# Optimal size enclosure and tune for 2) JBL W12GTI subs?



## lust4sound

W12GTi MkII - JBL US

Above is a link for the T/S parameters for the pair of JBL subs I have...

I need to know what the ideal/optimal size and tune would be for a ported box, box is split in half, I will have anywhere from 3.5 CF to 4CF (PER SUB) once I modify the box. (yes, it's huge 48" x 18" x 24")

Goal is SQL in 3 or 4 way active.. Want to be able to run 2 modes.. 1) pure SQ, where everything is balanced and tuned w T/A.. 2) uncork subs and let them wake the dead 

I need 30 to 60Hz, anything under 30 is a major bonus!!




I just picked up a very nicely made PA enclosure for 2-12s...

It's made of Birch Ply (close to 1" thick) has dual speakon connects, dual chambers..

I have almost 4 CF PER SUB!! Is that too much? Box is huge, but it fits nicely in the back of my minivan..

The plan is 3 way active for now, SQL, need a nice response curve from 30 to 60/80 hz.. Anything below 30 is a major bonus (FS is 18Hz on these subs)

So, is 3.5 to 4 CF per sub too large? What is optimal size for vented (per sub) and would a tune of 26hz be ideal for SQL?

I want to be able to run in pure SQ mode, where T/A tuning etc is all done to perfection, sound is balanced/reference quality..

I also want to be able to unleash all out fury when I uncork the sub section and wake the dead..

So, what to do? What would be ideal enclosure volume and tuning?

FWIW, I am temporarily running a Pioneer DEH-80PRS which seems to default to stereo on subs, also, the box is setup stereo (two inputs, two separate enclosures)

I also have a pair of JL 500/1 amps, 1 per sub, 500 watts RMS per side (plan on stepping up to 2k for subs, 1000 watts per side) will run in stereo for the simple fact that the Pioneer keeps defaulting to stereo when autotune is run)

Any help would be greatly appreciated!!


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## Lanson

I need to get on WinISD to do a plot but I can tell you that when it comes to ported boxes, it is very hard to build too big. If anything, you can build big and then tune very low in a "bass shelf" type config, and usually the results are amazing. 

So I think you'll be very happy, we just need to figure out the proper port tune. 

Edit: I'm wondering if you're better off making this box as one (like poke a hole between the two separate sections) just to even out any irregularities between the two, or not. May not make a big difference, but it may help. Again, best to get on WinISD or another box program, plot out response expected, and use it as a baseline. Tuning down to 26hz could be very nice though. A bunch of passive radiators may also be a nice option. It would be a bunch of them though.


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## lust4sound

fourthmeal said:


> I need to get on WinISD to do a plot but I can tell you that when it comes to ported boxes, it is very hard to build too big. If anything, you can build big and then tune very low in a "bass shelf" type config, and usually the results are amazing.
> 
> So I think you'll be very happy, we just need to figure out the proper port tune.
> 
> Edit: I'm wondering if you're better off making this box as one (like poke a hole between the two separate sections) just to even out any irregularities between the two, or not. May not make a big difference, but it may help. Again, best to get on WinISD or another box program, plot out response expected, and use it as a baseline. Tuning down to 26hz could be very nice though. A bunch of passive radiators may also be a nice option. It would be a bunch of them though.


Thanks so much for the response! The current internal measurements per side are 22.75" x 16.50 x 17 deep.. I will be removing the face and existing ports, I could actually mount the face flush on top, effectively bumping from 17 to 20" (ish) depth.. subs are currently recessed approx 2" back from the front of the box..

I'm wondering if the shape of the box will hurt or negate the type of response I want.. It's very wide, but not very tall or deep.. All of the sub enclosures I see for SPL are very deep, usually much deeper than they are wide/tall..

My box is the polar opposite.. Thoughts?

While I'm in there, I could also remove the baffle/brace which divides the two chambers..

External dimensions of the box are 48.50 x 18.25 x 23 ish (going by memory) YES, BOX IS GINORMOUS!!!

The box fits snugly in the rear of the minivan, almost like it was purpose built for my application..

Again, I will be removing the face, all of the existing ports (4 per side) and all of the excess related to the ports..

I will have a 3/4 shell with which to finish any way I choose.. I definitely want OPTIMAL response!!

Those subs dig deep, I'm partial to heavy impacting bass.. I am aware of the fact that majority of music is 30hz and above, I still love the option of being able to play those EDM tracks which have the ludicrous low end thrown in to flex subs.. I don't have a lot of power on hand for true pavement splitting 22hz response, but this setup is temporary..

Once I have HO alternator and additional gelcaps in place, I'll probably end up swapping the pair of JL 500/1s for a single MMats D3500.1, which does a proven 2700 watts RMS @ 1 ohm.. which should give me right around 2200ish to both subs combined.. (If I go single slot ported in the center)

(Edit) I will be running 3 way active for now, will step up to 4 way soon.. I'll need these subs to perform from at least 26hz to 60hz.. I originally mentioned that anything below 30hz is a bonus.. Well, these subs are designed to dig, so let's let them dig.. Anything below 26 is a bonus!! I will allow midbass (4x8" with 400 rms per side) to deal with 60 and above..

(Edit 2) How about 22hz to 40hz, let my JBL 15s give me the rest of the impact to 80hz? 

I had a pair of JBL 2226HPLs installed in a JBL 4648 subwoofer cabinet.. The low end was incredible.. I guess the minivans cabin gain bumped the sub 40hz response (box is tuned to 40, graph shows a pretty steep roll off below 40 hz.. Well, I had the subs firing against the back door, about 1.5' away from the door.. Perhaps this positioning bumped sub 40hz dramatically? Vehicle acoustics?

Regardless, I do regret pulling those 15s out.. With the Hertz ML165s in my doors, ML28 big chamber in pillars, music sounded absolutely incredible (considering the fact that I am using the Pioneer DEH-80PRS..

They gave a live club/concert venue type feel to drums and bass, but they did not impress with the infralows or pavement splitting lows.. which I do enjoy.. Still, when set to SQ mode, streaming from Tidal via phone, the sound was such that majority would be envious..

I am going to give these 12s a good run, let's see what they do.. If I don't get that impact club venue feel in the upper sub frequencies, I'd like to combine my 15s with these to make up my sub section (4 way active)

I have someone local who can help with tuning (specialized mic, laptop, O-scope, USB interface, tuning program etc)

(Edit 3) Vadrum, if anyone is familiar with Vadrum, the Italian drummer who plays with a full tilt orchestra. MIND BLOWN.. Orchestra sounded like it was in the van with me.. Drums sounded live, the clarity and detail absolutely insane (nothing nicer than a drum set tuned to perfection, recorded to perfection, played back through a nice system) imaging also quite nice (as good as it will get with an 80PRS)

Anyway, give Vadrum a listen on Tidal.. We're all here for the same reasons, we enjoy great music through a great sound system... Trust me on this, your ears will thank you for it..


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## lust4sound

OMG too much caffeine!! (as per the norm with me) SMH..


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## Lanson

Lots of questions, my answers in *bold* in your quote



lust4sound said:


> Thanks so much for the response! The current internal measurements per side are 22.75" x 16.50 x 17 deep.. I will be removing the face and existing ports, I could actually mount the face flush on top, effectively bumping from 17 to 20" (ish) depth.. subs are currently recessed approx 2" back from the front of the box..
> 
> I'm wondering if the shape of the box will hurt or negate the type of response I want.. It's very wide, but not very tall or deep.. All of the sub enclosures I see for SPL are very deep, usually much deeper than they are wide/tall..
> 
> My box is the polar opposite.. Thoughts?
> *Provided you have the airspace you want, the shape is largely irrelevant. Standing waves can occur in some shapes, but irregularities and strange shapes actually prevent this. Bonus!*
> 
> 
> While I'm in there, I could also remove the baffle/brace which divides the two chambers..
> *Not a bad idea but not a big deal either. But I like the idea of removing the brace, cutting it up to air can pass through unrestricted, and then re-installing. You probably still want the brace part of that, but the airspace can share. Mostly I'm thinking the share concept would help because you could then run a massive single port, or three ports, or whatever you want and they'll work together. It wouldn't need to be equal numbers then.*
> 
> External dimensions of the box are 48.50 x 18.25 x 23 ish (going by memory) YES, BOX IS GINORMOUS!!!
> *Can't stress this enough, BRACE heavily, and often. If you can't install something big, just use lots of small things like clothes hanger rod or whatever works.*
> 
> The box fits snugly in the rear of the minivan, almost like it was purpose built for my application..
> *Happy accidents and coincidences are great*
> 
> Again, I will be removing the face, all of the existing ports (4 per side) and all of the excess related to the ports..
> 
> I will have a 3/4 shell with which to finish any way I choose.. I definitely want OPTIMAL response!!
> 
> Those subs dig deep, I'm partial to heavy impacting bass.. I am aware of the fact that majority of music is 30hz and above, I still love the option of being able to play those EDM tracks which have the ludicrous low end thrown in to flex subs.. I don't have a lot of power on hand for true pavement splitting 22hz response, but this setup is temporary..
> *That's right up my alley, and I love it. Matt Darey's shows, the amazing Moonbeam - Ticket to the Moon episodes, etc... all of them are ultra-high sound quality and dig super-deep. You'll love it or probably already do. Keep in mind, if you port with a low bass-shelf tune, you won't need much power at all. The subs will hardly be moving but they'll put out big time down there. Personally, I'm jealous. I never get to build to that level. It is always stealth and space savings for the builds I get asked to make. I have to compromise constantly.*
> 
> Once I have HO alternator and additional gelcaps in place, I'll probably end up swapping the pair of JL 500/1s for a single MMats D3500.1, which does a proven 2700 watts RMS @ 1 ohm.. which should give me right around 2200ish to both subs combined.. (If I go single slot ported in the center)
> *The ports can be any number provided they are done right. Also, consider passive radiators, they can make even more use of this space, no port required.*
> 
> (Edit) I will be running 3 way active for now, will step up to 4 way soon.. I'll need these subs to perform from at least 26hz to 60hz.. I originally mentioned that anything below 30hz is a bonus.. Well, these subs are designed to dig, so let's let them dig.. Anything below 26 is a bonus!! I will allow midbass (4x8" with 400 rms per side) to deal with 60 and above..
> 
> (Edit 2) How about 22hz to 40hz, let my JBL 15s give me the rest of the impact to 80hz.. I had a pair of JBL 2226HPLs installed in a JBL 4648 subwoofer cabinet.. The low end was incredible.. I guess the minivans cabin gain bumped the sub 40hz response (box is tuned to 40, graph shows a pretty steep roll off below 40 hz.. Well, I had the subs firing against the back door, about 1.5' away from the door.. Perhaps this positioning bumped sub 40hz dramatically? Vehicle acoustics?
> 
> Regardless, I do regret pulling those 15s out.. With the Hertz ML165s in my doors, ML28 big chamber in pillars, music sounded absolutely incredible (considering the fact that I am using the Pioneer DEH-80PRS..
> 
> They gave a live club/concert venue type feel to drums and bass, but they did not impress with the infralows or pavement splitting lows.. which I do enjoy.. Still, when set to SQ mode, streaming from Tidal via phone, the sound was such that majority would be envious..
> 
> I am going to give these 12s a good run, let's see what they do.. If I don't get that impact club venue feel in the upper sub frequencies, I'd like to combine my 15s with these to make up my sub section (4 way active)
> 
> I have someone local who can help with tuning (specialized mic, laptop, O-scope, USB interface, tuning program etc)


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## Lanson

and let me add, the "impact" feel in the upper sub range is usually associated with timing, not just with the actual speaker output. Therefore, T/A and tweaking it just right so the bass and midbass is not "late", is crucial.


