Number of Ports and Firing Direction for Enclosure. (For Boat)

[funkyab 10+ year member]

Hi,

Sorry for the long post!

Before I start cutting my port holes I wanted to double check to see if I am doing it properly.

I am building 2 wedge type enclosures, each housing one Type R dual 4ohm running at 2 ohms.

This is the style enclosure I am building:

http://www.the12volt.com/images2/wedwdh2_.gif (sorry for not being able to paste the image)

My dimensions are to be

Width =18"

Height 1= 19"

Height 2=6"

Depth=24"

This will put be at appx. 2.5 cubes

As the consensus around the forum seems to be 2.5 cubes tuned at 32hz this is what I am after.

I am putting 450rms on each speaker (I know, some say to put more but for this season I am already over invested)

I am using 4" precision ports for my porting.

When I plug my numbers into the calculator at precision port, http://www.psp-inc.com/

I get the formula that by using one port, my length needs to be 11.30"; by using two ports my length needs to be 24.53"

Does this mean that by using two ports, EACH port needs to be 24.53" or total port length needs to be 24.53" so each port would be half of that?

Would it be better to use one port or two ports on each single enclosure?

On to firing direction.

The boxes will sit in my engine compartment on each side of the engine.

The box will be oriented as it is in the picture of the wedge.

I can only fire either out of the front of the box which is the angle side where the woofer will be placed or out of the back side (height 1).

From the front side of the box to the rear seat I have approximately 15" of space.

From the rear of the box to the back of the hull of the boat I have approximately 18" inches of space.

Essentially,

How many ports and where to fire them?

Thanks so much for the help

A

Click to read more...

 

[wesl56 10+ year member]

one 4" port is enough... it should be around ~10-11" long

and if you wanted 2, then each would need to be super long, like 24" cause thats just too much port area... so just use one per box

and this is a vdrive boat? or i/o? and they're gonna be inside the enclsoed engine compartment? can you mount the sub on the "height 1" side and have that facing the front of the boat?

 

[funkyab 10+ year member]

one 4" port is enough... it should be around ~10-11" long
and if you wanted 2, then each would need to be super long, like 24" cause thats just too much port area... so just use one per box

and this is a vdrive boat? or i/o? and they're gonna be inside the enclsoed engine compartment? can you mount the sub on the "height 1" side and have that facing the front of the boat?

It is an I/O and they will be on the inside of the engine compartment.

I need to mount the sub on the angle side because if i dont,, the sub will fire directly into the back of the seat with only 1 or 2 inches between them. Too close. By mounting it on the angle, i will have appx. 15 inches of space between the sub and the seat.

So if I only need one port, the question is whether to fire it at the angle on the same plane as the sub, or out the back!

 

[wesl56 10+ year member]

same direction as the sub... that boat should pound on the water //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif

 

[funkyab 10+ year member]

THANKS SO MUCH!!

ANYONE HAVE ANY COUNTERS TO THE CONSENSUS??

"one 4" port for each sub. 2.5cubes tuned at 32htz, 450 rms for each individual unit"

I do think it will pound. Although I only have 450rms at each sub,, it is very clean.

I will post my results, if there is no descent, after i do a quality control.

Please post any descent, to help fill my brain and help me before i start cutting on a fantastic marine project!

-------------------------------------------------------------------

Because it is related, Ill post my experience here and will move it to the right forum upon my inspection.

After fighting tooth and nail to find someone that would either reman or build me a new alternator for the boat, i found myself against a wall.

Of course I spoke with mean-green, ohio, and many other places mentioned on this forum 90% said they could not F^&k with my prestolite alternator and those that could, wanted 700-1000 dollars!! Well, I cant get in that ball park.

After 3 days of calls all over the U.S., I found a place that was sooo attentive and so capapable, they had the specs for my prestolite stock, asked me details such as the diameter of my crank shaft pully, diameter of my alt pully, what my rmp at idle is. I gave them all the info and they agreed to custom build me an alt that will do 120 at IDLE. I was concerned because they promised me a one wire Alt and i have a secondary wire. They asked me to test the voltage at dead as well as at ignition. I gave them the results, and they added the necessary switched terminal!! A very custom job for a VERY tricky alt.

Absolutely fantastic!!!

PRICE???

You would not believe it!!

190 shipped!!

Although i dont have it in hand, I feel good about these guys and they emphasize that they specialize in special requests, especially high amps at idle!

