Are Hammond reactor good for woofer crossover?

[ygg-it]

That is interesting. But what about in AC, with a variable audio current signal ?
What would be the inductance and will it be constant?

And why a normal ferrite line inductor should behave differently from a transformer EI coil?

I ask because I need to understand how simulate the first-order cutoff frequency with that -6dB slope.

I just found a local manufacturer which can build a transformer coil for me, like the hammond one.

[ticknpop]

Actually for 30 mh thats a low DC resistance. No difference between reactor, choke, and inductor - different names for the same part. You’ll never get an air core at that value (big as a house with a much higher DCR and what would it cost). I used big 20 amp 10mh Hammonds on passive Dynaudio subs and they were very good (big and expensive too).
Then I moved to powered JL audio F212 , those were even better, but cost a lot, lot more.

[ygg-it]

Thanks, so you probably used 195J20

Question is now: if your inductor is rated 10mH at 20A DC, how much inductance was in your crossover circuit, where there is no DC?

10% or 20% more?

[mondogenerator]

Originally Posted by ygg-it

Which is the difference between this reactor and an inductor?

Absolutely zero, no difference, except in name.

Anyone that says otherwise, has no idea, what an inductive reactor is used for!

It is just a laminated core Inductor.

[markbakk]

As the permeability of the core material will decrease when the core goes into saturation, the effective inductance will go down with rising (DC) current. But I think the specified DC value and the specified inductance on the coil will stand, e.g. as long as the current doesn’t exceed the specification, the inductance will be more or less stable. I don’t really see why DC and AC would give different outcome.
Another thing is that such a reactor might be more prone to microphony because it isn’t as tightly wound as you would like for audio applications. It has been mentioned in an earlier post in the thread. But there you’d have to eat the pudding.

[ygg-it]

Originally Posted by ErikdeBest

Another thing. The specification of 30mH is with the 5A DC current. Besides tolerances that may change this value, if there is no DC current the actual inductance will probably be higher.

Here, maybe, a clarification from Murata Power Solution inductors:
"The maximum DC current is defined as the DC current at which the inductance falls to 90% of its nominal value ....
....
When making comparison with Inductors, it is worth noting that many manufacturers quote a 30% drop which gives the impression of a higher current rating"
inductors - Murata Power Solutions

Here a definition of "saturation current"
"Saturation current is defined as the DC bias current that causes a specific amount of inductance decrease, usually 10%, 20% or 30% inductance"
How to Understand Power Inductors Parameters for DC/DC Converters | SOS electronic






According to that (10-30% drop in DC) and considering +/-15% tolerance it seems that if I need a 30mH working in AC only (40WRMS@8ohm = 3A peak < 5A ), I should purchase an inductor 10-15% less, that means 195G25 Hammond Manufacturing or order a 25-27mH 5A DC max transformer coil.

Would this be wise?

[markbakk]

Would you notice the difference? I mean, what brought you to the conclusion that you needed 30mH? I really don't think anyone will be able to discern the two in blind tests.

[ygg-it]

Got at excellent price (with shipment fm US to Italy free!) two monsters 30mH 8A 300milliohm inductors (EI laminated core plus air gap as in the photo) from Signal transformer.

3.6 Kg each!

Measure 30mH with 10% tolerance with two different LCR meters.

As a first test fantastic to cut everything at -6dB first order slope.

Just tried in serie with my loudspeakers, cut everything from 100Hz.

Attached the new design.

[markbakk]

Wow, those are ugly... good work, have fun with them!