I built a box for 2 MOFO-12's. Well it didn't turn out that good. The box is nice and solid but I get lots of port noise at high vol. I used 3in x 8.5in round ports. The box is divided into two chambers and each sub has one port. I really want to fix this.
Here are the box specs 1.688 ft^3 that is after subtracting everything Round Port 3x8.5 Tuned to about 36.5Hz
If I add some polyfil I will get a little less air velocity but lower the tuning to about 31Hz. If I took out the divider then I get almost twice the spl and half the air velocity. Problem is I can't take the box out of the car. It didn't fit very good and I had to force it in the car. Anyone have some tips.
I didn't use flared ports. Just some regular pvc I had around the house. If I remove the divider so the box is just one chamber with two ports instead of one port on each side. Then I get about 3db more spl and having both ports used by both subs gives me half the air velocity out.
Here's a suggestion: If you can, try using a hole saw and punch a bunch of holes in the partition. You will achieve your goal and still have the bracing strength of the partition.
what he meant by removing the divider = half the air velocity and twice the spl is that since he removes the divider to make it a single chamber box, it increases approx. 3 db's (around prolly more like 2.4 or somthin) and then half the air velocity comin out because of him removing the divider.. ^^ that above suggestion would help a little, but why dont you just flare your port ends yourself? then you will get no port noise..
just heat up the end of the pvc port, then get a round object (not too large) and push the end of the pvc port on top of the object so you get the "flare" affect. someone on this forum did it and had pics, but im not sure where the pics are
i would just remove the flares and flare them, thats what i would do even if you dont want to, and then you could also punch some holes in the partition but do one first (like punching the holes) and see if that helps, if that doesnt, then do the flares
I was thinking of cutting some holes in the divider with a hole saw. Just didn't know if that would create more noise. I could try to flare the ports, but they are liquid nailed to the box.
I really wish I had a box that fit in the car better. The trunk opening is really small as compared to the trunk itself. That will probably be a future project making a box that fits better in the car.
I now see what everyone is talking about these subs are no good. They have NO sq. Good thing I got them for free.
Adding another port to each side raises the tuning a lot. I would have to have ports 17in long if I had two of them. That would be a lot of work to make those fit in the box. Only way I know to do that would be if I did the ports half internal and half external.
Bobby, if you use a hole saw larger than 3" and punch enough holes in there to allow air movement, you will gain what you want and still have the rigidity the brace offers.
That box seems a little small and you really need some more port area. One 3 inch port is only about 7 sq inches of port. That is not nearly enough that is why you are getting a lot of port noise.
but do one first (like punching the holes) and see if that helps, if that doesnt, then do the flares