Il keep everyone posted.

A

 

[AlpineUser 10+ year member]

how many amps are u runing 1 for each sub or 1 amp total....if u are just running one amp say good by to 2 ohms...with two 4 ohm speakers and 1 amp u can only run the subs at 4 ohms or 1 ohm (1ohm depending if ur amp can do 1 ohm)...with 2 amps and 2 subs u can run both at 2 ohms

 

[funkyab 10+ year member]

I have one amp for each sub. Dual voice coils 4ohm wired for a 2ohm load. 450rms @ 2ohm.

 

[AlpineUser 10+ year member]

ok good just wanted to make sure....a buddy of mine had a 12" Sony Xplod in the back of his boat in the engine compartment sounded pretty good on a boat but nothing like in a car

 

[wilzyx 5,000+ posts]

one 4" port is enough... it should be around ~10-11" long
and if you wanted 2, then each would need to be super long, like 24" cause thats just too much port area... so just use one per box

and this is a vdrive boat? or i/o? and they're gonna be inside the enclsoed engine compartment? can you mount the sub on the "height 1" side and have that facing the front of the boat?

but he can get louder with more port area

 

[funkyab 10+ year member]

How much louder?

Those ports are quite big. There is no way that with 2 I could put them both on the same plane as the woofer. And with the size of the enclosure, with 2 ports at, say 23 inches, the whole enclosure will be mostly port. I am after as much sound as possible, as it is a boat and I have to compensate for the open air environment.

Any other input on port area? I am cutting my pieces now but don’t have to port till tomorrow or so.

Thanks

A

(edited for poor grammar and spelling)

 

[MadAudio 10+ year member]

i say go with a bigger port 6" round port will do fine or just make a sqaure one out of wood. my 12" subs had 4 inch round ports just over 11 inches long and im currently rebuilding the whole setup and im going with a much bigger port probably 5"x6" 22" long per sub if not bigger ( gotta recheck my final numbers ).

ohh and dont forget to compensate for port displacement !

my new box per sub will be 2.42 cubes my goal is around 2 cubes after displacement leaving plenty of room for ports

 

[funkyab 10+ year member]

//content.invisioncic.com/y282845/emoticons/eyebrow.gif.fe2c18d8720fe8c7eaed347b21ea05a5.gif Well,

I already have paid for the 4" flared precision ports. I have 4 on my workbench.

I would do 6" if I could.

Mind you (everyone) I have done my homework but still am having a difficult time conceptualizing port mathematics.

By having one 4" port at the proper length (11.30") in a 2.5 cubed box, I am tuned at 32htz.

If I want two ports at 4" in the same box (to be at 32htz), each one has to be twice as long app. 23" each, making total port length of over 46" and a rather large displacement. This will require a very tricky bending of ports to fit in the box (if you have seen my enclosure style you will understand).

I am SUCH A NOOB at precision box tuning and only need a little push in the right direction to supplement my searches of this great forum.

Obviously I am after SPL on the boat as we are dealing with open air.

Is there anyway that I could achieve my goal, with my numeric requirements using the 4" flared ports that I currently have on my table without having to fill my entire enclosure with port?

HELP HELP HELP!!

THANKS AGAIN!

A

 

[MikeyB 5,000+ posts]

//content.invisioncic.com/y282845/emoticons/eyebrow.gif.fe2c18d8720fe8c7eaed347b21ea05a5.gif Well,
I already have paid for the 4" flared precision ports. I have 4 on my workbench.

I would do 6" if I could.

Mind you (everyone) I have done my homework but still am having a difficult time conceptualizing port mathematics.

By having one 4" port at the proper length (11.30") in a 2.5 cubed box, I am tuned at 32htz.

If I want two ports at 4" in the same box (to be at 32htz), each one has to be twice as long app. 23" each, making total port length of over 46" and a rather large displacement. This will require a very tricky bending of ports to fit in the box (if you have seen my enclosure style you will understand).

I am SUCH A NOOB at precision box tuning and only need a little push in the right direction to supplement my searches of this great forum.

Obviously I am after SPL on the boat as we are dealing with open air.

Is there anyway that I could achieve my goal, with my numeric requirements using the 4" flared ports that I currently have on my table without having to fill my entire enclosure with port?

HELP HELP HELP!!

THANKS AGAIN!

A

I wouldnt be too concerned right now, until you can give them more power this should work fine.