JBL S1S-EX duct length

[Jakob]

Hi,
I was thinking of building either clones or just boxes equal in size. However, when using WinISD and putting in the 2242's parameters in a 185l box tuned to 25Hz with three 4" ports, the ports length according to the calculation should be 22,1" which is about the same as the original boxes depth.
How does this work out, are the ports bent?
Someone owning the real deal that know how long the ports are? And if they aren't 22", what's the story? Can't trust Win ISD or?

B.R Jakob

[bubbleboy76]

Here you can see how the ports looks like, they are straight:
http://www.jblsynthesis.com/tl_files/catalog//jblsynthesis/S1S-EX/S1S-EX%20Spec%20sheet.pdf

S2s-ex, on the other hand, has bent ports, according to this picture:
http://www.audioheritage.org/vbulletin/attachment.php?attachmentid=61639&d=1394709290

[Jakob]

Thank's bubbleboy!
Yes, I saw that document and it adds on to my confusion.
So, if the ducts are straight, they cant be as long as WinISD want. I trust JBL in this case. I wonder how long the ducts really are and how far from the back wall they end?

[rdgrimes]

http://manuals.harman.com/JBL/HOM/Technical%20Sheet/S1S-EX%20ts.pdf

FWIW, that shows that the flare used on both ends of the tube is the same part. Maybe you can get somewhere by searching those part numbers.

[Jakob]

Thanks, I did try to google the PN's (as well as all other phrases I could think of including the words S1S-EX, duct length and so on...) to no avail :banghead:.

The S1S are supposed to be tuned to 25Hz but what if it really is tuned somewhat higher? The length of the ducts change a lot when getting closer to 30Hz. According to WinISD, a box tuned to 29Hz requires ducts 16" long which leaves plenty of room to the rear cabinet wall.

My next step will be to try some other box building programs to see what duct length they come up with.

Thanks for all hints so far, much appreciated :)

[Jakob]

I think I just might have found something:

In this link at the talkbass forum, one member states he needs to subtract 1/3 of the WinISD proposed length to get the desired tuning:

https://www.talkbass.com/threads/bassbox-pro-6-vs-winisd-which-do-you-trust-also-12-driver-recommendation.1130103/

Have some one else experienced this? Is f.e. Bassbox Pro more dead on?