Port Length Confusion

[BEAVER.989 10+ year member]

I'm building a box for an IDQ12V2, but also need it to work for an IDQ12V3 (future). I've decided to go 1.5 cft. My confusion starts with the tuning...

I have the tech sheets for both drivers in front of me. The V2 says to use a 3" port @ 13.75" long. The V3 says 3" @ 8.30" long. This cannot be right, can it? Why the big difference for a very similar tuning frequency?

Have a look...

http://www.imagedynamicsusa.com/pdf/IDQ12%20D2%20V2.pdf

http://www.imagedynamicsusa.com/pdf/iDQ%2012%20D2%20v.3.pdf

Click to read more...

 

[BEAVER.989 10+ year member]

Odd, isn't it?

By my guesstimation, the 13.75" port is tuned to roughly 27hz and the 8.30" is at about 35hz... but I could be way off.

Is anyone able to shed some light on this for me?