Originally Posted by
RMC
Hi kartsmart,
Sorry for not being the Rob you're expecting, but I may still shine on this....
RE: "the help I need for know is calculating the port length"
Your thing isn't rocket science, but first you have to calculate the right box volume. And determine what box tuning frequency are you expecting or looking for?
RE: "what I did is carefully removed the front panel and replaced it with a new one flush mounted" Assuming you used the same front panel thickness and that your ESS Air Motion Transformer will be mounted on TOP of the box not in it, you have still changed (increased) the box volume considering the original 4628B front panel is recessed (yours is flush mounted) and no 2404 in the box (btw 4628B box volume is given at 4.5 cu.ft.-possibly net?- and no tuning frequency mentioned in Spec Sheet nor in Technical Manual).
I can certainly help you if you're patient (busy these days) but for this thing to make sense you need a correct box volume to start with. Then, since you measured the vent we can find a tuning frequency using the JBL tuning chart I posted recently in "General Product information/Has Anyone Ever Seen These" thread with reverse engineering to figure the original box Fb, as a starting point.
However, since Vb is changed the original Fb may not still be the best suited. So at that point my guess is that a remodel of the box in speaker software, such as Winspeakerz or Win ISD Pro I have, may be needed...
Regards,
Richard