Yeah, pretty big things, for the Fast Speakers - this was the major incentive to get started on the electronic Xovers and the different type of amplifiers and so on - still bumbling along towards a trouble free system (nearly there, one more year perhaps)- no more horror stories of giant sized chokes tho!
Off the parts-express shelf it is
If air is impractical, and I cant exactly find a ferrite to the specs I should have - I guess I'll use a 1.8 out of parts express -
OK I'll ask a related question then -
I have a 1.8 mh or a 2.2 mh choice in a ferrite core. There is already a 2mh ferrite core in this xo in that same circuit. Will the 1.8 mH let in a bit more freq on the top end, like it will not be 400 hz, it will be 420 hz where it rolls off the woofer (3rd order BTW)
Thanks.
Srinath.
If air is impractical, and I cant exactly find a ferrite to the specs I should have - I guess I'll use a 1.8 out of parts express -
OK I'll ask a related question then -
I have a 1.8 mh or a 2.2 mh choice in a ferrite core. There is already a 2mh ferrite core in this xo in that same circuit. Will the 1.8 mH let in a bit more freq on the top end, like it will not be 400 hz, it will be 420 hz where it rolls off the woofer (3rd order BTW)
Thanks.
Srinath.
You could order the 2.2mH and unwind (or backwind) a few turns...
I mention adding backwind just incase the enamel is all melded
and impossible to peel excess turns away non-destructively.
Adding forward turns to the 1.8mH also an option, but the core
will go into saturation at slightly lower amperage.
Increasing 1.8mH (100%) to 2.0mH (111%):
Requires square root of 111% original turns, or 105.4%.
The reciprocal of this is 95% of original current rating.
Decreasing 2.2mH (100%) to 2.0mH (90.9%)
Requires square root of 90.9% original turns, or 95.3%.
The reciprocal of this is 105% of original current rating.
Originally posted before #26, but edit timer ran out...
I mention adding backwind just incase the enamel is all melded
and impossible to peel excess turns away non-destructively.
Adding forward turns to the 1.8mH also an option, but the core
will go into saturation at slightly lower amperage.
Increasing 1.8mH (100%) to 2.0mH (111%):
Requires square root of 111% original turns, or 105.4%.
The reciprocal of this is 95% of original current rating.
Decreasing 2.2mH (100%) to 2.0mH (90.9%)
Requires square root of 90.9% original turns, or 95.3%.
The reciprocal of this is 105% of original current rating.
Originally posted before #26, but edit timer ran out...
Hi kenpeter,
Could you elaborate on this? I am intrigued by your description of inductance in coils. I have always been a bit mystified by this. Thank you for explaining it.
I don't get magnetism either dude. All at right angles to reality.
Why do three dimensions look indistinguishably alike, then time
and gravity and electric and magnetomotive(B) and flux(H) look
look nothing alike? But some or all are probably the same thing.
Food for some other thread...
Anyways, empty space is the only real inductor core.
Conveniently, air behaves about the same for this purpose.
If a practical working size is no factor, unlimited energy can be
stored in the form of magnetic flux and completely recovered.
Empty space is soft and gives it all back. It holds no remnance
or permanent memory of being previously magnetized.
However, empty cores are large enough to be inconvenient.
And wind up huge bales of wire that brings its own problems.
Wire is far from lossless.
Useful compact cores abuse the quantum ridiculousness of
ferromagnetic electrons to fake a shortcut through space.
Maybe its an entanglement or something, I don't know.
Don't get me to lying on this...
These shortcuts conduct only a limited amount of flux.
24,000 Gauss Supermendur having highest saturation
limit that I've heard about.
But these shortcuts can squeeze past some of space
and provide flux a better path. Permalloy for example,
conducts flux with a relative permeability 100,000 x
better than space! Up to the saturation, which for this
material is only 7,500 Gauss. Above 7,500 Gauss is still
no "limit", but conducts no better than empty space.
Pure iron is cheap, about 5,000 times slicker than space,
and will allow about 16,000 Gauss to pour through. You
obviously see a lot of this. Its electrical resistance to eddy
currents improves when alloy'd with about 6% silicon.
Thinning it between rollers makes it conduct flux better
and softer, but only along the orientation of those rollers.
Cross to the direction the sheet rolls through...
The best resistance against eddies is Ferrite. Here you got
a real weirdo, cause there's plenty of iron in it, but the iron
does absolutely nothing. Probably for the best, cause in
ferrite, iron is a hard permanent magnet. But as long as
you don't do anything stOOpid to disturb the iron (like
whack it with a hammer, pulse with huge ampere turns,
or stick a neodymium magnet to it) neighboring irons
have been annealed in an oven to cancel each other out.
Wait? So iron in Ferrite does nothing, WTF??? Yeah, its
MANGANESE, go figure. But manganese isn't magnetic!
Well, its plenty magnetic (and soft) when you put in a
crystal that bends its electrons just so. They call that
ferrimagnetic, or ferrimagnetism. Not "ferro" like iron.
You put in a crystal (spinel or garnet) with iron, and it
tends to get bent like iron, only not exactly like iron...
The most common flavor of ferrite is a whole lot of inert
oxides that insulate and shape this crystal, and a tad
of Manganese. Hense flux carried is not high as cores
that are uncluttered with inert stuff. Something like
4,000 Gauss typical. If you push too far (and magnetize
the hard iron) can ruin it. But this is still the best deal in
blocking eddies at high frequency...
You need some space, usually a gap. To prevent the core
from conducting too much flux, saturating before you can
do anything useful, and maybe damaging it. Only space
can store energy. Shortcuts don't store energy. Shortcuts
always waste some fraction of energy that travels through.
Wire doesn't store energy either, and wastes some of what
travels through. Its worth burning some energy in a lossy
core to reduce the amount wasted in excess wire. The ideal
balance of waste (and often close to the smallest in size) is
usually 50/50.
I'm not forgetting Sendust or Heusler alloys, just gotta
cap this rant at a pill size others are willing to swallow.
For sure I already gone past that...
Last edited:
Not after UPS was done with it
He he, the original part was broken and still sitting in the compartment in the good speaker.
The Bad speaker - well - its long gone. UPS dropped it, both on its head and on its bottom. The top bolt is bent, the plastic head is broken off, and the bottom board and the edge frame as well as the inductor are broken and long gone.
It suffered very little damage otherwise. Its other problems are the result of me doing a transfer of bad parts to this pair from my nearly mint pair and selling off that pair. That I could fix, or live with.
I also am making speaker stands for this set to a crazy new design ... LOL, its a never ending pile of fun now.
Cool.
Srinath.
He he, the original part was broken and still sitting in the compartment in the good speaker.
The Bad speaker - well - its long gone. UPS dropped it, both on its head and on its bottom. The top bolt is bent, the plastic head is broken off, and the bottom board and the edge frame as well as the inductor are broken and long gone.
It suffered very little damage otherwise. Its other problems are the result of me doing a transfer of bad parts to this pair from my nearly mint pair and selling off that pair. That I could fix, or live with.
I also am making speaker stands for this set to a crazy new design ... LOL, its a never ending pile of fun now.
Cool.
Srinath.
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