What's different between air core and iron core speaker inductors?

The two types of inductors used in loudspeaker crossovers are air core and iron core. What's the difference, which is better, and why? Have a question you want to ask Paul? www.psaudio.com/ask-paul/
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[@neverknowit11]

The iron core changes the inductance depending on the placement, the area of the iron in the core. Also the iron helps dissipate the heat generated by current passing through it as the magnetic field decays it generated a field in the opposite direction. Air core is less efficient and builds up more heat needs heavier wire and more turns to accomplish the same task. Inserting a Capacitor in the circuit creates a “tuned” circuit works kind of on the same principle as a pendulum.

[@neverknowit11]

May or not be 100% accurate. Tried to be as concise as possible.

[@stephencosta6814]

Very nice explanation as well. Thank you

[@mattmoreira210]

Also, the core can have an air gap to linearize the B-H curve and to increase the saturation current. Then, you can have the best of both worlds...

[@theresalong6573]

love playing around with passive crossovers, always enjoy your knowledge

[@elisha770]

Made sense, thks. I just love how you give the cue for your team to wave at the end :)

[@chrishershey5033]

Thanks for the explanation!

[@kenb4911]

Thanks for great information.

[@Made2hack]

Thanks for the explanation. Really useful.

[@nixter1nixter1]

Explained well and correctly. you can demonstrate the effect of an iron core by sliding one into the empty space in an air core inductor while being measured with an induction meter, the inductance goes way up when an iron core is inserted. A good source for iron cores is found in old radios that used iron cores in the AM antennae, they are ideal for use with an iron core inductor.

[@FungedeBagre]

Paul is back!

[@georgebedorf7950]

Great video Paul. Back in the 1970's I built some 3 way bass reflex speakers with 12db per octave crossovers. I was given a big coil of 18 gauge magnet wire and wound air core coils. The 18 gauge wire provided a high Q value. Fortunately the cabinets were about 7 cubic feet in size, but I got the sound I wanted. I also salvaged the woofers only spent a few hundred dollars. The labor was "free". I must say that my bookshelf Paradigms of the 90's with a sub-woofer sound much better and the wife is happier. It was a learning experience that illustrated why high quality speakers cost so much at the time.

[@kaedeschulz5422]

These day's with so many good driver's and crossover parts available you can build very good speaker's very cheap compared to something on the same level in a shop.

[@Woofy-tm8si]

Great video! I hope Paul is able to elaborate on the advantages and disadvantages copper foil inductors sooner rather than later as I have a speaker project that has Goertz inductors as an option and he's better at explaining this stuff than just about anyone else around. Please, Paul!

[@kaedeschulz5422]

Or just use active crossover wich has no negative effects apart from that you need multiple amp's.

[@taineasy]

I much prefer the sound of air core inductor' with 12-14 gauge solid copper wire in my designs. Its very expensive but when it comes to correct sound on a good set of speakers, who cares about a couple of extra bucks.

[@johnhodgson5313]

Thank you again Paul. Your explanation covers it fine for general knowledge. For those who want to read more I have added the following:For audio purposes the iron core saturates with amps and frequency, the lower the frequency the lower the amps that the core will tolerate before saturation. In the November 1990 Audio Magazine with the B&W 801 Matrix review starting at page 108, Don Keele jr. discusses the effects of an undersized core of an inductor in that particular speaker. To save you all digging through the closets, here is a link: www.americanradiohistory.com/Archive-Audio/90s/Audio-1990-11.pdf

[@nixter1nixter1]

Very cogent for today's insane power levels that amplifiers can deliver these days.

[@TheMirolab]

Thanks for the AUDIO mag link JH!!.... the Matrix 801s2 has been my favorite & primary listening speaker for over 20 years, and I still love it! I've done extensive upgrades to the original crossovers, but one of the very first was to address inductor CROSSTALK. Two of the midrange & woofer inductors were too close and not orthogonal to each other, thus creating a problem in the 300-400 Hz crossover range. I'm now wondering, if what was originally suspected as an undersized inductor, was just in fact a crosstalk problem?? In any event... I now have a new reason to tear into them again, and seek out possibly upgrading the L6 inductor anyway (space is limited however). I've already upgraded all the original capacitors.

[@IliyaOsnovikov]

Please note two things from that article: 1. The inductor in question is a FERRITE - cored, 6.5-mH inductor that apparently was undergoing core saturation... (ferrite cores work better on high frequencies, while iron cores are better for lows). 2. Note that for typical program material with realistic crest factors played through power amplifiers of 150 watts or less, inductor saturation and resistor overheating should be NO PROBLEM.

