port length modifcation on FE127E

bsv · 1st April 2007, 04:32 AM

Hi there,

I'm currently building Rabbitz full range vented bookshelf speakers designed for the Fostex FE127E as shown here:

http://www.rzaudio.com/rz52/fe127e.htm

The design calls for a 55mm diameter by 73mm long port. I have only been able to source a 50mm diameter port so I would like to know what length I should make it so that it performs the same as the 55mm?

Cheers,
Ben.

vinylkid58 · 1st April 2007, 06:07 AM

Hi Ben,

Your 50mm dia. port will be 57mm long to keep box tuned to 70Hz, based on a volume of 12.61 litres.

Jeff

bsv · 2nd April 2007, 02:23 AM

Thanks Jeff

rabbitz · 2nd April 2007, 01:31 PM

Another Newcastle dweller.... cool.

If you ever have to recalc the port, put the data in WinISD with the original port size and then change the diameter. It will give the new length.

... or the hard way L2=L1x(D2²/D1²)+(D2-D1)² where D2 and L2 is the new port length.

Try it without the BSC first so you can hear the difference it makes when BSC is added.

bsv · 2nd April 2007, 02:45 PM

Hey rabbitz,

Thanks for the reply and a great speaker design!

I'll try it without the BSC first and take it from there, thanks for the tip.

Cheers,
Ben.

1st April 2007, 04:32 AM	#1
bsv diyAudio Member Join Date: Oct 2006	port length modifcation on FE127E Hi there, I'm currently building Rabbitz full range vented bookshelf speakers designed for the Fostex FE127E as shown here: http://www.rzaudio.com/rz52/fe127e.htm The design calls for a 55mm diameter by 73mm long port. I have only been able to source a 50mm diameter port so I would like to know what length I should make it so that it performs the same as the 55mm? Cheers, Ben.

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1st April 2007, 06:07 AM	#2
vinylkid58 diyAudio Member Join Date: May 2005 Location: Victoria, B.C.	Hi Ben, Your 50mm dia. port will be 57mm long to keep box tuned to 70Hz, based on a volume of 12.61 litres. Jeff

2nd April 2007, 02:23 AM	#3
bsv diyAudio Member Join Date: Oct 2006	Thanks Jeff

2nd April 2007, 01:31 PM	#4
rabbitz diyAudio Member Join Date: Jul 2003 Location: Newcastle, Australia	Another Newcastle dweller.... cool. If you ever have to recalc the port, put the data in WinISD with the original port size and then change the diameter. It will give the new length. ... or the hard way L2=L1x(D2²/D1²)+(D2-D1)² where D2 and L2 is the new port length. Try it without the BSC first so you can hear the difference it makes when BSC is added.

2nd April 2007, 02:45 PM	#5
bsv diyAudio Member Join Date: Oct 2006	Hey rabbitz, Thanks for the reply and a great speaker design! I'll try it without the BSC first and take it from there, thanks for the tip. Cheers, Ben.

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