Can anyone identify this inductor?

Its a speaker crossover from a well known brand. Most coils on it are standard air coil style... but one looks like a transformer - wound vertically around a HUGE iron core which protrudes out the sides, then varnished/sealed and puttied to the board. Stamped with the company’s name on it. (All other components look sourced).

I reached out to the company waiting for an answer, so I won’t mention the name. But I don’t think they will reply.

Iron inductors seem like a no-no. In fact, I got huge coherency improvements by taking anti-static and EMI measures on it with some usual hi-fi tweak products. I do not know if they even tried to orient it correctly.

Anyone know? cheers




Iron inductors seem like a no-no. In fact, I got huge coherency improvements by taking anti-static and EMI measures on it with some usual hi-fi tweak products. I do not know if they even tried to orient it correctly.

Sounds like you identified it to me 😁 

Iron core inductors work just fine, in fact often better because their DC Resistance (DCR) is lower since they don't have to have nearly as much wire involved to reach a certain inductance value.

So what are the benefits to lowering the DCR? I'm trying to back-engineer the decisions they made on this crossover. I am somewhat new to them. thanks

You lower the DCR because you need to lower the DCR.  Lowering it in an existing/working crossover can be detrimental.

Working with DCR can help you compensate for baffle step effects without a separate baffle step compensation circuit.

One major reason you might want to go with iron core is that otherwise your coil would be too big.  If you need high inductance, low DCR and smaller size/cost iron core is the way to go. More inductance = more windings, longer wire.  Naturally, more wiring would normally add DCR so at a certain size of indcutance, like you might need with a very low frequency low pass filter a standard air core may be too big or heavy or expensive or impossible.

I just happened to discover it. Its a Lundahl which was rebranded to the loudspeaker company, maybe a slightly custom one, but markings on the label and the rest of it is identical. Its in the crossover.


Lundhal says :


Tube microphones. Silicon-iron C-core, which results in a transformer
with more "transformer sound character", compared to a classic mu metal
lamination transformer. PCB mount style.


So, was this chosen for euphonic character maybe? By the way, the crossover has some huge traditional copper coils on it so they are not afraid of taking up space.




It is a transformer! Interesting!

So what is the brand and model of the speaker?

Can you post a picture of the crossover?

Amphion. But there are no photos online, probably because the crossovers are tucked way inside and strongly glued in. When I asked them about it, they declined to answer.😏

Well I looked closer and its not that exact Lundhal. Its slightly larger and only has 30 windings, which seems much fewer than all their others. I can’t identify the core material - that one I mentioned for tube mics says 10x the THD than normal Mu Metal, so I can’t see why they would use that one. But the construction otherwise looks similar, with the putty. So it seems its a custom transformer for them. Unshielded no less. I don't know enough about transformers to know if there are other brands which look identical to this.

Anyone have thoughts on using transformers in crossovers?

I've got the parts but they were slow to arrive and now I'm in the vacation season so I haven't done the work yet.   I'm chaning all the inductors in my crossovers to wax/foil inductors. Some existing are iron core, some are not.   Replacements are Much larger.  the heaviest ones weight just over 5 lbs.  

Upgrading your inductors (and caps and resistors) is a fairly expensive but quite useful upgrade to most speakers under $50k.  And a good upgrade for many more expensive speakers as well.

Measure the inductance and order 2 upgraded replacements (one for each speaker).  While at it, upgrade other components on the crossover.  


If it only has 30 turns winding and two leads, It could be an C core inductor for woofer low pass filter, because of its extremely low resistance!

Well I can't be sure of the leads (crossover glued in place to the PCB), but it looks identical to the photo I posted but with 30 windings that I can count. Has the same Lundhal (F) marking but no logo.

Sounds like its just a high quality inductor manufacturer chose?