Hi guys,

A good friend of mine want to use his Fi btl n2 15" in a new ported box. He was using mine until I sold the box.

This will be a temporary setup, as he is in the process of ordering a second btl, and the box for the 2 is ready (he had 2 Xcons 15" in, before).

So, the box he wants to use has those dimensions:

83 cm x 37 cm x 50 cm

32.7" x 14.6" x 19.7" Those are internal dimensions.

He has 2 4" flared ports that he wants to use. What length should he make them to achieve a 32 Hz tuning ?

Thanks very much for your help.

I use to "work" with RAM Design for L port boxes, but I want to try the forum members for these round ports.

http://www.the12volt.com/caraudio/boxcalcs.asp

http://www.mobileinformationlabs.com/HowTo-1Woofer-Box-CAL%20Port%20lenth%201.htm

4.30481 cuft

so

i got between 13.45" and 12.44"

I ran through the numbers and got 5.15 cuft NET and 10.375" per port to achieve 32hz tuning with those dimensions. That's assuming those are definitely internal dimensions, sub and port displacements, and no bracing or anything else of the sort.

Don't mean to step on toes but if my math is wrong it would be good to know so I can correct it.

2 x 4'' port is gonna be way small on port area.

According to psp calculator, each should be 11''

http://www.psp-inc.com/tools.html

That's very true that it's very short on port area, but since it's only for the temporary I wouldn't think it's going to matter much.

10.375" , 11" or between 13.45" and 12.44" ?

So much numbers !

It's temporary, it should be fine with 2 4" ports.

I'll tell him to try 13" first, and the cut if he does not like it that way. (It's a little more than 5 cu ft with internal dim and no bracing and no sub dispalcement).

Thanks a lot guys.

I would just leave it sealed. You're not going to gain much output out of those two tiny ports.

Port compression is going to be so bad it's just going to act like a leaky sealed box.

I just told him.

He said he tried with the ports at 16" !!! on a saz 1000 at 2 Ohms : he likes it like that, but he only had 2 old 8" subs in a weird box on little power, for some times. So the change is huge.

He will work on it today. He needs 2 elbows for the ports and to change the way they're firing.

thanks again.

I love this forum !!!

I would just leave it sealed. You're not going to gain much output out of those two tiny ports.

Port compression is going to be so bad it's just going to act like a leaky sealed box.

Really ?

I used the same port config on a SSA Xcon 15" and it was not bad at all. I know it is not the same sub, but I'm not confident with using it sealed.

I would just leave it sealed. You're not going to gain much output out of those two tiny ports.

Port compression is going to be so bad it's just going to act like a leaky sealed box.

That's true, just leave it sealed, and be moderate on the volume, (or try decreasing the volume for it to operate safely sealed)

It would be a shame to cut those ports for no reason.

32.7" x 14.6" x 19.7" =9405.174

9405.174/1728=5.44 cuft

but if you account for the .75 thickness its gives you 4.30cuft

so if those are internal it would be 5.44

and i get 9.23 on both charts

Those are internals dimensions.

I'd rather use it in a ported box, even with those "small" ports !

Is this just for one sub or two? I'm under the impression it's for two subs

Is this just for one sub or two? I'm under the impression it's for two subs

Only 1.

Only one sub. Excuse my poor English ! It's not easy for me

We won't put 2 15" subs in such a small box !