1meanGTA

decided to get the ball rolling on this ported box, so i ordered the ports, bought the mdf, finished the plans and got cracking. started building today, thought i'd share a few pics. im planning on having 2 4 inch flared ports firing at the driver and passengers heads.

just test fitting here, actually wont block my rear glass at all with the hatch shut.



basically all i got done today after i finished the plans. i did 2 of the smaller side pieces, but only attached one.



this gives you an idea of the size of the ports i have to accommodate. 4 inch port my ***, its almost 7" at the widest point of the flare.



this is without the box in. going to see where it sits with it in, then drop the front to match. looks goofy all high like this, i know.

Gummie

Good work so far. I bet that you will finish your box before I finish mine because I've got so much other stuff to do before I can get it back in the car to trim, position the subs, and build the top

What kind of volume are you hoping to acheive?

1meanGTA

its going to be between 4 and 4.2 cubic ft. not exactly sure how to calculate the volume the ports will displace, or whether its just the displacement of the plastic itself, or the air inside the ports themselves also.

i could have gone up to almost 6 if i'd made it a little taller, and added the small section for the bottom of the well. i had so much, i decided to do it without that portion, simplify it.

im off work until thursday, knee is killin me so no overtime this week. think i can finish it up before i go back.

Gummie

I had all week completely off thanks to spring break and requesting off but the shier number of things I'm working on killed it for me. That and supplies (namely more resin), tools I didn't have (the welder), cure time, things that have gone wrong (the cage being too wide), etc. I decided to spend the weekend with friends so I didn’t get anything done but it was nice to be able to slack off for once. #1 priority right now is getting the manual conversion finished, which should happen tomorrow. After that I need to figure out whether or not the cage is going to work by trying to find someone locally who can rebend the main hoop so that it’s 8” narrower (or just scrap the cage idea), deaden the car (can’t do this till the cage gets welded in because I need to weld to the floor), finish the back seat amp rack, get the interior back in, trim the box to size, position the rings, and finally build the top of the box. It’s a daunting to-do list and will probably get spread out over the course of the next month unfortunately.

Volume ports displace = port area (the area inside the tubes). I’m not sure how to handle the flair on the end but I’m guessing you would probably just ignore it and treat it as a 4” port. From what I understand you’re going to be using 4 ports (two behind each seat) and one large common chamber (there’s no sense in using a diving wall at all). Given your 4” ports and a 4 cube box negating driver displacement and port volume you’re going to need each port to be 36” long to tune to 30 Hz. I'm guessing you're planning on tuning low for SQ and added kick in the low end?

1meanGTA

i was planning on using 2 4 inch ports. i was told by a few people they would only need to be around 14 or 15 inches for a 30 hz tune. im also thinking theres going to be port noise, and can't really figure a way around it. the 2 i have are about 18 inches each. 30 hz was the plan.

was planning on just building it, then figuring the volume in case i have to make any changes along the way, then doing the ports.

what doesnt make sense to me is that ports are measured in area, but everyone is telling me that if i use more ports, i need them all to be longer. would seem to me you would want shorter ports if you had more, to have less port area. are there other factors im not aware of? this is the first ported box i've designed btw.

any thoughts on a possible slot port? the decklid section is about 18x40x8 outside dimensions. i want to hear the least amount of port noise possible being as its going to be aimed at my head.

brewersprts

What kinda subs and amp are you gonna be running?

1meanGTA

i've already got everything, just going from sealed to ported. took everything out to make sure it would fit.

im running a kenwood x979 deck, a diamond d5 600.2 amp (300x2 rms) running a pair of alumapro alc components in some fiberglass kickpanels. using a crossfire vr2000d (2700 watts rms @ 1 ohm) to run a pair of soundsplinter rl-p 12's. have 1/0 gauge underhood wiring, and 1/0 runs for power and ground to the rear, an optima yellow top battery, and a 200 amp excessive amperage alternator.

