# How to properly build a ported enclosure?



## Tbagg

I have always used sealed sub enclosures for my car audio set ups. I’ve always thought sealed enclosures sound better, and some may agree. But when I started to search this forum on ported enclosures in an effort to educate myself on the subject, I have found that some pretty smart and talented guys (Chad, Dr. Telepathy, et. alt. are you listening?) argue that ported enclosures, if done right, can sound just as good as sealed enclosures. 

As I think about it, I’m not sure I’ve ever heard a properly designed and constructed ported or vented enclosure. So perhaps my initial opinion that sealed enclosures sound better was a bit premature and misconstrued. If this is true, I may have been ignorant of proper sub enclosures for the past 15 years!

So, to find out for myself, I have decided to build a few test enclosures to determine the enclosure type I should build for my current project. My plan is to build two simple MDF boxes, one sealed and the other ported. Both specs will be built to the manufactures recommendations. I will use the exact same sub and amp to test both enclosures. Sounds easy enough, right?

The argument for great sounding ported enclosures always includes a key phrase: ...If the ported enclosure is built right... Well here comes my question. How do I correctly design and build a ported enclosure? The manufactures instructions make it seem like it is as easy as building a larger sealed enclosure with a round port of a certain size and length cut into and sealed to the enclosure. Is it really that easy? From my research (using the search function on this forum) I have learned that pvc ports are fine, and the port can be inside the box or outside the box, as long and the port is sealed to the box.

I am looking for basic ported enclosure design and construction tips. Should I follow the manufactures ported enclosure design provided in the owners manual? Should I ask someone smarter than me to design a ported enclosure with their fancy pants computer program? Is building a ported enclosure as easy as cramming a pvc pipe of certain diameter and length into a sealed enclosure? Do I need flared port ends?

BTW, the sub in question is a 10” Rockford Fosgate P3 4 ohm DVC powered by the fifth channel of a Soundstream REF 705s (300 watts @ 2 ohms). The setup will be going into a 20’ Crownline boat.

Thanks in advance.


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## kappa546

if the manual includes T/S parameters, you can plug those into winisd and it'll basically design it for you or you can ask someone to help you with that. if you dont have the t/s then i would go with the recommended enclosure in the manual. It's true that ported enclosure can sound very good but eq is usually necessary to eliminate peaks in FR.


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## backwoods

The enclosure is more driver dependent, but I'd take the ported if feasible everytime.

Search around on here for some posts by audionutz, I believe it was, that really gives a good run down on properly built ported enclosures. 

Simple things, like good internal bracing, using insulation along the interior walls....etc.


*edit*

Here's a good thread for you...

http://www.diymobileaudio.com/forum/showthread.php?t=11192&highlight=ported+enclosure


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## Oliver

Tune low 25Hz-29Hz, for a boat , I would definately go ported !

Slot port is fine , flaring the ends or buying some flared end pieces will lessen the chuffing sound of the air at high output.


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## Fast1one

I wouldn't bother porting too low in a boat, unless it is sealed. Without pressurizing the cabin, anything below 40-50hz will become unpronounced and roll off quickly...


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## chad

Fast1one said:


> I wouldn't bother porting too low in a boat, unless it is sealed. Without pressurizing the cabin, anything below 40-50hz will become unpronounced and roll off quickly...


Exactly, I'd forget anything below 40 and go for efficiency.


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## Oliver

Tbagg said:


> BTW, the sub in question is a 10” Rockford Fosgate P3 4 ohm DVC powered by the fifth channel of a Soundstream REF 705s (300 watts @ 2 ohms). The setup will be going into a 20’ Crownline boat.
> 
> Thanks in advance.


He is interested in SQ ^^^^^^^[not output], unless I am missing my guess!


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## khail19

a$$hole said:


> He is interested in SQ ^^^^^^^[not output], unless I am missing my guess!


SQ is pretty hard to accomplish on a boat. Way harder than in a car even. You won't get much response below 40hz because you are out in the open air, not in an enclosed space like a car.


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## Oliver

khail19 said:


> SQ is pretty hard to accomplish on a boat. Way harder than in a car even. You won't get much response below 40hz because you are out in the open air, not in an enclosed space like a car.


So, do you think he is going for mad deebeez with that ten  

Get a digital designs port it to 40 hz and put some powa to it !


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## Tbagg

Thanks for the replies.

Although I typically go for SQ, it's silly to attempt that sort of install in a boat. 

