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best-one.agency
11-10-2009, 05:11 PM
Hello!

I need N1200 schematic with 16ohm.
Does anyone have N1200 schematic for 16ohm?

Thanks

BMWCCA
11-10-2009, 10:05 PM
The information is found in the Links section of the forum under "professional links" "network schematics".

http://www.jblproservice.com/pdf/Network%20Schematics/N1200.pdf

I believe they were all rated as 16ohm: http://www.lansingheritage.org/images/jbl/specs/home-comp/networks/page1.jpg

BJL
11-11-2009, 07:15 AM
In addition to BMW's link, G posted another different .PDF
Look here (http://audioheritage.org/vbulletin/showthread.php?p=209888)

BMWCCA
11-11-2009, 07:34 AM
In addition to BMW's link, G posted another different .PDF
Look here (http://audioheritage.org/vbulletin/showthread.php?p=209888)I was looking for that one! Thanks. Should be put in the Links forum somehow, somewhere, I would think. :)

jcrobso
11-11-2009, 08:21 AM
http://www.termpro.com/articles/xover2.html
http://ccs.exl.info/cust_cr.html
For those that want to get more in to the theory of crossovers look here.
http://sound.westhost.com/lr-passive.htm

Wagner
11-11-2009, 08:50 AM
So, if you have very old networks, "in the gray container", the only way to know for certain what the cross over point is is to open them up.
Correct?
http://audioheritage.org/vbulletin/images/attach/pdf.gif N1200.pdf (http://audioheritage.org/vbulletin/attachment.php?attachmentid=32542&d=1210872360) (Posted by 4313B in another thread; Thank You!)

Thomas

speakerdave
11-11-2009, 09:02 AM
Also, compare the 3120:

http://www.jblproservice.com/pdf/Network%20Schematics/3120%20Network.pdf

jcrobso
11-11-2009, 09:32 AM
So, if you have very old networks, "in the gray container", the only way to know for certain what the cross over point is is to open them up.
Correct?
http://audioheritage.org/vbulletin/images/attach/pdf.gif N1200.pdf (http://audioheritage.org/vbulletin/attachment.php?attachmentid=32542&d=1210872360) (Posted by 4313B in another thread; Thank You!)

Thomas

Maybe you could tell by looking a the value of the capacitors, if they are labeled.
More info on X-over design.
http://www.apicsllc.com/apics/Misc/filter2.html

grumpy
11-11-2009, 09:35 AM
the only way to know for certain what the cross over point is is to open them up.
Correct?

No. You could measure them with proper loads, or measure and compare
with spec's JBL provided when used with their specified load. Or let someone
who knows what they are doing measure them.

Wagner
11-11-2009, 09:52 AM
No. You could measure them with proper loads, or measure and compare
with spec's JBL provided when used with their specified load. Or let someone
who knows what they are doing measure them.

Yes, understood.
I meant for those of us who do not have the test equipment and relying only on schematics and values for identification.

Thomas

hjames
11-11-2009, 10:01 AM
Yes, understood.
I meant for those of us who do not have the test equipment and relying only on schematics and values for identification.

Thomas

Of course, values marked on components are only accurate to the tolerance they were rated to, at the time they were made.

Capacitors are known to age over time and change, which changes the performance of the network and the crossover points.
Thus, old gear bought off ebay or similar sources is a wish, at best, and a bad joke worst case.

Best approach is to create new crossover networks based on the original design.

Of course, thats assuming you don't have tools or test gear to engineer new designs.

Beowulf57
11-11-2009, 11:58 AM
Also note that although the test values show a Load Z of 8 ohms, that was I believe simply the standard test fixture used by JBL. The crossover may well have been used with a "nominal" 16 ohm driver. Often JBL specified the input impedance of the network and not the output load.

Wagner
11-11-2009, 10:28 PM
Of course, values marked on components are only accurate to the tolerance they were rated to, at the time they were made.

Capacitors are known to age over time and change, which changes the performance of the network and the crossover points.
Thus, old gear bought off ebay or similar sources is a wish, at best, and a bad joke worst case.

Best approach is to create new crossover networks based on the original design.

Of course, thats assuming you don't have tools or test gear to engineer new designs.


Hi,
Of course I understand the aging process, I was speaking to identifying which variant of N1200 one has.

It is also interesting to note however, that in a number of threads I have read here, several folks have commented on the fact that they have rarely found a cap out of spec in any of the JBL networks they have examined when "rebuilding" was under discussion, including those over 30 years old.

Thomas