DiyMobileAudio.com Car Stereo Forum banner

1 - 20 of 40 Posts

·
Registered
Joined
·
10 Posts
Discussion Starter #1
Hello all,

I am building a 2.53 cubic ft box for a 12" sundown x12. i am putting it in a narrow space, so i am going with an external aero port.

My question: how do i secure the external aero port to the box?


i need a port that's 46" long for 8" diameter. i was planning to route about 20" inside the box, then the remaining 26" on the outside. what parts do i need to do this?

i was thinking of mounting a pvc pipe coupling in the middle of the board of wood (where the hole is) and connecting one side to the inside of the box and the other to the outside. that way i can change lengths. how would i secure this in the box, so it doesn't gooch out either way when i am bumping?

my other option is using a 6" port, but that would put me at 28 in^2 of port diameter, which is 12 less than the required 40 in^2. in comparison, a 8" pipe puts me at 50".

please guide me either way regarding the 6 vs 8" port. the 6" requires less length.

also, how do i secure the pvc pipe in the box, mid port?

thank you
 

·
Premium Member
Joined
·
3,501 Posts
Hello all,

I am building a 2.53 cubic ft box for a 12" sundown x12. i am putting it in a narrow space, so i am going with an external aero port.

My question: how do i secure the external aero port to the box?


i need a port that's 46" long for 8" diameter. i was planning to route about 20" inside the box, then the remaining 26" on the outside. what parts do i need to do this?

i was thinking of mounting a pvc pipe coupling in the middle of the board of wood (where the hole is) and connecting one side to the inside of the box and the other to the outside. that way i can change lengths. how would i secure this in the box, so it doesn't gooch out either way when i am bumping?

my other option is using a 6" port, but that would put me at 28 in^2 of port diameter, which is 12 less than the required 40 in^2. in comparison, a 8" pipe puts me at 50".

please guide me either way regarding the 6 vs 8" port. the 6" requires less length.

also, how do i secure the pvc pipe in the box, mid port?

thank you
Why not just use an Earthquake SLAMP M12 passive radiator?
Everything will same but it is tuneable, and you avoid a big tube being in the way.
The only real valid reason against it, would be if the box was in a pickup truck bed.
 

·
Premium Member
Joined
·
3,501 Posts
How did you arrive at needing a 46" port?
Probably 25 Hz...
And an 8" pipe is massive, so it needs length... but it still probably chuffs more than a PR.

If there is ever a good excuse for a passive radiator, it is no volume for an internal port, nor and external one.
The anti chuffing, and tuning are just extras.
And the cost is a negative.

It looks like a no brainier case to me.
 

·
Registered
Joined
·
529 Posts
Use a rectangular port using box walls and wrap it around the enclosure! What your planning is just daft imo, an 8” aeroport for that length will put the mouth of the port out of phase with the driver (granted wavelengths are long, but part phase mismatching won’t help bass output!) 6” would be lots better! Even for a driver like that
 

·
Registered
Joined
·
10 Posts
Discussion Starter #7
Thank you all for the responses. For the first images, which would be inside the wood part?

I hadn't considered a passive radiator. I have seen them, but know very little about them. Do they function in place of a port? The only problem is the only place on the box for it is behind a center console so there's no room

Here are the specs for the box:


I am looking to get 6 months out of this box. I have a wood shop building me a custom box for the truck that fits 2 12's at 5.7 cu in. I don't like to tell people I am doing this, because everyone says it won't fit in a reg cab dodge, but my truck has an ample 15" of space behind the seats- the only bitch is the center console that narrows the area, but i designed the big box so it will fit if i remove the center console when installing. this will take more time to get right, given my shitty woodworking skills, so i am waiting till the fall when it's cooler outside to complete and install. the single 12" is temporary install, and it has a lonely twin that will stay in its box for a while lol.

anyway, i am thinking about a 6" port. although it is lower than the specs (sundown says 40 in^2)


by comparison, the 6" port needs 25" at 32 hz

 

·
Registered
Joined
·
2,743 Posts
WinISD modeling in recommended 2.5 ft^3 at 32 Hz yields a sharp peak of 4.1 dB at 32.9 Hz, and a wide 1 dB dip from 61 Hz to 75 Hz; 120.4 dB at 1,500 watts; 27.4 Hz F3. SQ would require substantial EQ to tame such peaky response.

