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JBL 2482 Drivers: each sounds different

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Posted on October 21, 2015 at 21:49:52
jpackard
Audiophile

Posts: 57
Location: Mountain West
Joined: October 16, 2001
 I use a pair JBL 2482s and tractix horns on my setup. When I play these horns by themselves, each horn sounds a little different. One driver seems to go lower than the other. It is not the crossovers.

I installed a new original diaphragm in the one that sounded inferior and it didn't make a difference. I did notice in the back cover of each driver is a layer of foam rubber, maybe 3/4" thick. In one driver the foam rubber appears to be original and the other appears to be a replacement. The original foam is memory foam rubber-like but it will tear easily. The non-original foam rubber in the other driver springs back like conventional foam rubber.

This driver is designed with the dome of the diaphragm facing the rear cover.

Should the foam rubber in the back cover always contact the dome of the diaphragm? See the photo with cover removed in somebody's auction:

http://www.ebay.com/itm/191718406512?ssPageName=STRK%3AMEBIDX%3AIT&fromMakeTrack=true

Would I be better off switching to Community M200a drivers?

 

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RE: JBL 2482 Drivers: each sounds different, posted on October 22, 2015 at 05:25:42
weltersys
Industry Professional

Posts: 685
Location: FL
Joined: September 28, 2004
 "Should the foam rubber in the back cover always contact the dome of the diaphragm?"

No, it should not contact the diaphragm at all. The foam is shot in the Ebay 2482.

2482 drivers are old, if one has been dropped or banged around more than the other, or run at very high power, it may have lost some magnetism, which will affect the frequency response.

The diaphragms also could have a slightly different impedance (or a completely different impedance) which also would affect the output.

And the damping foam being different will also affect the sound, especially if it is touching the diaphragm.

The diaphragms need to be exactly centered in a clean gap to perform "on spec", cleaning and alignment may need to be done on one or both.

As far as switching to M-200, you will be hard pressed to find a pair of old drivers of any brand that have exactly the same frequency response.

 

RE: JBL 2482 Drivers: each sounds different, posted on October 23, 2015 at 00:48:07
jpackard
Audiophile

Posts: 57
Location: Mountain West
Joined: October 16, 2001
 Thanks for the reply, Weltersys.

Today I swapped the the back covers with the different foam rubber damping material. Absolutely no change at all.

So you must be correct. One driver must have a shifted core, irregular gap, or magnet problem. I don't know of any company that can service these drivers.

Any other 2" horn driver with 4 bolt pattern you (or anyone else) might suggest that provides 400hz - 6khz?

 

RE: JBL 2482 Drivers: each sounds different, posted on October 23, 2015 at 05:30:08
b.l.zeebub
Audiophile

Posts: 9361
Location: 52deg 28'N,1deg56'W
Joined: April 17, 2006
 The people in the link may be able to help you.

The AlNiCo magnets of these (or any other driver for that matter) is very susceptible to physical shock. So if it has been knocked or dropped at any stage in its life it may well have demagnetized to some degree.
On the plus side AlNiCo is more immune to heat than any other magnet material.

 

RE: JBL 2482 Drivers: each sounds different, posted on October 23, 2015 at 07:26:05
Kloss
 EV DH1A

 

ASk GREAT PLAINS AUDIO if they would take a look, posted on October 24, 2015 at 08:00:19
rickmcinnis@dogwoodfabrics.com
Audiophile

Posts: 3040
Location: Atlanta
Joined: December 15, 2003
 Compression drivers are compression drivers even though they specialize in ALTEC.

They can re-magnetize the drivers.

These are very fine people. Send them a note.

In addition, I would use wool felt instead of any type of foam in the chamber.

Take care,

 

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