View Full Version : passive xover tips

03-10-2005, 03:20 AM
Hi I would like to get a better handle on use and design of passive xovers with JBL components.

I notice a lot of you guys seem pretty adept with constructing your own xovers with JBL projects.

I have acquired a few JBL pro xovers, all mid - low types eg 3160, 3110, N1200 and even a single 3110A. I am alo aware of the excellent collection of schematics for these on this site and the JBL pro webpage.

I am yet to try to acquire any HF units - eg 3105 because these seem fairly expensive (eg on eBay) for what they appear to be. My first question is whether it is fairly easy to build something equivalent from scratch if you have a collection of inductance coils and a suitable meter. I note that most of the JBL xovers use iron core inductors. Would there be any problem using aircore ones? A related question is how to account for the difference in coil resistance in DIY inductors compared to the ones JBL used. Is this a simple matter which can be worked out by a knowledge of ohm's law or are there other less obvious factors to take account off.

Now the JBL low- mid xovers normally use at least one autoformer. I remember reading somewhere on this site that these cannot simply be replicated by using a number of DIY coils. At a simple conceptual level I do not understand why not. Can someone explain why you cannot construct an equivalent circuit using a number of coils connected together and tapped appropriately? Is it something to do with the laminated core?

My third question related to replacing capacitors in JBL xovers. I have not disassembled any of mine to check the condition or type of cap used. Can anyone provide any tips on what can be usefully done here. I am aware of the quality differences with different types of caps and that some deteriorate more rapidly than others.

Hope I have not asked too many questions