Port Area

[asb2106 1]

Currently waiting on customer to pick out some vinyl so I can finish the truck box, but in the mean time I decided to get started on my next box for the kia. The quad SA8s were decent in the kia, I dotn like the layout and the way it goes in the trunk however, So Im making a new box.

Infact Im going to add the 2 refurbs Ive got on the way to the mix to do 6 sa8s in the kia.

So my question, how much port area should i use for 6 of these, Im going to tune to 34hz approx, maybe a few less, and Im gonna build the box at 3 cubes.

probably gonna get going on it tonight as long as I can figure out the port area.

Some calculators Ive tried put the port area much higher than I find comfortable, so Im hoping I can get some good info here, thanks!!

[asb2106 1]

Around 10" or ~ 78 sq in sound about right?

[Dictator 39]

Between 12-18inchs of port area per cube.

[asb2106 1]

i thought that sounded way too big..

thanks

[ibanender 2]

i thought that sounded way too big..

thanks

I wouldn't go over 12 sq in per cube, and not less than 8 sq in per cube for any reason

[95Honda 486]

The relation of enclosure volume to vent area is not really valid. It can be used as a"rule of thumb", but it isn't correct alot of time.

The major factor for vent area is going to be power used, sub efficiency and displacment. Box volume doesn't really factor in... If you really want to know the answer to your question, other than a "rule of thumb" you need to model your design with the expected power you will have a look at the predicted vent velocities. This is the only true way to determain minimum vent area... Every other way is either going to be overkill or a shot in the dark.....

And no matter what anyone says, this doesn't matter if it is free space or confined space, it will be the same...

[RAM_Designs 25]

The relation of enclosure volume to vent area is not really valid. It can be used as a"rule of thumb", but it isn't correct alot of time.

The major factor for vent area is going to be power used, sub efficiency and displacment. Box volume doesn't really factor in... If you really want to know the answer to your question, other than a "rule of thumb" you need to model your design with the expected power you will have a look at the predicted vent velocities. This is the only true way to determain minimum vent area... Every other way is either going to be overkill or a shot in the dark.....

And no matter what anyone says, this doesn't matter if it is free space or confined space, it will be the same...

This. The amount of air potentially displaced by the woofer(s) in a given install is the main factor.

[asb2106 1]

I've been putting the sa8s in pairs and running then on one cube with 16-18 sq inches with great success. That with running 800 watts per pair. I just am curious on 6 initially I'm only gonna run a single 1000 watt for them, but I'm working on getting a 1500d or maybe bigger for them. So I'm considering keeping the port around 36-40 sq inches..

I got an email in with Jacob, I'm curious to see what he has to say.

[asb2106 1]

The relation of enclosure volume to vent area is not really valid. It can be used as a"rule of thumb", but it isn't correct alot of time.

The major factor for vent area is going to be power used, sub efficiency and displacment. Box volume doesn't really factor in... If you really want to know the answer to your question, other than a "rule of thumb" you need to model your design with the expected power you will have a look at the predicted vent velocities. This is the only true way to determain minimum vent area... Every other way is either going to be overkill or a shot in the dark.....

And no matter what anyone says, this doesn't matter if it is free space or confined space, it will be the same...

This. The amount of air potentially displaced by the woofer(s) in a given install is the main factor.

this is what I thought. I thought the xmax was an important factor as well .. but I'm quite new to ported enclosures, so I'm gonna ask a lot of questions and get a lot of opinions... then I go from there and see with first hand experiencence.

Edited March 13, 2011 by asb2106

[Dictator 39]

oo didnt know any of that on port area learned something new. Confined area is considered a trunk?

[Impious 1,476]

oo didnt know any of that on port area learned something new. Confined area is considered a trunk?

Confined area being anything other than open air "free space".

A lot of people downplay the importance of certain modeled or predicted performance characteristics because the modeling programs can only model performance in basically open air without any close boundaries. This is true for certain performance characteristics such as frequency response. Others are going to be consistent for the most part regardless of the air space the system is playing in.

[asb2106 1]

oo didnt know any of that on port area learned something new. Confined area is considered a trunk?

Confined area being anything other than open air "free space".

A lot of people downplay the importance of certain modeled or predicted performance characteristics because the modeling programs can only model performance in basically open air without any close boundaries. This is true for certain performance characteristics such as frequency response. Others are going to be consistent for the most part regardless of the air space the system is playing in.

any recommendations for me to try?

This will be in quite the open air environment, all subs and port will be facing up, and its a hatchback with an open area to the entire car.

[ssh 924]

oo didnt know any of that on port area learned something new. Confined area is considered a trunk?

Confined area being anything other than open air "free space".

A lot of people downplay the importance of certain modeled or predicted performance characteristics because the modeling programs can only model performance in basically open air without any close boundaries. This is true for certain performance characteristics such as frequency response. Others are going to be consistent for the most part regardless of the air space the system is playing in.

any recommendations for me to try?