[@DavidG-vq3bk]

Paul. The word for an iron or ferrite core which you were trying to remember is Drum Core (looks like a spool). Also, there are iron or ferrite Rod Cores and Toroid (ring shaped) Cores. A Bobbin in some cases, is simply a metal or plastic form or spool to wind on or transport wire.

[@user-rv4fc5ky3e]

AC has two half periods, in the first one the voltage goes from zero to max to zero, then the polarity changes and the voltage repeats, following a sinusoidal curve. Current follows the voltage thru the load. When you put AC through a coil, in the first half period as voltage rises, some time (dependent on the inductance of the coil) is spent to store up some energy in the magnetic field in the core of the coil, while no current passes to the load until the field is complete, when the second half period starts there is already a field there with a magnetic polarity of the first half period, that started collapsing when the voltage hit 0, there can be no two polarity mag fields in the coil at the same time, so what happens is the supply voltage tries to push the current in the other direction, but that current, while trying to create an opposite polarity field is stopped instead from flowing thru the coil, by the current generated by the first field releasing its stored energy, until it completely collapses, this is called self inductance, delaying energy transfer, then some more energy is stored in the mag field of the opposite polarity. This is almost like magic because even a little amount of magnetic energy stored in the coil is able to momentarily overcome ANY electrical resistance in its way, when the field starts collapsing and inducing voltage that can reach some pretty unbelievable values... so you can imagine the power loss difference when you do it once per second vs 20000 times per second. While the frequency is increasing the coil spends more and more time collapsing and rebuilding its mag field while "wasting" energy in a given time period, and the time when the field is up and the current allowed to pass freely, decreases, it's like magnetic PWM of a sort, speakers are also made of coils, thus frequency response, but that has also a lot more to do with inertia and fluid dynamics... Iron needs way more energy then air to orient its atoms to form a magnetic field, making the once formed field way stronger, so you need less turns of copper wire for the same effect, but it doesn't do so in a linear fashion, it is called a hysteresis curve, and each material has one, air cores are perhaps the "cleanest" in terms of introduced noise due to hysteresis, but you need more copper, and since bass is a much lower frequency, and iron is much cheaper then copper, bmw probably made a deal sacrificing some audio quality for lowering price and size of the coils, or that they factored in for the non linearity curve elsewhere in the system, or that the solid core is iron dust or some other more linear composite... I hope that I explained it well enough, coils are probably the least understood things in electronics, and since magnetism is involved, quantum physics may be able to explain the phenomenon fully one day...

[@rangeend5773]

How about the wire wrap around an ferrite?

[@therugburnz]

Extra thumbs to y'all.

[@EitriBrokkr]

Well I officially learned something today

[@stephencosta6814]

I love it I always wondered about that you are an encyclopedia of knowledge LOL And if you do make a book I will be the first to buy it seriously your big fan Steve Costello

[@Paulmcgowanpsaudio]

Thanks! Book is available right now for preorder www.amazon.com/99-True-Almost-National-Bestseller-ebook/dp/B07RM9QLLG/

[@Audiojunkabus]

what does acrost mean? is that a make up word like heighth ?

[@johnsweda2999]

depends where the inductor is in a crossover, like a 3rd of 4th order linkwitz I find when you put the iron core in it allows more higher frequencies to pass then without.

[@kaedeschulz5422]

Frequencie response is the same if the inductance doesn't change.

[@ericnortan9012]

I am rebuilding a crossover in a set of speakers, just a mirrored upgrade to better components. The exsisting caps are garbage and its very tiny gauge iron core inductors on all bands. I purchased 16ga air cores for the tweeter and bandpass circuits, on the low pass I got a 14 ga iron core. It wasn't cheap but a 7mH 14 ga air core took me over the budget. To save a few bucks I used an Audyn Q4 68 uF on the LP also. Mids got Clarity-Cap CSA and Superior Zs for the tweets. My goal is to get more control down low, going from a 20 ga (maybe smaller) to 14 ga with a decent cap should tighten it up in my eyes. Also, i want to clean up the middle, at higher volume the mids kind of take a back seat to the bass, as far as the tweeters go, with the Z cap I am told they match well with soft domes, brighten them up. I guess we'll find out.

