unwinding a 1mh. steel laminate inductor into .8mh, good idea or not?

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Dear all,

I have a need for a low DCR .8mh inductor for my project.

I have a list of options.

#1. madisound .82mh w/ .19 DCR perfect lay inductor, unwound to .8mh. costing about $17-

#2. Goertz 12 guage .82mh w/ .111 DCR foil inductor, But cannot be unwound . costing about $34-

#3. Madisound 1mh w/ .1 DCR steel laminate inductor, unwound to .8mh. costing about $8.65-.

I'm thinking that my best option is to go for option # 3. As I already have an LCR meter.

But the question is , Is there anything wrong with unwinding the 1mh steel laminate to .8 mh? Would'nt that steel cored inductor suffer in performance with values lower than 1mh?

And , Is this really the best option?
There is nothing wrong with removing turns on a laminated core inductor.

Steel core inductors could saturate (especially in woofer circuits). Removing turns reduces the chance of saturation. Take the I max ratings seriously, if they are below any current likely to flow in your circuit go for it.

If an inductor in a series woofer circuit saturates, the inductance drops to near zero causing a loud bang from the woofer with at least a potential for driver damage.
Thank you.

But I dont know any current rating on that inductor. All I know is that, It uses #15 AWG magnet wire and it's supposed to be used for high power application. LINK .

The maximum possible amp. power I'll use for my project is 250watts/pc rms amp. and the load that will pass through the inductor is 4 ohms. ( two 8 ohms 7" woofers)

Do you think the inductor would be adequate for the job?
Hi marchel

The low DCR coil does not means s good sound. steel core
i had ever used it. Now i only use air core. marchel i had ever
known before that the steel core when it gets the high current.
The impedance of it that it's not correct linear. I often see the speaker to sell in the store. sometime a good speaker use the air cores are too much. Yes! you may be lose a damping factor just a little. But it does not means that you will get a good sound from it.

Hello Thawach,

So you're saying that air cored inductors might have better subjective sound quality than steel laminate cored inductors?


You might be right though, Cause , As I remember, There were 2 versions of B&W 800 ( not the D series), There was a plain version and a signature version. The plain version uses iron core coils and bipolar caps on strategic locations, The signature version uses air core coils and poly caps all the way. Of coarse the reviews favor the signature version in terms of sound quality, But wether the difference is true or not, I wonder how much the air core coils and poly caps contributed to the supposed improvement in SQ.
Hi marchel

i think that you must come back to a hi-school again.And learn
about english+distortion language. you will be better. sometime
I cannot understand my words that i write but you can translate
some words of mine.i think "oh my god" marchel you are good.lol

About steel laminate coil that i can remember a little.i had ever
heard it from the thai producers.they has a company to build the
speaker and sell in the stores. A speaker of them had ever shown in
the CHICAGO hi-fi festival and change the brand was song audio.
The speaker of them never use the steel laminate coil(the pic the use).

they told me about the flux of steel laminate coil. it has a problem.
the flux is easy to full when it gets the current.(this word i don't know)

marchel i understand you. you have a rcl meter.Why don't you wire the
coil by yourself? here is the pic that i wire by myself. i spend my
money about 5 dollars to buy a wire about 1 kg. i wire it 1 mh=4 coils
i use a little tool. 80 per i use my hand. and check it again by lcr meter.
1 mh i spend the times about 15 minutes.is it cheaper? marchel your home
is far from me.i would like to wire it for you but i can't.

marchel i send the graph about bobbin.about 10 years ago i had ever used
i used the bobin 1" 2" and lower than 1"(x) 3 coils had value about 0.6 mh.
i used 16 awg(3 coils) i listen each of it to used. the low freguency was
difference. marchel i used order 1 for the woofer.i knew the best coil
is i"(diameter)for 0.6 mh. and i had ever wired it for passive sub.
i used 11 mh. The bobbin(air core)is the best=2" Marchel you see the
graph x=bobbin. r=ohms below=mh


:D :D :dead:


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Here is a short explanation I wrote in another thread of why one might choose an air cored inductor over a ferromagnetic cored one.

Available in two basic types, air cored or ferromagnetic cored. The first having no ferromagnetic former on which the inductor is wound, the second having such a former. The reason for having a former is to increase the inductance for a given size (and usually cost) inductor. The disadvantage of ferromagnetic cores is increased distortion due to hysteresis of the core. This is more pronounced with higher frequencies than with low ones and with higher current than with low current. The usable frequency of a ferromagnetic cored inductor depends on the core type, but generally is fairly low, in the high hundreds to low thousands of Hertz. This makes air core inductors more suitable for high frequency crossovers such as midrange and tweeter crossovers.

Madisound's steel laminate core inductors should have fairly low distortion in a woofer circuit. A look at Erse's webpage (who makes similar inductors) claims that their SuperQ steel laminate cored inductors match an equivalent air-core from 0-3000Hz. http://www.erse.cc/coils/superq/superqcoil.asp They also rate the usable frequency for standard I core inductor as below 8000Hz. I don't know what level of distortion they consider "usable" so I would just stick with under 3000Hz as a generic guideline for steel laminate cored inductors.

Thanks for the info and the link, But I think I'll just order from madisound to save some shipping cost. cause I also have some other items in there that I need to order.

Thawach ,

Thanks so much for your help, I appreciate it. But unfortunately I barely have time to do This project here.. Let alone wind my own coil, As I dont have a coil winder. And even If I do, There is no guarranty that the coils I make will be of good quality.

To be completely honest though, I still have doubts about the metal cored inductors, in terms of subjective sound quality. I'm temted to just use the Goertz foil inductor, Just for some supposedly subjective sound improvements.

I still have few days to make up my mind.

I wasn't suggesting you purchase them elsewhere, rather I was linking you to some data about a similar inductor core design. Madisound does not give any information about the useful frequency range of their steel laminate inductors, but Erse's specifications for a similar core design should give you confidence to use the Madisound inductor in a woofer circuit.

Good luck with the project,
hi marchel

the coil picture that i sent. they use foil coil. i would like you to use it for your speaker. the cap they use scr brand.in the past they used sollen brand. they change sce. they tell that it's airy.
the connecter they use the michell engineering brand. internal wire use the vampire brand. the single wire for xo they had ever had one project. they used silver wire. they has ever told that the original silver that's not good. he bring it and build it again.
but it's expensive too much for 1 ft.i remember the B&W had ever used the silver air coil for xo. they had ever gone to the B&W manufacter.to saw a technics when the B&W 801 nuatilus began to finish. they had ever told B&W that the sound of 801 will be berter than this if it's in a good acoustic room. marchel i think the foil coil that you choose. it' the best.

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