This will be in quite the open air environment, all subs and port will be facing up, and its a hatchback with an open area to the entire car.

It will be more open verse a confined trunk, but the cabin itself is not the same as a open air environment, otherwise there wouldn't be ridiculous amounts of cabin gain

[asb2106 1]

gotcha

Ive liked my subwoofers for many years now, but really just started getting behind the acoustics and performance of the audio since joining here. so my newb status, is very correct

But Im willing to learn and I have the tools to get the job done right, so lay the knowledge on me!! haha

before i joined here, all my boxes were sealed, mainly because i did not understand the design principles and what you benefit from and what hurts you. I still know very little, but enough to be safe.

[Impious 1,476]

oo didnt know any of that on port area learned something new. Confined area is considered a trunk?

Confined area being anything other than open air "free space".

A lot of people downplay the importance of certain modeled or predicted performance characteristics because the modeling programs can only model performance in basically open air without any close boundaries. This is true for certain performance characteristics such as frequency response. Others are going to be consistent for the most part regardless of the air space the system is playing in.

any recommendations for me to try?

This will be in quite the open air environment, all subs and port will be facing up, and its a hatchback with an open area to the entire car.

Open air as in outside, not in a vehicle. Vehicle, room, etc.....they're all confined spaces acoustically.

As for suggestions.....yes, try what 95Honda suggested.

[ibanender 2]

The relation of enclosure volume to vent area is not really valid. It can be used as a"rule of thumb", but it isn't correct alot of time.

The major factor for vent area is going to be power used, sub efficiency and displacment. Box volume doesn't really factor in... If you really want to know the answer to your question, other than a "rule of thumb" you need to model your design with the expected power you will have a look at the predicted vent velocities. This is the only true way to determain minimum vent area... Every other way is either going to be overkill or a shot in the dark.....

And no matter what anyone says, this doesn't matter if it is free space or confined space, it will be the same...

Then take that model, and forget everything it says. They aren't at all accurate, period. Box volume has everything to do with port area. If your volume is too small it will choke the port, if it's too big it won't resonate. There is no blanket answer for every sub, because there are other factors that determine what is too little or too much port for a given sub. You can only go by a "general idea" to get you started if you aren't super familiar with the sub.

This. The amount of air potentially displaced by the woofer(s) in a given install is the main factor.

Yes, this is true. You require more port area for more displacement, this goes for more subs or just plain more excursion from a given size. But, there's another factor also, motor force. How much motor force and how linear it is through stroke makes a big difference too. Example, if you had a high throw suspension with an underhung coil, it could move a lot, but it wouldn't be doing it much on it's own power as it would be inertia. So, after the bottom of the coil goes past the top plate, there's no more "umph" left. If the coil is always well in the gap or there is something like XBL^2 going on, there will be motor force still working through full stroke, which will work better on a larger port.

[asb2106 1]

The relation of enclosure volume to vent area is not really valid. It can be used as a"rule of thumb", but it isn't correct alot of time.

The major factor for vent area is going to be power used, sub efficiency and displacment. Box volume doesn't really factor in... If you really want to know the answer to your question, other than a "rule of thumb" you need to model your design with the expected power you will have a look at the predicted vent velocities. This is the only true way to determain minimum vent area... Every other way is either going to be overkill or a shot in the dark.....

And no matter what anyone says, this doesn't matter if it is free space or confined space, it will be the same...

Then take that model, and forget everything it says. They aren't at all accurate, period. Box volume has everything to do with port area. If your volume is too small it will choke the port, if it's too big it won't resonate. There is no blanket answer for every sub, because there are other factors that determine what is too little or too much port for a given sub. You can only go by a "general idea" to get you started if you aren't super familiar with the sub.

This. The amount of air potentially displaced by the woofer(s) in a given install is the main factor.

Yes, this is true. You require more port area for more displacement, this goes for more subs or just plain more excursion from a given size. But, there's another factor also, motor force. How much motor force and how linear it is through stroke makes a big difference too. Example, if you had a high throw suspension with an underhung coil, it could move a lot, but it wouldn't be doing it much on it's own power as it would be inertia. So, after the bottom of the coil goes past the top plate, there's no more "umph" left. If the coil is always well in the gap or there is something like XBL^2 going on, there will be motor force still working through full stroke, which will work better on a larger port.

Yikes, this all makes sense, absolutely , but is a few levels ahead of my knowledge, so Im very thankful that Youve found my threads!

Would you have any recommendations of a design model I could go with? Something to get me started on? Should i just do a basic 3cube up firing slot port design? Ive never reached outside of the boxes youve seen me post here, Id be able to build more complex, but really what would benefit me is out of my design abilities right now. Basically I dont know of a box design that I am safe saying would be good..(outside of what Ive done and am happy with)

[///M5 2,833]

Then take that model, and forget everything it says. They aren't at all accurate, period. Box volume has everything to do with port area. If your volume is too small it will choke the port, if it's too big it won't resonate. There is no blanket answer for every sub, because there are other factors that determine what is too little or too much port for a given sub. You can only go by a "general idea" to get you started if you aren't super familiar with the sub.

