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I'm thinking about building a ported box to try out. I have a JL Audio 8w3 and I want to try get a little more bass.


1) JL has box designs for a "Purist," "dB Monster," and "Normal." I tried to look for what their exact meanign swere, but i'm still not positive. Which one should i be looking at?

2) If i do build a ported box, they call for a 2.5" port, but everywhere i've looked, i cannot find one. can i use a 3" port at a shorter length to achieve the same results?

Thanks
-Ed

 
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Any Ideas?

 
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even JL's "purist" boxes are poorly designed, any hardcore JL fanatic can and will tell you that (think Q of .8 for sealed.... boomy!)

rule of thimb is to build it a bit bigger than reccommendations, but youll need a port calculator.

as far as a bigger port, it actually needs to be LONGER to keep the same tuning frequecy!

i reccommend buildign a slot port. modeling up in winISD, a flat response curve is attained by porting that sub in .8 cubes, tuned to 38 Hz. slot ports are easier to construct by far, and require no additional investment, only your MDF scraps.

your port could be 2 inches by 3 inches, but your port would need to be 12.25 inches long. thats pretty big for that box!

your port COULD be 2 inches by 2 inches, and would only need to be 7.8ish inches long. much better! but you have to start worrying about port noise.....

build it! i say just build it and see for your self! will it work? i dunno! noone else here can say for sure either! we can tell you possible consequences of certain box designs (like factory box = boomy) but in teh end, why not just build a ton of boxes and stick with what works the best?

anything else you need? something i didnt clear up?....

 
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Alright, i see, i don't know why I didn't think of the slot ports [IMG]i/expressions/face-icon-small-tongue.gif[/IMG] So, longer port + bigger diameter = smaller port + smaller diameter. I have a question, how do i make slot ports? Is it basically a port that uses wood instead of a pipe? ALso, if i make the length of the port the length of my box, it would be very long and skinny, which i assume is bad. Which design is what i should be looking for?? also, should i round the edges of the wood along the inside of the port?




Attachments:
[IMG]/forums/themes/orbitz/paperclip.gif[/IMG] box.GIF (17 Kb)

 
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Rabbit...you gotta Know this really quick..

a flat responce on WinISD does not take into consideration cabin gain!!!!

If you have a LOW tuned enclosure you'll have too much low end extension and your system will not sound good as it will be heavily low end biased...which is why hard core SQ competitors use sealed enclosures because the low end roll off usually closely matches cabin gain and needs little equalization.....

RABBIT.. FLAT ON WinISD is NOT GOOD SQ WISE!!!!!..unless it's in an open room..not in a car..!!!!!!!!

Cheers
Mohawk

 
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ported box = 12 db/oct slope

cabin gain factor = 12 db/oct slope.


you dont see ported for SQ? the head of team CAF's SQ division sees it all teh time (arrogant bastage) its quite common!

as long as the rolloff of the ported enclosure happens at teh point of cabin gain, then you actually get a PERFECT flat response, all teh way down to zero Hz!

doesnt work this way in the real world, for many reasons....

what i CAN tell you, is that a flat response in winISD results in mych better bass and much better response than one with peaks in it. which is why i always reccommend large ported boxes.

my box was 4.4 cubes ported to 23ish Hz. soon it will be 12 cubes tuned to i havent decided yet, ill figure it out tho.

but dont take my word for it! go out and play sweeps in yoru car! i guarantee that for sealed, whether well built or not will MOST LIKELY start loud and get quiet, from 80 Hz down. a poorly built ported box will get loud, then quiet, then loud again, then roll off. and a well built ported box will be the same volume for as long as possible, then will finally roll off.

and surely you know that most "hardcore" SQ competitors have heavilly EQ'ed systems, no matter what type of enclosure they are running.

 
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Ported in car SQ enclosures are nearly impossible to perfect.. because of roll-off points. enclosure size, port size, port restriction, cone controll. limited air suspension. getting a flat frequency to the point of roll-off.....Generally sealed enclosures with an f3 of about 45-47hz usually result in the flattest possible unequalized response. Ported. Matching my cars gain..only a 15" Pyramid Hyperpro in 11.4 cubes tuned to 34hz would work to being nearly flat.. pretty dang rediculous..[IMG]i/expressions/face-icon-small-smile.gif[/IMG]...

also large enclosures with large ports offer VERY little suspension control for the sub which often results in alot of bass overhang and sloppyness. Smaller enclosures wit tiny port area's can work amazingly..but the second you turn it up all you get it port noise.. the trade offs are too many to count. If you want pure SQ..go sealed and get a good parametric EQ.....if you want preety dang good sound quality and great low end extension and a bit more efficiency go for a ported enclosure with about a very rounded peak at about 35ish hz..(depending on the sub.

If you wanna go Bandpass..well...I don't want to talk to you

Cheers
Mohawk

 
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ok, wow, that was a lot of big words i didn't know [IMG]i/expressions/face-icon-small-wink.gif[/IMG]

so, say i want mohawk says "if you want preety dang good sound quality and great low end extension and a bit more efficiency go for a ported enclosure with about a very rounded peak at about 35ish hz..(depending on the sub. "

I have a JL 8w3 D4, teach me [IMG]i/expressions/face-icon-small-smile.gif[/IMG]

 
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Ed..download WinISD...find that sub in their list..and play with alot of numbers..[IMG]i/expressions/face-icon-small-smile.gif[/IMG] and have fun.. he he

 
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your close to christopher evert, mowhawk, you should check out his project, its insane! has 12 8's lying around, decided to try to build a BP box for SQ. my lord, the details that went into design and construction.

it CAN be done! and it IS done, all the time....

your making it sound like anyone who builds a ported box for SQ is an idiot!

i remmeber when i was only a semi-noob, still trying to leard everything i could..... I was feeling cocky and was talking to one of the SQ competitors online, i said at one point in time "ported for SQ...lol" he went off on my for 15 minutes about that........

the fect is, its done all teh time...

sealed with F3 of 45? youll NEVER get your points for making it down to 20 Hz! never! jeez thats so high!

if you had a box like that, anytime you tried to play 30 or below, youd just get farting noises out your sub and NO response! you call THAT sq???

