I am building a ported enclosure for 2 L7 12" yea yea I already got bashed in another forum. For each 12 the interior dimensions for the box will be 30.6" wide, 13.5" tall, and 18.5" deep which yeilds 4.422 cubes. I have a cutout in the box to fit in the truck, which takes away 271 sq. in. leaving a total of 4.265 cubes per 12 before braces and displacement accounted for. First, is this box too big? And, second, how do I properly tune the box to 34 htz? Is there a reliable, accurate calculator to use? But it probably can't accout for that cutuout I have. I'm just going for good listening, deep, powerful everyday system. Thanks in advance.
And yes, I have used RE port calculator and tried rockford fosgate calculator, but to no avail. Would it be much different in tuning to just act like the cutouts are not even there? or could I shorten the width of the box just a bit in the calculator to account for the 271 sq.in. that are missing to get the same total cubes ?
first, yes the box is too large, in my opinion. I'd keep the box at around 2 to 2.3 cu ft per sub. For tuning, and general box calcs, look at www.bcae1.com and on the right menu, find the link for the page called "basic enclosure calculators" I believe it's called.
It has everything you need for tuning based on the type of port you desire. round or slotted.
End correction for a slot port - whatever your port length is, you subtract half of the port width for the actual tune. That's what the 12volt calculates to. It doesn't calculate an end correction, which means the end result of what it says is where YOU put/calculate the end correction.
Your box is 1" MDF, 30" depth, port width is 3". Subtract 1 from 30 (the back of the box), and then subtract 1.5 (half of the port width). The port length is 27.5".
Don't use more than 3 cubic feet per L7. 2-2.5 cubes is a sweet-spot.
Glass, I tried the bcae1. com calculator and there are so many abbreviations and acronyms I can't make sense of it. I am going to size the box down a bit, but I still want it on the big side of acceptable, like 3 cubes with port area subtracted. This is advantageous to get thundering lows right? And Huggi, what is the 12 volt port calculator? Sorry, I don't know what end calculation is.
The 12 volt calculator is everything you need to design any box.
If you want really good lows, don't use an L7. Use an XCON or a BTL or something better. I would even use 2 12's in a sealed box with double the power, anything but an L7 lol.
End correction:
The end correction is used on a slot port because the calculated length is taken from the center line of the port. The end of the port (inside the box) acts as if it travels up the outer port wall up to half the width of the port area. This means even though you calculator from the center line, it slants from the corner of the box to the end of the physical port area. Therefore, your port will always act as if it's +half of the port width in length.
The physical port length stops at "actual length" but the port length acts as if the port extends to the "calculated line". You then add the space the port isn't taking up (blue), and the green is your "extra" port length.
It's really very simple.
However long the port is (longest dimension, at any point - not center line), you subtract half of the port width, and that is the measurement you want from the calculator.
OK, like I said, port calculation for nube. I look at that picture up there and have no idea what is going on with it. What is center line? or actual length and extra port length? is the outer wall of port the wall that is consistent with the box wall? are you saying that whatever length the calculator gives, I subtract half the width of the port from the length and that should be how long I make the port? Meaning the inside wall which is not part of the box? I know this is a lot to be asking, but I have no idea what all this means, maybe I should get a pro to do my box. Please put it in simpler terms cuz i don't know all this terminology.
Just port calculations? Sorry if this isn't new info.
A ported box adds (generally) 3dB of SPL (sound pressure level/volume/measured in decibels) at the tuned frequency over a sealed box. Below the tuned frequency, it starts to roll off at -24dB per octave (dB = decibels/unit of how loud sound is), which means if the box is tuned to 30 HZ, at 20 HZ it will be @ -24 dB so every 10 HZ is an octave. A sealed box rolls off at -12 dB per octave, and the "QTS" (QTS .707 = flat response) is the measurement of how many dB's per octave the box rolls off. A low QTS (.5) will be like (I'm guessing) minus 8-10dB per octave, and a higher QTS 1 will be like minus 14 dB per octave. Sealed boxes are the better choice for low end response (like 20-25 HZ), unless you port & tune it to 20-25 HZ.