8” (50.27 in^2) x 46.8” vent yields peak vent velocity of 23.6 m/s, with little or no vent compression and zero vent noise/chuffing. However, 46.8” is simply too long a vent length. Recommended vent area of 40 in^2 yields 29.7 m/s, with presumably mild vent compression and possible/mild chuffing. 6” (28.27 in^2) x 25.3” vent yields 42.1 m/s, with presumably moderate vent compression and significant audible chuffing. However, chuffing could be eliminated by shaping a pair of adequately flared ends for the 6” PVC tube.

A smaller box would flatten response while exacerbating vent challenges. Conversely, larger box would help with vent challenges at the expense of even peakier response. Such is the nature of a subwoofer that seems to have been optimized for highest ~33 Hz output in least cabinet volume.

EDIT: The above modeling results are for the Sundown X 12 D2 version.
 

·
Registered
Joined
·
2,743 Posts
This 6" flared port would be ideal if you can make it work for your application.
https://www.parts-express.com/precision-port-6-flared-port-tube-kit--268-354

You'll need to add an extension (as the above port is 17"):
https://www.parts-express.com/precision-port-psp-6tb-6-dia-x-12-long-port-tube--268-390

...and a connecting ring or two:
https://www.parts-express.com/precision-port-psp-6rg-6-connecting-ring-for-port-tube--268-388

Flared vents need to be a bit longer than non-flared, so you'll want to use this Precision Sound calculator to determine proper flared vent length:
Products Menu
 

·
Registered
Joined
·
6,301 Posts
WinISD modeling in recommended 2.5 ft^3 at 32 Hz yields a sharp peak of 4.1 dB at 32.9 Hz, and a wide 1 dB dip from 61 Hz to 75 Hz; 120.4 dB at 1,500 watts; 27.4 Hz F3. SQ would require substantial EQ to tame such peaky response.

8” (50.27 in^2) x 46.8” vent yields peak vent velocity of 23.6 m/s, with little or no vent compression and zero vent noise/chuffing. However, 46.8” is simply too long a vent length. Recommended vent area of 40 in^2 yields 29.7 m/s, with presumably mild vent compression and possible/mild chuffing. 6” (28.27 in^2) x 25.3” vent yields 42.1 m/s, with presumably moderate vent compression and significant audible chuffing. However, chuffing could be eliminated by shaping a pair of adequately flared ends for the 6” PVC tube.

A smaller box would flatten response while exacerbating vent challenges. Conversely, larger box would help with vent challenges at the expense of even peakier response. Such is the nature of a subwoofer that seems to have been optimized for highest ~33 Hz output in least cabinet volume.

EDIT: The above modeling results are for the Sundown X 12 D2 version.
This is what i was getting at with my question. Your vent choice of 48" was way to long for practical use. Plus finding room inside for a 8" aeroport would be a challenge. I agree with trying to go to a single 6" port.
 

·
Registered
Joined
·
10 Posts
Discussion Starter #15
had to get 5 posts to post images..

This 6" flared port would be ideal if you can make it work for your application.
https://www.parts-express.com/precision-port-6-flared-port-tube-kit--268-354

You'll need to add an extension (as the above port is 17"):
https://www.parts-express.com/precision-port-psp-6tb-6-dia-x-12-long-port-tube--268-390

...and a connecting ring or two:
https://www.parts-express.com/precision-port-psp-6rg-6-connecting-ring-for-port-tube--268-388

Flared vents need to be a bit longer than non-flared, so you'll want to use this Precision Sound calculator to determine proper flared vent length:
Products Menu
Thank you very much. I didn't know you could buy these already made. I thought i had to make this myself. This looks like a great option. I am attaching a sketch up photo of the box. it looks like i will have to run the port slightly outside of the box, as there is only ~22" before the internal port flare would hit the woofer's coil.






would you recommend putting a connector in the hole in the wood, so i could adjust the port length?

does it matter if the port runs in the top, middle or bottom section of the box?


also, i just realized, the volume of the box is slightly higher at 2.78 cu ft. due to the way i cut the wood, the top and bottom boards will be between the baffles, giving it an extra 1.5" from the wood thickness (.75" x 2, top and bottom). this will give me a recommended flared port length of 23.377805305755395 (lol)






This is what i was getting at with my question. Your vent choice of 48" was way to long for practical use. Plus finding room inside for a 8" aeroport would be a challenge. I agree with trying to go to a single 6" port.
thanks.

