too low. it defeats the purpose of porting the box as the sweet spot is lower than what most source material provides. id recommend 40.

also dont forget to subtract the cubic area of the port from the enclosure net.

try and make only one port.

to get volume multiply length x width x height and divide by 1728. dont forget to take the internal dimensions, not the external (account for width of the wood)

good luck

 

[abladeafficionado]

40Hz will sound like absolute shit IMO. It'll be very peaky and loud, but have no low end extension. 32Hz is about the sweet spot IMO. Then again, I care about SQ/SQL, not SPL... 32Hz doesn't defeat the purpose, it is the purpose. The purpose of porting is to gain volume and low end extension at the expensive of steep rolloff below tuning frequency. A steep rolloff below 40Hz is not what you want.

A lot of the rap I listen to has heavy bass lines in the 30Hz-34Hz range. I have some stuff that's recorded at -2db at 33Hz. If I had my box ported to 40Hz, the subs would unload on those bass lines and potentially damaged themselves. Go model up those subs at 40Hz with WINisd and tell me what happens. It'll be peaky, and the power handling will drop significantly below about 34Hz.

Set your SSF an octave below your tuning frequency also to protect the sub.

 

[j.castro]

It's basically a matter of playing with the numbers until you find what works. I'm going to assume a 16 ft^3 box tuned to 32Hz for this example, with the subs and port both firing up.

Let's decide on a height and width, I'm going to assume 48" wide, by 24" tall based on your measurements, those will remain constant throughout our calculations. Don't forget that those are external dimensions, not internal. Assuming you use 3/4" MDF, internally, it's 46.5" wide by 22.5" tall.

Let's assume that there's 0.5 ft^3 of sub (like there is), and allow 0.2 ft^3 of bracing (round numbers for ease of calculations). Let's assume the port will be an L-port, running the width of the box, so 46.5" wide (internal dimensions), and let's make the port 5" wide, giving you 232.5 in^2 of port area.

For a 16 ft^3 box, to get a tuning frequency of 32.5Hz (I made a design change mid calculation so the tuning changed from 32Hz to 32.5Hz), with that port area, you need a 24.5" long port (taken from 12v's site). (46.5" x 5" x 24.5")/(12 x 12 x 12) gives us a port volume of 3.3 ft^3. Add that to the 0.7 ft^3 we allowed for sub displacement and bracing volume, and that gives us 4 ft^3 of volume that we must account for.

4 ft^3 of sub/bracing/port + 16 ft^3 of box = 20 ft^3 of airspace that must be factored into the box. Let's solve for the length of the box: 20 ft^3 = (22.5" x 46.5" x "X")/(12 x 12 x 12). "X" = 33" long (internally), so 34.5" externally + 0.75" for the thickness of the port wall on the inside = 35.25" long. Add 1.5" to the internal dimensions, and you get a box that's 48" wide, 24" tall, and 35.25" long.

So you external dimensions are 48" wide by 24" tall and 35.25" long, with a port that's 46.5" by 5", and 24.5" long. I haven't double checked the math or anything, but that gives you an idea of where to go with the design. You can go and double check the math if you want and use that design.

WARNING: I haven't double checked any math, or checked measurements with anything other than 12v's site, so don't use that design without going over the math and making sure it's all correct. I'm not responsible if that design isn't right. I'm not a box designer by trade, just a hobbyist. It takes a lot of time to do it right, and this was a quick design I generated, not a complete design that I've modelled up in sketchup and double checked like I usually do.

thanks alot man this really helped me out

 

[abladeafficionado]

No problem. It's not too tough of a process once you do a couple. If you have any more questions feel free to ask. You could also do aeroports instead of a slot port, I just prefer slot port for ease of design and added structural rigidity.

Don't forget to 45 all of the internal corners so that the air can flow smoother. The goal is to direct airflow as smoothly as possible to reduce any possible port noise. Also make sure there's no gaps or air leaks anywhere in the box. The only air leaving the box should go through the port, leaks are the enemy.

Should be very loud!

 

[j.castro]

ok so ive got all three subs all the zero guage and the kinetick battery.all i need are the amps and the alternator and the yellow top.are there any other amps or amp you guys would reccomend besides the hifonics preferably one that does 3000 rms tru watts

please and thank you

 

[abladeafficionado]

Are yours the DVC 2 or 4 ohm?

 

[j.castro]

dvc 4 ohm.. so i was planning to wire each down to 2 ohm and run it to its own amp..what are some options of wiring all three to one amp/what ohm load
my budget on the amps would have to be around 650ish

---------- Post added at 09:46 PM ---------- Previous post was at 09:39 PM ----------

would the zx2500 be able to handle all three?i was also looking into a sundown 3000.1

---------- Post added at 11:13 PM ---------- Previous post was at 09:46 PM ----------

ok ive done a bit of research and found that the best way to wire the 3 dvc 4ohm subs together is at 2 ohms(2.67) so now i need an amp that does 3000 watts rms clean at 2ohm? ideas?suggestions?

 

[abladeafficionado]

You probably would have been better off buying the DVC 2 ohm, because power is cheaper at 1 ohm than at 2 ohm, but you'll get better efficiency and less stress on your electrical running at 2 ohm, so there's an upside.

I would do 3 of these.
http://www.sonicelectronix.com/item_23875_MB-Quart-ONX1.1500D.html

Getting 3000RMS at 2.67 ohms is going to be more expensive than 3 of the amps I linked. Sundown are good amps, but you're not going to get 3000RMS from them at 2.67 ohm for $650 from Sundown, you can get 3000RMS at 0.67 ohm from Sundown, but that's below their rated impedance so you won't have warranty coverage (even though it'll be fine as long as your electrical holds 13V+ under load). I'd go with the MBQs personally. They should run fine at 2 ohm all day.