TWO AIR CORE INDUCTORS IN SERIES

[garage inc.]

I have to combine two air core wire wound inductors together in series because I couldn't find the exact inductance value in 1 single inductor for my passive bandpass crossover. How do I lay out the two inductors in series: 1 laying flat & the other inductor laying flat on top of the other or 1 flat & the other standing up so when you look through the hole of the inductor standing upright you can't see the other inductor or both standing upright lol, thanks for any input.

 

[jobrewer1983]

I've not ran them in series but this may be of some help ^^

 

[garage inc.]

yes these two inductors in series are for the high pass frequency side of the bandpass filter, the low pass frequency side will have a single inductor on the other side of the same crossover board, so since these two in series have to be close together, 1 standing up so when you look through the hole you can't see the other inductor next to it lying down, in this configuration can they both be a half inch from each other, it looks like they can in the pics above but I don't know the scale in inches they are using for those pics above, thanks again.

 

[a_retent]

I've not ran them in series but this may be of some help.

Good info to know, thanks.
I've ran across a couple factory crossovers in my time that had the coils stacked horizontal like example #8. One of them I still own, now I suppose I should get back in there and separate them....another project to put on the list.

 

[garage inc.]

Good info to know, thanks.
I've ran across a couple factory crossovers in my time that had the coils stacked horizontal like example #8. One of them I still own, now I suppose I should get back in there and separate them....another project to put on the list.

I thought maybe since the two inductors I have to put in series are for the same frequency point "high pass" that I could lay one on top of the other, I thought you just can't do that with a inductor for one frequency point with another inductor with a different frequency crossover point on the same crossover board so I am sure someone will chime in that knows for sure.

 

[mkane]

and does the number of the inductor have to be exact? Is close, close enough?

 

[a_retent]

I thought maybe since the two inductors I have to put in series are for the same frequency point "high pass" that I could lay one on top of the other, I thought you just can't do that with a inductor for one frequency point with another inductor with a different frequency crossover point on the same crossover board so I am sure someone will chime in that knows for sure.

I wish I could give you a proper educated answer to your question about stacking inductors, but unfortunately I can only think from a common sense perspective that in your application it would be...acceptable. My situation is 2 different crossover points so for me it ='s bad.

Like you I'll wait to see what the consensus is.

 

[garage inc.]

Yeah, its all about magnetic fields disrupting something.

 

[jobrewer1983]

yes these two inductors in series are for the high pass frequency side of the bandpass filter, the low pass frequency side will have a single inductor on the other side of the same crossover board, so since these two in series have to be close together, 1 standing up so when you look through the hole you can't see the other inductor next to it lying down, in this configuration can they both be a half inch from each other, it looks like they can in the pics above but I don't know the scale in inches they are using for those pics above, thanks again.

maybe I missed it... what values are your trying to accomplish?

 

[jobrewer1983]

and does the number of the inductor have to be exact? Is close, close enough?

Not when you want exact values LOL



OP did you look at the Jantzen Exact Value line?

 

[garage inc.]

I found a 14mh iron core inductor which I read isn't as good as air core inductors but this iron core inductor will be used in a narrow bandpass crossover for a midbass speaker which will have narrow bandpass freq's of 90hz to 155hz & I read if you use an iron core inductor its best for low freq's because of distortion iron core inductors can exhibit in high freq's but I don't know if this really is true.

 

[toddalin]

Actually, #8 can be a very valuable tool if done properly to effect. I use three 2mH chokes stacked like this. They were placed on a common spindle and glued together for "perfect" alignment. Using one choke produces 2 mH, two chokes produce 5 mH, and three chokes produce 8 mH. In this way, I've created a "tapped inductor."

But this is not what you want to do in your case.

 

[BinaryMike]

The reason to avoid stacking inductors on-axis is mutual coupling, i.e. transformer action. If they're in series, net inductance will be either greater or less than the sum of the two independent inductances, depending on hookup phase. This could be a good thing if you're prepared to measure net inductance, because you can get more inductance for your money and reduce DCR.

 

[Freds.Bands]

#8 may be OK if the wires run parallel, if you can tell this; the thing about toroids is the low leakage inductance;I would hope the winding wire size is the same for efficiency.

 

[garage inc.]

The reason to avoid stacking inductors on-axis is mutual coupling, i.e. transformer action. If they're in series, net inductance will be either greater or less than the sum of the two independent inductances, depending on hookup phase. This could be a good thing if you're prepared to measure net inductance, because you can get more inductance for your money and reduce DCR.

Awesome, the answer I was looking for thanks. Do you have any thoughts on iron core inductors if I use one for frequency crossover point of 90hz to 155hz narrow bandpass filter for a 8 inch woofer, thanks again.

 

[BinaryMike]

Do you have any thoughts on iron core inductors if I use one for frequency crossover point of 90hz to 155hz narrow bandpass filter for a 8 inch woofer, thanks again.

Iron core inductors saturate and cause distortion when signal current exceeds some threshold that you cannot know for certain without test equipment. In this situation, all you can do is select inductors with power ratings far in excess of what might be necessary. It's a cost of compensating for not having a test lab, and well worth it if you do this sort of thing only occasionally.

 

[garage inc.]

Iron core inductors saturate and cause distortion when signal current exceeds some threshold that you cannot know for certain without test equipment. In this situation, all you can do is select inductors with power ratings far in excess of what might be necessary. It's a cost of compensating for not having a test lab, and well worth it if you do this sort of thing only occasionally.

Thanks on that, your right you need test equipment to really be able to design a crossover there are too many variables like all the speaker specs I would have to be Einstein even with test lab equipment. What are the power ratings your talking about VOLTS ? AMPS ?

 

[BinaryMike]

What are the power ratings your talking about VOLTS ? AMPS ?

Well, the ones at Parts Express are specified in Power Handling Watts. It's hard to say what that really means, because maximum inductor current depends on many things besides amplifier output power. If you're able to measure or simulate actual worst-case conditions, then you would want the spec in volt-seconds or current vs frequency. Still, the 250W power rating for Parts Express' iron core inductors is probably sufficient for most hi-fi projects.

 

[garage inc.]

Well, the ones at Parts Express are specified in Power Handling Watts. It's hard to say what that really means, because maximum inductor current depends on many things besides amplifier output power. If you're able to measure or simulate actual worst-case conditions, then you would want the spec in volt-seconds or current vs frequency. Still, the 250W power rating for Parts Express' iron core inductors is probably sufficient for most hi-fi projects.

Of course Watts I don't know what I was thinking. My rig is in the garage, Kenwood, Dayton 1000w plate amp, Sony CD player, 7 foot tower enclosure so perfection isn't that critical since I lean against my car 6 feet away from the tower when I play CD'S, Thanks again.