Figuring Sq-inches of port per cube

[bgowdy 5,000+ posts]

This may be sorta confusing lol....

Ok so generally speaking when figuring the amount of port per cube, what is taken into account for aeroports(
In my build im using aeros either 2-8s or 1-12".... i know that they roughly equal the same amount of square inches, tho the 1-12 has a couple more square inches then 8's. I also know that less ports are more efficient.

Heres what im looking at in my system if anyone wants to give their input:

-- 2 Obsidian V2 18's

-- 2 8" aeros(100.48 sq-inches) VS 1 12" aero(113.04 sq-inches)

-- 3kw

-- 10 cubes net after all displace

My goal is most SPL output, but NOT on burps, i play music.

What are your opinions for the amount of inches per cube of port using aeros would you think,

and please dont insist on other options, my only item in question is the aeroports to go 2-8s or 1-12?

Click to read more...

 

[bbeljefe]

Port area and volume aren't related. At least, not to any appreciable degree. Port area has a direct relationship to tuning and xmax.

Thus, if you have too little port area it isn't because your box is too small or large, it's because at the tuning you chose, your sub moves more air than the port can pass. Likewise, if your sub doesn't move much air and you have a huge port, it's subject to unload... regardless of box volume.

In answer to your question about which port to use, I'd have to know xmax and tuning to say.

 

[bgowdy 5,000+ posts]

Port area and volume aren't related. At least, not to any appreciable degree. Port area has a direct relationship to tuning and xmax.
Thus, if you have too little port area it isn't because your box is too small or large, it's because at the tuning you chose, your sub moves more air than the port can pass. Likewise, if your sub doesn't move much air and you have a huge port, it's subject to unload... regardless of box volume.

In answer to your question about which port to use, I'd have to know xmax and tuning to say.

ok im tuning my enclosure to 38 hz because i dont listen to really low stuff usually nothing below 34hz honestly.

so tuning will be 38hz & sub xmax is 20mm

 

[bbeljefe]

ok im tuning my enclosure to 38 hz because i dont listen to really low stuff usually nothing below 34hz honestly.
so tuning will be 38hz & sub xmax is 20mm

I wouldn't tune those subs that high in that small an enclosure, unless I was shooting for a burp box. They're low EBP subs (really low) and small enclosures will make them peak higher than tuning to begin with. Not to mention, higher tuning needs more port area. That's why OA recommends such low tuning and if it were me, I'd tune them at 25Hz. Even there, they will still have a peak at ~40Hz but they'll also have some decent low end response.

But anyway, I modeled these subs in WinISD Beta and you're good with either two 8" or one 12" port at 38Hz and below. Obviously, the 12" port would be more efficient.

 

[bgowdy 5,000+ posts]

I wouldn't tune those subs that high in that small an enclosure, unless I was shooting for a burp box. They're low EBP subs (really low) and small enclosures will make them peak higher than tuning to begin with. Not to mention, higher tuning needs more port area. That's why OA recommends such low tuning and if it were me, I'd tune them at 25Hz. Even there, they will still have a peak at ~40Hz but they'll also have some decent low end response.
But anyway, I modeled these subs in WinISD Beta and you're good with either two 8" or one 12" port at 38Hz and below. Obviously, the 12" port would be more efficient.

my blazer it self peak is at 50hz tho. And i dont like tuning super low because i want it to be able to still meter pretty well, and i know its harder to get higher numbers at lower freqs. So idk if i want to tune to 25hz.

again i dont listen to a alot of stuff under like 34hz, if i tuned to 34hz were would potentially peak at?

 

[bbeljefe]

my blazer it self peak is at 50hz tho. And i dont like tuning super low because i want it to be able to still meter pretty well, and i know its harder to get higher numbers at lower freqs. So idk if i want to tune to 25hz.
again i dont listen to a alot of stuff under like 34hz, if i tuned to 34hz were would potentially peak at?