Gummie

Yeah, my math was for 4 ports total instead of 2. The people you talked to were correct, the port length should be 16.91" (just call it 17 and be happy). With your 18" this will put you just above 28 Hz @ 4 cubes and 2 4" round ports.

all that matters is port area for port noise. Port noise is caused by high-speed wind. More displacement/excursion (and possibility a larger cone) means more air is going to be moving in/out of the port. The larger the port the slower the wind moves, the less chance there is for noise. The smaller the port the faster the wind moves, the greater the chance of noise. This is probably the most important thing in this whole post. Also, adding additional ports will reduce wind speed and the chance of port noise.

The goal of a port/vent is to create standing waves inside the port to achieve a boost in output. It makes sense that port area (cross-sectional area) would impact port length. Box volume and number of ports require more math. Here's a general list of things that change port length:

box volume
- big box = shorter port
- small box = longer port

port area
- large port area = shorter port
- small port area = longer port

number of ports
- the more ports you have the longer they all have to be. It just works this way. If you want I can try to dig up the math. Saw it a while ago in physics and it made sense once you saw it.

Generally speaking with a slot port you want to stick with a 1:5 ratio at the most. 1”x5”, 2”x10”, etc. Slot ports have one very large perk: they have plenty of port area (most of the time) so they very rarely generate port noise. The downside is a direct byproduct of this: since they have lots of area they have to be grossly long. The general result of this is building a folded port or a L port.




This is defiantly doable for you with your fairly large box but keep in mind that all that area is taken away from the box volume, which means an even longer port. Two 4” ports should be pretty quiet. If you’re worried about port noise add another one or two. You can extend the ones you already have with PVC and a sleeve on the outside to couple them together.

Good plan unless you decide to go slot port

1meanGTA

think im going to have to go with just the 2 ports. 18 inches is basically all the room i have to play with inside the box, couldnt have any longer of a port. i guess the only other option would be to slot port.

i'll probably finish the front section of the box with screws only, im good enough with the tablesaw i can get it just about perfect without glue or silicone. if i really dont like the sound of the round ports, i'll redo it with a slotted port. airspace is no problem, theres a lot more space back there than i expected, i think i could maybe even port a pair of 15s with some 6 inch ports and a slightly bigger box. i might just try that next

Gummie

Be ready to pull apart the box to glue/silicon everything together if you have any leaks. They sound pretty odd, let me tell you.

1meanGTA

i just meant to see how i liked the sound, was planning on finishing the box right for final assembly.

how about port placement? i imagine you want some space between them, but should i try and keep them close, so they aren't firing DIRECTLY at my head, to try and cut down on audible port noise?

Jim85IROC

iTrader: (2)

That's one big-assed box dude.

When I used those massive ports, I trimmed the flares to make them fit. The point of the flares is to eliminate port noise due to turbulence, but as long as there's a wall next to the port, you won't get the turbulence, so they can be trimmed to accomodate walls.

Here's the ported box I made:



Make sure your enclosure volume isn't too big. It will have a major impact on the response of the subs, plus it'll drastically change the port tuning frequency, which will have an even worse effect.

You want to make sure your volume and your port tuning is as accurate as possible.

1meanGTA

is there an advantage to having the ports side by side in the middle like that, as opposed to more spread out?

Jim85IROC

iTrader: (2)

Nope. I did it just for cosmetic reasons.

1meanGTA

i dont think i really can trim any of the flare off, theres a flat section towards the outside of the flare, to fit flush with the box. if i took more than like 1/8 inch off the outside, i'd lose that and only have curved surfaces. could fix it up with silicone, but it'd look like ***, so i'll probably just do the ports the way i was planning.

are those aeroports? the ones i have are precision ports from parts express, i've just been using the word aeroport generically like kleenex, or q-tips.

i'm interested in hearing your thoughts on a slot port jim. right now, i'm refiguring the airspace i have, will post back after i finish.

1meanGTA

ok it looks like im working with 4.35 cubic feet after sub displacement and ports.

i think i did the ports right, pi(radius squared x length) i came out with 226.08 per port for 18 inch long 4 inch ports, or 452.16 for both. that gave me .26 cubic feet, sounds right to me.

seems a bit on the big side, but i'm planning on adding quite a bit of interior mdf bracing so that should help a bit, maybe take another tenth off.

if i have to i could make it a little narrower to get the airspace i need, wouldnt really be any extra work, couple cuts on the table saw.

