Interesting indeed, so from best to worst, all else being equal*, the air gap size is decreasing.
This tells me even if OEMs spec'd Isat, it may not be useful for selecting the best cored audio inductors!
*they are never equally compared, Ae core cross sectional area must be included.
Jantzen warns against their use in critical parts of the crossover and advises to limit their use to parts of the circuit where high inductance in a small package is required. So at least they hint at the fact that the inductor may misbehave.
Yes, of course, that is one of the many reasons to read tests in the audio magazines. However, it seems that specified Isat is a good indicator when the distortion skyrocket.
well we all don't live by audio mag tests.
to the catalog designers of course Isat is the keep away zone, but the 'unknown zone' between Idc and Isat is still unknowable, except to the engineers and perhaps a few subscribers.😀
BTW those EI cored chokes with small air gaps used to be called 'swinging chokes' due to their soft saturation but higher initial inductance. today it's same deal with powdered iron toroids. useful for either current fed linear PS or SMPS not so much audio.
I reckon the class D designs wrestle with some of these factors to tame EMI but live with the delta L somehow.
to the catalog designers of course Isat is the keep away zone, but the 'unknown zone' between Idc and Isat is still unknowable, except to the engineers and perhaps a few subscribers.😀
BTW those EI cored chokes with small air gaps used to be called 'swinging chokes' due to their soft saturation but higher initial inductance. today it's same deal with powdered iron toroids. useful for either current fed linear PS or SMPS not so much audio.
I reckon the class D designs wrestle with some of these factors to tame EMI but live with the delta L somehow.
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The cutoff frequency of a class D output filter is ultrasonic, so a slight variation of that frequency shouldn't affect things inside the audio band too much, unless the filter is poorly implemented and very peaky with a realistic (i.e. reactive) load. Also, when the output filter is inside the feedback loop, the feedback largely clears up inductor issues. So yes, the issues in a class D amp are somewhat less severe. An interesting read (although severely OT) is this:
Trevor Marshall - Class D Audio Amplifier Design - TDA7498 Output filters
If the Monacor inductor mentioned to earlier (post 53) really behaves like a swinging choke, then it is simply inappropriate to sell it as a filter inductor. At least, I assume that's the one you are thinking about, so correct me if I am wrong. The inductance change of a swinging choke is often more than 50% over its nominal operating current range, and this does not fit with the specified (and confirmed) 3% THD at the specified saturation current. In order to truly make a choke swing, it needs something like a V-shaped or stepped air gap. I doubt it is constructed like that, although it may roll off the same assembly lines, and use otherwise similar materials.
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I cant comment on the test data vs items tested until I see it.
and the particular EI choke design, it is distorting at fraction of its "rated" current then clearly it's being sold in the wrong application. ( another reason why its not useful to define Isat just for audio.) Ive seen them used in some old speaker and tube designs for sure, but I reckon in the former uses being gapped higher than what was tested here. I have NOT seen them for sale lately in the usual speaker places round here tho. Naturally based on my experience, I'd approach a EI cored choke with much more hesitation than the eye bar kind.
and the particular EI choke design, it is distorting at fraction of its "rated" current then clearly it's being sold in the wrong application. ( another reason why its not useful to define Isat just for audio.) Ive seen them used in some old speaker and tube designs for sure, but I reckon in the former uses being gapped higher than what was tested here. I have NOT seen them for sale lately in the usual speaker places round here tho. Naturally based on my experience, I'd approach a EI cored choke with much more hesitation than the eye bar kind.
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This particular inductor is touted by Monacor as suitable for PA, where small size for a given inductance matters more than with high quality audio, at the expense of distortion performance. Classic case of design compromises tailored to a different application than the one we're looking at here, not a bad inductor per se.
+1
good on Monacor > maybe they meant it for a HPF for 16 ohm horn loaded mids , who knows. all I know is take "Isat" with a grain of salt unless you know what's going on.
maybe "Pro" in Monacor talk means "beware DIYers ,this might not be your cup-o-tea". haha
maybe "Pro" in Monacor talk means "beware DIYers ,this might not be your cup-o-tea". haha
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Air gap vs toroid
I think is not best way ...
The air gap is right if is all ideal that way is linear but we are nearest a big magnetic field generated from the woofer , it's impossible to determinate the impact on
the inductor value and B-H plane diagram .
For me a fine evaluation of toroid is now possible by a computer simulation and simple to test , if we use the air gap or free air inductor a magnetic shield is necessary
for best results .
I think is not best way ...
The air gap is right if is all ideal that way is linear but we are nearest a big magnetic field generated from the woofer , it's impossible to determinate the impact on
the inductor value and B-H plane diagram .
For me a fine evaluation of toroid is now possible by a computer simulation and simple to test , if we use the air gap or free air inductor a magnetic shield is necessary
for best results .
Position of cross over
Ok if the cross over is so far from woofer we need only a cylinder of ferrite
to made a big inductor .
But if you have a small standard 2 Way the speaker magnet is to close to the cross over .
In the end a metal shield is always the best way to reduce noise at 50 or 60 hz (power networks) and the variable fields produced from woofers ... I think...
Ok if the cross over is so far from woofer we need only a cylinder of ferrite
to made a big inductor .
But if you have a small standard 2 Way the speaker magnet is to close to the cross over .
In the end a metal shield is always the best way to reduce noise at 50 or 60 hz (power networks) and the variable fields produced from woofers ... I think...
