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Bestsmurfs
12-04-2003, 08:33 PM
I own a vintage pair of S8's. The LE-15a's were just reconed by a JBL repair shop in Hamden CT. Now I am hearing distortion from the 375 horns, you can actually hear them rattle at certain frequency's (violins). The 075's are still nice and clean. My question is should I have the diaphragm replaced in the 375's with a 2440 diaphragm? That is what Alltel in Bridgeport, CT shows for a replacement or the 2441 diamond pattern if it's available. I also damaged the dust screen when a screwdriver got sucked down the horn. Wow, those are strong magnets!

When it comes time to downsize would you recommend parting them or selling them whole? My cabinets are only in fair condition.

Another little story….. I bought a second stereo system with B&W N804's and a Velodyne HGS15 sub. This stereo is a thousand times more tonally and spatially accurate than the JBL’s but lacks the kick in the chest the JBL’s deliver. The JBL sound is very much like a live performance all the time vs a studio recording. Are B&W’s for wimps? Are JBL’s outdated and obsolete? Are horns too harsh? What are your thoughts? Thanks for your time.

Mr. Widget
12-04-2003, 09:43 PM
There are several things that could cause a 375 driver to buzz or distort. The throat could be cracked, the diaphragm could be out of alignment, or most likely assuming these haven't been shipped recently or physically abused is the aluminum diaphragm has fatigued and needs replacing. In your system you should use the 2440 diaphragm. It is the exact replacement part.

If you would like to improve your system to sound more neutral (Like your B+W system) but maintain that JBL slam you are in for a bit of a project but relatively easy and not too expensive if your current components are in good shape. You will need to replace the crossovers, swop LE15As to 2235Hs and retune the cabinet (about an even trade at today's eBay prices) put in the 2441 diaphragms, get better horns (I like the 2397), and swop the 075s for 077/2405s. ( Again about an even trade depending on the cosmetic condition of your 075s)


Obviously this is only one guy's opinion, but I am pretty confident based on your statements this would put a big smile on your face.:)

Widget

Earl K
12-05-2003, 07:27 AM
Hi Bestsmurfs


I also damaged the dust screen when a screwdriver got sucked down the horn. Wow, those are strong magnets!

Before committing to buying new diaphragms - have the gaps of the 375(s) cleaned by a qualified JBL reconer. You could easily have metallic derbis in the gap - especially with a hole in the drivers dust-screen.

<. Earl K :)

Mr. Widget
12-05-2003, 09:59 AM
That's a good point Earl.

However If those are original diaphragms, it is a pretty certain bet they are due for replacement even if the offending buzz is caused by debris in the gap. The aluminum diaphragms don't last forever. Their levels of distortion increase with time.

Widget

Bestsmurfs
12-06-2003, 05:47 PM
I think I will go with the 2440 diaphragm replacements. Both drivers have the same distortion and are presumed to be original so I agree with the possibility that they are fatigued. They spent a little time coupled to a Crown 350 watt amp and that can be a little fatiguing too.

Thank you Mr. Widget and Earl for your suggestions.

Earl K
12-07-2003, 04:49 AM
Hmmmm

Before cracking open the back of those drivers - explore the possibility that you have "fried" a capacitor in the HF leg of your crossover.

If it was me and if I was thinking of parting these out to eBay ( as you mentioned ), I'd be very reluctant to unneccessarily open up the drivers ( if the red wax seals are intact ). That's why I would want to eliminate every other possible source of distortion .

A qualified JBL service center can put a tone sweep through those drivers to determine if the diaphragms are distorting. That nomimal service fee will be much cheaper than a "blind" commitment to $ 400 to $500 for new diaphragms .

<> EarlK:)