View Full Version : LE 20 resistence

RALPHX

09-08-2004, 02:14 PM

Hi. New to any electronics, so I appreciate whatever help any one might ofer. I purchased a nice LE 20 replacement for a blown one in my cabinet, but it turns out to be 8 ohm while the woofer and speakers in the other cabinet are 16 ohm. Is there a way to use this replacent, or do I need to find another?

Thanks so much.

4313B

09-08-2004, 03:01 PM

What is the DCR value of each working LE20?

Just out of curiosity, what are the woofer model numbers?

RALPHX

09-09-2004, 03:00 AM

Ummm....what is DCR? The speakers actually belong to a buddy, so will check on woofer model. Thanks.

Figge

09-09-2004, 03:13 AM

hi :wave:

and welcome!

if u can get hold of a multimeter u can meashure the dcr, very simple...just put each cable from the multimeter onto a terminal on the tweeter. and u get a value. this doesnt neccesary have to be 8ohm. but post the value here and the experts here will help.

also try this on the other tweeter aswell.

regards fredrik

johnaec

09-09-2004, 05:52 AM

Originally posted by RALPHX

Ummm....what is DCR? The speakers actually belong to a buddy, so will check on woofer model. Thanks. I believe DCR stands for Direct Current Resistance, or the resistance in ohms when measured across the speaker terminals.

John

Don C

09-09-2004, 06:15 AM

A pair of LE20-1 that I have measures 4.3 ohms. Both measure the same.

4313B

09-09-2004, 06:25 AM

Sounds about right but I'd have to look it up to make sure.

*****

Maybe you could post a picture of you measuring one so people can see what it's all about to measure DCR? :) It would end up in the Tech Ref section so make it pretty :p

RALPHX

09-09-2004, 09:48 AM

so lets assume the DCR is the nominal 8 and 16 ohms....what then?

Thanks!

RALPHX

09-09-2004, 01:52 PM

sorry to be a dense pest. Once the DCR is known, how would one adapt the nominal 8 ohm tweeter to work in the 16 ohm system...

Zilch

09-09-2004, 08:04 PM

The impedance is the opposition to AC current flow at a given frequency. It is a combination of resistance and reactance and is measured in ohms.

The DC resistance, also in ohms, we can easily measure with an ohmmeter at f=0; measuring impedance is tougher....

Alex Lancaster

09-09-2004, 10:01 PM

Impedance= to impede, restrict, etc etc.

It is reactive according to freq, and if You measure it, You get some wild curves, You are getting into 3D, the Z axis, even negative and then You get into "i" (imaginary), donīt loose any sleep about it.

Earl K

09-10-2004, 05:30 AM

Perhaps someone on this forum can remember a time when a "D16RLE20" "16 ohm" kit was available. I sure can't. And they sure aren't available now.

Giskard :

My mid 70's , JBL Service center info refers only to 2, le20 ( 8 ohm ) variants . So, as early as 1976, JBL was putting 8 ohm replacement diaphragms into all le20's that came to warranty stations . My service center documents do reference the le30, to give an idea of their "completeness". I highly doubt if there ever was a "real" 16 ohm , le20. Most likely, the 16 ohm le-20 is just another 8 ohm le20 - .

RALPHX : to cut to the chase, Just install the 8 ohm le20 replacement into your "friends" enclosure, give it a listen to see if it sounds right. You're not going to blowup anything by doing this. If you're not comfortable with this advice, then take the pieces into a JBL service center for a proper "fitup", plus get them to run a Frequency Response examination .

Also: You still haven't answered the earlier queston of; What JBL woofers are in these boxes ? In fact, is it a two or three way system ?

<. Earl K

4313B

09-10-2004, 06:54 AM

Thanks Earl! I suspected as much but wanted to make sure there really weren't any "16 ohm" versions around. I guess we'll have to wait until someone with a VTVM or DMM runs across an original LE20 with "16 ohms" stamped on the foilcal. I'm glad you cut to the chase.

speakerdave

09-10-2004, 08:34 AM

Originally posted by Giskard

I guess we'll have to wait until someone with a VTVM or DMM runs across an original LE20 with "16 ohms" stamped on the foilcal.

I have a pair of these. They are the version with the black body, the heavy mounting plate and the screen. One is open, the other shows a DCR of 3.9 ohms. Another example of JBL's fleximpedance strategy?

David

4313B

09-10-2004, 08:40 AM

Yep, thanks for the info David. This is the kind of stuff we're looking for! :yes:

Now for an impedance curve or two. ;)

We'll figure out where in the frequency range an LE20 is 8 ohms and where it is 16 ohms. :)

speakerdave

09-10-2004, 08:54 AM

Just occured to me to wonder, and, Yes, the famous red wax seals are in place.

David

RALPHX

09-10-2004, 03:16 PM

Per my "friend", DCR of the 8 ohm replacement is 4.4 ohms, while the original unblown 16 ohm is 4.1...so curious. Anyway, he has installed the new tweeter in the enclosure (2 way, sorry still don't know the woofer model) and says they sound great. Thanks to all for your help.

speakerdave

09-10-2004, 04:32 PM

Originally posted by RALPHX

DCR of the 8 ohm replacement is 4.4 ohms, while the original unblown 16 ohm is 4.1...so curious.

I find that how you measure matters. With the probes held on the terminals of the one I measured this morning the resistance was somewhere between 4.1 andd 4.4. When I depressed the springs and let the terminal cap bite the probes it settled very solidly at 3.9 ohms.

David

RALPHX

09-15-2004, 07:47 AM

Still waiting on my friend to get me the woofer/crossover models....thanks for your patience.

Paul

boputnam

09-15-2004, 08:19 AM

Originally posted by Giskard

Maybe ... post a picture of you measuring one so people can see what it's all about to measure DCR? :) Here's how I do it - pretty straight forward, really...

4313B

09-15-2004, 08:39 AM

Originally posted by boputnam

Here's how I do it - pretty straight forward, really... Yeah baby!

Thanks for the visual! :yes:

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