[@eugenepohjola258]

Howdy. Yes. The iron core has three main disadvantages that must be considered in High End. 1. As mentioned the saturation. When the iron goes into saturation its inductance fades away. 2. Hysteresis. Ascending magnetization follows a different curve than descending. Causes phase unlinearities. 3. The permeability factor is not a constant. It varies with varying magnetization It is not a straight line in a BH chart. The inductance will vary with varying volumes causing the cutoff frequency to roam. Regards.

[@therugburnz]

Could someone address soft iron vs sintered ferrite or even nickel or CuNiFe ?

[@tristanjones7735]

They all have different permeability. The goal of any transformer or inductor is to provide a certain amount of inductance at all frequencies of interest while at the same time using the least amount of wire possible. Lets pretend that we have two inductors of the same size and the same number of turns. One inductor is using just plain silicon steel which is probably the most common type of core used in audio. The other core has some nickle iron alloy. The nickle iron will have a higher permeability and in turn will give you more inductance. However it will also saturate a lot sooner. So you have to balance out the metallurgy of the core such that it gives you the inductance you want without saturating during normal operation. Soft core iron, nickle ferrite, and all that stuff are just variations on metallurgy to achieve better inductive performance for the same size transformer.

[@therugburnz]

@@tristanjones7735 Thanx, TJ . I thought permeability was important. Coming from the guitar community,and we are gullible to 'mojo' I wonder about eddy currents making uncontrollable artifacts. BTW I thinking more about magnetism, inductance and transducers from the pick-up end mostly. Thanx again.

[@tristanjones7735]

@@therugburnz Wellllllllll things start to go sideways with guitars. In audio we usually aim to minimize distortion where possible. In guitar world, you are aiming to achieve a certain type and level of distortion. Different core materials can cause different types of distortions and that might create different resonances ect ect. In audio thats generally viewed as a bad thing, with guitars, you might leverage that type of distortion to flavor the sound characteristics. Good news is that winding your own guitar pick ups is fairly easy and cheap, so you can play with different core material and figure out what works best for you.

[@coldfinger459sub0]

I just noticed for the first time today after these years of watching your videos just buy your cover picture thumbnail you use I can tell it’s one of your videos even if it has nothing to do with audio in the picture

[@ShellstaTube]

It's the PS Audio logo - likely depicting a sound wave.

[@IliyaOsnovikov]

Has anyone ever compared the distortion figures of a good quality iron-core inductor to the distortion of an air-core?

[@IliyaOsnovikov]

Apparently some people have. Here is the link: hificompass.com/en/projects/experiment/test-couple-iron-core-inductors

[@WingStop-zv1sk]

After I heard clipping from a iorn core inductor I won't use one ever again unless I absolutely have too

[@tristanjones7735]

I don't mean to be rude, but im pretty sure iron cores don't saturate on frequency alone until 50khz. Depending on the core material, this can actually be much much higher. I don't really buy the idea that an air core inductor is superior for audio. I think a properly designed nickle iron core is probably better but it would certainly cost 3-5 times as much.

[@ronmatthews1738]

There are also metal dust core inductors that arguably give the best of both worlds.

[@tristanjones7735]

@@ronmatthews1738 Well you shouldn't need to go that far. Powered iron cores are really nice for high frequency applications. However we are not dealing with Mhz frequencies in audio and it won't give you the same inductance that a normal laminated core would give. I think the real reason paul prefers air core inductors is because iron cores do introduce non linearity into the mix which has very little to do with saturation. My thought is that if you design an inductor that minimizes some of these non linearities, you could theoretically end up with an inductor that has wayyyyy less wire in the audio path while at the same time not introducing any unwanted distortion.

[@carlosoliveira-rc2xt]

Air core is better if either one will do the job. You don't have to buy into it as it's a given.

[@kaedeschulz5422]

It saturates with power..

[@tristanjones7735]

@@kaedeschulz5422 Yes it can, but as long as you design the choke correctly, it should be able to handle a fair amount of power. IDK. I just bought some iron cores and will do some experimentation. I will get to the bottom of this.

[@hardcorecap]

IIRC... Air core = less hysteresis, higher DCR Solid core = more be hysteresis, lower DCR

[@andershammer9307]

I don't like iron core as they saturate and limit dynamics.

[@super-z8943]

Iron core gives distortion at saturation. But higher DCR of air core limits dynamics. You got it all wrong. If you want good dynamics, use a huge expensive air core inductor.

[@IliyaOsnovikov]

If you choose a good size iron-core you might have a hard time trying to saturate it. You would need to apply like 500-1000 W of amp power.

[@jjhack3r]

It’s disappointing that you spend more than half the video NOT answering the question and proceeding to explain obvious information I didn’t need to hear you say...