 
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Rabbit..with a single Audiomobile EVO-R and 1100Wrms I'm hitting 139.2 at 50hz and 134.8 at 24hz...sealed..f3 45hz. To play that low that loud a sub needs yes NEEDS alot of excursion to play that low in a sealed application. a sub with 11mm Xmax will never do it..won't move enough air and will sound farty..

And ported for SQ is done all the time..yes..but at world Finals 9 out of 10 setups are runnign sealed or I/B ....it's rare indeed to see ported subs make it that high up in points...

for Bandpass enclosures for SQ it can be done..but you'll need to build the enclosure very well and have it tuned very very well.. then put in the car and tune it again and again and again and again untill you get it right...Mathematically it's a nightmare and then some.. Math..and in car tuning it's many many mnay many many many hours of work and tunign and re-building and tuning...

Simplified much Sealed is easier for SQ..ported is harder..much harder and has better iffiency..as does Passive Radiator setups... I/B seems to work for best most musically accurate SQ.. but SPL suffers massively..
Bandpass is the ultimate in efficiency but the hardest to tune..and get right...there's also dual chamber, ported ABC enclosures now as well as space shared ported/sealed setups that are confusing as all bagonias..which is why you'll most likely never see it done...

 
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<< If you have a LOW tuned enclosure you'll have too much low end extension and your system will not sound good as it will be heavily low end biased...which is why hard core SQ competitors use sealed enclosures because the low end roll off usually closely matches cabin gain and needs little equalization.....

RABBIT.. FLAT ON WinISD is NOT GOOD SQ WISE!!!!!..unless it's in an open room..not in a car..!!!!!!!!
>>



so you admit now that you CAN port and have SQ...... unless you dont wanna take the time to build a good box. ok. I'll accept that as a reasonable explanation.

 
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You can have great SQ in a car with a ported enclosure.. but that generally requires building a rough enclosure and port..and play with enclosure size and port tuning as well asport diameter alot.. it's possible..but for us who are **** about SQ..it's a few weeks work or building..re-building..tuning analyzing..finishing..

Sealed is Easy..find your Cars Cabin Gain.. Model up about 5 or 6 really good quality subs..and see which best matches your cars cabin gain while maintaining as close to a Q of .707 [IMG]i/expressions/face-icon-small-smile.gif[/IMG] The easy way usually has better results that going ported too...but won't have the same SPL output.. that;s why you run 2 Subs for sealed setups. to equal the SPL of a single ported sub low tuned.....the price of the second sub is cheaper than the countless hours of labor for getting a ported setup right.. even a DIY'er time means $$$ or if you're like me and work 55-88 hours a week..time is a luxury that's you;d rather spend with your finacee doing fun thigns instead of getting coated in MDF dust and PVC shavings from trimming your test port...

 
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=/

;D

 
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A couple last questions (for now [IMG]i/expressions/face-icon-small-wink.gif[/IMG]):

My box size prevents me from having my port straight while staying on the same plane as the sub. I'm pretty sure it's ok, but I just wanted to make sure that it is allowable to have a 90 degree bend of the port within the box. Like this:



And, I plan to use PVC pipe and I was wondering whether i should buy a flare type thing to reduce the port noises or if i should just round the edges of the port.

Thanks a lot for you help!!!


Attachments:
[IMG]/forums/themes/orbitz/paperclip.gif[/IMG] port.GIF (3 Kb)

 
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90 degree angles are fine.. just make sure for port length your mesuring the distance from the center of the bend.

Just use the top and bottom measurement and divide by 2 [IMG]i/expressions/face-icon-small-smile.gif[/IMG].

What diameter port are you using.. a 4" or 3". Also what's the other specs on the box. Having too small a port is not a good thing when you crank it.

 
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I'm thinking about a 3" port and it says that it needs to be about 17" long. my outer dimensions will be 12" x 17" x 10" and that should come out to be around .8 ft^3 using .75" thick MDF.
-Ed

 
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Okay.. find anywhere that sells Lightning audio stuff. and buy a 3" Aeroport. They are very rounded and will pretty much negate any channces of port noise.. they are also available at sounddomain.com I would VERY highly reccomend them. specially for such a small port.

Cheers
Mohawk

 
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I use a program called WinISD for designing boxes, its great for designing ports. you tell it the box volume, all the speaker thiele parameters, and you tell it what porting frequency you want and the diameter and number of ports and it tells you the length. I have my box ported to 32 hz, and it bangs pretty good...
the program does graphs and all kinds of fun stuff, its really worth checking out, it even has a database of a bunch of subs to do comparisons...

get the program here:


http://www.linearteam.org/download/w...winisdbeta.exe

 
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Port

So i can buy that and instead of using the included tube, i can buy thin walled pvc pipe with a 90 degree bend in it so it fits in my box?

 
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Yupper..that be the one!

 
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Awesome, thanks!!! So i don't have to use their pipe, right?? and 3" pvc tube will work??

 
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3" will work, just like 2" or 4", just make sure that your sub has enuff air, since port and speaker displacement take away from box volume....

 
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use the aeroport and just add 3" PVC pipe to make it as long as desired.

 
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Awesome, thanks a lot!!!