# Help with 8w7 Custom Ported Enclosure



## TypeR (Apr 28, 2011)

I was hoping to get some help designing a custom ported box for a single 8W7 being powered by a HD900/5.
I am currently running it in the JL recommended sealed box, but I'd like to get some more kick out of it. The only issue is my trunk space is fairly limited and I would like to keep the weight of the box to a minimum. I would rather do a custom round port than the JL spec'd slot vented enclosure to help keep the size/weight down.
Anyone have some box design they'd like to share, or help me with designing one?


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## TypeR (Apr 28, 2011)

Forgot to specify that I'd like to use an aeroport


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## The Baron Groog (Mar 15, 2010)

Ok, how much space can you give up to the box and what response would you like?

Optimum in bbpro is coming up as 1.784cf with a 4" ID port 39.87" long, tuned to 23.44Hz


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## [email protected] (Jun 12, 2008)

In the recommended 1 cube box, that 8 is awesome. I dont see a need for anything bigger. I know there is a seller on Ebay selling them for under 100 shipped, built to JL's specs. It has a slot port.


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## The Baron Groog (Mar 15, 2010)

What's the JL enclosure tuning? I'll model them both and post the response graphs


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## [email protected] (Jun 12, 2008)

The Baron Groog said:


> What's the JL enclosure tuning? I'll model them both and post the response graphs


34.33hz, 1 cube net interior

8W7AE-3 - Car Audio - Subwoofer Drivers - W7AE - JL Audio


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## TypeR (Apr 28, 2011)

Thanks, I'm curious to see the results.
I would ideally like to keep the box at the 1 cube net to save on space/weight and I would like to keep the aeroport internal to the box, so the port length has to be kept at a minimum.
I used the port calculator on PSE's website on got a port length of 6.7" with a 2" diameter port. Is that a good match for the 8W7?
Products Menu

Some other questions:
-What is the best sub/port position?
-Is it better to have the sub facing the back seat and the port towards the trunk? (trunk in a compact car)


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## The Baron Groog (Mar 15, 2010)

Right, modeled the JL enlcosure, as per the dimensions they list on their site-this does not give a 1cf net volume or a 34.33Hz tune as they state-that is the light blue trace on the graph below. gross vol 1.214cf

The orange line is a 1cf net volume enclosure, with a 34.34Hz tune-close enough to what they describe the recommended to be. gross vol 1.417cf

The green line is BBpro's optimum, much flater and will give better results in a hatch back. gross vol 1.638cf

A 2" ID port will start chuffing at 65wrms, so a pointless exercise.


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## TypeR (Apr 28, 2011)

Cool thanks. I'll see what I can make work in my trunk. Couldn't I just use 2 of the 2" ports to get the same flow as a 3" port? Unfortunately I am stuck with putting the port of the shallow dimension of the box.


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## The Baron Groog (Mar 15, 2010)

2x 2" ports will see you chuffing at around 250wrms


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## minbari (Mar 3, 2011)

TypeR said:


> Cool thanks. I'll see what I can make work in my trunk. Couldn't I just use 2 of the 2" ports to get the same flow as a 3" port? Unfortunately I am stuck with putting the port of the shallow dimension of the box.


also dont forget that (2) 2" ports are NOT going to be the same length as (1) 2" port. both 2" ports will be significantly longer.


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## Richv72 (May 11, 2012)

Im getting 7.065 cu inches for a 3 inch port and only 6.28 cubic inches for 2 2" ports. Is that correct?


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## TypeR (Apr 28, 2011)

I just got bassbox pro6 and stated playing around with it. 
I got a Vb of 1.5 cu ft and a port length of 22.85" for a 3" diameter vent. (183.4 cu in. of port volume)
I have to take some measurements in my trunk to make sure it's going to fit where I want against the back seats. 
**I will have to put a 90 elbow in the port to make it fit in the box...will that make it chuff more? I plan on flaring both ends...


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## The Baron Groog (Mar 15, 2010)

The elbow shouldn't cause any chuffing


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## smgreen20 (Oct 13, 2006)

Truck: 05 Dodge Dakota
Sub: JL 8W7, 1 cf ported, (net to JLs specs), 250 watts 

I was highly impressed with an 8 off of 250 watts. Tight and loud as hell. Sounded like a 12.
I despise JL, but this I would own this little bugger.


