port conversion

[audiobahnkid592]

I need to turn two 2" DIA ports 6.5" long into slots. could i use a 2"W 3"H and 6.5D port? or what size would i need

[Perry Babin]

Yes. The 2x3 port would essentially be the same.

[audiobahnkid592]

Thank you Perry. You have to be one of the most helpful person that this site has

[bottomfeeder]

Originally posted by Perry Babin
Yes. The 2x3 port would essentially be the same.

Can you help me ?
Unfortunately my Alumipro BP12 bandpass , looks to big sitting in my pickup !
My plan is to turn it to a lower longer cabinet that sits nice on the floor (I got a kingcab) the bandpass chamber sizes are .8 & 1 cubic but my problem is the ports , I need to covert the 2x 4.5x13" (heavily flared at all ends) to a slot port but of the 3 charts I found on diyaudio did not help .
Can somebody help me !

[spooney]

you could checkout caraudio.com/forum for help . they have a few people that could probably help you come up with a whole new bandpass design .

[bottomfeeder]

I put in a post (caraudio.com) for the port questin, a couple of questins but no info yet .
I hope someone can help me , it is a shame to have a bp12 and not use it

[tsmith1315]

Originally posted by bottomfeeder

I need to covert the 2x 4.5x13" (heavily flared at all ends) to a slot port but of the 3 charts I found on diyaudio did not help .
Can somebody help me !

Are you changing the cabinet volume? If not, just keep the (front)surface area of the port and length of the port the same as what it is now.

There are a couple of kinks, however:
- Narrow slots tend to resonate at lower frequencies than a round port with equal (front) surface area because the increased internal surface area presents a larger boundary layer. If you need to use a narrow slot, increase the (front) surface area or reduce port length a bit to compensate.
- You'll have to make a judgement call on what size to consider the existing port since it is heavily flared. A reasonable estimate would be an average of the "throat" and "mouth" areas. Or you can try to locate the port frequencies in the spec's and calculate it from there.


If you are changing the internal volumes significantly, you'll need to start from scratch with port tuning.

[bottomfeeder]

Originally posted by tsmith1315



Are you changing the cabinet volume? If not, just keep the (front)surface area of the port and length of the port the same as what it is now.

There are a couple of kinks, however:
- Narrow slots tend to resonate at lower frequencies than a round port with equal (front) surface area because the increased internal surface area presents a larger boundary layer. If you need to use a narrow slot, increase the (front) surface area or reduce port length a bit to compensate.
- You'll have to make a judgement call on what size to consider the existing port since it is heavily flared. A reasonable estimate would be an average of the "throat" and "mouth" areas. Or you can try to locate the port frequencies in the spec's and calculate it from there.

I plan to use the same cabinetS volume , I could use the same exact port sizes but the lower heigth of the cabinet wont allow for a fit of the round ports .
So a slot port is ideal (as long as I can figure out the conversion) .
Maybe I can figure it to a single square port ??
I read (if you convert) the flare ads 1/4 to the length .

[tsmith1315]

Originally posted by bottomfeeder


I read (if you convert) the flare ads 1/4 to the length .

That's a rule of thumb, but could be reasonable.

So you have two 4.5" dia ports 13" long?

That's 31.8 square inches of port area. Roughly equivalent to 3"x10" or 2.5"x12.75" rectangle openings, and 13" long minus the flare compensation.

[Perry Babin]

Let me know if I have any mistakes.

http://www.bcae1.com/temp/simpleportconverter.swf