98_Z24

iTrader: (3)

Well, I had elaborate plans to use 2 corner boxes I picked up, and re-vamp the system with 2 12's, replacing my current 15. Then I started thinking...Why mess with a good thing? Plus I'd have to find another 2 decent 12's to buy, sinking more money in.

So, I'm back to my old plan. My current box is 3.5 cubes, ported to 34Hz, 36W X 16H X 19D, and was done up on RE Enclosure Calculator about 2 years ago. The box is painted red, looks shabby as hell, hence the reason I'd like to make a new, much cleaner version. I've had a few people tell me that the RE calculator is way off on the specs it gives in terms of the tuning frequency, is this true?

I've been looking at the calculators on 12volt, and was thinking on building a 3.5 cube box, and using 1 or 2 6" PVC ports with curved edges (Using the old heat up the pipe and press on a metal bowl trick) The calc tells me for 33Hz in the 3.5cubes, and 1 6" port, I'd need 15" for lenth.
So I have a few questions here:

In telling the calc 3.5 cubes, I assume that means after sub displacement?

With 3.5 cubes, is that after port displacement as well?

Instead putting 1 15" port in there with an elbow on it (I was thinking I'd make the depth 15" this time around, so I'd need an elbow to get to 15") could I put 2 6" ports with 7.5" lenth each?

Ethier way, will that 15" of 6" port provide me with enough port area so I don't get port noise? I know 16 per cube is usually good, and I can calculate it for a slot port, but what area am I looking for in a round port?

I look forward to hearing your responses. Thanks in advance for the help, I appreciate it!

Denonite

iTrader: (1)

1. displacement is net, so after port and speaker displacement is removed.
2. two 6" ports would have to be approx. 33" long each to have the same tuning..33hz, tuning doesn't work the way you think.
3. port area for a round port is; pi x R^2= 3.1415 x 3 x 3 = 28.27 inches square, which based on your 15 inches/cubic feet is about 1/2 what you should have.

98_Z24

iTrader: (3)

Hmmm, well how can I acheive enough port area to save myself from port noise?

Any comments on the RE Calculator?

Denonite

iTrader: (1)

Haven't used the re calculator...i like winisd. As for the port, if you can find 8" pipe, then a piece 28" long will do the job nicely. You'll probably have to go to a plumbing or construction supplier for that size or possibly the scrap yard. Otherwise, four 4" pipes that are 28" long each will also do the same thing, as would a slot port 14.5" x3.5" x 28". Basically you want approx 50" of port area that is about 28" long for no port noise at max output. Since i didn't have the specs for your sub, i substituted an alpine type r 15" at 1000 watts for port velocity numbers. Unless your sub moves significantly more air (has a lot more than 20mm xmax, and is capable of a lot more output via higher input power) then these numbers will work for you as well.

98_Z24

iTrader: (3)

Slot port seems to be the best solution right now then. That's a lot of pipe to fit in the box if it's only going to be 15-16 inches deep. Sub is an Mmats ProCast 15, definatly doesn't have that much Xmax haha.

Denonite

iTrader: (1)

The box is 36" wide, so the pipe could go from the side...port doesn't have to be on the front or back. Personally, the slot port is what i'd use if i had a choice.

Just as an FYI, unless you're always at or near max output, you may not notice port noise with a smaller port. sometimes you need to compromise, and if so, then a port area 70-75% of what's perfect will work, but the length will change as well...shorter as the area decreases.

98_Z24

iTrader: (3)

It could, but at that 36 it's near bar tight to the sides of the trunk, so the port would basically be blocked. Wouldn't making it shorter mess with the tuning as well?

Sorry for all the newb-type questions. None of them have ever arised to me, since I always messed with the RE Calc until I got my frequncy within my design dimensions.

Denonite

iTrader: (1)

Yeah it would interfere, so in your case the slot port is best and preferable anyway. With ports the smaller the port area the shorter the length for a given tuning frequency, so for a port 70% of the another, the length would also decrease to maintain the same tuning. Anyway, your's is a no brainer, slot port all the way!!