Inductor interference what to do?

[Roland]

Hi all, this is my first post on this very informative forum.

How it all started: searching for a strange distortion in my mid driver i heard interference from my bass inductor (iron core) ending up in my mid speakers via the parallel notch inductor (iron core) of the mid speakers.

The set up:
-amplifier set on twelve o clock playing music:
-bass driver disconnected, amp connected on bas x over (12 db+par.notch)
-middriver connected to the x-over, x-over and driver not connected to amp.
-tweeter x-over connected to amp, tweeter not connected to filter.

Bass serial inductor 4 inch away from the mid parallel notch inductor (impedance flattening network). No drivers connected to the amp and still there was sound coming from my mid driver. Even after i turned the coils to minimize crosstalk effects, i still could hear music coming out of my mid speaker.

I dont have much room to place all inductors very wide apart from each other in this particular loudspeaker, the crossover network has an seperated enclosure in the bottom part of the speaker (4*4*8 inch)

-Is there a big difference in magnetic strayfield form and strength between diffferent inductors: Air Core Inductors, Copper Foil Inductors, Iron Core Inductors?
-Are there types that stand out for their particular low strayfield or pick up tendencies?
-Are there ways to reduce crosstalk other than increasing the distance between inductors or turning them around so their fields don's interfere?

Best Regards Roland Breteler,the Netherlands

Sorry for my highschool English, I red the "plain ol wire vs foil inductors" thread and had to ask it on this forum, clearly Jon is an expert in this field.

[Dennis H]

Hi Roland,

Welcome to HTGuide! You're right, Jon is the resident expert so we should wait for him to give us the real answer.

Meanwhile you might try something. I remember Jon saying inductor coupling is much worse when the inductors are feeding a high impedance load, like a disconnected driver. I think he was referring to using a voltmeter on the "receiving" circuit but it may apply to the "transmitting" circuit as well. Try feeding the woofer and tweeter circuits to 8 ohm resistors rather than to open circuits. Also, short the inputs of the midrange circuit together to simulate the low output impedance of an amp. Then do your listening test again. Maybe it will be better and maybe it won't but it should be closer to what is going on when everything is connected correctly.

[JonMarsh]

Inductors in close proximty is a no-no. :naughty: :naughty:


While it's true that a laminated or other ferrous core will reduce the size of the stray field by concentrating it at the core, it also will act to make two iron core inductors close to each other couple pretty well. The other downside to iron cores is they are non-linear and have hysterisis in the BH curve. In audio terms, this translates into additional distortion. For this reason, I don't use anything except air core inductors, Luddite that I am.

That means heavy gauge, expensive wire. And for either type, reasonable spacing. Father Physics just doesn't give us any alternatives on that... (other than going active, etc).

~Jon

[kgveteran]

How about an iron core next to an aircore inductor?

[JonMarsh]

Inductors next to inductors = Bad. Any type. Allow at least a couple of inches spacing or more. Three is better.

~Jon

[Dennis H]

Roland said he had 4 inches between them which seems like it should be enough. That's why I suggested he repeat his crosstalk test under more realistic conditions.

[Roland]

Hi

I did not test the resisitors to replace te driver load yet. In this x over there seems to be no other choice than to use an iron core inductor, the inductor value is 8.2 mh, the woofer impedance is 7.3 ohm. An air core inductor with the same resistance (0.32 ohm) would cost 137$ and is 6.5 inch wide...

Best regards Roland

PS. it seems i have been jumping to conclusions. Thank you all for the replies.