I was going to explain this in my original post, but I figured I was long winded enough: The reason why I am interested in a ported enclosure is for output. No I am not going for grazy DB's in a boat with a single 10" and 300 watts. My thought was I only have (1) 10" and only 300 watts. I need to get all I can out of this set up for the sub to even make a difference. Further more, 300 watts is on the low side for this sub, and from what I have seen (read on other threads) when you are limited on power, ported is a good option. This will be a very simple set up, so there will be no eq (unless I can find that old PPI unit in the bottom of my closet) It's a boat, so there is zero opportunity for cabin gain.

Thanks again for your help.


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## khail19

a$$hole said:


> So, do you think he is going for mad deebeez with that ten


In a way, yes. He needs efficiency (more "deebeez"  ) in the higher sub bass range, so a fairly high tuned box will make better use of the power available.


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## Tbagg

khail19 said:


> In a way, yes. He needs efficiency (more "deebeez"  ) in the higher sub bass range, so a fairly high tuned box will make better use of the power available.


You've got it, my motivation for a ported enclosure is for efficiency. 

I don't have any computer programs that can help me design this enclosure. I don't understand how to tune a ported enclosure. The last thing I want this thread to turn into is "buy this sub and amp", or "does sealed sound better than ported" (god knows there is enough of those topics discussed already).

My intent is to build both enclosures and choose a style and sound that works best for my application. What I need help with are tips and tricks to building ported enclosures. My point of view is that I want to give a ported enclosure a chance and forget about my thoughts and opinions I've had for the last 15 years. But to do this, I need to design and build a proper ported enclosure. 

I don't know things like:
What do flared ports do? (which I think was already answered)
Is PVC pipe a suitable port material?
Is a square vent better than a round port?
Can I turn a port 90 degrees; if I can, how does that effect my overall port length?
How do I tune a ported enclosure?

I'm sure these are very basic questions for most of you. 

When I have time, I will read the link that was posted early in this thread, perhaps that will answer most of my questions.

Any additional pointers is much appriciated. Thanks to all.


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## Oliver

If you search here

http://mobile.jlaudio.com/support_pages.php?page_id=141

Download a program called WINISD [free box building program ].

You'll not only end up with a vented box ,you'll understand it too!


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## khail19

Tbagg said:


> I don't know things like:
> What do flared ports do? (which I think was already answered)
> The flare helps cut down on port noise.
> Is PVC pipe a suitable port material?
> Yes, PVC or ABS pipe works just fine.
> Is a square vent better than a round port?
> Both have their applications, one is not better than the other.
> Can I turn a port 90 degrees; if I can, how does that effect my overall port length?
> Yes, measure your port length down the center of the port.
> How do I tune a ported enclosure?
> The size of the box, and the length and diameter (or area) of the port determine the tuning frequency.


Hopefully that helps you out a bit.


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## Tbagg

Perfect, thanks for the great info.

I will download the software from JL Audio and get to know it.

Any other tips for a ported or vented enclosure for a RF P3 4DVC with 300 watts in a boat? It was mentioned earlier that i shouldn't tune the enclosure below 40 hz due to the lack of cabin gain. If I listen to a compete variety of music, what should I tune the enclosure to? Other speakers involoved include Polk or Kicker marine grade 6.5" coax. with 50 watts each from a Soundstream REF 705s amp.

Thanks again


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## Fellippe

The short and simple answer is that YES, vented enclosures can equal sealed enclosures if done properly. You'll get sealed SQ with more SPL....a nice win, win for all at the expense of some room. 

You start off with science (t/s parameters) and you finish up with art (playing around with the final enclosure parameters like volume and tuning frequency). This is how the best designs are done...science alone will not get you there, 99% of the time...that 1% being luck. 

Now I'm quoting a golden ear purist here.....a run of the mill manufacturer's recommendations might do the job for some.


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## Fellippe

Tbagg said:


> Perfect, thanks for the great info.
> 
> I will download the software from JL Audio and get to know it.
> 
> Any other tips for a ported or vented enclosure for a RF P3 4DVC with 300 watts in a boat? It was mentioned earlier that i shouldn't tune the enclosure below 40 hz due to the lack of cabin gain. If I listen to a compete variety of music, what should I tune the enclosure to? Other speakers involoved include Polk or Kicker marine grade 6.5" coax. with 50 watts each from a Soundstream REF 705s amp.
> 
> Thanks again


You still need to take into account RIPPLE...I gotta scan the old school car audio mag article on accounting for ripple. 

