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Dieter
05-24-2003, 03:11 AM
Hi,
im looking for a crossover-schematic 7500 Hz 12 or 18 db for the 2405 16 Ohm.

Can somebody help?

Thank you for the answers.

BestRegards

Dieter

4313B
05-24-2003, 06:21 AM
You might want to look at the 3106 or 3107 high pass filters

http://www.jblproservice.com/navigation/Network%20Schematics.html

The "best" is probably the 3145 or 3155 high pass filter.

Dieter
05-24-2003, 09:56 AM
Hi Giskard,

thank you.

In the "frequency dividing Networks" pdf JBL says, that the 3105 and 3106 is for 16 Ohm.
But in the:
http://www.jblproservice.com/pdf/Network%20Schematics/3106%20Network.pdf

JBL say it is for 8Ohm.
Am i wrong?

In:
http://www.jblproservice.com/pdf/Network%20Schematics/3105%20Network.pdf
JBL says it is for 16 Ohm
What is about this network for he 2405?


In:
http://www.jblproservice.com/pdf/Network%20Schematics/3107%20Network.pdf

JBL says it is for 8Ohm.

Thank you Giskard: you are very helpful.

Dieter

4313B
05-24-2003, 10:21 AM
I think you are referring to the test loads in the network service bulletins. JBL has to have a standardized way to test networks and the answer is:

http://www.jblproservice.com/pdf/Network%20Schematics/Standard%20Test%20Fixture.pdf

If you are measuring the voltage drive of a network LOAD Z tells you what to load the network with to obtain the values in the table:

Mr. Widget
05-24-2003, 11:28 AM
Originally posted by Dieter
Hi,
im looking for a crossover-schematic 7500 Hz 12 or 18 db for the 2405 16 Ohm.

Can somebody help?

Thank you for the answers.

BestRegards

Dieter

I am using the 3155 circuit and it really allows the 2405 to sound great.

Don't worry about it being referred to as an 8 ohm circuit. JBL is a bit weird about driver impedance. Since the 2405 is not as low an impedance as a true 8 ohm device they have been referred to as 16 ohm drivers. The actual impedance at the crossover region is more like 10 ohms I believe. For some reason they have also been referred to as 8 ohm drivers in other years.

JBL has only made one impedance of the 2405/2405H even though the name plates say 8 or 16, and the JBL circuits are also labeled some 8 and some 16.

The 3145 and 3155 crossovers are much more recent designs than the 3107 or 3108 and in my opinion are vastly superior. I realize that these are both crossed over higher than your stated 7500Hz, but the 2405 sounds better crossed over higher.