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## lust4sound

fourthmeal said:


> and let me add, the "impact" feel in the upper sub range is usually associated with timing, not just with the actual speaker output. Therefore, T/A and tweaking it just right so the bass and midbass is not "late", is crucial.


Thanks so much for taking the time to answer all my questions, you're a gentleman and scholar!

I will definitely use the central divider trimmed down for bracing, although there is plenty of bracing for corners and sides, only the one divider for central bracing for the length of the box..

Also, I picked up a nice piece of 3/4" 11 ply sheathing, I've had it cut down to size, will glue/clamp two pieces to make up face where subs will mount, effectively giving me a nice solid 1.50" surface for both subs...

I've never worked with slot ports, so I'm not sure how to calculate for correct tune..

I will say this.. I had a large box made of MDF which had taken water damage, so it wasn't 100%.. It was approx 6CF, 34 wide, x 14 tall, by seriously deep (I forget the depth of the box.. 1 large slot port in the center)

Not sure what it was tuned to, but I temporarily installed the pair of W12s in there, ran them off a single Punch 800A2 (3 ohms per channel which equals roughly 250 watts ish??) 

In keeping with the comment you made about not much power being required, the OUTPUT WAS LUDICROUS!! Rear view mirror fell off within minutes, LOL.. I was totally unprepared for what these subs would do off that amp in that raggedy old box..


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## lust4sound

and of the minimal wattage available, much of the energy of which was being lost to a sagging box which was coming apart at the seams, the output was still completely absurd..

In hindsight, with that thought in mind, I can't imagine what these subs will do with 500 per side in a properly prepped box..

Can't wait!

(EDIT) I almost regret pulling the pair of JBL Pro Audio 15s (2226HPL) I had playing through a JBL 4648 "fixed application" commercial sub enclosure.. Although the specs of this combo show a sharp rolloff below 40hz, I had them firing toward the rear door.. (cabin gain?)

with the Hertz ML165 IB in OEM door location, ML28 (big chamber) in pillars, I let the 80PRS autotune and MY WORD!! The impact and SQ was as good as it gets given the limitations of the HU and subs.. 

I didn't get that mirror breaking low end, but I did get well balanced live venue type response with very nice imaging, Vadrum sounded like he was setup in the van with his full on orchestral ensemble LOL.. 

I will def look for the music you mentioned, I've never heard of it.. Can't wait!


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## Lanson

I'm going to go model these up, brb

edit, done. 

Any enclosure from 6 to 8 cubic feet, and tuned to 23-25hz, and you basically got it. Just make sure you with accurately plot the port once you have the box size properly calculated.


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## Justin Zazzi

lust4sound said:


> (FS is 18Hz on these subs)


Where did you find this spec? It's not listed on the website you linked.




lust4sound said:


> I'm wondering if the shape of the box will hurt or negate the type of response I want.. It's very wide, but not very tall or deep.. All of the sub enclosures I see for SPL are very deep, usually much deeper than they are wide/tall..
> 
> My box is the polar opposite.. Thoughts?


Won't make any difference at the frequencies you want to play.


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## lust4sound

Jazzi said:


> Where did you find this spec? It's not listed on the website you linked.
> 
> 
> 
> 
> Won't make any difference at the frequencies you want to play.


18hz FS. You are correct, there's no spec for that.. 

When I posted that, I went by memory, I recalled reading 18hz, for some reason I recall that as the FS..

Turns out that's the low end of the frequency response, no real data for FS, just states an 18 to 1khz +/- 3dB response.. 

I should have double checked before I posted that. Thanks for clearing that up..


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## lust4sound

fourthmeal said:


> I'm going to go model these up, brb
> 
> edit, done.
> 
> Any enclosure from 6 to 8 cubic feet, and tuned to 23-25hz, and you basically got it. Just make sure you with accurately plot the port once you have the box size properly calculated.


I am about to cut out the old face, remove old slats and ports, start clean with 3/4 of a box..

I have two pieces of ply I'll be gluing together, roughly 1.50" thick when done.. 

I went with round PVC for ports, I had an old holesaw collecting dust, 3.5/8" diameter, so I went with 3" PVC.. 

Now to calculate 24hz using 2 pieces of 3" PVC per side.. 

(round ports simplest way considering the limited tools I have available)

Now, with 3" PVC, I'm assuming that's the inner diameter? I have a 3-5/8" hole saw, outer edge of teeth match up with outer diameter of PVC, will be a snug fit once hole is cut out.. 

Man, it's been so long since I've done all of this, I recall using this holesaw once before, 3" PVC, used two ports per sub on an old install (10 years ago) I ended up having to tap the PVC in with a hammer, used glue and a thin finishing nail on each side to secure it..

With 4- 15" L-7 solobarics in a 12CF box tuned to 26hz, two Mmats D3500.1 amps, (1 per pair = approx 3K RMS per side) output was absolutely insane!

I had 2 pairs of the old school Boston Acoustics Pro 6.5" (3 way) used 4 midbass, 2 mid, 2 tweets, powered by a pair of MMats SQ4160 4 channels.. WOW.. Just... WOW... I'm not sure why I go through all the trouble, enjoy for a month or two, document nothing (via photos or portfolio) then tear it all down and sell everything.. ?? Still trying to figure me out..


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## Lanson

Um... 3" PVC...you are going to need a TON of ports to keep the velocity below scary numbers.

I would suggest returning 3" PVC asap. There's virtually nothing 3" can do with a bad ass sub like the JBL GTI. 3" ports may go well in an 8" sub config, that's about it.


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## lust4sound

OK, so inner diameter 3" (3.5 outer) too small? got it.. I went with this without first modelling in Winisd because I have a 3-5/8 holesaw collecting dust, had great success with it years back.. I happened to be at Lowes shopping for router, saw a few shorter cut lengths of 3" on sale, grabbed it impulsively..

I'll check for myself on Winisd, what are we trying to avoid in terms of port velocity? Another thing I noticed, sometimes when you enter more than 1 port, the dimensions of the ports required become unmanageably long, often don't match dimensions of box.. 

Glad you pointed it out.. Although I would not have cut anything till I modelled on Winisd first, you just saved me multiple trips to Lowes.. I happened to be heading out there today, will check Winisd first, if this won't work, I'll return for appropriate size..

Slot porting is a bit out of my depth at the moment, I do not have appropriate tools.. I may not have the depth required either.. 

It's looking like I'll be spending approx $30 to $40 for a holesaw which will cut correct size for the larger PVC, which I think is 6".. (I should have kept all that thick cardboard tubing I had leftover from my cousins art gallery.. some of that material would have been perfect.. 6" 8" 10" diameter 1/2" thick heavy duty cardboard for shipping artwork.. tough as nails, looked like the same **** JBL uses in their cabs..

When plugging numbers into Winisd, the port diameter it asks you to enter, is it asking for inner diameter??


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## lust4sound

Just plugged some numbers into Winisd.. I have the very basic version, nothing about port velocity..

What I came up with is this.. For 8 cf, 2 drivers, 4 ports 3" inner diamter, tuned to 22 hertz, I came up with 0dB @ 22, slight bump to .5dB from 25hz to 30hz, then beautifully flat along 0dB straight across the board.. 

I'm guessing port velocity is the speed at which the port propels the wave of the sub, I'm also guessing this leads to chuffing, will also skew waves? 

Will it actually accelerate the wave? If so, your mention of "scary" I'm assuming it will behave beyond an acceptable margin of performance.. 

How does that work? Does it accelerate the speed at which the wave hits your ears, causing problems with phase cancellation or something like that?

Or does it simply have to do with chuffing or port noise?


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## lust4sound

Also want to point out, when I plug in the standard 6" PVC, the port length Winisd suggests goes way beyond the depth of my box.. Do I have to add curved joints (u bends, or 90' angles) to achieve the length? How will I then calculate displacement?


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## Lanson

You will want to seek and download the WinISD Pro 0.7 version. It is still completely free. It will definitely serve you to find your port tune, and velocities and much more.

And yes, when the port length exceeds, consider bends. My best suggestion is to construct a port. A slot or square one. OR we can work out passive radiators.

edit:

Chuffing is an acoustic annoyance at low levels, and at higher velocities it becomes a hindrance to the performance, basically a restriction.

Air velocity is not congruent with air pressure waves


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## lust4sound

fourthmeal said:


> You will want to seek and download the WinISD Pro 0.7 version. It is still completely free. It will definitely serve you to find your port tune, and velocities and much more.
> 
> And yes, when the port length exceeds, consider bends. My best suggestion is to construct a port. A slot or square one. OR we can work out passive radiators.
> 
> edit:
> 
> Chuffing is an acoustic annoyance at low levels, and at higher velocities it becomes a hindrance to the performance, basically a restriction.
> 
> Air velocity is not congruent with air pressure waves


I'm aware of chuffing, I'm still in the dark on the topic of port velocity, I'll do some reading.. 

I basically stripped the box down to 3/4 of a box, glued two pieces of 3/4 ply to make the face.. 

In the interest of maximizing internal volume, I can flush mount the new face to the outside of the old box, whereas the old face was recessed.. 

Not only does this give me the benefit of increased internal volume, it makes for a perfect guide for my router. No need for the inaccuracies of the cheap table saw I'm working with.. 

I can install internal bracing while it's open.. Once it's good and proper, I can simply lay the 1.50" face on top of the open end of old box, secure it, run my router across it to trim to perfection.. 


