How to spot a sunk cone

[subwoof]

Here's a JBL 2206H that is on ebay for an attractive price - and here's the reason.

http://cgi.ebay.com/ws/eBayISAPI.dll...m=121019584715

(A) The gasket has been compressed flat to the frame. It should extend at least 1/8 past. It takes a LOT of pressure to do this - NOT just by "setting it down on a shelf"

(B) The 3 roll surrounds outer roll was flattened also by some means - most probably by one of those infamous bug-eye grills they sell in the music stores and (sigh) JBL did use on some of their concert series monitors. You can tell because the mounting holes are not perforated and there are no clamp marks on the gasket. Those bug grills have an inside diameter that is too small and WILL interfere with the surrounds on pro series JBL's.

(C) The surround rolls should be level - they are actually tapered inward (down ) meaning that a long-term mechanical issue forced the cone down. this is not recoverable alas. This can be seen also by looking at the spider from the side but the sellers pictures don't show this very well.

sub

[DogBox]

Hi Subwoof,

I've got some weird scenarios going through my head as to how this "might" happen, but.. What causes a cone to 'sag' like this? would
it 'sag outward' if you hung it up by its magnet? That spider must really be stretched beyond its 'spring'...?

DogBox

[subwoof]

this type cone will NEVER sag no matter WHAT the usage, storage or age.

the sunk cone was caused by a long-term external mechanical influence, period.

Somebody screwed up when assembling the cabinets...a LONG time ago.