@Timpert: This is the cored inductor I am using in 2.2mH guise:
LSIF-820
Isat is claimed 5A. I haven't been able to find any B-h curve data
I haven't heard any noticeable distortion, although it may exist. My amplifier is 25Wrms, so I'm likely to hear amplifier distortion beforehand.
@SpeakerScott: Ah...NI boards...the DAQs I'm using are based on the same architecture, and IVI drivers. They are capable of 24bit at maximum 100kHz, using modbus TCPIP interface. They typically have SNR of around 120dB, perhaps a touch better, in common with NI stuff. Miles better that a scope of a similar price, all that remains is to build a decent high speed Labview based plotter....
LSIF-820
Isat is claimed 5A. I haven't been able to find any B-h curve data
I haven't heard any noticeable distortion, although it may exist. My amplifier is 25Wrms, so I'm likely to hear amplifier distortion beforehand.
@SpeakerScott: Ah...NI boards...the DAQs I'm using are based on the same architecture, and IVI drivers. They are capable of 24bit at maximum 100kHz, using modbus TCPIP interface. They typically have SNR of around 120dB, perhaps a touch better, in common with NI stuff. Miles better that a scope of a similar price, all that remains is to build a decent high speed Labview based plotter....
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shielding magnetic fields is very difficult with metal. best done by rerouting the magnetic circuit at the interference source with iron shapes and short circuit rings. increasing distance is very often an easy /best fix IF you have a problem. lots of folks come up with solutions to fix no problems for good money. this is called snake-oil. Audio is field filled with snake-oil guys AND just inventing problems is part of their job.
"buried in the noise"
1) the effect is detected very low levels by moving the magnet to cause shifts in > no movement no noise> the coils are used like a guitar pickup in low-mid uV at best ( notice the power line hum was a bigger issue! )
2) the XO is operating at much larger levels in 1000s of mV.
shilding
OK shielding is difficult because need more than one alone shield best metal is simple Fe but yes highest thickness is obligatory ,
On my small 2 way i found an higest interaction from woofer and the cross over but
the distance is too close ...
Intresting is the difference form not expensive woofer and a best woofer for the air field around the cabinet
OK shielding is difficult because need more than one alone shield best metal is simple Fe but yes highest thickness is obligatory ,
On my small 2 way i found an higest interaction from woofer and the cross over but
the distance is too close ...
Intresting is the difference form not expensive woofer and a best woofer for the air field around the cabinet
My experience
To know was happen on my cabinet i have used a free air inductor connected to scope
and applying vibrations to the inductor and signals to the woofer
To know was happen on my cabinet i have used a free air inductor connected to scope
and applying vibrations to the inductor and signals to the woofer
^microphonics of an air core inductor for a speaker XO is a non issue.
I think you can add 2 part epoxy to coat all coil surfaces , mounting coil use tie wraps and /or caulking to wood panel.
I think you can add 2 part epoxy to coat all coil surfaces , mounting coil use tie wraps and /or caulking to wood panel.
Monacor is rebranding stuff to their name (IMO looks low quality no reductions in costs)
I would advise this brand they seem to understand engineering better
Speakers Intertechnik - Shop
I like bar cored inductors for lowest Rdc at reasonable cost and better durability.
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Thanks Infinia, however I am taking a somewhat marginal interest in passives now, and have since moved to analogue active filters, and don't regret going this way.
Though for what it is worth, the previous build I used Alphacore 12 gauge copper foil chokes, some 1/2 lb each, 4" diameter, and rather costly relatively speaking. Although these are not without issues themselves, not least soldering and capacitance.
But all info is handy, hence my interest
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im sure Alphacore is sad to hear you have moved on.
I reckon your passive Xover budget must of exceeded all the driver costs together.
OT what is your (multi) amp preferences?
I reckon your passive Xover budget must of exceeded all the driver costs together.
OT what is your (multi) amp preferences?
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I am running some lm4780 in parallel, audiosector kit. Its not even in a cabinet yet so I am using two Cambridge audio A1, setting volume to set relative driver levels, and adjusting master volume from pc or mp3 source. It works well for a hatchet job, and was a definite improvement over passives, in my case.
I have the active filters about as well set up as I can manage, without DSP and more work. I'm lazy 🙂
The aircore coils are just expensive, with shipping and the wait the alphacore coils cost about the same as the audax I got them for...
Now I have learned much more, and can source easier and perhaps cheaper alternatives.
I appreciate the purist opinion of air cure, the cost is just a little annoying. Ive wound my own coils, but not ever being able to get them perfect is another source of frustration. Else.id wind them all, and always air core.
From my background.in electrics machines I know cored inductors will be lesser in performance in most cases, wrt to saturation but couldn't hear it so the "that'll do" in me prevailed.
I have the active filters about as well set up as I can manage, without DSP and more work. I'm lazy 🙂
The aircore coils are just expensive, with shipping and the wait the alphacore coils cost about the same as the audax I got them for...
Now I have learned much more, and can source easier and perhaps cheaper alternatives.
I appreciate the purist opinion of air cure, the cost is just a little annoying. Ive wound my own coils, but not ever being able to get them perfect is another source of frustration. Else.id wind them all, and always air core.
From my background.in electrics machines I know cored inductors will be lesser in performance in most cases, wrt to saturation but couldn't hear it so the "that'll do" in me prevailed.
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