Need help with ported 2 15Q

[appleyard 0]

As titled says. my max dimension is

W33 H17 D26

which I calculate would be 6.52cu^3 after speaker displacement. I have 6.25 round ports and I know its kinna small for the 15Q but thats what I'm planning to use. When I use winisd (i know) with 6.5 cu^3 and 2 round 6.25" port tuned to 30hz I got a 23.57" long.

I know my calculation is off because I have not deduct port displacement but hope someone can give input. I know the box is kinna small for the 2 15 but thats the only space I can spare. Most online port calculator wouldn't allow me to calculate 2 ports.

Also the sub will be powered by 2 SAZ1500d.

Thanks

[shizzzon 461]

i dont know how thick your round ports are... i'm gonna assume they are 1\4" thick.

Port displacement is 0.94 cubes which would definitely put you under the minimum requirement.

Also, since you are using that program, look at your port velocity, you are using a lot of port area for what power yo u have. You can shrink the port size some to accommodate.

Rule of thumb i go by is as long as the velocity is no more than 15% of the speed of sound, then you are ok.

[appleyard 0]

sorry forgot about the port thickness.

Its 2mm thick.

Uhmm where can I find the port velocity? Noob at its best here.

thanks

Edited June 19, 2008 by appleyard

[kippo 0]

sorry forgot about the port thickness.

Its 2mm thick.

Uhmm where can I find the port velocity? Noob at its best here.

thanks

if u click the drop down menu with the default 'transfer function magnitude' displayed, look in the port velocity.

i think u should aim lower than 100mph (i can't remember that well)..

[appleyard 0]

found out that the TS in Winisd if off so any result is skewed.

Any idea on other program which let you calculate for 2 ports?

[kippo 0]

u don't need T-S parameters to calculate port length. you only need to key in the box volume.

[KU40 173]

also, you can change the t/s specs in winISD. They aren't set in stone.

[nickeveready 0]

i dont know how thick your round ports are... i'm gonna assume they are 1\4" thick.

Port displacement is 0.94 cubes which would definitely put you under the minimum requirement.

Also, since you are using that program, look at your port velocity, you are using a lot of port area for what power yo u have. You can shrink the port size some to accommodate.

Rule of thumb i go by is as long as the velocity is no more than 15% of the speed of sound, then you are ok.

how did u get that port displacement? wouldn't u do 6.25x23.57=/1728 for each port

[KU40 173]

area of a circle is pi*r^2. Then you multiply by the length to get port volume.

[appleyard 0]

would this be right?

2 6.25" port with length of 21.79" in will give you 0.762 cu. ft? yes? no?

got this from here

http://www.mathopenref.com/cylindervolume.html

so my box will be 5.79 cu ft net tuned to 31hz with box dimension of w33 h17 d26.

[KU40 173]

but you have to remember that taking out the port displacement lowers your box volume down to that 5.79 cubic feet. So plug that into your box volume now on winISD. your port will change again, it will get longer. You have to just keep subtracting the new port volume from the box volume you entered until they add up to your overall box volume.