Looking for DIY sub advice, volume 2 - Page 2

No, because as you increase the port surface area the port length needs to increase to maintain the same tune, so reducing the surface area (one less port) will allow for a smaller length to reach the same tune.

As long as there is at least 3" of clearance from the end of the port opening to any obstruction (with a 3" round port), the port should function properly. Any of those designs could work, hard to tell what the interior spacing is. The 4 on the bottom would definitely work.

I said I do not recommend dropping the port area from 4 ports to 3. The possibility of audible chuffing and port compression could result from not enough port area. Decreasing length without changing the number of ports simply raises the tuning point.

As an alternative you could also use passive radiators instead of the ports. This would increase cost slightly but decrease cabinet size and eliminate all concerns of chuffing at high volumes.

You should be okay with more then one 90 degree angle, it's done all the time with slot ports.

In regards to what tsloms suggested, a pair of these would allow you to tune the box to about 15hz, if you don't decrease the dimensions.

http://www.creativesound.ca/details.php?model=APR15

Yes, they would replace the ports. How they work is you add weights to them to get the correct tuning frequency. In regards to your ports I think you should do the last pic as it provides enough clearance around the ports and you know you'll be safe. I believe a general rule of thumb is to make sure that there's at least the amount of clearance around the ports by whatever the diameter of the ports are. For instance if you're using 3" ports you'll want at least 3" of clearance around ALL sides of the ports. One thing that you might want to consider is not placing the ports so close to the back wall. Shorten up the length a little bit to provide clearance from the back wall and make them a little longer after the bend to make up for that shorter length to keep the correct port length. You'll probably also want to flare the inside and outside of the ports as well.

To be honest, I think a slot port is cheaper and easier to implement than round ports. For example I built a box for a 10" sub that has a slot port of 4"x10"x48". That would've been really difficult to achieve with round ports and would've cost significantly more to implement plus you use the walls of the box as one side of the slot port so you really only have to build three sides or maybe just one side depending on how wide it is of the slot port and glue it to the walls of the box to close it up.
Edited by Audiophile1178 - 2/21/13 at 10:11am

3" inner diameter. That's a very nice rendering! I would try to add four dowels or strips of wood that connect the front to back, but other then that your bracing looks good.

The sweeping elbow will be better, and I would just go with the pvc at HD with a roundover bit flare.

If you use something like pl premium to adhere the pvc, you can then fill and fair the gap with the pl.

I would glue it so there isnt air leaks. You could at least run a bead around where the gap will be. Its really not going to make a huge difference though, there will just be slightly more turbulent air flow at really high output.

I wouldn't worry to much about it. There's the possibility of internal sound leakage, but your ports have a 180 degree turn, and are very long. They're likely referring to a straight port directly behind a driver.

Which woofer are you going with (I think I recommended the ultimax 15)? The inuke filters only work to 20hz, so an ep4k with a minidsp would be abetter choice

I'm sure there's other places to source stuff like this from

http://www.parts-express.com/cat/steel-speaker-grills/323

The ports can all be right next to each other, they're working together. As long as there's nothing within 3" of the port opening you're good. I cant answer your questions about bending PVC, never tried it.