A port controls how a sub moves. More movement (or less) at certain frequencies is achieved, thus better (custom really) performance. A sub needs a port large enough to breath, yet restrict the motor from full mechanical movement, preventing damage. When you double the cone area (from one 12" to two 12"), you gain 3dB. When you double the power, you gain 3dB in output also. The difference between 24 & 48 subwoofers can be as low as 3 dB but it's quite the jump from 150-153 dB - it's thousands and thousands of watts. If you had a 12" sub on 1000 watts, and then switched to 2 12's on 2000 watts, the difference is a gain of 6 dB. Combine that with a better install, box, and electrical, you can gain 4 dB, which means you can go from 140 dB to 150 dB without trippling the cone area and power. It's much easier than 150 dB to 160 dB. Youtube "bob perillo does bass race 160". It's some LOOOOUUUDD SH!!!!TT SON!!! 150 dB is really loud on music too. The lower the frequency, the harder it is to reproduce but the "louder" it'll seem. Like in a setup where 30 HZ sounds (and feels) louder than 50 HZ, but say 50 HZ puts up better numbers. It's like that.
Don't EVER EVER EVER play below the tuned frequency. I mean, you can play music if you have a decent cross over and you have everything set properly. If you're listening to rap you'll want to tune into the low 30's so that when you listen to chopped & screwed music the sub doesn't move past its mechanical movement. Subs in boxes in cars usually don't ever reach full excursion so a maximum tuning of 40 HZ is okay for music. 40 HZ is high for any kind of sound quality, 35 HZ is a good mix of lows & highs, and if you like your lows than 30 HZ is much better.
A subwoofer motor (VC/Voice Coil - the part that moves) acts very differetly when in and out of a box (as in mounted in the box vs sitting on a floor) because of the different pressures being applied to the cone (parts that you see moving when the sub is in a box - the outer part is called a surround). A car environment will restrict air from escaping so there is more pressure on the cone, allowing it to move less. This is where a port comes in - you can control how & how much the cone moves. More movement = more linear displacement = more air being moved = louder. A hole in a box depressurizes it so the cone moves more freely at whatever frequency. A sealed/more pressurized box allows for better sub power handling because it restricts cone movement more than a ported box. The longer the port, the lower the tuning. It depends on a sh!tload of math that I don't know.
It's very easy to exceed the mechanical limits of a subs motor when it's not in a box. Some subs are designed to do exactly that in an "IB/Infinite Baffle"" setup.
"are you saying that whatever length the calculator gives, I subtract half the width of the port from the length and that should be how long I make the port"
Yes. I win.
Boxes are easy to make, get Home Depot to cut the wood. Glueing, pre-drilling, and screwing is easy. It's fun too. All that sticky glue inside the pieces that fit together just right.
It would be easier to design a sealed box. I would sell the L7 and get two Eclipse SW8210's ($150 each) for 3 cubes sealed, it would handle 3000 total watts but no more. That's 4X the RMS of the L7.
BTW the Eclipse SW8210 rolls off at 28 HZ in 1.5 cubes, QTC .5X. Efficiency 86.5 dB. It's a low end monster, 750W RMS / 1500W MAX. Eclipse recommends up to 1500 watts in the manual "but only if it's clean power", which means constant voltage, which means a high output alternator and batteries.
The Eclipse's would need 750W to be as loud as the L7 if the L7 were on 750W. The sealed box would be -3 dB from the ported box but because of the doubled cone area it would cancel out (+3 dB). You can then safely double the power (1500W RMS total) for +3 dB over the L7. Not to mention the L7 has around 87-88 dB efficiency, while the Eclipse has 86.5 dB efficiency so +3 dB = 89.5 dB. If you're limited on space, that's the way to go unless you can afford an Fi BTL 12" and a 3000W amp. A BTL 12 (89.5 dB sensitivity) in 3 cubes tuned to 30 HZ would be about the same as the 2 sealed 12's on 3000W but the sealed box would sound way better.
The sound quality would jump ten fold, that's for sure.
Huggi, that was really informative. But, one more question: I have a 271 cubic inch cutout for each box that I can not plug into the calculator. Would it be the same if I shortened the width of the box by just a hair in the calculator to total 271 sq in taken away to get ~accurate results? And the total length of a port would be the inner wall length of the L port? Measure both sections of the L? Is that what I subtract half the width from?
