I recently picked up a couple of JBL 4645 boxes with 2245 drivers in them. I'm trying to check things out, and here's what I've noticed:
-surround replacement done less neat than I like
-one box buzzes when the cone is tapped
-almost all the mount screws have their phillips heads cammed out
So I decided to pull the driver on the box that buzzed when tapped. Had to drill out 4 mounting screws. Noticed that the front gasket (thick rubber) was not aligned with screws, and was of two different thicknesses.
For the drill out, I kept a vacuum near the drill bit to capture the shrapnel. It took a while because I didn't want to chance breaking the bit or slipping.
Expected to find a screw or something on the back side, making the buzzing. I did not. I did find a piece of particle board.
Out of the box, the driver made the normal damped thump when tapped. Putting some bass into it, I found that it was distorting significantly with a manually induced excursion of about 3mm. Seems like too little, but I haven't checked Xmax for this driver yet, etc. Since everyone is home, I have stopped my play for the day.
I need to get some more mounting screws, as all but one I would not put back in, and 4 have been destroyed by drilling. As a result, this box will be open for a while.
Does anyone have some suggestions on how to test this, and determine if I have a problem?
As near as I can tell, the less than ideal bad foam job is not skewing the cone off center, but I could be wrong.
I did run this driver through the crossover (DCX2496) and using a cutoff of 100 Hz there was audible buzzing. However when I gave it broadband music, I could not readily detect any buzzing. For now, I will assume that the piece of wood (15mm x 3mm x2mm) may have been captive somewhere making that noise.
Thanks.