Anyway, I am finally going to post pics.. I have a good jigsaw now, so I can cut for slot porting.. I have no experience with this, do not know anything about calculating port size (do we work with inner or outer dimensions when inputting data in Winisd? )

I've attached some pics, also want to point out, 8.5 CF is bare bones internal volume with new face mounted atop old box.. That's before sub, bracing, port displacement..

I'm actually going to wait for instructions from you for proper bracing and port size.. (If you'd be so kind) Fire away!!


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## lust4sound

Nothing like a new lease on life.. This is what I started with..


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## lust4sound

Here's where I'm at


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## lust4sound

I'll just search Google and the forum for the answers that I need, you guys have been great, thanks so much!!


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## Lanson

I don't think a jigsaw will suffice for cutting a slot port, unless you are REALLY good with it over long distances. If someone can cut the long side or if you can pick up some wood pre-cut like with a saw at Home depot assuming it is accurate enough, this is doable.


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## lust4sound

fourthmeal said:


> I don't think a jigsaw will suffice for cutting a slot port, unless you are REALLY good with it over long distances. If someone can cut the long side or if you can pick up some wood pre-cut like with a saw at Home depot assuming it is accurate enough, this is doable.


I meant for cutting the hole for the face.. I've picked up a a table saw, circular saw, sawzall, I've also got the router with a few tips.. learned to set up jigs for circles and square cuts..

Correct/square cuts are no longer a concern.. I may actually go so far as to remove all the carpet, hit it with orbital, spray bedliner on the box, route the edges smooth..

I'm just not sure if I'm supposed to be working with/ inputting inner or outer dimensions for port calculation.. 

If the port has to be a long and shallow, running lengthwise along the bottom of the box, would probably make my life easiest..

.. ..


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## Lanson

Ah, looks like you're in the clear with a table saw and so on, then.

So yes, always measure INSIDE, that's all the air "cares" about. Any 90 or 180 degree bends or whatever, use the middle measurement for the number. Example, a 4x8 port, turns 90 degrees... you'd go in that port and visualize the 45 degree angle of each piece of wood it would take to make it, and use the measurement from the inside middle of that. Simpler done than even explained.

edit: Here's a pic to explain better than words











lust4sound said:


> I meant for cutting the hole for the face.. I've picked up a a table saw, circular saw, sawzall, I've also got the router with a few tips.. learned to set up jigs for circles and square cuts..
> 
> Correct/square cuts are no longer a concern.. I may actually go so far as to remove all the carpet, hit it with orbital, spray bedliner on the box, route the edges smooth..
> 
> I'm just not sure if I'm supposed to be working with/ inputting inner or outer dimensions for port calculation..
> 
> If the port has to be a long and shallow, running lengthwise along the bottom of the box, would probably make my life easiest..
> 
> 
> .. ..


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## lust4sound

fourthmeal said:


> Ah, looks like you're in the clear with a table saw and so on, then.
> 
> So yes, always measure INSIDE, that's all the air "cares" about. Any 90 or 180 degree bends or whatever, use the middle measurement for the number. Example, a 4x8 port, turns 90 degrees... you'd go in that port and visualize the 45 degree angle of each piece of wood it would take to make it, and use the measurement from the inside middle of that. Simpler done than even explained.
> 
> edit: Here's a pic to explain better than words


Appreciate all the trouble, the JPG made it clear.. 



On port velocity, I'll do some reading, but what are acceptable numbers for these 2-12s within this much airspace? You mentioned 3" as a no go.. I now have the option of 4" (found another hole saw)

You see, I'm working with a seriously limited budget and dare I admit, woodworking skill set.. round ports would be simplest, although I'm up for the learning experience of working the wood for slot port..

Still, I'm limited by the tools available to me, my old table saw dug up from my Uncles house is missing the rip fence (mind you, I purchased it new for a job at his house, used it once, left it there 10 years ago, found it buried under a mountain of ****, two critical pieces missing.. The stand and the rip fence) I have to use a pair of clamps, tape measure, and a long level as straight edge for makeshift rip fence. NIGHTMARE... 

I will stop by Lowes or Home Depot, see if I can purchase a rip fence for the saw I have.. otherwise, a few simple cuts will end up taking half the day..

I could get the slot port done, but round would be simplest..

I will download the version of Winisd you recommend, will poke around for a bit then it's off to get some work done..


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## emilime75

Just wanted to say, if it hasn't been already, be extremely careful with your table saw and make shift fence. With your self admitted limited wood working experience and a fence that isn't properly secured, that saw becomes extremely dangerous. Just look up table saw kick back and you'll see what I mean. I'm 40, been a carpenter and cabinet builder most of my life and I've had a couple of kick back scenarios even with a good quality fence that was properly secured. Any shift in the work piece while it's being cut can catch the back of the blade and it can be shot back at you. It happens so quickly you have no time to react. If your hands are near the blade they can be pulled in to the blade, seriously not a good thing. I've once had a piece of 1/4" plywood shot back at me and it hit me in my upper thigh, just below of my waist and just shy of my "area". It caused a welt the size of a golf ball and a cut requiring 18 stitches. Just saying, be careful...better yet, get a proper fence or a saw with one. The most killer sub box isn't worth the risk.


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## lust4sound

I just skimmed through this thread, apparently I missed the part about passive radiators.. 

I know what they are, but I would not know how or where to begin with calculations...


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## Lanson

lust4sound said:


> I just skimmed through this thread, apparently I missed the part about passive radiators..
> 
> I know what they are, but I would not know how or where to begin with calculations...


Again, use of WinISD Pro can provide necessary info. 

They aren't cheap but it works great because you don't take up space with ports, AND they are tune-able. 


OK so I modeled an approximately 8 cubic foot box with two subs, and two 15" CSS passive radiators. With 500g of added weight on the the radiators, this matches (roughly) a 24hz tuned port.

Comparatively, that tuned port requires Three 4" round ports to avoid heavy chuffing.

In both of these sims, I used a 15hz infrasonic filter to keep excursion from possibly being an issue.


At 500W total power, SPL for either of these options is about 115.5dB anechoic.


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## lust4sound

emilime75 said:


> Just wanted to say, if it hasn't been already, be extremely careful with your table saw and make shift fence. With your self admitted limited wood working experience and a fence that isn't properly secured, that saw becomes extremely dangerous. Just look up table saw kick back and you'll see what I mean. I'm 40, been a carpenter and cabinet builder most of my life and I've had a couple of kick back scenarios even with a good quality fence that was properly secured. Any shift in the work piece while it's being cut can catch the back of the blade and it can be shot back at you. It happens so quickly you have no time to react. If your hands are near the blade they can be pulled in to the blade, seriously not a good thing. I've once had a piece of 1/4" plywood shot back at me and it hit me in my upper thigh, just below of my waist and just shy of my "area". It caused a welt the size of a golf ball and a cut requiring 18 stitches. Just saying, be careful...better yet, get a proper fence or a saw with one. The most killer sub box isn't worth the risk.


I missed this too! 

I have the actual saw blade cover with the anti-kickback mech secured.. It's just the actual rip fence which is missing.. I am using a a long level as straight edge w clamps to secure for straight cuts. 

Thanks for all the info, appreciate the concern!..


----------



## lust4sound

fourthmeal said:


> Again, use of WinISD Pro can provide necessary info.
> 
> They aren't cheap but it works great because you don't take up space with ports, AND they are tune-able.
> 
> 
> OK so I modeled an approximately 8 cubic foot box with two subs, and two 15" CSS passive radiators. With 500g of added weight on the the radiators, this matches (roughly) a 24hz tuned port.
> 
> Comparatively, that tuned port requires Three 4" round ports to avoid heavy chuffing.
> 
> In both of these sims, I used a 15hz infrasonic filter to keep excursion from possibly being an issue.
> 
> 
> At 500W total power, SPL for either of these options is about 115.5dB anechoic.



Since I dug up a brand new 4" holesaw which I forgot I had, I've already purchased the 4" PVC.. 

I'm having a nightmare of an ordeal fixing broken tools (turns out the router I purchased brand new from Lowes was returned by previous owner with broken handle and broken height adjustment lock release..

Since I decided to make it a Sat night project, I was relegated to trying to rig a router.. Threw in the towel after I mangled the doubled up plywood panels..

Sorry I put you through the hassle of researching passive radiators, I'm not sure why I even posed the question, I was hoping to get the box done tonight..

Anyway, Matt from Parts Express modelled my subs in whatever program they use over there..

Showed a decent plot with only 500 watts, calls for 2 4" ports and 7.5 cf internal..

Plot showed a minimal dip below 0 from 22hz all the way to 50 where it hits the 0 line..

I asked about port velocity, according to his program, the pair of 4" PVC ports won't be a problem..

Not sure if it makes a difference that I'm actually running 500 rms per sub, not sure if he was aware of that when plugging in data..

Anyway, time for a movie  Thanks again guys, I'll keep you posted!


----------



## Lanson

Matt from PE mis-calculated, unless you are operating under 400W. 34 meters / second is the target at least as far as the most you'd probably tolerate. Bear in mind, that is ~.1 MACH.

With two ports 4", you'd be best off adding a large infrasonic filter @ 25hz. By doing this, you'll be able to keep port chuffing below crazy levels. 




lust4sound said:


> Since I dug up a brand new 4" holesaw which I forgot I had, I've already purchased the 4" PVC..
> 
> I'm having a nightmare of an ordeal fixing broken tools (turns out the router I purchased brand new from Lowes was returned by previous owner with broken handle and broken height adjustment lock release..
> 
> Since I decided to make it a Sat night project, I was relegated to trying to rig a router.. Threw in the towel after I mangled the doubled up plywood panels..
> 
> Sorry I put you through the hassle of researching passive radiators, I'm not sure why I even posed the question, I was hoping to get the box done tonight..
> 
> Anyway, Matt from Parts Express modelled my subs in whatever program they use over there..
> 
> Showed a decent plot with only 500 watts, calls for 2 4" ports and 7.5 cf internal..
> 
> Plot showed a minimal dip below 0 from 22hz all the way to 50 where it hits the 0 line..
> 
> I asked about port velocity, according to his program, the pair of 4" PVC ports won't be a problem..
> 
> Not sure if it makes a difference that I'm actually running 500 rms per sub, not sure if he was aware of that when plugging in data..
> 
> Anyway, time for a movie  Thanks again guys, I'll keep you posted!