Or to be safer, take everything you type and forget it. You can't read and obviously don't understand this. If you do, explain EXACTLY how the relationship for port area is related to the box volume but please leave out ALL other factors since "box volume has everything to do with port area". Don't type ANYTHING else as it will be garbage trying to change the subject as always. Stand up to your statement for ONCE please.

Yes, this is true. You require more port area for more displacement, this goes for more subs or just plain more excursion from a given size.

Nice, way to contradict yourself just one paragraph later.

If the coil is always well in the gap or there is something like XBL^2 going on, there will be motor force still working through full stroke, which will work better on a larger port.

No, just no. Where did you get this garbage from? Wherever it is you should stop paying attention to any of it and forget everything you think you know.

[///M5 2,833]

Yikes, this all makes sense, absolutely , but is a few levels ahead of my knowledge, so Im very thankful that Youve found my threads!

Would you have any recommendations of a design model I could go with? Something to get me started on? Should i just do a basic 3cube up firing slot port design? Ive never reached outside of the boxes youve seen me post here, Id be able to build more complex, but really what would benefit me is out of my design abilities right now. Basically I dont know of a box design that I am safe saying would be good..(outside of what Ive done and am happy with)

I hope the makes sense part you are referring to are 95's posts and not the garbage Ibanender is spewing.

There are no rules of thumb that are always accurate, nor none in this case worth using. You should keep the port air velocity to an acceptable level which is EASILY modeled.

[Duran 387]

i thought that sounded way too big..

thanks

I wouldn't go over 12 sq in per cube, and not less than 8 sq in per cube for any reason

Derka DURRRR!!!!!

I hope people aren't listening to your verbal diarrhea.

OP, use this to calculate port area.

[asb2106 1]

OP, use this to calculate port area.

so either this link was an accident, or it was some sort of joke!? idk, either way Im just looking for some help and instruction on what others would recommend I do.

I come and ask because Ive came across a few people on here, who know ALOT, and quite a few of them have seen this thread, all your info is greatly appreciated, it really is.

But can I ask for alittle more assistance in this matter?

Heres the exact specs of what Im going with, 3 cubes, I can go down in size, or up as much to 4 if recommended. (4 would be my gross maximum and its pushing it, but i doubt Ill need that much)

*Im starting on a small amp for all 6 subs, A RF 1000BD for all 6, going to run at 1.33ohms for the set. With intentions of stepping up to a 1500D or something similar in the future, potentially adjust ohm load as well (and when that change takes place, a new box isnt a big deal - so if your determining based on my amp size preference, lets use the 1000bd as a guide)

*Electrical is as stated in my sig, power and grounds are taken care of under the hood, and I got a spair batt in the trunk, no alt yet. and hopefully it wont be needed with only the one rf1000.

*Subs are d4's

*using 10 gauge speaker wire

*0 gauge under the hood to a distro, then running 4 gauge to the amps.

*Subs and port would be pointing upwards with what I have in mind, if someone could recommend something else I should try, that might sound better, Im all for it

*Car is a Kia Spectra5 hatchback

*maximum dimensions in the trunk for the enclosure, is 37 wide, 18 deep, 14.5 high. and that 14.5 is the maximum, so if the subs are facing upwards, 12 is the max.

just looking for some basic layout ideas, something different from what im used to, something that might benefit me more, anything really

**and mainly how much port area i should use

Edited March 14, 2011 by asb2106

[Duran 387]

Try the link now, sorry, lol

[asb2106 1]

Try the link now, sorry, lol

Thats the one I started with actually, which started this thread..

if Im not mistaken the xmax of the sa8 driver is 16.5mm

using that, with 6 drivers, and 30-34hz measurements its putting port size around 10"" or 80 sq inches.

Im currently using 17 sq inches per pair so it just sounded kinda high to me.

Ill trust that number and put one together. Ill report my findings.

**Just got shipment update this morning, the next 4 sa8s are on the way.

[asb2106 1]

Heres a design i put together, simple but im hopeful it will work out nicely

extrenal dimensions are 37 wide, 18 deep, and 14.5 high. figuring basically .7 cubes in speaker displacement. Tuning to 34hz.

running 2 ports, each port is 2.5" x 16.5", @ 25.5 inches each.

leaving me 3 cubes net volume.

Any potential problems I might see with this setup?

Edited March 14, 2011 by asb2106

[dbsupra 69]

That's weird that you put identical fingerprints on every sub

Are you going to do any bracing? That's 150lb of subs on the baffle and a lot of open space. Don't forget to include that in your calculations if so.

I found a real nice calculator on port sizing, I'll see if I can dig that up for you.