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## TypeR (Apr 28, 2011)

Here's my first proto design. Space is pretty tight to use that 3" port with the 1.616 cu ft.
The added flares of the aeroport will make the end of the port pretty close to the sub. I might play around with the box size a bit more...


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## The Baron Groog (Mar 15, 2010)

Looks good.

I'd have the sub and the port exit on the same level as each other, that way the port inside the enclosure can go diagonally, will give you a little more length to play with and better clearance of the driver.

Excuse my special needs sketch:


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## TypeR (Apr 28, 2011)

Cool, I'll look into that. I'm thinking of buying a PVC pipe and heating it up and flaring the ends. Might be a bit tricky to flare on a diagonal, but I'll see how it all fits in Solidworks.


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## The Baron Groog (Mar 15, 2010)

What are the gross dimensions of your enclosure? I'll play with the set up in bbpro


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## TypeR (Apr 28, 2011)

Vb is 1.51 cu ft. Total is 1.616 cu ft. Internal dims are 11" tall x 25.5" wide x 10" deep.
I am considering slanting the back face to get more useable volume against the rear seats and gain a bit more room for the port.


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## The Baron Groog (Mar 15, 2010)

Ok, modeled it with your spec.

BBpro is showing port noise on 300wrms if you don't heavily stuff the box, stuff it and you'll be fine.

F3 24.09Hz
FB 23.13Hz

Get a subsonic on it @ 20Hz


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## TypeR (Apr 28, 2011)

Ok, The HD900/5 has a "infrasonic sub filter" at 30Hz that prevents over excursion. The manual says to turn it on for ported boxes and leave it off for sealed.


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## The Baron Groog (Mar 15, 2010)

All good then


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## TypeR (Apr 28, 2011)

I think I've pretty much got my design finalized. I had to shrink it down a little bit to get the fit right in my trunk:
Vb is 1.25 cu ft
In BB Pro internal dims are:
A-11 B-24.5 C-10.2 D-7.253 E-11.39 G-105 H-75

It got slightly more "peaky" with this design, but not by much. The flared ports are still going to be a tight fit but I think I can make it work.


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## The Baron Groog (Mar 15, 2010)

What length port are you using? Sticking with 3" ID?


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## TypeR (Apr 28, 2011)

Yeah that's the 3" ID port still. Port length came out to 23.87". I hit the "suggest Fb" button and it gave me 25.24 Hz.


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## Oscar (Jun 20, 2010)

you can reduce port length significantly by using a slot port that uses 3-enclosure walls as the port walls. 40% reduction in port length. Then just "L" it around the back, and you can use an actual port area that won't make the woofer loathe you.


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## The Baron Groog (Mar 15, 2010)

ok, I get slightly different-have you got the driver volume included? What have you got the port material thickness set as? Also did you note a bit of port noise on 300wrms?


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## beerdrnkr (Apr 18, 2007)

I'm about to install 2 JL Audio 8w7's. Don't mean to thread jack but would either of you mind designing a nice ported enclosure for me? 

I have a hatchback with 42"w x 16 1/2"h x 13" bottom depth x 10" top depth. Any help is appreciated. Once again sorry to threadjack.


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## TypeR (Apr 28, 2011)

Oscar said:


> you can reduce port length significantly by using a slot port that uses 3-enclosure walls as the port walls. 40% reduction in port length. Then just "L" it around the back, and you can use an actual port area that won't make the woofer loathe you.


I"ll take a look at that. The height and depth of my design are pretty specific to my trunk, so I'll see what the program comes up with.




The Baron Groog said:


> ok, I get slightly different-have you got the driver volume included? What have you got the port material thickness set as? Also did you note a bit of port noise on 300wrms?


You are correct! I forgot the driver volume. Vb is 1.25 and total is now 1.429 cu ft - is that closer now? Port thickness is 1/8" wall, so 3.25" OD of pipe. Is port noise anything above 35 m/s where the graph cuts off?


