Cab "porting" help for live sound mains...

[tsnave]

Hi all!

New to the forums and need some expert advice. I've been slowly upgrading the drivers in my PA rig to neodymium drivers to cut weight and to hopefully improve sound quality so I'll provide the following history/details before I ask my questions.

The mains started out as Mackie/EAW S408 (specs attached) and then I swapped out the P-Audio 1" exit compression drivers for JBL 2431H high compression neodymium drivers. The backs of the speakers had small perforated grills which I made solid to help with feedback in tight stage situations.

Question #1: I do believe the cabinet could benefit from venting/porting, but I do not know the proper size and/or length to make the port? Once determined, I will port out the front side of the cabinet.

Question #2: I want to install new 8" neodymium drivers and have narrowed it down to three choices. After reviewing the specs (attached), can someone please offer some insight as to helping me make a decision.

Let me also add the fact that the crossover networks have been removed and I can adjust via a DBX DriveRack 260.

Thanks to all in advance!

[richie00boy]

You've got about 154 litres to play with, so 38.5 litres per driver, which is about right for a ported design. What frequency are you using them down to, porting might not add much.

[tsnave]

Keep in mind, the horn takes up a fare amount of space and so do the recesses for the handles (sides), handles/pole mounts (top & bottom). I have been running the subs up to 100-125 Hz. Not sure how much overlap to run between the mains and subs? The mains are also bi-amped and I'm running the high compression drivers down to 1.2Kz and up to 20Khz.

Thanks for the reply. So, if I did port the cabinets, what size port and how long would you recommend. Lowest noise as well

[tsnave]

Any more input?