Help With Expansion Rate For Flared Ports

[kelticwizard]

I am have an enclosure which requires the equivalent of a round port of 2" diameter, five inches long.

The enclosure is 40" H by 8" W by 4" deep-that is right 4" deep- and I cannot use a flared port because the flanges, for 2" pipe, are 5 inches long and high.

A port 1.75" square is the equivalent of 2" round pipe. What I would like to do is to make a piece with two flares ojn the end which expand at the same rate as the Parts Express/Madisound flares, only the expansion takes place in the verical direction only-not the haorizontal direction. In other words, the port remains 1.75" wide, but expands up to-10 inches? 14inches?-or whatever at the ends.

Toward that end, I envision cutting a piece of 1.75" inch softwood with the appropriate curves on the ends, and sandwiching them between two pieces of 0.5" plywood, then gluing everything together. After the glue dries, simply take the reciprocating saw and trim off the excess in the middle.

I include an illustration, front view on the left, side view on the right. The plywood on the edges is in green, the softwood inthe middle is in red. On the side view at the right, it is in dotted lines, since we are seeing "through" the plywood in that view.

If someone could give me the expansion rate of the Parts Express/Madisound flared ports I would be grateful. Of even greater help would be a picture of the necessary curve which I could copy, enlarge to life size, and print copies of so I can tack the curve to the softwood as I cut it with the reciprocating saw.

Anyone have any idea woth the expansion rate is for the flares?

Any advice or help on any aspect of this would be appreciated.

[pinkmouse]

I would guess it's just a parabolic curve, and you should be able to get the dimensions for the depth and width from the datasheet, or even a good photo. You might want to make up a simple test box with a removable side so you can adjust the port length before you build the final version.

[kelticwizard]

Thanks, Al. However, that still leaves me with figuring out the curve for a parabolic curve. It's been a little while since I did that math.

Anyway, there seems to be a weath of info to be found on Bill Collison's website. It really makes you want to give the idea of a DIY round pipe flared port a go.

The 2" unflared pipe is rated by WinISD as having 40% more area than is necessary to prevent "chuffing", but you always want to give yourself generous clearance on these things, if you can. Apparently you can make flares of different expansion rates, depending on how involved you want to get. According to the website, you can take a router bit for a handheld router and just route out the port hole, and do yourself a lot of good without going through a lot of fuss.

[pinkmouse]

What a cracking site. A great find, and it's gone straight into my bookmarks.

This site gives a simple way of drawing out parabolas. Much easier than all that maths.

[KBK]

I've tried just about every single port design --and a few I haven't seen yet. Angle cuts with flares aren't too bad, but one of my favorite solutions is the one that is almost a tranny line in design, when dealing with tiny boxes. Cuts the velocity issue way down...keeps you out of the diode effect issue when it comes to the loadingof the port on either end. or, the ole' panty hose on either end to cut the chuffing and add a bit of resistance.

Now for my whiny bit. after 10-20 years (off and on) of farting around (literally) with holes in boxes, I've decided that ported boxes are a big no-no. Never again, over here. I want one of those mugs that 'Hales' issued, before they started making ported boxes and went bankrupt. They said : "Death Before Bass Reflex". I guess the gods were listening.

[ocool_15]

Alot of the ones I looked at were like the radius of a circle. like a quarter circle... Theres pics near the bottom.
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