type r sub box

Hi guys. so I need a little help. I just bought a Alpine swr-1043D sub. I built a box for it yesterday. I took the measurements out of the manual for the box size witch is 12.5x12.5x 20.5 . That comes to 1.33cubic ft I changed it to 13.5 wide x 20.5 deep x 13.125 tall x 9.875 . that comes to 1.32 cubic ft. I kind of did the same thing with the port measurements. They call for a slot port that is 11 tall x 1 wide x 18.5 long. That comes to 203.5 cubic inch. I changed it to 12 tall x 2.25 wide x 7.8125 long. That comes to 210.94 cubic inch. some where I messed up on my math for the port. I was trying to match the cubic inch of Alpines specs. I installed it yesterday and It is just not hitting like I think it should. Could The size I made the port be causing this? I'm Pushing it with a 500 rms fosgate amp. It's in an 05 quad cab dodge truck. I made it down fire with a angled bottom. I would be very thankful for any help on this. I can take photos if it will help.

What ampmexactly and do you have the sub wired at 2 or 8 ohm's?Gary Sather

tonanzith wrote: What ampmexactly and do you have the sub wired at 2 or 8 ohm's?

It's a fosgate 1000a2 Its a old one. Im using just one channel. The sub is wired for 2 ohm's

You can't recalculate port size like that. In 1.32 cuft, the Alpine specs would vent the enclosure at approx. 32 Hz. Your port size changes the tuning frequency to approx. 65 Hz. To keep a 32Hz tuning with your 12 X 2.25 opening, the length needs to be 48.5 inches. You need to rebuild your enclosure. You might see if a 3" diameter round port at 12" long can be made to fit.Support the12volt.com

DYohn wrote: You can't recalculate port size like that. In 1.32 cuft, the Alpine specs would vent the enclosure at approx. 32 Hz. Your port size changes the tuning frequency to approx. 65 Hz. To keep a 32Hz tuning with your 12 X 2.25 opening, the length needs to be 48.5 inches. You need to rebuild your enclosure. You might see if a 3" diameter round port at 12" long can be made to fit.

Okay I see the problem now. Duh! Thank you! So I can prob rework the box. Is it okay to have bends in the port to get your Hz where you need them? And if you do have bends in a slot port how do you account for the bend? Just measure length off the center line of the port? Also when doing slot parts do you need to account for the space the port takes up? Thank you so much!

Okay so if I make my port 1 x 12 x 21.07 that gets me down to 32 Hz. That would require a bend in the port. I could do a round port 2.5 x 7.96 and that would get me to 32 Hz. Would one be better then the other?

Yes, it's OK to bend a port and yes, you measure along the approximate center line. Any way you can get the tuning frequency closer to 32Hz will do the trick. :)Support the12volt.com

DYohn wrote: Yes, it's OK to bend a port and yes, you measure along the approximate center line. Any way you can get the tuning frequency closer to 32Hz will do the trick. :)

Okay thank you side much! Do the calculators on here acount for the port displacement? And should i subtract my sub displacement from the value i enter into the calculator ?

The calculators compensate for port volume. They do not compensate for driver or braces volume, so subtract those first. In general if yo are within +/- 10% you'll be close enough to get useful results.Support the12volt.com

DYohn wrote: The calculators compensate for port volume. They do not compensate for driver or braces volume, so subtract those first. In general if yo are within +/- 10% you'll be close enough to get useful results.

Thanks so much for your help! I think I'm on the right page now!!