----------



## lust4sound

fourthmeal said:


> Matt from PE mis-calculated, unless you are operating under 400W. 34 meters / second is the target at least as far as the most you'd probably tolerate. Bear in mind, that is ~.1 MACH.
> 
> With two ports 4", you'd be best off adding a large infrasonic filter @ 25hz. By doing this, you'll be able to keep port chuffing below crazy levels.


OK, this is the last I will trouble you with this.. I have figured out how to quickly make straight square cuts for building slot port.. 

So port velocity will be too high @ 22hz regardless of the quantity of ports? Adding a few ports won't solve the problem will it? I'm assuming it won't, or the port lengths required will equal some absurd type length..

I don't have a box building program, hence all the badgering.. I will check back later today, if 4" down to 22/24hz is an absolute moot point, I'll build a slot port..

Heading downstairs to work on the box.. Will check back later!


----------



## Lanson

It isn't trouble, so please don't think of a conversation of this stuff like that. Nobody is born with an innate ability to figure out audio, we all learn it. My first box was a ****ing mess, as was my second, and third, and around the 4th I started getting a grip on it, etc. 

Port velocity drops with the addition of ports. However port length will increase per port. Just stay accurate with your calculations, and remember that the ports take up room so you're working with a moving target. The trick is to calculate, think it through, re-calculate, etc before cutting a single board.

When you say you don't have a box building program:

https://www.facebook.com/WinISD/posts/126113234166443

Now you do.



lust4sound said:


> OK, this is the last I will trouble you with this.. I have figured out how to quickly make straight square cuts for building slot port..
> 
> So port velocity will be too high @ 22hz regardless of the quantity of ports? Adding a few ports won't solve the problem will it? I'm assuming it won't, or the port lengths required will equal some absurd type length..
> 
> I don't have a box building program, hence all the badgering.. I will check back later today, if 4" down to 22/24hz is an absolute moot point, I'll build a slot port..
> 
> Heading downstairs to work on the box.. Will check back later!


----------



## lust4sound

fourthmeal said:


> It isn't trouble, so please don't think of a conversation of this stuff like that. Nobody is born with an innate ability to figure out audio, we all learn it. My first box was a ****ing mess, as was my second, and third, and around the 4th I started getting a grip on it, etc.
> 
> Port velocity drops with the addition of ports. However port length will increase per port. Just stay accurate with your calculations, and remember that the ports take up room so you're working with a moving target. The trick is to calculate, think it through, re-calculate, etc before cutting a single board.
> 
> When you say you don't have a box building program:
> 
> https://www.facebook.com/WinISD/posts/126113234166443
> 
> Now you do.


Appreciate all of this! I know I sound like such a noob, been doing this a while although I've always had boxes built to order as per manufacturers recommendation.. (with great results) I can install, I can tune, not great with fab, have always outsourced.. Another thing I want to point out, I was active 5 or 6 years back, fell out of the loop, back in the saddle, much has changed, much remains the same.. 

SQ/SQL is a recent thing when compared to the length of time I've been tinkering with car audio (late 80s, early 90s) a bit more involved these days 

I've learned more with my time on this forum (member since 2008?) than I have in all my life..

It's all info I get from good folks like you.. Appreciate all the info, I'll let you know how it goes!


----------



## lust4sound

Ok, here's what I have.. With 6- 4" ports (easiest for me) I peak out at 55.155 m/s @ 23.79 hz.. 

From 22.07hz I have 34.366 m/s, sharp peak to 55.4 m/s @ 23.90hz, then sharp drop to 35.6 m/s @ 25.69hz... almost vertical drop from there..

That's w 6 4" PVC @ 40" each.. I definitely have the room, box is 46.5" x 19.1" x 16.5" internal..

Will displace about the same as a single slot port..

A single slot port, 6" x 19.50" x 57.76 will peak out at 35.6 m/s @ 24hz. While this is much closer to ideal as per your suggestion, I will need a friend to help build that.. 

Not sure how much internal volume it will displace.. Bare bones box without bracing, port or sub displacement measure just over 8.5 cf!!

I'm just not sure if I'm calculating properly.. I plugged in 8cf for displacement..

What is the correct procedure for inputting data? I've got a bare box, no subs or bracing yet, no port.. 

As internal dimensions diminish with displacement, this gives me an obvious change in port length..

How is the input of data correctly done?


----------



## Lanson

You need to basically shoot the moving target. 

In other words, you're best off doing plans several times, taking the calculations into consideration. For instance, find the displacement of your ports (break out your math for cylinder volume). I actually use SketchUp all the time for this. It gives square area of a given space, and then I just multiply by height. I can also use plugins for volume with "weird" shapes. But you can do this on paper as well. For instance, 3.1416 x radius squared x height, and on a 4.5" (outside diameter), it would go like this:

2.25^2 = 5.0625
x 3.1416 = 15.904
x 40" = 636.174 cu inches displaced. And then x6 for four ports, and you get 3,817.04 cubic inches, which is 2.2 cubic feet of displacement. 

Which is one reason when I modeled your stuff, I tried using 7 cubic feet instead of ~8.

Now unless I have incorrect specs (not sure about that), I modeled these subs again (on my new laptop computer, ergo new software), and I calculate you'll be able to get acceptable velocities with 3 4" vents. Again, using an infrasonic filter (18hz in this sim), and I'm using 1000W total power, this reduces the velocity at the very bottom end, and it keeps the sub out of excursion limits. If you go with 4 vents, port velocity drops down into very acceptable limits, likely not audible even at full boogie. For instance (again, guessing box size around 7 cubic feet final), 4 vents would be at 27.91" and 3 would be 20.2". That will end up being much less displacement due to ports, giving you a bigger box overall. IMO, if you can swing it, go with the 4 vents and the reason is, even if you don't flare the ports or anything, you're likely not going to hear much port noise if any. 4 vents with this size would turn out to be a tick over 1 cubic feet of port displacement, at 1.027 or so. Remember your bracing should be extensive with subs like this, but that shouldn't take up too much space. You can "buy" some space back by using Polyfil or other kinds of batting-type stuffing. The jury is out on how much space you can pretend to increase with, but my recommendation is to line the box heavily just to reduce impedance even if you don't need the space.



Have fun, be safe!


Oh and if my numbers aren't adding up, throw me the specs of this driver, I'm using WinISD's W12GTi specs but they may have changed over time.


----------



## lust4sound

fourthmeal said:


> You need to basically shoot the moving target.
> 
> In other words, you're best off doing plans several times, taking the calculations into consideration. For instance, find the displacement of your ports (break out your math for cylinder volume). I actually use SketchUp all the time for this. It gives square area of a given space, and then I just multiply by height. I can also use plugins for volume with "weird" shapes. But you can do this on paper as well. For instance, 3.1416 x radius squared x height, and on a 4.5" (outside diameter), it would go like this:
> 
> 2.25^2 = 5.0625
> x 3.1416 = 15.904
> x 40" = 636.174 cu inches displaced. And then x6 for four ports, and you get 3,817.04 cubic inches, which is 2.2 cubic feet of displacement.
> 
> Which is one reason when I modeled your stuff, I tried using 7 cubic feet instead of ~8.
> 
> Now unless I have incorrect specs (not sure about that), I modeled these subs again (on my new laptop computer, ergo new software), and I calculate you'll be able to get acceptable velocities with 3 4" vents. Again, using an infrasonic filter (18hz in this sim), and I'm using 1000W total power, this reduces the velocity at the very bottom end, and it keeps the sub out of excursion limits. If you go with 4 vents, port velocity drops down into very acceptable limits, likely not audible even at full boogie. For instance (again, guessing box size around 7 cubic feet final), 4 vents would be at 27.91" and 3 would be 20.2". That will end up being much less displacement due to ports, giving you a bigger box overall. IMO, if you can swing it, go with the 4 vents and the reason is, even if you don't flare the ports or anything, you're likely not going to hear much port noise if any. 4 vents with this size would turn out to be a tick over 1 cubic feet of port displacement, at 1.027 or so. Remember your bracing should be extensive with subs like this, but that shouldn't take up too much space. You can "buy" some space back by using Polyfil or other kinds of batting-type stuffing. The jury is out on how much space you can pretend to increase with, but my recommendation is to line the box heavily just to reduce impedance even if you don't need the space.
> 
> 
> 
> Have fun, be safe!
> 
> 
> Oh and if my numbers aren't adding up, throw me the specs of this driver, I'm using WinISD's W12GTi specs but they may have changed over time.


OK, so here's where I'm at.. Again, I have very limited prior experience with box building/woodworking, I'm on a super limited budget, I am working on the street with cheap tools which I had to "rig" 

Trouble with 4 or even 3 4" vents if lack of room.. 

I am posting pics, but I will try to draw something up which better illustrates the hurdle I'm faced with..


----------



## lust4sound

Box is 48" in wide, will be approx 20 deep, is 18 high (external) subs will mount on face, with all the internal bracing, depth of subs, narrow height, (top to bottom) I am faced with a few problems..

A) Can't get all 4 ports to fit from one side 
B) Can't run ports on either side (box is wedged snug against passenger side of rear, on the drivers side, there's a cavity which has room enough for ports to breath..

I can manage 3 on the driver side ( I think) however, the ports will not be even with subs inside box.. Will this matter?

Also, if I decide to run from front or back of box, I'll need 90' bends, still haven't mastered the calculations for that yet..

Also, I wanted to point out, those are 4 x 6s cut to triangles.. I started with 5.25ish blocks (cut board into perfect squares, then ripped those into triangles, there are +/- 1/8" variations)

the two vertical strips along the back walls are 3/4" ply, obviously installed with the strong end against the back wall (exposed ply ends are secured to back wall)

the center brace is a pair of 3/4" plywood boards glued together, measure 2.5" in width, plenty strong..

triangles measure 5" x 5" x 7" x 3. 75 " (ish)

('m pretty sure I have plenty of bracing for the back of the box, as for the front, because I have the thick center brace, as well as doubled up 3/4" ply for face where subs will mount, I don't think I'll need to duplicate the rear.. I will reinforce the edges of the front where the face mounts using strips of 3/4" ply, this should be plenty strong..

If you see anything wrong with the way I've braced everything, please let me know!!

What are some other options for porting?

Could I go in from front and use 90' bends? If so, could you help with calculations?

Also, I've gotten proficient enough with use of jigsaw, also picked up router with circle jig..

They sell large cardboard cylinders for the purpose of building concrete foundations for light projects (decks, sheds etc) If memory serves correct, the cardboard is treated for moisture, reinforced, super sturdy (thick) and is something in the neighborhood of 10" diameter? (going by memory, it's been so many years)

Basically, I am no longer limited to 4" round ports, also, 4" round ports are really not to viable an option at the moment..

