how long should this port be?

Jimmy154 · 19th July 2002, 12:23 AM

HI,

I'm almost done building my speakers and I think my boxes might be tuned wrong. I used WinISD to design rectangular ports for some speakers that I'm building. The wider I make my ports using the program (keeping the same cross section area; 14.25 sq. in.) the shorter the port becomes. My questions is why does it do this? It seems to conflict with the tuturial on rectangular ports at this link http://www.jlaudio.com/tutorials/ports/index.html The webpage states that the rectangular port is the same length as the round port if you keep the cross sectionarea the same. I'm not sure what to believe. Anyone know who's right?

Also this link suggests that when using ports near a wall you should subtract a correction factor from your calculations that you make if the port wasn't part of a wall. Does WinISD already take into consideration that a rectangular port is against a wall? Any suggestions?

I already built a port 1.5 x 9.5 x 6.15" (6.9 - .75" suggested correction factor), but I haven't closed the boxes yet. It's in a 44.4 lter box tuned to 46.87 Hz. Is this right?

Jimmy154 · 21st July 2002, 02:48 PM

If you have a box 44.4 liters in volume and you have a rectangular port with three sides being the walls of the speaker, 3.8 cm (1.5") x 24.1 cm (9.5"). Would you make the port 15.6 cm (6.15") or 17.5 cm (6.9") long or something else?

Ron E · 21st July 2002, 03:23 PM

The jlaudio site is right about the cross sectional area.

WinISD has a lot of errors, some of which I have reported to the author. He doesn't seem to care enough to change or remove bad functionality. The new version, pro alpha, is better but still has calculation errors. Due to the author's attitude to my previous error report, I have no desire to help him out by telling him what they are.

If you want a decent program, use Unibox or Isaac's (f4ier) subsim. The only problem with those is that you need to know something to use them, and many people get incorrect results because of the increased functionality

The correct port length to tune your 44.4 Liter box to 46.9 Hz with a 1.5x9.5" port would be 8 inches.

19th July 2002, 12:23 AM	#1
Jimmy154 diyAudio Member Join Date: Jun 2002 Location: Los Angeles	how long should this port be? HI, I'm almost done building my speakers and I think my boxes might be tuned wrong. I used WinISD to design rectangular ports for some speakers that I'm building. The wider I make my ports using the program (keeping the same cross section area; 14.25 sq. in.) the shorter the port becomes. My questions is why does it do this? It seems to conflict with the tuturial on rectangular ports at this link http://www.jlaudio.com/tutorials/ports/index.html The webpage states that the rectangular port is the same length as the round port if you keep the cross sectionarea the same. I'm not sure what to believe. Anyone know who's right? Also this link suggests that when using ports near a wall you should subtract a correction factor from your calculations that you make if the port wasn't part of a wall. Does WinISD already take into consideration that a rectangular port is against a wall? Any suggestions? I already built a port 1.5 x 9.5 x 6.15" (6.9 - .75" suggested correction factor), but I haven't closed the boxes yet. It's in a 44.4 lter box tuned to 46.87 Hz. Is this right?

21st July 2002, 02:48 PM	#2
Jimmy154 diyAudio Member Join Date: Jun 2002 Location: Los Angeles	Okay time for a new question . . . If you have a box 44.4 liters in volume and you have a rectangular port with three sides being the walls of the speaker, 3.8 cm (1.5") x 24.1 cm (9.5"). Would you make the port 15.6 cm (6.15") or 17.5 cm (6.9") long or something else?

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
What can I do with this 8" TB sub without a 100 foot long port?	The Paulinator	Subwoofers	15	17th September 2007 05:13 AM
30" long 4" Precision Port	PoorboyMike	Subwoofers	4	11th May 2007 12:01 PM
long external port idea	dwk123	Subwoofers	4	22nd November 2006 08:50 PM
comlicated port/driver combo question. (long read)	exhausted mule	Multi-Way	19	10th August 2005 12:42 AM
Long vent/port as bracing in Ambiorix?	Cordraconis	Subwoofers	16	23rd July 2005 10:04 AM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

21st July 2002, 03:23 PM	#3
Ron E diyAudio Member Join Date: Jun 2002 Location: USA, MN	The jlaudio site is right about the cross sectional area. WinISD has a lot of errors, some of which I have reported to the author. He doesn't seem to care enough to change or remove bad functionality. The new version, pro alpha, is better but still has calculation errors. Due to the author's attitude to my previous error report, I have no desire to help him out by telling him what they are. If you want a decent program, use Unibox or Isaac's (f4ier) subsim. The only problem with those is that you need to know something to use them, and many people get incorrect results because of the increased functionality The correct port length to tune your 44.4 Liter box to 46.9 Hz with a 1.5x9.5" port would be 8 inches.

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)