You'd be be okay at 34 as far as SPL but the low end extension is gonna fall more steeply as you raise tuning... unless you have another 2-4ftⁿ to give each sub.

 

[bgowdy 5,000+ posts]

You'd be be okay at 34 as far as SPL but the low end extension is gonna fall more steeply as you raise tuning... unless you have another 2-4ftⁿ to give each sub.

yea im at my max with the 10 cubes lol, unless i did subs and port firing up, but that just seems to difficult to design. But again with the low end i dont listen to really low stuff anyway. for example the lowest song i may listen to is probably "Walk with a waddle by gorilla zoe" and thats like 35hz at the lowest note.

 

[bbeljefe]

yea im at my max with the 10 cubes lol, unless i did subs and port firing up, but that just seems to difficult to design. But again with the low end i dont listen to really low stuff anyway. for example the lowest song i may listen to is probably "Walk with a waddle by gorilla zoe" and thats like 35hz at the lowest note.

Well, lets face it... with two 18s it isn't like you're not gonna be able to play anything low, lol. So with that said, I think you'll be fine with 34 but I seriously wouldn't tune higher because with the box volume you have your peak is gonna happen on the high side of the tuning frequency.

 

[bgowdy 5,000+ posts]

Well, lets face it... with two 18s it isn't like you're not gonna be able to play anything low, lol. So with that said, I think you'll be fine with 34 but I seriously wouldn't tune higher because with the box volume you have your peak is gonna happen on the high side of the tuning frequency.

i see so tune it around 34hz then, i just dont want the bass to be punchy. so in your opinion do you think i should go with 2 8s or 1 12"? im gonn be making them myself so...

 

[Buck 5,000+ posts]

Port area and volume aren't related. At least, not to any appreciable degree. Port area has a direct relationship to tuning and xmax.
Thus, if you have too little port area it isn't because your box is too small or large, it's because at the tuning you chose, your sub moves more air than the port can pass. Likewise, if your sub doesn't move much air and you have a huge port, it's subject to unload... regardless of box volume.

In answer to your question about which port to use, I'd have to know xmax and tuning to say.

Port area and volume are related because if you increase the size of an enclosure with the same woofer, the port will need to get larger in order to keep the same vent speed.

Now to get the port area to use in the first place, depends on box size, power levels, port tuning, and a lot more woofer parameters than just Xmax like Fs, BL, Vas, Sd.

 

[Buck 5,000+ posts]

And almost every woofer in car audio will work somewhere within a port area of say 10-17 in^2 of port area for cube for regular ported. Even though it's dependent on individual vent speeds for one single box to determine size, they usually fall within that range of 10-17. So I don't see how port area per cube is completely irrelevant.

 

[bgowdy 5,000+ posts]

Port area and volume are related because if you increase the size of an enclosure with the same woofer, the port will need to get larger in order to keep the same vent speed.
Now to get the port area to use in the first place, depends on box size, power levels, port tuning, and a lot more woofer parameters than just Xmax like Fs, BL, Vas, Sd.

ughhhhhh lol...... you know what im going to keep it simple. Is 10 - 11 sq-inches per cube enough for this enclosure...

 

[Buck 5,000+ posts]

ughhhhhh lol...... you know what im going to keep it simple. Is 10 - 11 sq-inches per cube enough for this enclosure...

I think I'd do the 2 8's here.

 

[bgowdy 5,000+ posts]

I think I'd do the 2 8's here.

ok that will do. now just have to build the enclosure and will put the 2 8s along the bottom/middle of the box side by side and see how it goes. so should i tune by what he was saying to tune lower or go with my original tune of 38hz

 

[Buck 5,000+ posts]

ok that will do. now just have to build the enclosure and will put the 2 8s along the bottom/middle of the box side by side and see how it goes. so should i tune by what he was saying to tune lower or go with my original tune of 38hz

Tune wherever you want. If you aren't going to play lows and you just want it as loud as possible, just tune it where you usually do. You know what you like.