Any and all suggestions greatly appreciated.. Thanks in advance!!


----------



## emilime75

I think you'll be just fine with a total of (4) 4" ports.

I just modeled it myself, 7.5 cuft box, 25Hz tune. With 1000 watts of system power, air velocity peaks at 29m/s at 23Hz. With 2000 watts, it peaks at about 41m/s, again at about 23 Hz. In that alignment, response models great, flat to 25Hz and -3dB at about 21Hz. Most music, even modern electronica, rarely reaches much lower than 25-30Hz. 

Cone excursion also looks good in that model, they'll stay below xmax at 1000 watts until 21Hz. With 2000 watts, they'll exceed xmax once at 35Hz by only about 1-2mm, then again at 22Hz and below. 

Keep in mind, you'll rarely reach full system power with typical music listening unless you just crank the **** out of it on a regular basis. So, both excursion and vent air velocity will stay well below these limits most of the time. Also, if you have the capability of a highpass on the subs, that will also help tremendously with keeping the excursion and vent air speed in check.

As an example, I use 2 W15GTIs in my home theater. The box is 20cuft with a 17Hz tune, powered by pro amps currently capable of 750 watts per driver. There are (2) 4" ports and they are located at the ends(sides) of the box along with the woofers, so (4) 4" vents total. I used a large(2") round over bit in my router to ease the end of the port at the baffle to help with any chuffing. Modeling this without a highpass in place, I exceed xmax once at 25Hz and then again at 15Hz. According to WinISD, my vent velocity reaches 27m/s at 20Hz, 25m/s at 18Hz, 40m/s at 17Hz and finally peaks 49m/s at 15Hz.

With a highpass at 15Hz, vent velocity peaks at 35m/s at 16Hz. Xmax peaks twice by 2-3mm, once at 25Hz and then again at 13Hz where it drops off again due to the highpass filter in place.

I never hear any chuffing what's so ever. The only time I hear the woofers struggle a bit is when I'm cranking it and the amplifiers start clipping. Again, this is in a house and a room that is waaaaaay bigger than the cabin of a car and in a box tuned lower and bigger than these woofers are meant to be in. I think your 7.5cuft box with a 25Hz tune and (4) 4" ports would be excellent.


----------



## lust4sound

emilime75 said:


> I think you'll be just fine with a total of (4) 4" ports.
> 
> I just modeled it myself, 7.5 cuft box, 25Hz tune. With 1000 watts of system power, air velocity peaks at 29m/s at 23Hz. With 2000 watts, it peaks at about 41m/s, again at about 23 Hz. In that alignment, response models great, flat to 25Hz and -3dB at about 21Hz. Most music, even modern electronica, rarely reaches much lower than 25-30Hz.
> 
> Cone excursion also looks good in that model, they'll stay below xmax at 1000 watts until 21Hz. With 2000 watts, they'll exceed xmax once at 35Hz by only about 1-2mm, then again at 22Hz and below.
> 
> Keep in mind, you'll rarely reach full system power with typical music listening unless you just crank the **** out of it on a regular basis. So, both excursion and vent air velocity will stay well below these limits most of the time. Also, if you have the capability of a highpass on the subs, that will also help tremendously with keeping the excursion and vent air speed in check.
> 
> As an example, I use 2 W15GTIs in my home theater. The box is 20cuft with a 17Hz tune, powered by pro amps currently capable of 750 watts per driver. There are (2) 4" ports and they are located at the ends(sides) of the box along with the woofers, so (4) 4" vents total. I used a large(2") round over bit in my router to ease the end of the port at the baffle to help with any chuffing. Modeling this without a highpass in place, I exceed xmax once at 25Hz and then again at 15Hz. According to WinISD, my vent velocity reaches 27m/s at 20Hz, 25m/s at 18Hz, 40m/s at 17Hz and finally peaks 49m/s at 15Hz.
> 
> With a highpass at 15Hz, vent velocity peaks at 35m/s at 16Hz. Xmax peaks twice by 2-3mm, once at 25Hz and then again at 13Hz where it drops off again due to the highpass filter in place.
> 
> I never hear any chuffing what's so ever. The only time I hear the woofers struggle a bit is when I'm cranking it and the amplifiers start clipping. Again, this is in a house and a room that is waaaaaay bigger than the cabin of a car and in a box tuned lower and bigger than these woofers are meant to be in. I think your 7.5cuft box with a 25Hz tune and (4) 4" ports would be excellent.


Thanks so much for info!

My problem now is getting 4-4" ports to fit.. I will have to mount ports front or back 

original plan was 2 per side, with each sub offset for clearance issues.. in other words, if you're looking at the subs mounted, one will be mounted top left corner, the other bottom right. 2 ports to a side, mounted horizontally..

so the left side of box will have sub mounted near top, if you look on the actual side of the box, the left side would have ports mounted low, both mounted side by side horizontally.. Inside the box, the ports will just clear the left side sub, extend all the way to the right side of box, vice versa and opposite mounting for right side of box, ports mounted horizontal at top, extending into left side sub area, and sub mounted low in box. 

That is the only way I can mount these subs in this box with 4-4" ports tuned to 22/24hz (clearance issues with subs and bracing..)

Summary, two ports per side, left side ports mounted horizontally on bottom beneath sub, extending all the way into right side of box.. Right side ports mounted horizontally at top of box above sub, reaching all the way into left side of box (right side sub mounted on bottom of box) 

I could port through front or back, 90 degree angle, but I'm not entirely sure how to calculate port lengths divided by elbow, not sure what to subtract from displacement for elbows..

Passive radiators are sounding real simple and worth the expense at this point!!

I have yet another option..

I own a pair of BNIB JL Audio 13W3-V3-8 subs.. I can sell the pair of JBL, purchase two more of the JLs, effectively giving me 13" x 4 cone/surface area with a total of 2600 watts RMS power handling.. Frequency response 22hz and up, 600 watts RMS single 8 ohm voice coils each.

These are the latest JLs, black cone..

Thoughts?

Also, love that you're a home theater enthusiast!! I have all Adcom amps, high end Pioneer receiver with the latest surround tech, 24 bit Burr Brown DAC on all channels, have a pair of 15" JBL 2226HPLs in 8CF tuned to 32hz, 1000 watt Crown amp on JBLs.. 

Mirage mains center and surrounds, Adcom GFA 555 MKII on the mains, 5 channel Adcom on center and surrounds.. (100 x 5 @ 8 ohms)

Pioneer/Adcom sound amazing (entry level audiophile is all I can afford, Adcom best bang for the buck) 

the Mirage speakers are the weak link..

When I sell my townhouse, I'll get a pre-owned JVC projector (I forget the model number) a few years back when I worked for home theater installs, this particular projector was $7000.. They now sell used for under $1000.. It's more than I'd ever need..

One of the showrooms which featured this projector had an 8' x 12' screen (if memory serves correct) I watched King Kong, the contrast and detail on the black and dark colors was astounding, the glimmer in his eyes on closeup, no jitter or rainbowing, just amazing what this tiny projector is capable of..


----------



## Lanson

Consider slot-loading ports, across the 18" height, but what is the internal? Say 16.5? 

I'm not to a place where I can do the calcs but it wouldn't be hard to fab a slot port based off the walls. Or one very big single port, need to look into it. But ~16.5" internal height x (unknown yet) width, you'd just need to cut that piece pretty square and then secure it in place, and you'd probably contend with one 90 degree angle, again not a big deal.

After I finish my project out there, I'll hop on and see what it takes to do that. But find me the internal height dimension (assuming 16.5) to be sure.


----------



## lust4sound

fourthmeal said:


> Consider slot-loading ports, across the 18" height, but what is the internal? Say 16.5?
> 
> I'm not to a place where I can do the calcs but it wouldn't be hard to fab a slot port based off the walls. Or one very big single port, need to look into it. But ~16.5" internal height x (unknown yet) width, you'd just need to cut that piece pretty square and then secure it in place, and you'd probably contend with one 90 degree angle, again not a big deal.
> 
> After I finish my project out there, I'll hop on and see what it takes to do that. But find me the internal height dimension (assuming 16.5) to be sure.


Update..

I wasn't thinking clearly late last night when I was trying to figure out port arrangement.. 

I took a look today, it seems simple enough, I can add the 4" round ports front or rear, then just bend them 90 degrees..

A few issues I am having now..

A) I don't exactly know what I have in terms of internal volume now that I've added all the bracing
B) I'm still a bit unclear on calculating port lengths with the 90, additionally, a bit unclear on displacement with said ports on 90..

I am going to upload a video to Youtube, it's about 3.5 minutes long, it will clearly explain and illustrate what I've ended up with..

I am posting some pics, I'll try to explain once they're up


----------



## lust4sound

so, that second photo shows the center brace, which is two pieces of 3/4 laminated.. It measured 19.1/8" front to back, 16.50" top to bottom, finally, a tick under 1.50" thick. I cut out the center, leaving 2.50" on all 4 sides..

The pic also shows triangular bracing.. Those started life as 4x6" boards, I ripped 6 squares which measured 5.50 sq x 3.50" thick.. I cut those squares into 12 triangles which are +/- 1/8" off.. I now have 12 triangular braces which measure 5.25" on two sides, x 7.45 (ish) on one side, by 3.50" thick..

My guess was to just subtract 5.50" x 5.50" x 3.50 x 6 from the internal volume.. The confusion lies with the center brace and it's relationship with the triangular braces I've surrounded it with..

Bear in mind, the rear of the box is a single piece of 3/4" ply, vs the face which will be a pair of 3/4" laminated, will yield a tick under 1.50", same as thickness of center brace..

With that in mind, I kept bracing on the sub side to minimum, limiting it to the 4 outer corners..

I am completely lost in terms of internal volume now.. (I don't do maths..)

Also, displacement of each sub is .149 CF as per JBL specs.. mounting depth is 10.25", I'll have the additional 3/4" which should subtract from both depth and displacement no?

(EDIT)

I forgot to mentiion, there are two braces which run top to bottom on rear of box.. Those measure 16.50" top to bottom, 2.50" deep and it's 3/4" plywood.. Tons of glue, predrilled and screwed like an inmate..


----------



## lust4sound

It started life as this.. In hindsight, would have been so much easier to just block all but one of the 5" x 2 vents on each side, used the box as is..

But the woodworking experience I picked up was well worth it.. Again, working on the street, self taught, had to totally rig the table saw for both a rip fence, as well as a jig to cut the triangles, which I then had to carefully eyeball..