And dustin, or huggin, I wanted to do slot port cuz I think it would be hard to make a round port look good. Are there easy fixes to make a pvc port in mdf look clean and smooth?
and just so you know I have a 2 l7 box, just simplifying things by talking of one sub with one box. And space isnt much of an issue seeing that I have too big a box at 62x20x15 outer dimensions. It's going in the back of ext. cab 98 dodge ram.
"And the total length of a port would be the inner wall length of the L port"
Measuring from the center line is the port length but so is the outer wall, I suppose it depends on which you're refering to. I go by the calculated length. You get your calculation and then build around it.
I can design you a box real quick, what are the outer useable dimensions you're working with? I'll do all the math and explain it.
My total usable space for the 2 12s is 62Lx15Hx20D outer dimensions with 3/4 inch mdf. The middle will have a divider making 2 boxes. On the far ends are cutouts that protrude into the box with total displacement 271 cu inches per side. I was thinking of shallowing(is that a word?) the depth just a bit to make the box smaller, cuz that is my variable. It has to be 62 long and 15 high. I want to tune to 34 hz. I feel that is the best frequency for thunder lows and a decent full range.
You're using two L7's? I thought you were using one.
Which direction is the sub & port firing?
62 L (as in vehicle width) x 15 H x 16-20 D
1" MDF 2" Baffle
60 x 13 x 17 (total depth 20, +1" baffle) = 13260 cubic inches /1728 (divide by 1728 for cubic feet) = 7.67361111 (cont.) cubic feet
OR
62 x 15 x 16 (+1 extra baffle/total 17" depth) 60 x 13 x 14 = 6.31944444 (cont.)
The port will take up little space so 16" (17") depth is more preferable if the tune is low enough. If the tune isn't low enough, the port will have to be longer, thus less than 62" width to keep it the same NET space.
I'm shooting for 6 cubes @ 30-35 HZ.
The port depth will be either around 17.5" length or 14.5", even less if it's up-fire.
I need to know the directions the port & sub are facing.
the subs fire forward with the ports firing forward in the middle, divided. And I love the screwed and chopped, so what depth do you recommend? and whats the final word on the port?
It would help me if the port wasn't in the middle. It doesn't sound any different, besides better air-flow & output. I'll design two boxes - one with less port area and a shorter port, and one with lots of port area and a longer port.
First box...
I don't know what the sub displacement is, what year are they? I can't find any info.
I'm calculating for .12 cubes displacement each (6.24 cubes)
Outside dimensions
1" MDF // 2" baffle
55.3 width 15 height 20 depth (19 + 1)
Port 45.5 square inches 7.58 square inches per cubic foot (a little low) 3.5 width 13 height 17.25 depth (calculated - physical length is 15.5")
so to get 3 cubes of air for each speaker, instead of narrowing it, I would cut the depth on it a lil cuz it has to be 62 inches length just because.. so I would have to cut the depth by a few inches yeilding a 15.68 depth. 62wx16dx15h= 148800 = 8.61 cubes dammit thats outer dimensions haha. Correction -- 60.5x14.5x13.5= 6.85 cubes minus baffle and displacement and braces and after factoring those cutouts on each side I have ~= 6.03 cubes for 2 speakers. So 3.015 cubes including port area per l7... I believe these are my final dimensions. Could you figure the port length and width on those dimensions for a 32 htz tune please? I know you have better things to be doing and I'm sorry to keep wasting your time, but I think I'm real close to figuring something out.
I heard it was better to separate the ports from each other. but change of plans... lets put the ports together for just one big port in the middle. gotta be in the middle. And the outside depth is 16.25 inches, not 20. Outer height 15, outer width 62. I figure in about .5 cubes of total displacement from drivers, cutouts, and braces. what dimensions should my port be? and is it a double L port kinda like a JL sign or does the port still only stick out one way, still like a single L port? I'm working on the box now, and would like to finish it, so your help is appreciated.
You MUST put a spacer between the opposing port directions or else air will hit itself. This is why it made sense to use 2 31" wide boxes or a 61" long box.
I thought you said could go up to 20" total (outside) depth?
Bracing... dimensional changes... this just changes everything.