Jim85IROC

iTrader: (2)

I think mine were the "aeroport" brand, but they're all the same thing. I may have used the 3" version though, I don't really remember.

Slot ports work well, but I've found that they need to be pretty large to prevent port noise. I've got 1x7" slot ports in my girlfriend's car, each one for an 8" woofer and I still get chuffing. A 1x7" port is the same area as a 3" round. But, my slot port makes 2 180* bends and one 90* bend.

*F-BodyFanatic*

iTrader: (2)

I built a ported box for my car too... just running a single 10" though.

9177

I got 286 per port using a diameter of 4.5" for the outside of the port tube A slot port will take up ALOT of room and you can do a 10:1 ratio on port length vs height as long as you have a router to round over the edges but no more than a 9:1 is usually recomended. Going with the round port you should be less likely to get port noise though.

1meanGTA

yeah i suppose 4.5 would come out a little closer, accounting not just for the plastic of the port but also the extra volume at the flares on each end. so i should be right at what i need once i add the bracing, about 4.1-4.15 net.

i got quite a bit done today, but it was getting dark by the time i went to get some pictures and my camera doesnt take such good pics unless its bright out, so i'll have to add todays along with tomorrows. dont think i'll have a problem finishing it up before thursday.

as far as the bracing, can i use solid mdf pieces screwed top and bottom? i was thinking of putting a 14 inch long solid piece in the larger front section, which is about 18 inches long. would put it in between the ports, right about the center, and the same thing in the middle of the rear section where the 12's will be. will this affect the way air moves inside the box in a negative way, and if so i can get around it by cutting away some of the inside right? something like this brace? am i likely to need corner braces or anything? i've never built such a big box so i dont know how much flexing to expect.

ScrapMaker

are you gonna make us some sub **** after this?

make sure you get the t-tops flexing...

1meanGTA

i guarantee you some hardcore ****, although it may have to be on my soundless digi camera. i dont have t-tops, but even sealed, they got the windshield jumping a bit.

i did a lot of procrastinating today, started on a second 4'x8' mdf sheet, really only cut 3 or 4 pieces, drilled the holes for the angled piece (easier said than done) and countersunk most of the holes. had to run to sears, got a new tablesaw blade, old one was over 20 years old and kept binding up, a router, circle jig, and a few bits.

heres the pics of what i got done yesterday, took these before i started today, it was getting dark again when i finished up todays work, but i'll get some more tomorrow.

this is most of what i'm using, other than the router.



heres the tablesaw, thing's older than i am, seriously. i'm 23, i believe its about 25.



closeup of my first angled cut, didnt bind up too bad actually, this is with the old blade. theres no gap, just looks like it because the one piece is recessed about 1/16th inch.



these 2 are the box as it looked this morning.

ScrapMaker

your box isn't going to engulf the entire well area?

Jim85IROC

iTrader: (2)

I guess that answers my question of why the top part is so massive.

ScrapMaker

it would be sweet to see a box use EVERY available square foot in the car... hell, build it up against the hatch, and put a plexiglass window to see out!! awesome...

then you could put a remote actuator to open the hatch, and blast people behind you in traffic...

oh the tickets and/or fun I would have with that...

Gummie

fireturd350 did that. He pulled all the interior trim and managed to grab about 7 cubes just from the well if I remember correctly. His links are in the fiberglass FAQ: https://www.thirdgen.org/forums/car-audio/259377-fiberglass-box-material.html

Airspace is defantly avilable in our cars, you just have to work for it.

1meanGTA

well ported boxes are touchy about the airspace. i originally designed it with the section for the bottom of the well and when i calculated it, i had entirely too much space, so i took it out, and simplified the box quite a bit in the process. my 12's should put more than enough weight there to keep it in place.

as for the size of the front section, thats the smallest i could make it and have room for the ports. right now, its built as a sealed box, im about to go get started with the router and do the circles, hopefully i'll have everything done and drying tonight, and put the subs in tomorrow or the day after. i'll put up a couple more pics after i'm done tonight, just takin a little break now. i still have to countersink about half the holes, glue about half of it, and do all the silicone.