(Edit) what a disgrace LMAO


----------



## lust4sound

I had to add a piece of the 4x6" to the angle fence or whatever it's called, this put my fingertips to within mere inches of the blade of the table saw on either side.. 

The results? A stack of near perfect triangles.. 

Improvisation has always been strong with me.. The photo shows a scrap piece screwed to the jig from the back..

The other pic shows a makeshift rip fence for circular saw, using a level as straight edge, of course I have a square which made all of this possible..

End result, the box is almost dead square atm.. although I must admit, I butchered the inside cut of the center brace.. I was using a jigsaw with dull blade, rushing (hot as blazes outside) plus I was distracted by almost every neighbor in my neighborhood.. In hindsight, I wish I had trimmed it cleaner before I glued it in..

Also, everything was predrilled, tons of wood glue and I used 2 1/4" fine thread drywall screws, screwed the crap out of everything in sight LOL..



What should have taken a few hours ended up taking a full day to do.. (all the rigging, plus the learning curve and "winging it" with improvisation)

So, how'd I do so far?


----------



## lust4sound

Could you guys please help with 4- 4" ports, mounted front or rear? One other thing I wanted to point out.. It seems that I get some bonus low end, a definite extension in low end when I face subs toward rear deck.. 

Now, this was true when I briefly ran the pair of 15" JBL 2226HPLs in the 8CF 4648 sub cab which was 8cf tuned to 40hz.. When I faced that toward the rear deck, I heard a definite increase in low end extension..

I also ran these W12s in a large slot ported box (which was crumbling due to water damage) subs facing me with large slot port in center.. Output was ludicrous..

Point is, should I port from front or rear? Or is that an unknown variable, subject to variation as per vehicle type?


----------



## lust4sound

Or 2 slot ports on bottom front, I have approximately 6" x 8" available on both sides, and they can go as far and 16 inches deep


----------



## Lanson

OK there's a lot going on here in all these posts, let's try to get some answers but let's do it in an organized way.

First, I would usually recommend the ports go on the same face as the sub. It doesn't always have to be that way, but I'd say it is optimal. Face everything toward the rear, if the enclosure will be near the rear of the vehicle.

Second, bracing can be calculated very simply, just get your math out and add things together. A triangle is 1/2 a square of the same size, so it is (L*W*H/2) or if you cut a piece to make two, then just count two at a time as a square. Braces with holes in them are simple as well, just take the size of the brace (L*W*H) and then subtract the same from the hole in it. 

Third, to calculate a 90 degree or 180 degree bend in a port, you're looking for the port's average length, the inside number. So you can measure the outside of the bend, and then the inside bend, and divide by 2, or just measure as if you're 1/2 way in the port by width. 

Fourth, the addition of a 3/4" board to lift the subwoofer up 3/4", won't change displacement in any way you'll need to worry about, so use the factory displacement number. 


Did I miss anything? Oh, are you committed to doing the round ports, or do you want to explore a slot port with that 16.5" side?


----------



## lust4sound

fourthmeal said:


> OK there's a lot going on here in all these posts, let's try to get some answers but let's do it in an organized way.
> 
> First, I would usually recommend the ports go on the same face as the sub. It doesn't always have to be that way, but I'd say it is optimal. Face everything toward the rear, if the enclosure will be near the rear of the vehicle.
> 
> Second, bracing can be calculated very simply, just get your math out and add things together. A triangle is 1/2 a square of the same size, so it is (L*W*H/2) or if you cut a piece to make two, then just count two at a time as a square. Braces with holes in them are simple as well, just take the size of the brace (L*W*H) and then subtract the same from the hole in it.
> 
> Third, to calculate a 90 degree or 180 degree bend in a port, you're looking for the port's average length, the inside number. So you can measure the outside of the bend, and then the inside bend, and divide by 2, or just measure as if you're 1/2 way in the port by width.
> 
> Fourth, the addition of a 3/4" board to lift the subwoofer up 3/4", won't change displacement in any way you'll need to worry about, so use the factory displacement number.
> 
> 
> Did I miss anything? Oh, are you committed to doing the round ports, or do you want to explore a slot port with that 16.5" side?


Ports on sub side, got it..

As for the triangles, I had already assumed I'd be subtracting the dimensions of 6 squares vs 12 triangles, which is why I posted both. The part I'm a little hazy on is where the center brace meets with the triangles.. not sure how the relationship between the two affects calculation of displacement..

At this point, I am open to suggestion.. My woodworking skills have slightly improved *pfft* so I am open to slot porting.. (I wouldn't dream of posting those pics anywhere but here)

When you say slot port with the 16.5" side, which side are you referring to?

Were you able to figure out from the pics and all the haphazard babble what I've got going on at the moment? LOL..

At this point, I'm ready to follow step by step instructions.. Just tell me what to put where, I'm all ears 

If you need a better description or pics of what I have, please let me know..


----------



## Lanson

To help with spacial descriptions, I'm going to label your box sides, so when I say a certain side, you'll know. Now, assuming the box with the subwoofer baffle (yet to be made) is on its side as shown in most of the pictures so the woofers would be vertically placed directly in front of me, let's call the subwoofer baffle (to be) "FACE". Still as viewed from this position, lets call the left side "SIDE 1". We'll call the back wall "BACK", and right side "SIDE 2". The top will be "TOP" and bottom "BOTTOM", just for accuracy's sake. 

So, in the case of a slot port, let's start on SIDE 1 from FACE to BACK, one single board to the back wall, basically reinforcing that whole side. We need to do this because the SIDE 1 has a big ass hole in it already, so we need to make a new flat board for the port to work. So, first part of the port is this piece, which should be 16.5" by whatever depth we need, and we can assume it will probably need to be a 90 degree port. The second board would then be this second part of the port, a board that needs to be placed on the BACK, up against our new port board over next to SIDE 1. The length of this is still unknown, but we'll figure that out. Together, these two boards make up the OUTSIDE half of the port, make sense? The INSIDE half of the port will be determined once we know how much width the slot port needs. You'll be able to use the smooth TOP and BOTTOM walls to make the thing work right. 

Over the course of this conversation, we covered a lot of numbers. Let's get clarity over some specific numbers one more time, you probably already have them written down"

A: What is the height from the inside of BOTTOM to TOP (aka how tall our port should be)? Is that 16.5"? 

B: How deep is the box from FACE to BACK, with the bracing in place? Have you glued the braces on the BACK wall by SIDE 1, down to the point where they could not possibly be removed safely?

So once we know all of that for certain, then we can calculate the slot port's planned width, and then length properly. With that, then you can fabricate the INSIDE two port boards, and your port is basically done! Slot ports can actually be easier in some ways, because you're able to use the box itself to make most of it, plus it is basically free bracing. 

To skip ahead to the future just a bit, Once the port is fabricated, then the top FACE board can be built for the subs, and the port itself. Because we're talking about a slot port, it will be as easy as cutting a rectangle hole in a board, which is easy with a jigsaw and a straight edge. If you have a way of sanding or filing, after the slot board is installed directly over the port, you can slowly sand or file a smoother "roundover" around the port to keep the airflow smooth as possible.


OK all this make sense?





OK so the easiest way to make a slot port is to have the side of the box be part of the port. Now because you have a hole in that side, imagine just laying a sheet up against the wall there, basically level with your box's opening. So that would 16.5 x whatever the depth is we need. I haven't yet modeled how big the slot port would need to be, but if it needs to go 90 deg, then you just lay another board on the back wall (opposite the sub baffle) 



lust4sound said:


> Ports on sub side, got it..
> 
> As for the triangles, I had already assumed I'd be subtracting the dimensions of 6 squares vs 12 triangles, which is why I posted both. The part I'm a little hazy on is where the center brace meets with the triangles.. not sure how the relationship between the two affects calculation of displacement..
> 
> At this point, I am open to suggestion.. My woodworking skills have slightly improved *pfft* so I am open to slot porting.. (I wouldn't dream of posting those pics anywhere but here)
> 
> When you say slot port with the 16.5" side, which side are you referring to?
> 
> Were you able to figure out from the pics and all the haphazard babble what I've got going on at the moment? LOL..
> 
> At this point, I'm ready to follow step by step instructions.. Just tell me what to put where, I'm all ears
> 
> If you need a better description or pics of what I have, please let me know..


----------



## lust4sound

fourthmeal said:


> To help with spacial descriptions, I'm going to label your box sides, so when I say a certain side, you'll know. Now, assuming the box with the subwoofer baffle (yet to be made) is on its side as shown in most of the pictures so the woofers would be vertically placed directly in front of me, let's call the subwoofer baffle (to be) "FACE". Still as viewed from this position, lets call the left side "SIDE 1". We'll call the back wall "BACK", and right side "SIDE 2". The top will be "TOP" and bottom "BOTTOM", just for accuracy's sake.
> 
> So, in the case of a slot port, let's start on SIDE 1 from FACE to BACK, one single board to the back wall, basically reinforcing that whole side. We need to do this because the SIDE 1 has a big ass hole in it already, so we need to make a new flat board for the port to work. So, first part of the port is this piece, which should be 16.5" by whatever depth we need, and we can assume it will probably need to be a 90 degree port. The second board would then be this second part of the port, a board that needs to be placed on the BACK, up against our new port board over next to SIDE 1. The length of this is still unknown, but we'll figure that out. Together, these two boards make up the OUTSIDE half of the port, make sense? The INSIDE half of the port will be determined once we know how much width the slot port needs. You'll be able to use the smooth TOP and BOTTOM walls to make the thing work right.
> 
> Over the course of this conversation, we covered a lot of numbers. Let's get clarity over some specific numbers one more time, you probably already have them written down"
> 
> A: What is the height from the inside of BOTTOM to TOP (aka how tall our port should be)? Is that 16.5"?
> 
> B: How deep is the box from FACE to BACK, with the bracing in place? Have you glued the braces on the BACK wall by SIDE 1, down to the point where they could not possibly be removed safely?
> 
> So once we know all of that for certain, then we can calculate the slot port's planned width, and then length properly. With that, then you can fabricate the INSIDE two port boards, and your port is basically done! Slot ports can actually be easier in some ways, because you're able to use the box itself to make most of it, plus it is basically free bracing.
> 
> To skip ahead to the future just a bit, Once the port is fabricated, then the top FACE board can be built for the subs, and the port itself. Because we're talking about a slot port, it will be as easy as cutting a rectangle hole in a board, which is easy with a jigsaw and a straight edge. If you have a way of sanding or filing, after the slot board is installed directly over the port, you can slowly sand or file a smoother "roundover" around the port to keep the airflow smooth as possible.
> 
> 
> OK all this make sense?
> 
> 
> 
> 
> 
> OK so the easiest way to make a slot port is to have the side of the box be part of the port. Now because you have a hole in that side, imagine just laying a sheet up against the wall there, basically level with your box's opening. So that would 16.5 x whatever the depth is we need. I haven't yet modeled how big the slot port would need to be, but if it needs to go 90 deg, then you just lay another board on the back wall (opposite the sub baffle)


Ok, I get what you're saying.. A few things I forgot to mention..

