I am building a new speaker to replace my Volt 2208/ Home monitor.
The new design will be three way and I am trying to use up some existing
high grade inductors.
So to make up my 3mh units I am considering the 1.8 air cored and the 1.2
ferrite cored in series.
Having read all the supposed disadvantages of iron cored units,
My question , Is their a theoretical difference in which way around these should be placed in series?
Does it matter higher first or aircore first?
It is going to be biwired.
I am aware that they should be 20cm apart and at 90 degree angle to each other to
avoid crosstalk.
Any theories and explanations as to why?.
The new design will be three way and I am trying to use up some existing
high grade inductors.
So to make up my 3mh units I am considering the 1.8 air cored and the 1.2
ferrite cored in series.
Having read all the supposed disadvantages of iron cored units,
My question , Is their a theoretical difference in which way around these should be placed in series?
Does it matter higher first or aircore first?
It is going to be biwired.
I am aware that they should be 20cm apart and at 90 degree angle to each other to
avoid crosstalk.
Any theories and explanations as to why?.
AFAIK when a current runs into an inductor, a magnetic filed comes up. this virtual magnet is sensitive to frequency changes and will vary with frequency changes going to speaker so the magnetic field direction will change according to the frequency change for example 1000hz/seconds, considering this the magnetic field keeps changing with the frequency all the time. the magnetic field is a bit lazy with a direct relation to the inductance value, so when the frequency is change the magnetic field of previous freq. is still there and will fight back with new signals 
and the magnetic field will nullify the new frequency to a certain amount so some of the frequencies pass through and some will get blocked... this is how an inductor works 
(Thank God I don't have to explain heart surgery in English )
so I think an inductor should be there to do the filtering job. maybe two in series won't create that much of magnetic field needed to do the freakin' job
and the magnetic field will nullify the new frequency to a certain amount so some of the frequencies pass through and some will get blocked... this is how an inductor works (Thank God I don't have to explain heart surgery in English )so I think an inductor should be there to do the filtering job. maybe two in series won't create that much of magnetic field needed to do the freakin' job
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I want pose a question
I want to know how can be estimate the saturation deadline of an iron core inductor? you know we can increase inductance of a for example 1mH air core inductor by putting a very small screw inside of it and it will show for example 1.1 mH... you know what I'm talking about... I think saturation and distortion depend on the mass of the iron we use and also the inductance. we can wind iron core but less than expected and then add more turns so I think it would take turn for less distortion and so we can obtain a balance between Iron core (less resistance) and air core (less distortion)... aint we?
as part of my job i test electrical machines, and a common task is the saturation curve. From my working knowledge i would run a similar test. This is what i would do. Get a variable ac supply, take a curve of V against I, working from 1.3 times inductor current rating down to 10% rating or lower. For a real valid test, winding temp would need to be monitored also. Then the Z, this is found from the trace and plotted. Temp compensation should be employed to correct for winding heating effect. The resultant corrected plot will be linear to the point of saturation. However, ferrite cored inductors whose typical use is in SMPS supplies are rated at a level where minimal or no saturation occurs, or they would fail to fulfill their purpose. A revealing question to ask yourself is: what current peak would i expect? Decide an answer,0hen pick an inductor whose current rating exceeds that level. Then you can be fairly sure that saturation will not occur. I have used 10amp ferrites with no issue whatsoever, 3amp rated arent so good. I reckon that the core diameter and wire gauge and number of turns is very relevant though. Scale core dia to inductance. Im using 2mm wire on a 1.5 inch ferrite. Monacor 'high power' at 2.2mH. Works well. The 0.6mm 3/4inch lower power monacor ferrite in 2.2mH is ok, UNTIL you add another L in series, even just 0.22mH makes it saturate wildly. Going for 10amp rating MINIMUM will work well. Even doing this hysteresis is still present, but it is a comprimise between DCR and size and saturation as sreten was inferring. Use 1 coil if possible, be it air or ferrite cored.
really? Not alot to pick between them, in comparison to no core at all. Silicon steel lammed cores saturate rather alot in my scope of experience. Air cored is better, but either DCR or expense may be a problem, as Sreten stated. The trade off is a high current iron or ferrite core. For 3mH a transformer could be used. By taking OCC and SCC curves saturation can be found. In this way, using 1 winding, you could 'tune' the secondary Rload, and experiment. An inductor of this type could be very low in saturation and distortion, and likely still cheaper than the equivalent air core
Hi and thanks for interesting replies.