Gummie

Good job on the progress. I hope to have my car finished tomorrow in regards to the new trans so I might get something done somewhat soon on the stereo. Then again, I don't have money for carpet right now so I can only do so much

©Ø®€¥

Can those subs handle that much power? And how do they sound I was thinking of buying those.

1meanGTA

i wouldnt feel comfortable giving them the full brunt of that amp sealed, especially not ported. i gave them about 1100 each daily for a few months, and they took it, sealed. a couple of times they bottomed out. very tough suspension on these woofers.

i'm planning on giving them about 800-900 each in this box.

as for the sound quality, its easily the best of any subwoofer i've ever heard, and i've heard more than a few high end subs.

Gummie

I'm curious as well so I'm going to play some devil's advocate.

I'm not sure what to think of TC subs. I mean, I own two of them but I got them for a good price and I haven't heard them yet so I really don't know what to expect. Due to a lot of reading I have the feeling that if I was going to buy another sub it would either be a w7 or a brahma. I’m also willing to be that my current TC built subs will sound very good and that they will fulfill my every need.

Here's an interesting thread on motor technologies: http://forum.carstereos.org/showthread.php?t=56398

Obviously it's bias toward Adrie and their motor but most of the arguments make sense. Jim's interpretation of the RL-p specs lead him to believe that there would be a relatively low inductance spike when we were talking about subs a while ago and it turned out he was right. This would seriously hamper the sub's ability to play higher frequencies, which may or may not be a problem for a buyer depending on how low the rest of their system can play. This is my biggest single biggest qualm with TC drivers because my components aren’t worth much below 80 Hz.

... but then again I own two TC drivers.

me = for making this post

cooltc2004

iTrader: (4)

DAMNIT, stop it with the TC this and TC that. TC is my name, and Im getting confused.


Subbox looks good.

1meanGTA

i guess i'd have to swap subs out in the same box to make an honest comparison, but going by other sealed dual 12 setups i've heard in f-bodies, the rl-ps more than hold their own for higher bass. (60-80hz)

i've never heard the a.22's either, but im pretty sure they'll put a smile on your face. heard nothing but good things about them. i'm not sure, but i believe they use the same tc9 motor, i know the magnet looks about the same as on my 12's. the cone is obviously a bit different, i couldnt get a real good look at the motor itself from the pics you posted. cool, tc sounds is the name of the buildhouse for soundsplinter, eclipse, old elemental designs woofers, and a few other companies i'm entirely too stoned to remember right now. you can also order subs directly from them, but they dont really advertise.

my slacker *** didnt get around to posting the pics last night, and i'm getting ready for work now, but i'll put em up when i get home.

edit - if i buy a new pair of subs though, it's gonna be some audioque HD 12's.

r0nin89

Your definatly making me think about taking my back seats out...

ScrapMaker

as long as you don't take out your back seats... everything will be okay..

1meanGTA

just putting up the pics from the other day, been working so i havent gotten anymore done on it, other than the small 2 inch piece to finish it up as a sealed box.

still have to glue most of it, silicone it, finish countersinking, and cut the holes for the ports and woofers.

i built this box the way i did so i could keep my back seat, what do you mean ronin?

no beats, but i got new meats kumho 285/40/17's
pardon my dirty *** car. those pipes are actually chrome under all that
note the burned rubber chunks on the fender behind the tires





no more binding with the new blade, should have gotten it before i started

1meanGTA

unrelated, but what the hell. bout a year ago, before i had the ss wheels.

ScrapMaker

haha I always wondered why people did that... I'm guessing you needed new tires already??

1meanGTA

yeah those tires were done already. i have a line lock, so it wasnt tearing up my brake pads.

ScrapMaker

How hard is it to put in a line lock? it just locks the pressure to the front calipers, right?