Man huggi, is there any way I could call you? but if not, my outer dimensions aare 62x15x16.25. I have 2 l7 but want different ports, not running into 1 port. I went with a less depth to decrease my total area cuz yall said it was too big. It's cut now and those are the dimensions. I'm glueing and sanding, waiting to put the port in. I wish I could finish tonite, but it aint looking good for me. Like I said earlier,
" 6.03 NET cubes for 2 speakers. So 3.015 cubes including port area per l7... these are my final dimensions.
"15.6 square inches of port per cube" - Is that the ratio to tune to ~30 htz? cuz I could prolly figure that out. It would be 47.03 cubic inches total for ONE port for ONE speaker. Well that cant be right cuz I came with a 1.6 inch long port at 3 inches wide. UGGHH!
You can't have different ports, that's wack. You can however, have two ports lol.
You didn't need to decrease the depth when those two boxes would be perfect.
Now you're at...
2" port width // 38.75" length - and you reeeeally can't go any lower than a 2" port width! 2.04348 cubes BEFORE displacements @ 28.25 HZ 12.72 square inches of port area per cubic foot
So I need to make each port 2" wide, 13.5" tall and the inner L wall will be 38.75 " long? Will a 2 " wide port create wind noise? And that's a good thiing it's tuned so low right? for the screwed and chopped and panel shakin lows? I'm stayin up all nite if I hafta to get this mother done! But then no amp. theiven b@stards!
2 cubes is fine for that sub but it's weaker sauce than what you could have.
Port noise happends when you have too little port area. You have/had around 12" per cube, which is a little more than enough. I wouldn't go lower than 12.
3 cubes @ 29.5 HZ with 15.6" per cube is wayyyy better!
" 2" port width // 38.75" length - and you reeeeally can't go any lower than a 2" port width! 2.04348 cubes BEFORE displacements @ 28.25 HZ 12.72 square inches of port area per cubic foot Sorry chief. "
If the box is 3.015 before taking away area that belongs to the port, and the port is only 12.72 cu. in. for every cu. foot of air, then 12.72 x 3.015= 38.58. So 3.015 cu. ft. minus 38.58 cu. in. (.022 cu. in.) is 2.99 cubes per sub. That's how I understand it. Am I completely wrong?
Subtract 5 (4" of port and 1" seperating them) from 62 total width = 57 / 2 = (outer dimensions of sealed portions) 28.5" width x 12.25 (box depth) x 15 height = 26.5 x 10.25 x 13 / 1728 = 2.043 cubic feet.
Am I just trippin, or is every time you write the dimensions they are different, haha. I don't know where you got the 12.25 depth or the 10.25 depth. Or the 13 high cuz it's 13.5 high, 14.25 deep and 26.5 wide. I'm getting -- 26.5width x 14.25deep x 13.5high (interior dimensions) = 2.95 cubic feet before port subtracted.
16.25 total depth minus the extra baffle minus the port width from the back of the box, and the outer wall = 16.25-4 = 12.25 sealed box depth outside dimension.
I'm calculating for 1" MDF thickness, you're using .75". I don't like .75" MDF, so...
Thanks for your help, but I'm going to the sound shop in Monticello tomorrow. This is too much for my lil ole heart to handle. Im going to handle this 60 grit now...
Test them first. Ask them specific questions, like if they'll resin the box inside & out, or if they'll double the baffle. Make sure you don't get yourself a crappy custom box!
I'm doing 100 % of the work myself. I'm just going to get an exact measurement and I'll do it. Why would you want to double the baffle?? And how bout if I put Gorilla wood glue on all joints, put biga$$ pilot-drilled drywall screws for the joints and put actual gorilla glue on all seams inside and press a .75 inch x .75 mdf onto the gorilla glue to seal down the seams, then get REAL wood, prolly 2x4 s to cut little triangles to be the main braces, like an L bracket, also secured with drywall screws. Should I need some baffle material?
So I put in the port. 2.5 inches wide, 26 total inches of inner port wall.....Inner volume for one box is as follows: 30" x 13.5" x 14.5" minus my Protrusion == 3.25 cubes per. subtract port area (.507 cubes) and displacement (.1) and you get 2.643 net cubes! With a tuning of 30 htz. I figured it would end up tuned to between 30 and 34 from the additional area taken up in the box ( thought it would act like tuned higher?)