WinISD modeling in recommended 2.5 ft^3 at 32 Hz yields a sharp peak of 4.1 dB at 32.9 Hz, and a wide 1 dB dip from 61 Hz to 75 Hz; 120.4 dB at 1,500 watts; 27.4 Hz F3. SQ would require substantial EQ to tame such peaky response.

8” (50.27 in^2) x 46.8” vent yields peak vent velocity of 23.6 m/s, with little or no vent compression and zero vent noise/chuffing. However, 46.8” is simply too long a vent length. Recommended vent area of 40 in^2 yields 29.7 m/s, with presumably mild vent compression and possible/mild chuffing. 6” (28.27 in^2) x 25.3” vent yields 42.1 m/s, with presumably moderate vent compression and significant audible chuffing. However, chuffing could be eliminated by shaping a pair of adequately flared ends for the 6” PVC tube.

A smaller box would flatten response while exacerbating vent challenges. Conversely, larger box would help with vent challenges at the expense of even peakier response. Such is the nature of a subwoofer that seems to have been optimized for highest ~33 Hz output in least cabinet volume.

EDIT: The above modeling results are for the Sundown X 12 D2 version.
thank you. i had to read this several times to figure out everything. looks like we want to stay in the 32-33 hz frequency range. it will be the 4 ohm speaker with a 1800 watt amp.
 

·
Registered
Joined
·
2,743 Posts
I use packing tape and connector rings to temporarily assemble vent tube at various lengths until I hear what I like (for this process, it might help to have an extra tube or two on hand, and a couple extra connector rings). Then you can use ABS glue to permanently assemble the final length. In any case, it is of paramount importance to achieve an airtight seal between the vent and enclosure, and within the vent itself (EDIT: just do the best you can, by whatever means, to temporarily seal the tube to the box during the experimentation process).

Vent from front, rear, top, bottom …so long as there’s plenty of room for unobstructed air movement.

As for the 32-33 Hz frequency range, you’ll arrive at what’s best for you as you play with various vent lengths.
 

·
Premium Member
Joined
·
3,501 Posts
...
I hadn't considered a passive radiator. I have seen them, but know very little about them. Do they function in place of a port? The only problem is the only place on the box for it is behind a center console so there's no room
...
I would suggest to review your install and box thoughts.
External ports looks like a leaf blower or an overweight armadillo.

And whether external or internal it is going to be at least ~1 ft^3 of volume based upon their specs.

There is only 1 way to zero out the need for extra volume and still have the box a 4th order box.

It is your call.
 

·
Registered
Joined
·
529 Posts
I have been thinking, your enclosure has x amount of port inside the enclosure which will take up space in the enclosure and raise tuning which you don’t seem to have allowed for, bass box pro works this out for you to a degree, but still can’t utilise half in/half out ports unless you add displacement on top, either way it’s not gonna be tuned to 32hz unless you take some out of the box for the inner

You were initially speaking of 20” of 8” pipe inside the enclosure which would take up over 1 cubic foot I’d think! Just doesn’t add up
 

·
Registered
Joined
·
6,301 Posts
exactly, you need to make sure when making your 2.5cft box that you add to the overall size the amount of space the port will consume. so its 2.5 PLUS port volume when building.

Have you considered doing a slot port?
 

·
Registered
Joined
·
2,743 Posts
I have been thinking, your enclosure has x amount of port inside the enclosure which will take up space in the enclosure and raise tuning which you don’t seem to have allowed for, bass box pro works this out for you to a degree, but still can’t utilise half in/half out ports unless you add displacement on top, either way it’s not gonna be tuned to 32hz unless you take some out of the box for the inner

You were initially speaking of 20” of 8” pipe inside the enclosure which would take up over 1 cubic foot I’d think! Just doesn’t add up
Good catch. I hadn't payed much attention to the cabinet dims, and simply assumed that the OP's 2.5 ft^3 was net volume. In hindsight, it's glaringly obvious that such prodigious vent volume had not been taken into account.
 
1 - 20 of 40 Posts
Top