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Air Core Inductors


Deang

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This is not an apples to apples example but, the way it was put to me was. Use bigger air core wire instead of smaller iron core or magnet wire and you get a much better bottom end because of the low DCR... The example was if you have a motor with 600 horse power and you have a 2inch exhaust system you don't get all the power, if you have a 4inch exhaust system well things move much more freely and you get alot more power!!!

The iron core allows fewer turns for the same inductance. With less and/or smaller wire the DCR of an iron core inductor is often lower than an air core inductor with larger wire.

Changing an inductor to one with a lower DCR changes the Q of the inductor, which changes the filter characteristics. It's not the lower resistance allowing more power to flow, its the hump in low frequency response that results from changing the damping of the filter that you are hearing.

Don,

I understood it as the larger wire has a lower DCR in itself, I did not understand it to be that you change to a wire with a lower DCR. I thought because of it's size it had a lower DCR???

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This is not an apples to apples example but, the way it was put to me was. Use bigger air core wire instead of smaller iron core or magnet wire and you get a much better bottom end because of the low DCR... The example was if you have a motor with 600 horse power and you have a 2inch exhaust system you don't get all the power, if you have a 4inch exhaust system well things move much more freely and you get alot more power!!!

The iron core allows fewer turns for the same inductance. With less and/or smaller wire the DCR of an iron core inductor is often lower than an air core inductor with larger wire.

Changing an inductor to one with a lower DCR changes the Q of the inductor, which changes the filter characteristics. It's not the lower resistance allowing more power to flow, its the hump in low frequency response that results from changing the damping of the filter that you are hearing.

Don,

I understood it as the larger wire has a lower DCR in itself, I did not understand it to be that you change to a wire with a lower DCR. I thought because of it's size it had a lower DCR???

I am not sure what you are saying, but all things being equal it is true that a larger diameter conductor has lower resistance than a smaller diameter one. With an inductor (coil of wire) the core material affects the inductance. Stick an iron bar in an air core inductor and the inductance increases. If you then remove turns of wire to bring the inductance value back to what it was with the air core the inductor's DC resistance will be lower because there is now less wire comprising the inductor.

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"Not helpful Dennis, not even a little bit -- all we know is what we've always known, that Wilson is ripping people off in the worst kind of way. Man, you were supposed to blow me away with at least a paragraph of something I couldn't understand."

Hey, I try.

Barkenhausen noise (sudden, discontinuous jumps in magnetization, sudden changes in the size and orientation of ferromagnetic domains, or microscopic clusters of aligned atomic spins) is virtually inaudible in a well designed inductor.

Barkhausen_jumps.png

This would argue for fine laminations of a high permeablity material. M6 is fine for inductor cores (Madisound SledgeHammer), solid cores (Madisound Sidewinder), and ferrite drum cores (certain Klipsch products), have room for improvement.

Small signal transformers (mic, line, etc) can benefit from better materials than M6 (but at a higher cost).

"if you have a 4inch exhaust system well things move much more freely and you get alot more power!!!"

So, if bigger is better, should I go to a 6"? How about I just take off the manifold?

Edited by djk
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"Which of these inductors types provides the best damping for the woofer?"

Conventional wisdom says that as long as you keep the inductance and DCR the same, it doesn't matter. If you're paranoid like me and think it might make a difference, and it doesn't cost too much extra -- why not use an air core?

A word about DCR:

It is incorrectly believed that getting the DCR as low as you can get it is the best thing you can do. However, the DCR of the coil is factored into the design, and doing that changes the Qes and Qts, which changes the tuning of the cabinet, which changes the output level of the midrange. The same goes for tweeter circuits -- a nice big fat coil is a great way to ruin the 'Q' of the circuit. Think about it like this: a coil has built in resistance, which is basically a resistor in series with the coil. This resistance becomes part of the model for the circuit, designed to work with a specific driver. A lot of crossover work involves knowing what NOT to do.

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"if you have a 4inch exhaust system well things move much more freely and you get alot more power!!!"

So, if bigger is better, should I go to a 6"? How about I just take off the manifold?

This was just used as an example of how it was described to me, it was a quick and effective way for me to grasp the overall situation...

