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tv506
10-02-2003, 02:31 AM
Hi,

I have pair of JBL 2441 (rated at 16 ohms) compression drivers. When I measured the impedance, one measured at 7.9 ohms and the other measured at 9.3 ohms. Should both be the same value? Should they measure at 16 ohms? At 7.9 and 9.3 ohms, will these effect the sound quality?

Thank you,
Peter

4313B
10-02-2003, 05:59 AM
How are you measuring the impedance?

The 2441 is a "16 ohm" driver and the DCR should measure 7.3 ohms to 8.6 ohms.

tv506
10-02-2003, 09:47 AM
I used a volt meter switch to ohm, and measured both units. one measured at 7.9 and the other measure at 9.3 ohm. What is the proper way to measure? should both unit be the same rating? Since they are not match, will this effect in sound?

Thank again,

4313B
10-02-2003, 10:00 AM
You're measuring the DCR correctly and 9.3 ohms is definitely out of spec and can indicate a "suspension" problem. It can also indicate a different diaphragm is in use. You might want to have that driver checked out.

If you have the means to do a frequency sweep the test sweep for that particular driver is 3.5 volts input swept from 350 Hz to 1200 Hz. Be careful of your hearing! It's probably best to just have a service center check it for you.

Oldmics
10-02-2003, 02:19 PM
Giskard,Could you elaborate on the DCR and suspension.In the event of a catastrophic suspension failure and the coil is chaffed open or referenced to ground the DCR would change.I have not encountered any other DCR changes due only to suspension issues.Sounds like you have encountered situations that are unique and intriguing.Please enlighten me so that I may pass these failures onto the warranty codes.(kidding)Best regards,Oldmics

Alex Lancaster
10-02-2003, 03:19 PM
How about a faulty solder joint?, That would give You a higher DC resistance; It used to happen to us in cone speakers at the coil to Litz wire pigtails, they would work, but funny, or cut in and out.


Alex.

4313B
10-02-2003, 03:38 PM
"I have not encountered any other DCR changes due only to suspension issues. Sounds like you have encountered situations that are unique and intriguing. Please enlighten me so that I may pass these failures onto the warranty codes."

Hey Oldmics, me neither! :rotfl:
I got confused!
I read "impedance" and had impedance curves on the brain when I answered the post :)
Sorry! :D

Oldmics
10-02-2003, 03:46 PM
AHHHHH, Impeded brain curves !!!!! It happens to me to,mostly after a long day of reconing.Thanks,Oldmics

4313B
10-02-2003, 03:49 PM
Ahhh! I love the smell of MEK in the morning!

Oldmics
10-02-2003, 03:53 PM
You are one SICK puppy!!!!!!!!!!!!!!!!! I am rollin,LOL,Oldmics

tv506
10-03-2003, 01:43 AM
Thank you very much to all of you for all your input. Well, I will bring it to the JBL shop and them check it out and hopefully not a major problem.

By the way, what is DCR? Is it DC rating?

Thanks again,

4313B
10-03-2003, 04:38 AM
DCR = Direct Current Resistance

Here's a quick example of some impedance curves where resistance is measured against frequency. :)

The top graph shows the impedance curves of two different diaphragms in a compression driver.
The bottom graph shows the effects of "loading" those compression drivers with a horn.

Anyway, sorry if I caused any confusion. :rolleyes: