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6th December 2002, 11:09 PM  #1 
diyAudio Member
Join Date: Dec 2002
Location: Brisbane, Australia

help, need some figures
hi guys,
does anyone have/know a link to find the following numbers: Linear Exercursion  Xmax & Exercursion  Vd for: Vifa M25WO4908 and if possible Vifa C17WG6908, Vifa D26NC1506 thanks in advance, Alex 
6th December 2002, 11:42 PM  #2 
diyAudio Member
Join Date: Jan 2002
Location: Bucks County, Pa


6th December 2002, 11:47 PM  #3 
diyAudio Member
Join Date: Dec 2002
Location: Brisbane, Australia

that's where i've got everything so far except for Xmax and Vd, vifa don't state the xmax or vd
unless they are codewords for something else? Alex 
6th December 2002, 11:48 PM  #4 
diyAudio Member
Join Date: Dec 2002
Location: Brisbane, Australia

is Xmax Air Gap height?

7th December 2002, 12:15 AM  #5 
Wizard of Kelts
diyAudio Moderator Emeritus

Hang ongot the figures right here. Take a moment to calculate.
Air Gap Height is part of the Xmax calculation. Will explain momentarily. 
7th December 2002, 12:19 AM  #6 
diyAudio Member
Join Date: Dec 2002
Location: Brisbane, Australia

thanks bud, so can you work it out with a formula from the stats provided from vifa?
if so the D26NC1506 datasheet can be found HERE as dst only have the newer 5506 version, if you use a formula can you provide it so i can work out future xmax values, thanks in advance, Alex 
7th December 2002, 12:36 AM  #7 
Wizard of Kelts
diyAudio Moderator Emeritus

First the formulas for Xmax and Vd
Xmax = maximum one way excursionfrom center to extreme Vd = Volume of air displaced, (moved), by the driver. Sometimes Xmax is given as fronttoback linear travel, but it should be given as centertoend. Here are the formulas: 
7th December 2002, 12:51 AM  #8 
Wizard of Kelts
diyAudio Moderator Emeritus

For the Vifa M25W04908:
The Effective Diaphragm Area, (Sd), = 346 square cm. The Voice Coil Height is 14 mm. The Air Gap Height is 6 mm. Therefore, the Linear Xmax is (+ or ) 4 mm. Therefore, Vd = 346 sq. cm times .4 cm = 138.4 cc. For the Vifa C17WG6908: The Effective Diaphragm Area, (Sd), = 143 sq. cm. The Voice Coil Height is 12 mm. The Air Gap Height is 6 mm. Therefore, the Linear Xmax = (+ or ) 3 mm. Therefore, Vd = 143 sq. cm times .3 cm = 42.9 sq. cm. For the Vifa D26NC5506, (the new substitute for the 2615) Effective Diaphragm Area, (Sd) = 7 sq. cm. The Air Gap is longer than the Voice Coil by .5 mm. I assume that means it can move linearly (+ or ) .25 mm. Don't hold me to that. It's a tweeter anywaythings are different. Estimated Vd = 7 sq cm times .025 cm = .175 cc. By the way, mechanical Xmax for woofers is usually 1.5 to 2 times the Linear Xmax. Do you have the response charts for the C17 WG? If not, they are located here: http://www.mass.com.au/masssales/pdf/C17WG6908.pdf I'll recheck the figures and edit if necessary. If I am off on the calculations, as an American I can blame it all on Metric!! 
7th December 2002, 12:54 AM  #9 
diyAudio Member
Join Date: Dec 2002
Location: Brisbane, Australia

thanks,
now when the software calculates port sizes, when you chnage from 1 to 2 ports the length doubles plus a bit. for e.g. currently with one port 66mm diameter and 100.4mm long when i change to two ports @ 66mm diameter i get 249.1mm length. now is the 249.1mm the total length for both ports or 2 ports @ 249.1mm length? being around 500mm total? thanks, Alex yes i have the charts 
7th December 2002, 01:01 AM  #10 
Wizard of Kelts
diyAudio Moderator Emeritus

That would be 249 mm for each port tube. Each tube will be 66 mm times 249 mm.

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