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Guido
05-25-2003, 04:06 PM
Hi everybody!

I'm planning to buy a pair of 2012H. Problem is that the datasheet have no information about the inductance of voice coil (Le). Can any of you help me out?

I need this information to compare this speaker with the 2121.

Thank you!

Guido

tomp787
05-27-2003, 04:46 PM
Hello,

You can find some information about the 2012 in "technical notes, volume 1, number 24" on the jblpro.com website. In it it states that Le is purely resistive at 1KHz. There is also an impedance graph.

Before you purchas the 2012, you may want to consider the 2251. This appears to be the newest 10 inch cone and it has NDD. Some info about the 8 inch version (2250) can be found in "technical notes, volume 1, number 29". The 2251 is used in the model 4348, which has been mentioned in these forums as well.

I hope this helps.

Best Regards, Tom

Guido
05-28-2003, 12:42 AM
Purely resistive at 1kHz?

What can I do with this? How is this compared to the 0,9mH from the 2121?

Thanks, Guido

4313B
05-28-2003, 08:23 AM
Purely resistive Le means there is no inductive reactance. If you look at the 2012H specs it will tell you the minimum impedance is 7 ohms. Inpecting it's impedance curve you can see that it presents an ~ 7 ohm load across most of the bandwidth you would use it and hits ~ 10 ohms around 10 kHz, well beyond the cutoff of any low pass filter you would use. In other words, simply treat it as a 7 ohm load; you don't really need to be concerned with adding a conjugate (zobel) to flatten it's impedance like you would with a 2121H.

Guido
05-28-2003, 08:35 AM
Hi Giskard!

Again a very detailed answer. Thank you for that.
But my problem is that eventually I want to use this speaker in my 4343 and I see no impedance correction in the 3143 network for the mid speaker.
So I think I can use this 2012H without any corrections in the network. Of course except changing the resistors for equal the sensitivity.
The 2012H has 100dB.

Am I right?

4313B
05-28-2003, 09:03 AM
Well, guess what? I can't find my spec sheet on the 2121 so I'll have to try to get hold of another.

JBL didn't employ conjugates on a lot of their 12 dB /octave and higher filters because theoretically it isn't required (plus it adds to cost).

"So I think I can use this 2012H without any corrections in the network."

Who knows? I would be inclined to try it though. I think your problem in this particular system would be more of an acoustic match than an electrical match. And if you don't have a stock set of 4343's to A/B against, and if the 2012H sounds right to your ears, who's the wiser?

Oh yeah, looking at the schematic it's slop anyway, they used a 16 ohm L-Pad (for power handling purposes) so you've got quite a bit of slop already built into the filter because of that. I wouldn't even worry about electrical load if only because of that. You're issue will be mostly acoustic. Fiddle with the 2 ohm and 30 ohm resistors to get the sensitivity down.

BTW, have you thought about using the 3145 filter instead? It is degrees better and would be the one I would consider running if I still had 4343B's...

Guido
05-28-2003, 09:06 AM
Thank's again for your help!

I will let you know how it goes.....

Guido

Guido
05-28-2003, 09:08 AM
Before I think of using 3145 Filter I have to complete my 4343.

But then, who knows....

Earl K
05-28-2003, 10:43 AM
Hi Guido

Originally posted by Guido
The 2012H has 100dB.
Am I right?

No,
I'd say the sensitivity you'll be dealing with is in the mid 90's area, not the 100 db as speced by JBL . That JBL spl spec. is an average derived between 500 hz - 2.5 khz . A mid 90's figure should suit your purposes better for your project when matching to your woofer choice. I think 95-96 db is what you'll end up with, once you electrically deal with the rising midband response ( ie , some lowpass inductor kicking in around 750 hz - for example ) .

I own and use 2012h speakers in SR applications ( I also own 2123h, le10a, le10h & le10h-1 woofers ) . The 2012 is a great little speaker ! I especially like the heavy duty motor-drive . It's really like a mini le15 with a 12.6 mm deep gap but with a slightly overhung voice coil ( 20.3 mm winding depth which is deeper than a 2235h ) . BTW, this is essentially the motor topolgy that JBL introduced with their mid 1990s' K2 S-5500 speaker. It should offer great motional-control/speed ( if you don't compromise it somewhere in the crossover circuit ). I'll be curious to hear of your impressions for the speaker within a hifi setting .


regards <> Earl K

Guido
05-28-2003, 10:59 AM
Yeah!

I got them in German Ebay. Never used in original box for 223 Euro!

Wonderful!

Now I only need 2 2235H and then I'm almost finished.

Thanks to all for your help

Greetings from Germany, Guido