JBL 2440 HF Loss

[teddy.edwards1]

Hello,

I have a pair of JBL 2440's with JBL 2395 horns as part as an actively crossed over system (800-8000Hz 18db/oct).

I have noticed a distinct decrease in HF output from one driver recently.

I tried swapping over the amp outputs, the speaker cables and also the protection capacitors (22uf bi-polar electrolytics)

But the HF decrease remains only on one side - so I have narrowed it down to the compression driver/diaphragm - but which is it!?


the driver is not going to suddenly demagnetise itself is it?! It would have to be dropped for this right?

So I have ordered two JBL Diaphragm D16R2441 - for 2441, 2441J to try fix the problem

anyone got any suggestions at all?!

Thanks
Tom

[Earl K]

Hi,

One ( somewhat far-fetched ) possibility for the loss of HF, might be crumbling foam ( from within the back-cap of the driver ) , dis-attaching & resting on the metal dome .
Foam contacting the diaphragm will reduce it's top end .

Yes, typically one would need to have dropped the driver in order to demagnetize it ( or hit the magnet with enough voltage/current , which would also shatter the diaphragm ) .

$ 338.00 ? , wow ( I think I would continue saving for a pair of TruExtent diaphragms ) !

[teddy.edwards1]

Hi,

$ 338.00 ? , wow ( I think I would continue saving for a pair of TruExtent diaphragms ) !

Nah, I got em here in the end for $182 each which is bad enough... considering it probably won't fix it!
I'll open it up and have a look inside... maybe you're right. That would be nice and easy.

[teddy.edwards1]

But have you used those really expensive berylium diaphragms inside a JBL driver before? Never even knew that was an option, albeit an expensive one! Thanks for the advice...

[Earl K]

But have you used those really expensive berylium diaphragms inside a JBL driver before? Never even knew that was an option, albeit an expensive one! Thanks for the advice...

I haven't used them , but other LHF members have .

The "word" on the street is they might have a harder time fitting properly into the gaps of the older Alnico drivers ( such as the 2440/1 ) .
- I'll admit this is mostly hear-say / but for those of us not in the continental US, it's a concern never-the-less .

[Fort Knox]

Hi,

One ( somewhat far-fetched ) possibility for the loss of HF, might be crumbling foam ( from within the back-cap of the driver ) , dis-attaching & resting on the metal dome .
Foam contacting the diaphragm will reduce it's top end .

I've had the foam thing happen ..

[ivica]

Hello,

I have a pair of JBL 2440's with JBL 2395 horns as part as an actively crossed over system (800-8000Hz 18db/oct).

I have noticed a distinct decrease in HF output from one driver recently.

I tried swapping over the amp outputs, the speaker cables and also the protection capacitors (22uf bi-polar electrolytics)

But the HF decrease remains only on one side - so I have narrowed it down to the compression driver/diaphragm - but which is it!?


the driver is not going to suddenly demagnetise itself is it?! It would have to be dropped for this right?

So I have ordered two JBL Diaphragm D16R2441 - for 2441, 2441J to try fix the problem

anyone got any suggestions at all?!

Thanks
Tom

Hi teddy.edwards1;,
be careful as diaphragm 2440 and 2441 are not the same, even both are aluminum.
2440 can more easy 'goes' to the lower frequency, especially if the horn is smaller, then 2441, that has stiffer suspension and can be used up to the almost 20kHz depending to the horn too). Using 2441 diaphragm under 1200Hz , you have to be very careful.
I have no experience with the 2390 hirn, but fir 2311+2308, using 2441 diaphragm is , I think, 'risky business'/


regards
ivica