general sub enclosure and vent design calculation

[renxun]

i had always a question playing on my mind.....so i hope sifu here can clear my doubts....

scenario.....
lets assume a sub enclosure of NET volume 2.7cubic feet (volume after minus speaker volume and port volume) to be ported to 33hz. and there is so many design out there and many ways to obtain port tuning to 33hz. for example a slotted port of 2"wide x 6"length x 7" will get u somewhere there... however a 20" x 3" x 47" can get u somewhere there too and not to mention the round 4" diameter times 8.5" as well....

so the question is which design could give much louder output since the volume remain the same. and does the vent design affect amp power requirements as well?

 

[appleyard]

Yes when it comes to ported there are some points to understand. Its not something you build and hopefully it sounds good.

1. Bigger port area will yield higher SPL (in theory)
2. Small port area will have port noise.
3. Its not recommended to have long port (more than 40")

I think you look at it at the wrong angle. Get your box dimension and design the port based on your box not design the box based on your port dimension.

To have 47" long port will have lots of turns as if you are building a T-Line enclosure.

with port area too big the sub will act as IB and pushing more power and you will have a blown sub.

 

[renxun]

Yes when it comes to ported there are some points to understand. Its not something you build and hopefully it sounds good.

1. Bigger port area will yield higher SPL (in theory)
2. Small port area will have port noise.
3. Its not recommended to have long port (more than 40")

I think you look at it at the wrong angle. Get your box dimension and design the port based on your box not design the box based on your port dimension.

To have 47" long port will have lots of turns as if you are building a T-Line enclosure.

with port area too big the sub will act as IB and pushing more power and you will have a blown sub.

so appleyard i remember somewhere back then i read b4 that u own a FI 15" rite? so could you share with me what is your box design and your port dimension?

 

[appleyard]

Box would be: D 22.75, W 34, H18
Port: W 5.25, H 16.5, L 38/39 (couldnt remember which one) @ 34hz

Will be building a new one with same box dimension and port will be 3.5" X 16.5" X 30.5" @ 28hz with box volume of 5.4 cu^3 net.

 

[appleyard]

Box would be: D 22.75, W 34, H18
Port: W 5.25, H 16.5, L 38/39 (couldnt remember which one) @ 34hz

Will be building a new one with same box dimension and port will be 3.5" X 16.5" X 30.5" @ 28hz with box volume of 5.4 cu^3

 

[renxun]

how many units u running...? 1 or 2 units of 15" ?

 

[appleyard]

single 15 daily and 2 15 for comps/show

those enclosure are for single 15