As for the "big ass holes" on the side/s (LOL) I forgot to mention, there were handles on BOTH sides which I still have, planned on putting them back on in the interest of covering the two "big ass holes" on either side, for ease of removing the box (when I need to move bass guitar equipment around) holes will be airtight, handles fit snug, made of metal.. 

There's also a "big ass hole" on the rear of the box, that which had a pair of speakon input terminals (Pro Audio use) which I also planned on re-using since I already have a pair of heavy duty Speakons.. They are essentially a pair of sleeved/insulated 10 gauge wires, both capped with a twist on plug on one end, bare wire on the amp end.. I'd essentially push a clip, twist, pull, cab safely disconnected from amp, no fear of accidental grounding etc..

As for all of the bracing, it's all been thoroughly glued and screwed, it's in for life.. I don't think I can remove any of it without actually destroying the box at this point..

The center brace however, let's focus for a minute on that.. I can easily cut the middle portion of the center brace out, leaving both the sides and the back intact.. Would this afford us ample space/clearance to port dead center of box? If so, could we then also use the remaining side and rear bracing as reinforcement for the port?

As for measurements, if you're referring from lengthwise from left to right as side 1 and side 2, then the INTERNAL/bare box measurements before bracing were as follows, 

- 46.5" (side 1 to 2) or left to right as it were..
- 16.5" top to bottom 
- 19 1/8" front or face (sub) to rear of box (deep)

I had a tick under 8.5 cf before any bracing was added..

the triangles were 6 squares, each measuring 

-5.5" x 3.5" ( 6 squares)

Then the two thin slats on the rear of box, running top to bottom are 

- 16.5" top to bottom x 2.5" deep x 3/4" thick or wide (3/4" ply cut to 16.5" long, then 2.5" wide, glued to rear of box with cut side facing rear for strength, 2 of those as pictured, 1 per side)

Thoughts?


----------



## lust4sound

Oh wait, I get it.. You're talking about a single slot port vertically mounted against side 1, heading straight back, then 90 toward center along back? this could be accomplished using 2 pieces of wood, using the actual box as makeup of outer portions of port.. I wish I had known before I glued those triangles in place..

I could possibly remove all 4 triangles from side 1, it would most certainly cause damage to the top layer of ply (1/8 veneer) but then again, that type of damage exists all over the box.. Technically, I should be able to remove the triangles if it would greatly simplify things in the end.. I could also trim the center brace as well..

As for the big ass hole (LOL) on side 1, I could just put the handle back in, and pour epoxy to fill any gaps and level it smooth to avoid any turbulence?

However, all things considered, I'd be complicating things in order to simplify things..

Had I known the port would be on one side, with a 90 bend prior to all that hard work with bracing, I would have gone for it..

If center port is not an option, then I'll remove bracing and port from side 1..


----------



## lust4sound

Hold on a minute, what about porting outside the box? 

I can simply add a few strips of 2x4, or 4x6, or I have precut 2.5" x 48" strips of 3/4" ply, could trim and add those to form 3 outer edges of the vent, create the framework for an external vent.. top or bottom of box (although I prefer top) then simply cover with a sheet of 3/4 MDF or ply? 

If it's possible to do this, I can cut the box open to form the opening for the vent.. I don't mind an odd shaped box either, so if the vent has to be smaller/narrower than the actual width of the box, I'd be willing to do that (top or bottom) If it has to be bottom, I can always add "legs" on the bottom of sides 1 and 2 for stability.

If it's possible to vent outside the box, I can then have a vent with which I can retain internal bracing, as well as volume, vent would face forward.



Another benefit to the external port would be aesthetics.. when I tore the box down, outside of box got a little beat up.. tore up the 1/8" veneer or outermost layer of ply all along the outside.. I'll need a bunch of wood filler and a day with a sander to prep it for spray on finish..

Thoughts?


----------



## Lanson

Woah, lots of stuff going on again.

You can vent outside the box, but you really don't need to. The box doesn't need to be any bigger, and there's no reason to go outside of the box. Around 7 to 7.5 cubic feet, and you're still golden. One big slot port should do. The outside can always be re-worked, or you can add thin wood as a new cover for it. It would be nice to see cover boards made to match the contours of the rest of the car, and then carpeted. Use the box as a skeleton for a more "installed" setup.

What I need to know at this point before we build a model (and I plan on 3D-ing this for you) is, those handles, how deep do they intrude into the box? Do they sit flush with the 3/4" wall, or do they go further inboard?

You can build a port in the center, but you'd have to run the port short, and not go all the way to the back wall because that would divide the box. This can still be done, and done right if you want to use the "port" as a brace in the center. No problem. We can either build two slot ports and have them come from center toward BACK (but not all the way back, say about 10" back first) and then split to SIDE 1 and SIDE 2, which would serve as internal bracing as well. A little more complicated, a little more wood, but doable. 

What I'm thinking at the moment, is to leave the center brace in place, and use it as a guide to build slot ports from the center to each side, twin ports. This will give you maximum bracing, minimal re-working of the box, and really the only "cost" is more wood than a single port. But it should sound and look really good.


----------



## lust4sound

fourthmeal said:


> Woah, lots of stuff going on again.
> 
> You can vent outside the box, but you really don't need to. The box doesn't need to be any bigger, and there's no reason to go outside of the box. Around 7 to 7.5 cubic feet, and you're still golden. One big slot port should do. The outside can always be re-worked, or you can add thin wood as a new cover for it. It would be nice to see cover boards made to match the contours of the rest of the car, and then carpeted. Use the box as a skeleton for a more "installed" setup.
> 
> What I need to know at this point before we build a model (and I plan on 3D-ing this for you) is, those handles, how deep do they intrude into the box? Do they sit flush with the 3/4" wall, or do they go further inboard?
> 
> You can build a port in the center, but you'd have to run the port short, and not go all the way to the back wall because that would divide the box. This can still be done, and done right if you want to use the "port" as a brace in the center. No problem. We can either build two slot ports and have them come from center toward BACK (but not all the way back, say about 10" back first) and then split to SIDE 1 and SIDE 2, which would serve as internal bracing as well. A little more complicated, a little more wood, but doable.
> 
> What I'm thinking at the moment, is to leave the center brace in place, and use it as a guide to build slot ports from the center to each side, twin ports. This will give you maximum bracing, minimal re-working of the box, and really the only "cost" is more wood than a single port. But it should sound and look really good.


DONE.. It's settled then.. let's do it that way.. 

As for the handles I will double check, but I am almost certain they do not extend into the box.. assuming we'll need that area smooth and flush on both sides, I'll make sure to it, no problem..

I love the idea of dual ports from the center down to a pair of 90s left and right, that's 10 gauge birdshot on a flock of pigeons.. (killing more than two birds with one stone)

Ready when you are.. (can't wait!)


----------



## Lanson

If you want to get a head start, DL WinISD pro 0.7 if you haven't already, throw the specs in and then start modeling ideal ports given a slot size of 16.5" by (X), and we can fool with anything with 1000W of power or so, getting air velocity in the 30m/s range or less should be ideal. 

Fiddling with box size a bit here and there, and fiddling with the tune hz a bit should find the sweet spot. Taking a wild guess without the software around me (here at work), I'd guess 16.5 x 2.5" should be a good starting point. We'll need to also watch for port resonance, you don't want a port to resonate in the range we'll be playing. 

Once we know approximately how big (wide) that port needs to be, of course its length will end up being calculated relative to how big the box is. Now of course, the box will end up having less displacement with the port inside of it, so this becomes the "moving target", I was talking about. But it won't be hard because you can fudge a few inches here and there, and still end up good to go. Like a moving target but we're hitting a big target anyway.





lust4sound said:


> DONE.. It's settled then.. let's do it that way..
> 
> As for the handles I will double check, but I am almost certain they do not extend into the box.. assuming we'll need that area smooth and flush on both sides, I'll make sure to it, no problem..
> 
> I love the idea of dual ports from the center down to a pair of 90s left and right, that's 10 gauge birdshot on a flock of pigeons.. (killing more than two birds with one stone)
> 
> Ready when you are.. (can't wait!)


----------



## lust4sound

fourthmeal said:


> If you want to get a head start, DL WinISD pro 0.7 if you haven't already, throw the specs in and then start modeling ideal ports given a slot size of 16.5" by (X), and we can fool with anything with 1000W of power or so, getting air velocity in the 30m/s range or less should be ideal.
> 
> Fiddling with box size a bit here and there, and fiddling with the tune hz a bit should find the sweet spot. Taking a wild guess without the software around me (here at work), I'd guess 16.5 x 2.5" should be a good starting point. We'll need to also watch for port resonance, you don't want a port to resonate in the range we'll be playing.
> 
> Once we know approximately how big (wide) that port needs to be, of course its length will end up being calculated relative to how big the box is. Now of course, the box will end up having less displacement with the port inside of it, so this becomes the "moving target", I was talking about. But it won't be hard because you can fudge a few inches here and there, and still end up good to go. Like a moving target but we're hitting a big target anyway.


2- ports 16.5 x 2.5" (ish) got it..


----------



## lust4sound

I tried using the program.. I'm a bit unfamiliar with some of the features (not sure what data to input in certain areas)

Also, driver integrity is corrupt or inconsistent in their database, without correct data, aren't we farting in the wind?

Just sent JBL an email requesting all of the missing info for the Winisd database.. Hopefully they'll provide the info needed to fill in the blanks..


----------



## Lanson

lust4sound said:


> I tried using the program.. I'm a bit unfamiliar with some of the features (not sure what data to input in certain areas)
> 
> Also, driver integrity is corrupt or inconsistent in their database, without correct data, aren't we farting in the wind?
> 
> Just sent JBL an email requesting all of the missing info for the Winisd database.. Hopefully they'll provide the info needed to fill in the blanks..



You don't need every spec, most can be extrapolated (automatically) by the program.

This spec
JBL W12GTI SPECIFICATIONS Pdf Download.

and what is in WinISD are close, it is suspected the one in WinISD was actually measured and not as written in the book. I built one with the included measurements and built one with JBL's specs, and pretty much got the same result +/- a few %. Anyway, I'll just use the specs gathered from JBL here, and give you some info.