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Dean,

A word about DCR:

It is incorrectly believed that getting the DCR as low as you can get it is the best thing you can do. However, the DCR of the coil is factored into the design, and doing that changes the Qes and Qts, which changes the tuning of the cabinet, which changes the output level of the midrange. The same goes for tweeter circuits -- a nice big fat coil is a great way to ruin the 'Q' of the circuit. Think about it like this: a coil has built in resistance, which is basically a resistor in series with the coil. This resistance becomes part of the model for the circuit, designed to work with a specific driver. A lot of crossover work involves knowing what NOT to do.

Not saying you are wrong here but, if your above is true then we should just stick with what comes with the speakers to start with!!! Because of all the variables you named how could it ever be right? Here is where I agree with Craig, the sound is what is important not the math or calculations!!!

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Of course I'm right -- you think I make this stuff up? :)


Craig didn't say that. Imagine what his work would sound like if he didn't rely upon instruments and testing. Craig is a testing freak. Once you have your baseline, you can tweak to suit personal taste -- but you can only stray so far before it just becomes plain wrong. It is the same with networks.


If the coil I'm replacing is say, 2mH and has a DCR of .3, I stay as close as possible -- for the reasons already stated. I'm also not an engineer, not a seasoned loudspeaker designer, nor do I have the necessary and required testing equipment that is needed to see what any departures from the model might cause. However, I'm smart enough to know that the loudspeaker I'm building a network for was designed by someone or a group of someones that used gobs of brainpower, time, and measuring equipment to get it "right".


So, what CAN an audiophile do, who wants a performance gain from a coil?


Air cores are better -- there's about a half a million links that say so, so it must be true. If there is an issue, it relates to loss, which is overcome with larger gauge wire (for the same inductance). Iron and steel laminate types suffer from issues that air cores don't. However, they are mostly related to power, and in our world, this just isn't the issue that it is in the world of low efficiency -- but we'll go with "air cores are better".


Even if we say there is a performance gain, it doen't free us from the boundaries decreed by the engineering model. IOWs, you can't do away with the maths. So, inductance and DCR must be reasonably close to the iron core or steel laminate you are replacing. It is what it is.


I like all the air cores that are out there. Northcreek makes the best, but they really give out a lot of bad advice. Solen, Erse and Jantzen -- all make very good air cores.


I really like what UT sent me. Aesthetics aside, it's a great coil and an amazing value.


Bottom line: I can really appreciate a nicely wound air core with a lot of varnish, but it's of no use to me if it's the wrong value! This is like Craig putting the wrong choke in his amp. People who DIY their networks not only need to learn about networks, but their speakers too. I only needed to get burnt by the big coil bug one time to learn my lesson.


In the case of Al's designs, he models using Litz type air cores because they have lower loss at the frequencies they're being used. This relates to 'Q'. While DCR dominates in low pass sections in the area of loss, it is 'Q' which dominates in the high pass. In other words, an air core wound with solid wire will might have lower DCR than the Litz type, but the Litz type will actually have lower loss in the circuit (while having higher DCR for the same value).


Dennis taking your example with the exhaust to the extreme is somewhat ironic -- it's pretty much what you did by incorporating the use of those 8 AWG paper weights. You moved too far outside of the engineered model. It may sound "good" to you, but the reality is that you have no idea what your loudspeakers are actually doing.



Edited by DeanG
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"if you have a 4inch exhaust system well things move much more freely and you get alot more power!!!"

So, if bigger is better, should I go to a 6"? How about I just take off the manifold?

This was just used as an example of how it was described to me, it was a quick and effective way for me to grasp the overall situation...

Actually the 4" exhaust being more power is not always true. Some motors will produce more power with a smaller exhaust... The key is to get the right diameter to maximize the performance.

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I work with Cisco switches/routers and design cable plants. My title is "Network Engineer" -- talk about irony. At any rate, I work in a shop with guys who think they're real "engineers". I have to listen to really bad analogies all day long.:)

This just in from Al:

Dean,

I did a bit of computer simulation to prove a theory. I think I explained to you how a filter that is not properly terminated with the correct load will have a rough passband. This is the same as a woofer filter poorly designed for a given load, it will show a peak below the crossover, which would make it sound boomy. "De-Qing" the inductor by adding DCR will drop that peak. A well designed filter does not need the DCR to load down the peak, it will already have a flat response. So, the conclusion is that lowering the DCR on a crappy crossover can create a peak which could make it sound boomy. On a good one, it will improve things by allowing the amp to see through the inductor to the driver for better damping.

