I picked up a btl d2 for 250 tonight, and have it in 4 cubes at 32 hz. I need a box to really let it shine. I was thinking 8cubes @ 30hz. I am unsure of how much port to have though. Most likely a slot. My question is what is a good rule of thumb to go by for port area? I've heard mixed things about the 12-16in/cube rule.

Edited December 30, 201311 yr by SpeakerBoy

There is no rule of thumb, especially if you don't know the power you will be applying to the driver.

 

Have you modeled yet to see the difference between the two boxes?  You should really do that before cutting any wood.

 

And if you do indeed end up with an 8 cubic foot box, that is big, you should have no problem with an adequate vent for a single 18" driver...

I will be using a hifonics brx 2000.1

OK, model with that amount of power,  Shoot for low enough vent velocity.  It won't be too tough to get a slot port in a box that big, 30Hz isn't really too low at all...

Try to stay below 20 m/sec, which should be easy, even around tuning.   And honestly, you probably will be fine, in a car, with higher velocity...

He offered me a ten cubic foot box tuned at 31, but it has cutouts for two eighteens; we are going to plug one and shoehorn it in; it's one inch too wide. Should I adjust the port size? I'm only feeding it 750 @ 1ohm for now, and by the time I get a new amp i'll redesign a box. I'll get the specs later today on the dual box.

Edited December 30, 201311 yr by SpeakerBoy

This will be a good chance for you to use the skills you have learned here.

 

Carefully measure the enclosure dimensions and model it with your driver. 

 

-Find out what the vent velocity will be. 

-Actually verify the tuning.

 

You have no idea if it was even designed right in the first place...  Here is your chance to do this right...

Challenge accepted

Will post back after we get it in there.

I wouldn't bother with either enclosure. Both bad ideas. My BTL UFO did really well in a 7cube box tuned to 32hz. I can't stress enough how much I recommend you building a new enclosure.

Sounds leagues different than any woofer i've ever owned. Just better and better. Can wait for full power.

So clear. Dumped my box full of poly, measured and calculated 6 lbs. sounds so clean