So, at first I modeled with two ports, but really it is overkill. There is nothing wrong with overkill, of course. Here's the table with two ports, all of these are well below any chuffing noises, FYI.

For 24 Hz tune, 16.5 x 1.5 x (_X) _port


Box size 8 cu ft, 24.72"
Box size 7.75 cu ft, 25.65"
Box size 7.5 cu ft, 26.64"
Box size 7.25 cu ft, 27.70"
Box size 7 cu ft, 28.84"
 
for 25 Hz tune, 16.5 x 1.5 x (_X_) port


Box size 8.0 cu ft, 22.46"
Box size 7.75 cu ft, 23.32"
Box size 7.5 cu ft, 24.23"
Box size 7.25 cu ft, 25.21"
Box size 7 cut ft, 26.26"


You can go single port if you want to, and as example of that, a 16.5 x 3 x 23.02" vent would fit an 8 cu ft box at 24 Hz. So if you want to go that route (single slot) we can re-calculate.




Oh and I'd like to point out there is a rule I'm breaking, with the 16.5" x 1.5 x (_X_) slot ports, which is the port ratio rule, most people suggest a max of 8:1 and this 16.5 x 1.5 idea here is 11:1 Basically, a port with two much ratio of height to width has the propensity to chuff. However, I still feel that even with this narrow port, you should still not be able hear it unless you are completely full-tilt at ~25Hz. The single larger port doesn't break this rule, if it matters to you. Personally, I don't think it will.




Oh and the reason I made you the table of all the sizes, those ports of course take up room themselves. Some may be in the .7 to .75 cubic foot range per port (assuming the wood that makes the the outside of the port also becomes displaced space), so my hope is you can use my calcs to then find the sweet spot.


----------



## EricP72

question for fourthmeal, i also plan to run a pair of jbl w12mk II subs, but with a 4.5 cuft vented enclosure. My question is which port design is better for sq, slotted or ported? i was under the impression a slotted port design was better than the round ports. which is better for these subs? forgive me because i never ran a vented sub setup, always sealed. and the only reason i'm going vented because i have been reading as many older threads on this sub as i can and everybody who i know has a ear has stated that with this sub, going vented , you still keep the SQ of the sealed but adds the spl and efficiency of a vented box. BTW my music taste is fusion jazz and limited rap (roots/dr.dre).


----------



## cubdenno

Something most people forget when designing ports. WE all mention chuffing but what most don't know is that above 20 M/S we are near or above 3db of port compression. This renders the port useless. You are running a leaky sealed box at that point along with the added noise/distortion that "that" leaky box is adding.

So maintaining that balance of port area under power is essential to having a bass reflex design that performs and sounds how you want it to.


----------



## Lanson

manish said:


> question for fourthmeal, i also plan to run a pair of jbl w12mk II subs, but with a 4.5 cuft vented enclosure. My question is which port design is better for sq, slotted or ported? i was under the impression a slotted port design was better than the round ports. which is better for these subs? forgive me because i never ran a vented sub setup, always sealed. and the only reason i'm going vented because i have been reading as many older threads on this sub as i can and everybody who i know has a ear has stated that with this sub, going vented , you still keep the SQ of the sealed but adds the spl and efficiency of a vented box. BTW my music taste is fusion jazz and limited rap (roots/dr.dre).


Near as I can tell, and I'm not an authority on this, there makes no difference in how the port is constructed so long as it is made large enough and rounded over enough for it to not make noise that you can hear, thus something that would take away from the music. My gut says to use a heavily flared port for best SQ, and that seems to be the agreement in home audio as well. But slot or round, either can be flared. A ported box has more group delay near the tune freq, so I'd tune very low to minimize that effect in the listening range where your ears could pick up the delay.


----------



## Lanson

cubdenno said:


> Something most people forget when designing ports. WE all mention chuffing but what most don't know is that above 20 M/S we are near or above 3db of port compression. This renders the port useless. You are running a leaky sealed box at that point along with the added noise/distortion that "that" leaky box is adding.
> 
> So maintaining that balance of port area under power is essential to having a bass reflex design that performs and sounds how you want it to.


I wasn't sure it was around 20m/s but I knew that port compression is a real thing. I thought it was around .1 Mach, which is ~34 m/s


----------



## lust4sound

Happy New Year guys! Quick update. Everything installed and very basic tune using mic supplied with Pioneer 80PRS. 

This setup has far exceeded my expectations. I'm sure the sheer size and volume of the box have much to do with the fact that I've got low end which far exceeds the output capability of my front stage... by a wide mile..

Sound is seamless, wide/tall imaging, nice detail, hits like a well balanced sledgehammer.. that's when listening to "normal" music

When I "uncork" the subs and throw some Bass Mechanik on there, bump sub level and EQ, they absolutely blow the roof off my minivan, it's absurd.. As a whole, the system for what it is, just wow..

I'm supposed to meet up with a member who happens to be local.. He's got the gear needed to optimize this setup which atm is probably operating at only 1/3 of it's actual capability..

Once it is properly tuned and I have some hard data, I'll be able to update with a bit more than "just wow"

Mannish, get it right and your ears will thank you for it.. Fouthmeal, thanks so much for all your help, it really made the difference.. 

I'm so glad no one took me up on these subs when I offered them for sale on this site.. 

THANKS FELLAS!!


----------



## lust4sound

I will update with photos and graphs when I am completely finished.. Now that my subs are rattling panels loose, I realize I'm only halfway there.. LOL


----------



## Lanson

Excellent, I'm happy the advice worked out.

Enjoy!


----------



## cubdenno

fourthmeal said:


> I wasn't sure it was around 20m/s but I knew that port compression is a real thing. I thought it was around .1 Mach, which is ~34 m/s


I have a pic I saved of a graph I got from DIYAudio I believe where it shows the compression vs port speed. It matches very closely with what John from AE told me. He said stay under 10 ideally. Realistically stay under 20 at full power. I need to find that pic!!

After taking his advice, I lost all interest in sealed enclosures. Ported and PR designs are the way I go mostly any more. Not counting Tapped and front loaded horns...


----------



## lust4sound

cubdenno said:


> I have a pic I saved of a graph I got from DIYAudio I believe where it shows the compression vs port speed. It matches very closely with what John from AE told me. He said stay under 10 ideally. Realistically stay under 20 at full power. I need to find that pic!!
> 
> After taking his advice, I lost all interest in sealed enclosures. Ported and PR designs are the way I go mostly any more. Not counting Tapped and front loaded horns...


According to Winisd, the 8cf enclosure I modelled with dual 1.5" x 16" ports topped out at 26 with 1000 watts RMS (if memory serves correct)

In my real world application, the only chuffing I'm hearing is from some of the screw holes I missed with woodglue.. FWIW, I've never heard a sealed box which provided the type of low end response I'm getting from the ported box I "rigged"


----------



## lust4sound

fourthmeal said:


> Excellent, I'm happy the advice worked out.
> 
> Enjoy!


Thanks so much! "Enjoy" is an understatement in my case.. Pie eating grin every time my rear view mirror falls off..


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## EricP72

@lust4sounds..thanks for the updates! sounds like your more than happy. And im going to take your advice and do it right. 
@fourthmeal would you be so kind to point me to a person or yourself who could design and send me a cutsheet for a sub enclosure? and i right to assume that since one sub needs 2.25cft, that 2 would would be 4.5cuft?
i think since i have no real tools yet, previous tools was stolen, i should go for the round ports as i can make them with pvc pipes and use elbows if needed. and you mentioned flares, so i should look at some premade flared ports. actually, i eed to just find a really good box builder. anybody know of one?


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## Lanson

manish said:


> @lust4sounds..thanks for the updates! sounds like your more than happy. And im going to take your advice and do it right.
> @fourthmeal would you be so kind to point me to a person or yourself who could design and send me a cutsheet for a sub enclosure? and i right to assume that since one sub needs 2.25cft, that 2 would would be 4.5cuft?
> i think since i have no real tools yet, previous tools was stolen, i should go for the round ports as i can make them with pvc pipes and use elbows if needed. and you mentioned flares, so i should look at some premade flared ports. actually, i eed to just find a really good box builder. anybody know of one?


I didn't design one in this case, we were just using WinISD Pro 0.7 to calculate stuff but I never made a 3D model of it. I don't use cutsheet programs, though. I always just make stuff up as I go, once I have a model or an idea in my head. 

If you lack the tools, best to find someone that can do it and do it right for you for sure. Not sure who to recommend in your area, might want to post something in a fresh thread so people can suggest where to go.


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## lust4sound

I came here looking for that Winisd download link, figured while I'm here I'll provide an update. 

The subs have broken in and I must say... the low end, detail and the riotous output from these 2 12s... absolutely insane! (using a smallish pair of JL 500/1 amps, 1 per sub) 

I haven't had time to meet with a friend and have everything tuned properly with O-scope, proper mics/program EQ etc. For a baseline tune, the mic provided with the Pioneer 80PRS provided surprising results, did not expect this kind of performance from that mic .. I will definitely need to tune properly, will get that done soon.. 

Thus far I'm pretty impressed by what I have.. (especially considering the fact that I'm using D class power on subs, isn't there a raging debate for A/B vs D?) I have to say, I was never a fan of JL amps till I stumbled on the 3 500/1s which I now own.. Have always LOVED their subs, am now a fan of their SUB amps.. (never got into anything mid oriented by them)

When dialed WAAAAYY down, they blend nicely with the Hertz Milles. Subs, midbass/midrange detail is pretty awesome,

For a balanced sound, by default, it keeps setting my sub section to 63Hz w 12dB slope, sub level pulled way back down to -16. It keeps setting the 6.5" Hertz Milles (mounted in doors) to 100Hz with 18dB slope. I'm assuming that huge gap between sub and midbass is it's way of compensating for cabin gain as well as the output/capability of the subs?

When I turn the sub level way up for bass music (EG: Excision "swerve" streaming through "Tidal") the sub midbass experience is absolutely incredible. Jaw dropping output, bass hits hard and fast, really tight.

When I dial the subs back for balanced listening mode and listen to "Vadrum" (through Tidal) equally impressive. While imaging not quite there, the detail tone and impact of a masterfully tuned drum-kit accompanied by a full on orchestra is incredible. Can't wait to hear the same music once it's properly tuned with imaging and EQ.

I've never heard a pair of 12s hit this hard accurate AND LOUD with only 1000 watts RMS...


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