I was just trying to save on the cost of a large 3MH inductor and avoiding throwing away two heavy units.
Well these were each rated 150 watt and Im using two now in series. 300W????
Amp is a conservative genuine 110 watt
It may well be that the physical location of the items in the cabinet determines which way around as I want to avoid interaction with the tweeter inductor.
ie 20mm away and 90 degree angle.
Im still not finalised where the individual parts will go but keeping the midrange xover
section away from bass end seems my only option.This has a 2.5mh and 1mh as well as the two(4) caps and it looks like Im going to locate this section right behind my new Morel midrange.
This now begs the question,should I make the midrange a boxed off unit.
Or at least some protection.
Allegro Loudspeakers
The Wilmslow audio designed xover does seem to be for an open ported internal.
Im guessing 400/3000k ish points.
I was just trying to save on the cost of a large 3MH inductor and avoiding throwing away two heavy units.
Well these were each rated 150 watt and Im using two now in series. 300W????
Amp is a conservative genuine 110 watt
It may well be that the physical location of the items in the cabinet determines which way around as I want to avoid interaction with the tweeter inductor.
ie 20mm away and 90 degree angle.
Im still not finalised where the individual parts will go but keeping the midrange xover
section away from bass end seems my only option.This has a 2.5mh and 1mh as well as the two(4) caps and it looks like Im going to locate this section right behind my new Morel midrange.
This now begs the question,should I make the midrange a boxed off unit.
Or at least some protection.
Allegro Loudspeakers
The Wilmslow audio designed xover does seem to be for an open ported internal.
Im guessing 400/3000k ish points.
ok, i dint wish for my post to lead to a degradation of this thread. The cored inductors I use DO NOT saturate appreciably below their current rating, or their function in SMPS supplies i use would be severely comprimised.
I DO NOT recommend the toroid SMPS chokes though, they are less than adequate. That being said, power inductors have to meet IEC test criteria for their current rating, if you fancy looking it up (IEC regs at work, i am away) perhaps they would help clear things up...
Should i get 5 mins free at work ill take the curve and you can view at your pleasure David. Going oversize is my approach in both air and cored inductors. That is a must AFAIAC. i use 10amp or more for a 25 watt amplifier. Ample headroom.
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@ raffells: 2 in series would still be 150WATT or which is the lower of the 2 coils, roughly speaking, due to total current being similar in each and the volt drops across each. However your coils arent equal DCR, rating or inductance. That complicates matters considerably. Id still use only 1 coil, and as large current rating as possible whether using iron or air core. Although you MAY be able to use 1 of the coils you have, and simply recalculate the shunting cap to make the filter fit your requirements.
@ mondogenerator Again many many thanks for the reply, sorry I was only opening up the availability of someone claryfying that issue about power rating.
Yes i have considered upping the cap value from 40 mf to 100 mf and using just one wound to down to 1,2MH.Ok now you can laugh as this is more of a problem due to the fact I had previously soaked the coils in a PVA glue to reduce rattle possibility.
So unwinding may be harder than usual.
Note some of my improvements go to extreme lengths.
Yes i have considered upping the cap value from 40 mf to 100 mf and using just one wound to down to 1,2MH.Ok now you can laugh as this is more of a problem due to the fact I had previously soaked the coils in a PVA glue to reduce rattle possibility.
So unwinding may be harder than usual.