1meanGTA

hmm. problems. i dont have a circle jig (dont know what the hell the guy at sears sold me, but i can't figure out any way to cut a circle hole with it attached to my router) so i thought i'd get a little creative, put a nail in the center of my circle, tied a string to it and my router and went to town. turns out this wasn't such a great idea (imagine that) and i ended up with a pretty screwed up hole.

as it was anyway, the woofers would just barely fit on the part where they'll mount, the circle would have to come within about 1/8th inch of the edge, and i didnt really dig the look once i set my subs on it.

so plan of action for tomorrow and the day after, is to remove the 2 inch piece that connects the front to rear sections. you know, where the angled part the subs mount on comes straight up to screw into the front section of the box. i'm just going to have the angle continue into the front section, would have done this in the first place, but i didnt picture the angle correctly in my head and thought it would have to be screwed into a very thin piece of wood.

as of right now, the rest of the box is done except for silicone and glue, and some of it has that already. i cut the holes for the ports with my jigsaw, they actually came out just about perfect, but i was planning on sealing it from the rear with silicone anyway so wasnt too worried.

Gummie

Do it with your router! The circles will come out perfect. Scroll to the bottom of my thread to see a quick easy circle jig. Simply screw your router onto a piece of thin material (wood/metal) and then run a screw through the jig and into the piece of wood you want to cut. The last screw will act as a pivot will give you a perfect circle. I can’t cut circles for my life but my MDF rings sure look pretty

1meanGTA

thanks for the tip gummie, worked awesome, after about an hour of trial and error, and 5 practice holes to get the size just right.

everything is cut, all holes drilled and countersunk. i've got about half of it glued and drying now, going to glue the other half tomorrow and silicone it the next day, should have it in the car in 3 or 4 days.

i knew it was gonna be difficult, but DAMN. i think i've got 7 or 8 days work into it. granted, i work off and on, i'll actually get out there and get stuff down for a couple hours, come downstairs, toke some reefer, drink some beers, play some games, so i probably only got about 4 hours of actual work in each day, but i still had no idea so much would be involved.

probably would have taken a couple days less if i hadn't had to delete the 2 inch section and redo both side pieces, and the piece the subs mount on. went through a whole 2 4x8 sheets, and had to buy a 3rd just to get an 18x40 piece because i screwed it up the first time, took about 1/16th too much off, and it was in a place that it was unacceptable.

all in all, it was a fun project though, and hopefully it'll sound great.

Gummie

It was Jim's idea initially. Of course, he had a nicer piece of wood with a slide down the middle and routed edges. I figured that this would be the only time I would use it so I went the easy way

1meanGTA

i want pics of that thing, hook it up jim...

Jim85IROC

iTrader: (2)

I took a 1/4" piece of scrap wood, cut and countersunk the mounting holes that hold it to the router, then set it up on the work bench with a straight edge to guide the router. I used the router to cut a 1/4" slot along the whole thing, then I did a 1/2" wide pass at 1/2 depth to create the rabbet. I found an angled bracket, flattened it out, and tapped the hole so that a screw could thread in.

When you decide where your circle should be, you just drill the right sized hole in the center, and the screw goes into that hole, allowing the whole assembly to rotate around that center point. The adjustability allows you to move your pivot point so that you can change the diameter of your circle.

ScrapMaker

I like that idea... now, if I only had a router to use it with..

1meanGTA

pretty freakin slick. what type of router is that, looks nice?

i've got an old school porter and cable plunging router, always like porter and cable power tools.

Gummie

It's a royal and can be had at home depot a little shy of $100. It's not a bad piece of equipment and managed to cut through 3/4" of MDF in one pass without any fuss. It was certainty nice to use the plunge feature to get started on the edge of the circle compared to having to work my way out with the first router I tried. I only know because I ended up buying the same one after I broke my friend’s dad’s 20 year old craftsman router

Jim85IROC

iTrader: (2)

Ryobi, not Royal.

It's no Porter Cable, but at 1/3 the price, I'm happy. When I'm cutting out circles in 3/4" MDF, it takes 3 passes for this router to happily cut through it, but even a good Porter Cable isn't going to like cutting through much more than 3/8" thick MDF at a time.