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## The Baron Groog (Mar 15, 2010)

beerdrnkr said:


> I'm about to install 2 JL Audio 8w7's. Don't mean to thread jack but would either of you mind designing a nice ported enclosure for me?
> 
> I have a hatchback with 42"w x 16 1/2"h x 13" bottom depth x 10" top depth. Any help is appreciated. Once again sorry to threadjack.


Keep those dimensions, slot vent made out of 1/2" MDF, same for walls, vent 15"H x 1.5"W x 40.61" long.

F3 26.84Hz, no vent noise on up to 1000wrms (didn't check higher, but presumed 1000wrms would be enough)

Nice flat response, if you have the driver displacements I'll include that in the design-will change the tune slightly.


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## The Baron Groog (Mar 15, 2010)

TypeR said:


> You are correct! I forgot the driver volume. Vb is 1.25 and total is now 1.429 cu ft - is that closer now? Port thickness is 1/8" wall, so 3.25" OD of pipe. Is port noise anything above 35 m/s where the graph cuts off?


I'll check-what is the driver displacement?

Yup, port noise is the shaded curve over 35m/s


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## TypeR (Apr 28, 2011)

Driver displacement for the 8W7 is 0.06 cu ft. 
I might be ok for port noise because I usually have the volume at 50% and that's plenty loud for me. I am wanting to switch from a sealed to ported box to get more lower frequency punch.
Having a pipe port is a bit of a pain, but I would really like to have the rear of the box angled, so a slot port won't really work...


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## The Baron Groog (Mar 15, 2010)

This will defo give you more low end

Slot will work with the slanted rear, bit harder to design and harder to get the same response as the material thickness eats into box volume.

Re-modled with the driver displacement:
FB 25.28Hz
F3 23.4Hz

No port noise on 300w


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## TypeR (Apr 28, 2011)

Excellent, thanks for all your help. Definitely learned a lot!
I'm going to start building on the weekend and I'll post some pics.


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## beerdrnkr (Apr 18, 2007)

The Baron Groog said:


> Keep those dimensions, slot vent made out of 1/2" MDF, same for walls, vent 15"H x 1.5"W x 40.61" long.
> 
> F3 26.84Hz, no vent noise on up to 1000wrms (didn't check higher, but presumed 1000wrms would be enough)
> 
> Nice flat response, if you have the driver displacements I'll include that in the design-will change the tune slightly.


I think u saw on the other post, driver displacement is .006 and they will be receiving about 700wrms each. Is there anyway u can pm me a design? I'm having a shop build my box and don't trust them to go through that type of effort, they'll probably just go with jl specs. I can send u some funds through paypal for your help. Thanks


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## The Baron Groog (Mar 15, 2010)

Ok, re-modeled with the driver displacement, keep the dimensions you posted, change the port length to 36.98"

Fb 24.25Hz
F3 22.37Hz

Subsonic @ 20-25Hz (shows over excursion at 21Hz)

No fee


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## beerdrnkr (Apr 18, 2007)

The Baron Groog said:


> Ok, re-modeled with the driver displacement, keep the dimensions you posted, change the port length to 36.98"
> 
> Fb 24.25Hz
> F3 22.37Hz
> ...


AWESOME! Thanks I appreciate it.


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## The Baron Groog (Mar 15, 2010)

No worries, I'll grab a beer next time I'm in San Diego


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## X on 22s (Oct 26, 2007)

I just did a box for a 8w7.


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## TypeR (Apr 28, 2011)

So I began construction - got all the pieces of the box cut and bought my ghetto plumbers 3" port. I decided to calculate the internal volume of the port on Bassbox pro to double check. It came out to 2.6 L. I had a feeling the elbow that I modeled in Solidworks was a bit different that what I actually bought, so I decided to fill the pipe I bought with 2.6L of water and see where it came up to. The length I modeled it at was way off, so the port is actually much shorter because the elbow has more internal volume than I thought. So this is what it's going to look like:


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## TypeR (Apr 28, 2011)

DONE. Sounds exactly as I was hoping...gets nice and low with some kick. Turned it up a bit and it was much louder than my last sealed box and didn't have any port chuff. Fits nice and tight against the seats so now I can get my hockey bag in.


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## The Baron Groog (Mar 15, 2010)

Great work-wish my enclosure building skills wereon that level, need to get some more practice in


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