Al K.

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(Dennis taking your example with the exhaust to the extreme is somewhat ironic -- it's pretty much what you did by incorporating the use of those 8 AWG paper weights. You moved too far outside of the engineered model. It may sound "good" to you, but the reality is that you have no idea what your loudspeakers are actually doing.)

Dean, Two things here; if it sounds good isn't that what we are all after? Also why does it matter what my speakers are actually doing? As long as they are sounding good?

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I work with Cisco switches/routers and design cable plants. My title is "Network Engineer" -- talk about irony. At any rate, I work in a shop with guys who think they're real "engineers". I have to listen to really bad analogies all day long. :)

When I was in engineering school, I was working at a hotel in Las Vegas. I was advised that I was an idiot because I was wasting my time getting a degree. If I wanted to be an "engineer" all I had to do was go to HR and tell them I wanted to work in the engineering department.

I didn't really fit in there...

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Of course I'm right -- you think I make this stuff up? :)
Craig didn't say that. Imagine what his work would sound like if he didn't rely upon instruments and testing. Craig is a testing freak. Once you have your baseline, you can tweak to suit personal taste -- but you can only stray so far before it just becomes plain wrong. It is the same with networks.
If the coil I'm replacing is say, 2mH and has a DCR of .3, I stay as close as possible -- for the reasons already stated. I'm also not an engineer, not a seasoned loudspeaker designer, nor do I have the necessary and required testing equipment that is needed to see what any departures from the model might cause. However, I'm smart enough to know that the loudspeaker I'm building a network for was designed by someone or a group of someones that used gobs of brainpower, time, and measuring equipment to get it "right".
So, what CAN an audiophile do, who wants a performance gain from a coil?
Air cores are better -- there's about a half a million links that say so, so it must be true. If there is an issue, it relates to loss, which is overcome with larger gauge wire (for the same inductance). Iron and steel laminate types suffer from issues that air cores don't. However, they are mostly related to power, and in our world, this just isn't the issue that it is in the world of low efficiency -- but we'll go with "air cores are better".
Even if we say there is a performance gain, it doen't free us from the boundaries decreed by the engineering model. IOWs, you can't do away with the maths. So, inductance and DCR must be reasonably close to the iron core or steel laminate you are replacing. It is what it is.
I like all the air cores that are out there. Northcreek makes the best, but they really give out a lot of bad advice. Solen, Erse and Jantzen -- all make very good air cores.
I really like what UT sent me. Aesthetics aside, it's a great coil and an amazing value.
Bottom line: I can really appreciate a nicely wound air core with a lot of varnish, but it's of no use to me if it's the wrong value! This is like Craig putting the wrong choke in his amp. People who DIY their networks not only need to learn about networks, but their speakers too. I only needed to get burnt by the big coil bug one time to learn my lesson.
In the case of Al's designs, he models using Litz type air cores because they have lower loss at the frequencies they're being used. This relates to 'Q'. While DCR dominates in low pass sections in the area of loss, it is 'Q' which dominates in the high pass. In other words, an air core wound with solid wire will might have lower DCR than the Litz type, but the Litz type will actually have lower loss in the circuit (while having higher DCR for the same value).
Dennis taking your example with the exhaust to the extreme is somewhat ironic -- it's pretty much what you did by incorporating the use of those 8 AWG paper weights. You moved too far outside of the engineered model. It may sound "good" to you, but the reality is that you have no idea what your loudspeakers are actually doing.

Dean,

I may have got it wrong but i understood this statement by Craig as what I said earlier. Quote: (I think my best motto in this arena is....When it comes to audio remember what is technically better is almost never musically better. To me this is about music and its natural sounding reproduction.) End quote.

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(I think my best motto in this arena is....When it comes to audio remember what is technically better is almost never musically better. To me this is about music and its natural sounding reproduction.) End quote.

If something technically better is not musically better, then I'd suggest you are not correctly correlating technical qualities to musical qualities. Audio engineering is so much more fascinating if you define technical excellence as that which maximizes musicality. In other words, if it doesn't sound better, then it's actually not technically better.

It is impossible to change something without affecting something else - perhaps that something else plays a larger role in your listening enjoyment?

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