I recently purchased an A.P. Axis 15 and was suggested to make this box. Box is to be 3.0 cu. ft. net and to use 4 - 4" pvc ports. Because of box dimensions I'm not able to use flare ports so this is gonna be straight 4" pvc. I'm told the beauty of this type of box it the ability to change tuning and also seal up the box using plumbing inside pipe plugs. A ported and sealed box combination. My concerns is port noise. When I brought this up I was told that I would not have that much and that I would certianly not hear it while playing normal music, just on bass tracks. Is this accurate information? I think this box concept is great but if it's so great why isn't there more people doing it? I've never got to listen to a box using pvc ports so if somebody can give me a little more info that would be great. I just don't want to go through the effort of building this box and have a ton of port noise. Also if anyone has any suggestions on using pvc and helping with any port noise that would be great too. Thanks

You can flare them

http://www.subwoofer-builder.com/flares-25mm.htm

I personally used them and rounded over the port opening (along with some of the pvc). You can also cut some mdf rings, round over those openings and used them inside the box.

As long as there is enough port area, port shape doesn't matter (use common sense when choosing the shape though).

Thanks for the link Adrian. So just straight pipe is really bad?

I've always used straight pipe and it is NOT better than flared- but if your going to be just driving around beating it will do fine.

two things i use- 1) small router roundover bit to smooth the inner edge on both sides 2) or old school get a file and just work it around the inside till the edge is gone.

-Drew

Thanks for the link Adrian. So just straight pipe is really bad?

Slight chance of port noise. Haven't done the math but if port area is well enough for a speaker, then I say flared or straight, it's a bit unlikely to make a diffrence to the ear.

Cool. Thanks it doesn't sound bad so I may give it a shot.

for daily straight ports wont make that much difference, but on the meter i have gained as much as 3 db going to flared.

i have always heated the ends of pvc with a heat gun, and pushed them onto a basketball to flare them. works very well but takes a little practice to get your own technique down. you can also do custom tube and flare sizes this way. 1 port vs multiple ports has always been louder and more effcient for me.

Wow 3 db. I don't intend on competing or getting metered just want some nice tight hard hitting bass for my personal pleasure . I really what this box can offer so I guess I give it a shot. I just don't want a big box that's sealed because it sounds terrible ported. If all ports are open it's 50 sq. in. of port, 3 open - 37 sq. in. I think all open tuning is around 34-35hz, one closed 28hz and two closed it's 24hz.

Yea DD's that's kind of what I was thinking. Is flaring the inside more important then the flaring the outside? Or both the same?