Note some of my improvements go to extreme lengths.
haha no need for apology, im just not about to get drawn into another inductor debate! The sensible answer came from Sreten a few posts back. Ie just use a single coil, which type you use is your choice. I murt admit i prefer air core, but iron or iron dust CAN be 99.9% as good, if chosen wisely. Re the PVA, I have done a similar thing with the monacor coils i have, using epoxy 'varnish', followed by raychem heatshrink sleeving. The next lot i buy will be vacuum impregnated with the same varnish. for what its worth, i would space the coils further apart than 20mm, maybe 100mm? I couldnt say for sure, but i dont think 20mm is large enough.
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Polite discussion leads to a degradation of the thread? I think all here don't mind what has been discussed so far
I was referring to POORLY designed ferrite or iron cores that do saturate below their rated wattage. I'm sure there are plenty of properly designed coils out there.Power ratings for the inductors you work with in power supplies probably are meeting IEC test criteria. Inductors made for speaker use probably aren't held to any such requirements sadly.
Yes some measurements would be appreciated, thanks.
Do you think the reason for two inductors in series causing one to saturate is caused by close placement of the coils and the collapsing fields of one affecting the other or perhaps the current of the collapsing field in one overdrives the second coil through the physical connection itself?
There are sadly hardly any tests done online about audio inductors, seeing if they do meet their rated wattage but seeing as how much they cost,it would take someone with lots of spare money to do such tests.
Well now you have thrown a spanner in the works.100mm spacing is a whole new ballpark for the positioning of internals in this build.
I am actually using a long metal bolt for internal cross bracing.Also have additional 3 ply birch ready to be glued to side and rear internal panels with Deflex and bitumastic damping applied already.
Thinking about the ideas presented has made me think about designing it so that I can quite easily switch between the two different value component crossovers.
Ie Connections via plastic screw blocks.At least for initial firing up.
I am minded to remove the second inductor and locate a parallel block of PP capacitors to build up to the desired extra cap value I need.
Now that you have revived my thought processes.(I started my mods in 1961-2) I may post another help question re any other ideas,suggestion that I havent picked up from the many many many threads.
thanks again.
I am actually using a long metal bolt for internal cross bracing.Also have additional 3 ply birch ready to be glued to side and rear internal
panels with Deflex and bitumastic damping applied already.Thinking about the ideas presented has made me think about designing it so that I can quite easily switch between the two different value component crossovers.
Ie Connections via plastic screw blocks.At least for initial firing up.
I am minded to remove the second inductor and locate a parallel block of PP capacitors to build up to the desired extra cap value I need.
Now that you have revived my thought processes.(I started my mods in 1961-2) I may post another help question re any other ideas,suggestion that I havent picked up from the many many many threads.
thanks again.
choc blocks sound like a good idea, i do this myself with no issue. Dont quote me on the inductor spacing, i took a guess. Air cores will need more space than iron, again If i recall. In my last filter, shown in my signature link, the M10 cored inductor is about 35mm from the large ferrite and at right angles, and i dont have any problems, LUCKILY. the compact dense field is less of an issue, with air cores id not chance such a close placement.
Regarding saturation tests, it would be interesting to test my assertions concerning high current cored types, and ive been meaning to try it out for some time. Saturation does of course occur, but without tests its a little egotistic for me to be so confident. The 2 series ferrites is a toughie though, they were over 80mm apart and still...
I blame the small core murata 2.2mh i used, id hazard a guess that the field of this coil was very dense, so perhaps also a larger leakage field than the 0.33mh.
Regarding saturation tests, it would be interesting to test my assertions concerning high current cored types, and ive been meaning to try it out for some time. Saturation does of course occur, but without tests its a little egotistic for me to be so confident. The 2 series ferrites is a toughie though, they were over 80mm apart and still...
I blame the small core murata 2.2mh i used, id hazard a guess that the field of this coil was very dense, so perhaps also a larger leakage field than the 0.33mh.
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Refer to the first post in this thread. You can place inductors close together as long as you use proper orientation. Example number 6 and 7 in the diagram.
Inductor Placement *PIC*
Inductor Placement *PIC*
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