The Le value of JBL2445J [Archive] - Lansing Heritage Forums

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Flemming Skov

11-23-2009, 11:21 AM

Hi,

I have searched the net for info regarding the Le value of the JBL2445J driver. Have'nt had any succes :blink:.

So, if some of you Gent's have an idea of the number then please respond :D

I'm using the driver on my JBL2350 horn and need it in rebuilding/update my crossover (zobel network etc...) ;)

Regards
Flemming

jcrobso

11-23-2009, 12:52 PM

Flemming Skov

11-23-2009, 02:44 PM

robertbartsch

11-23-2009, 03:37 PM

...not sure about Lee values in Euros in Denmark or local currency but in the U.S. the 2445js can be had used for 150-175 USD.

Since the value of the USD is declining at an alarming rate recently, you may get a bargin if you find a dollar denominated seller who is willing to ship this to you from America.

..good luck - obviously they are heavy as hell!

P.S.

...some people here at the cite frown upon folks who ask about the prices and values of JBL/Altec equipment. ...not sure exactly why, but it is somewhat of a no-no!

speakerdave

11-23-2009, 05:15 PM

Rough day at the office.

Inductance.

4313B

11-23-2009, 09:10 PM

I appreciate your help but it's not mentioned there!!! I also have looked in the technical letters concerning the compression drivers, it seems that JBL do not care about this figure?Nope, they really don't.

I changed the diaphragms in mine to 8 ohms and don't feel like pulling them out of the loudspeakers they are in and changing them back just to measure their Le. :( It's pretty much a non-issue.

Flemming Skov

11-23-2009, 11:03 PM

Nope, they really don't.

I changed the diaphragms in mine to 8 ohms and don't feel like pulling them out of the loudspeakers they are in and changing them back just to measure their Le. :( It's pretty much a non-issue.

You can say so, but if your running the crossover figures in a program (LTspiceIV), then the passband will harm depending upon the figure your choose for the Le.

For test I have choosen the Le to 2.2mH. The impedance measured is from 12.3 to 24.9 ohm, on my 2445J, so it' will depend a lot. The crossover can be "flat" if the "right" value for Le can be found :D

4313B

11-23-2009, 11:53 PM

Well if you care that much then you should have the gear to measure it yourself. The impedance of the horn/c.d. combo is more important and if you feel that you need a zobel then it will be quite easy to come up with one in realtime. You might also want a trap filter to kill off the resonance peaks.

Flemming Skov

11-24-2009, 06:43 AM

I'm using my pro JBL gear for hifi pleasure and is tweaking it as my hobby. :)

So, from my experience, small deviations is audible and I find the tweaking nessecary. Maybe the reason for the, sometimes bad reputation, JBL do have in "harsh" or "rough" sound is coming from the much to weak developed standard crossovers used by JBL?

I also find it nescessary to notch a few dB around 2kHz due to some peaking in the 2445/2328/2350 setup which end up in a better voice expression. The high deviation in the impedance and the unknown Le do have a big impact on my 24dB L-R filter. Fh(highcut) and Fl(lowcut) will change alot and the variation of the Le will give significant ripple in the passband.

Therefore I will load the driver with 5.6 ohm across the terminals and 2.2 ohm in series. The impedance variation will then be very small seen from the filter. If I then know the Le (I do agree on trial and error) the ripple wil be controlled by the zobel filter or so..

Thats the reason for asking for the Le. I'm not able to measure the figure so...:o:

4313B

11-24-2009, 09:04 AM

So, from my experience, small deviations is audible and I find the tweaking nessecary. Maybe the reason for the, sometimes bad reputation, JBL do have in "harsh" or "rough" sound is coming from the much to weak developed standard crossovers used by JBL?Here's an example of a full blown conjugate that LEAP cranks out for a 2441 bolted to a 2311 horn. The red curve is the flattened impedance curve.

The second schematic with R8 and C6 shows what I would use instead to deal with Le if I were so inclined (blue curve).

Eaulive

11-24-2009, 09:08 AM

I'm afraid to ask, but why the "e" :blink:

I'm maybe too old but but for me resistance was always "R", not "Re", and inductance was "L", not "Le"...
What about capacitance? :dont-know:confused:

4313B

11-24-2009, 09:11 AM

And if I was compelled to deal with the resonances I might put in L2 and R1 which are just a couple of values I came up with off the top of my head:

4313B

11-24-2009, 09:15 AM

Therefore I will load the driver with 5.6 ohm across the terminals and 2.2 ohm in series. The impedance variation will then be very small seen from the filter.Ok. R9 and R10.

4313B

11-24-2009, 09:19 AM

Just the two resistors:

4313B

11-24-2009, 09:25 AM

Of course we would have to look at the SPL curves with each iteration to see the results but you get the idea.
I also find it nescessary to notch a few dB around 2kHz due to some peaking in the 2445/2328/2350 setup which end up in a better voice expression. The high deviation in the impedance and the unknown Le do have a big impact on my 24dB L-R filter. Fh(highcut) and Fl(lowcut) will change alot and the variation of the Le will give significant ripple in the passband.Yep.

You'll need to get an impedance and SPL plot for that combination. Once you get that data you can play around with it as desired and try all kinds of stuff. Some solutions will sound good and some will suck the life right out of the whole mess.

Flemming Skov

11-24-2009, 10:03 AM

Once you get that data you can play around with it as desired and try all kinds of stuff. Some solutions will sound good and some will suck the life right out of the whole mess.

:D Yep!

I have a measurement which I did in the anechoic chamber for the 2445/2328/2350 from 300Hz to 20kHz (my former work). This measurement is the "backbone" in my filtering process :)

Thanks alot for you simulations, I appreciate it....

Regards
Flemming

Flemming Skov

11-24-2009, 10:07 AM

I'm afraid to ask, but why the "e" :blink:

I'm maybe too old but but for me resistance was always "R", not "Re", and inductance was "L", not "Le"...
What about capacitance? :dont-know:confused:

It refers to the electrical part of the speaker model (which also consist of a mechanical part to).