Vented enclosures being the fussy bitches they are cannot be tuned too high or too low just for the hell of it. 

It's rare to see a 10" sub tuned above 40 hz....most common is 32-35 hz...occasionally sub 30. 

Get the #s out....I know there's plenty on here ready to run a simulation for you. Try it out and see what happens.


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## Tbagg

a$$hole said:


> If you search here
> 
> http://mobile.jlaudio.com/support_pages.php?page_id=141
> 
> Download a program called WINISD [free box building program ].
> 
> You'll not only end up with a vented box ,you'll understand it too!


Thanks for the link. Lots of good info there, but couldn't find the WINISD.

I'm sure a google search will turn up something.


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## Tbagg

Fellippe said:


> You still need to take into account RIPPLE...I gotta scan the old school car audio mag article on accounting for ripple.
> 
> Vented enclosures being the fussy bitches they are cannot be tuned too high or too low just for the hell of it.
> 
> It's rare to see a 10" sub tuned above 40 hz....most common is 32-35 hz...occasionally sub 30.
> 
> Get the #s out....I know there's plenty on here ready to run a simulation for you. Try it out and see what happens.


I would appricate anyone that wouldn't mind taking the time to run a simulation or help design a ported enclosure. I'll be happy to provide the information needed for such a simulation or box building computer programs. 

I just don't know the variables that I need to provide.


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## chad

http://www.rockfordfosgate.com/rftech/library/2007/5_Subwoofers/P3D410_revA-TS.pdf

Fs (Hz): 29.0
Re (Ohms): 6.60
Le (mH): 5.1
Qts: 0.55
Qes: 0.60
Qms: 6.00
Cms (m/N): 0.18
Vas (L): 24.5
Mms (g): 164.6
Mmd (g): 161.5
Rms (kg/s): 5.0
Airload (g): 3.1
No (%): 0.1
SPL (dB - 1W/1M): 82.0
BL (T*M): 18.4
*Xmax10 (mm): 16.2
Sd (cm2): 310
EBP: 48
Krm (mOhms): 3.03
Erm: 1.08
Kxm (mH): 177.3
Exm: 0.59
Rem (Ohms): 38.32

Rockford's box does not look too bad, it's smallish and tuned arund 40, it does have a hump though.

I'm out of time to model it up now so I'll try tomorrow. Any reason to pick a shallow mount driver? Are you out of space? How much room do you have to work with?


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## Tbagg

I didn't choose the shallow mount version of the P3. Mine came with all the meat! 

I have the P3D410: 

http://www.rockfordfosgate.com/prod...y_id=11&item_id=108287&locale=en_US&p_status=


I think you may be refering to the P3*S*D410

Thanks for your willingness to help!


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## khail19

The PDF and T/S specs that chad posted are for the non-shallow mount version. I don't know what made him think that was the shallow P3. The factory enclosure recommendation is 1.4 cubes tuned to 40 hz.

Hopefully, someone that's good with WINISD can model that up and see what the most efficient enclosure would be.


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## Oliver

1 possibility:

http://www.subwoofertools.com/forum...Vd=.05&NumW=1&Vb=1.4&Fb=35&Qts=&Vas=&Fs=&CE=0

1.4 cu ft.

Port Width: 1.25 inches 
Port Area: 13.125 Square Inches 
Port Length: 17.5 inches 

External Dimensions: 20 wide x 12 tall x 16.25 deep.


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## Tbagg

Port Width: 1.25 inches 
Port Area: 13.125 Square Inches 
Port Length: 17.5 inches 

External Dimensions: 20 wide x 12 tall x 16.25 deep.[/QUOTE]

Thanks for the suggestion. This would probably work well for my test enclosure, however, my final enclosure that will be installed in my boat, whether it be sealed or ported, will need to be much shallower than 16.25". I assume as long as I keep the port area and overall port length as well as internal volume of the box the same, my enclosure can be whatever porportions I want it to be, correct?


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## nstereo

Tbagg, you are correct. As long as you keep the same internal volume, and the same overall port length and diameter you should be fine! I realize it's been a little while since your last reply? Did you ever come to a decision?


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## Tbagg

Thanks for the reply.
For that application, I went with a sealed enclosure to save space. However, I will be doing a RE Audio SE12 ported for a friend in a few weeks. Looking forward to it!


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