Gettnbig

I have a 4.5 cub box that I want tuned to 28htz. I know that for sure. I was going to orignally going to use 2-3"x8.5" ports. I now have to use a square port. It is going to be fabricated into a viewing panel on my sub box which will be 10.5" by 21'5". Can someone please calculate or show me how to calculate a square port that will tune my box to 28". thanks.

Orion_95

thats not enough port area. its only like 14 sq inches.

Gettnbig

thats te measurements that I got from the linearteam site. Why don't you tell me what would I should be using to tune my 4.5 cubes to 28hz.

Chadxton

iTrader: (1)

28Hz? Your ports are going to be a billion inches long!

Ty, if his ports are going to be 3 x 8.5", he's going to have 25.5 sq in per. So that's 102 sq inches of port, I think he'll be fine.

Give me a minute here, Gettnbig

[ September 30, 2003, 08:57 AM: Message edited by: Chadxton ]

Chadxton

iTrader: (1)

Man, don't even bother tuning it that low. For one, 4 ports is a huge waste of box space. Secondly, for a single port at 28Hz at 102 cu in total (assuming you total all 4 port areas), you'll need a port length of say...6 carlengths maybe?

Say if you cut the port volume by half to...50 sq in with a single port, you'll need a 40¾" port length for roughly an 8½ x 6" port.

See if you can rethink some numbers to allow a more humble box design. [img]graemlins/thumb.gif[/img]

[ September 30, 2003, 09:40 AM: Message edited by: Chadxton ]

Gettnbig

28hz gave me the flattest curve and the most output at the lower end. I would like to keep it at 28hz. I am not using round ports as they will have to be too long. I can make the square port as high or as wide as needed as long as it fits into that 21.5" x 10.5" range. This is a very custom fit box that has to be wide and long but not very tall. I'm doing a cut through on a single cab sonoma and don't have a lot to work with. The dimentions are 12"x24"x35" with the box being made of 3/4 mdf an the front (12"x24") being plexi. 3 sides of the box will be extended by 3" with the front staying at 12". This will give the sub clearance so it may fire down. Do we understand what I am trying to accomplish now?

Gettnbig

WinIsd Pro gives me a 4.5ft^3 tuned at 28hz using a 4"x6"x14" port. Anything wrong with that?

Chadxton

iTrader: (1)

Nope, nothing wrong with that. It's near equivalent to a 6" round port. The only point I was trying to make was that you'd have to make smaller port area for it to work. And you don't want to make the port area too small or else then you have backpressure issues = port noise and a quieter box. What size of sub(s) are you putting in? The only determining factor is whether or not your port will be big enough.

That box design is very similar to my stroker box (13.5x24x34 with ¾" MDF and no extensions).

What is the speaker(s) displacement?

I know you were going to use slot ports. That's all I work with. [img]tongue.gif[/img]

What's the maximum port length you can do without the port coming close to the back of the box? Is it the 21.5" that you were saying, or is that just the one side dims of the box that allow for port height/width?

[ September 30, 2003, 11:27 AM: Message edited by: Chadxton ]

Gettnbig

It's an P.G xmax 15". The box will be 4.5 cubes before displacement. It will be 3.92 cubes after displacement.

Chadxton

iTrader: (1)

I'm assuming the port is going to be on a different side than the sub? I don't see how it would be possible otherwise to mount a 15 when you only have 10.5" on one side, even with a 3" extension.

But yeah, if I see it right, the port length will go along the 35" side of the box, then the BIGGEST I would suggest is a square port 10½"x 3 2/3" by 31¾ long. That'll get you 28Hz tuning and 38 sq in of port area, sufficient for most 15's.

[ September 30, 2003, 12:02 PM: Message edited by: Chadxton ]