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Factory Buyout bobbin core inductor and the cost of copper
I know some of you wind your own inductors. PE has some buyout 7.5mH 20 Gauge Ferrite Bobbin Core Inductors for $7 . They also have the ERSE Super Q 7.5mH 16 AWG 500W Inductor for $31. (They also have buyouts of 12mh for $11 and 9mh for $9.50)
(1) What do you think of bobbin core inductors? (I think I have heard to stay away.)
(2) Would the amount of copper wire on the buyout bobbin cores be a good deal if interested in winding my own?
https://parts-express.com/12mH-20-Gauge-Ferrite-Bobbin-Core-Inductor-269-2126
Comments
I think the ferrite core bobbin inductors get a bad rap due to the core's fragility and the packaging isn't always up to the task of dealing with the realities of mass shipping - they get broken.
Concerning them saturating - you must be listening at extreme sound levels (high current through the coils) to hear these effects - check out this link explaining it --> https://electronics.stackexchange.com/questions/80371/saturation-current-in-inductor-definition
I too am interested in others experiences with them, though.
Fwiw you can buy 1/2 lb of magnet wire at PE for $20
https://www.parts-express.com/Consolidated-18-AWG-Magnet-Wire-1-2-lb.-100-ft.-101-750
I've been ordering magnet wire from Temco. Best price and selection I've found, except of course, for unwinding some of the scrap motors from work.
Ha! I've never even heard of "magnet" wire. It always amazes me how much stuff PE sells other than the basic DIY speaker stuff that I look at.
Thanks guys!
I've used some of the PE buyout ferrite core with reasonable luck. They tend to fare better than the powdered core style. Powdered core (looking at you Jantzen) start saturating immediately, but exhibit a gradual increase with current, a ferrite or laminate core is more linear until it isn't.
I'm not convinced it is an issue in most applications. If you are running pro-audio speakers with passive crossovers and high output, you will definitely soak the non-air core inductors. For a DIY gathering where 10-20 watts is generally enough to get to typical listening levels it is doubtful the saturation is an issue.
On the other hand, Marty had issues with the buyout ferrite core and distortion. Took him quite a while to track it down to the coils. I forget the exact details.
I've also bought from Temco, and only use ferrite/rod-core coils in conjugate low-current areas. Super-Q/Steel-Laminate or air-core for lowpasses.
InDIYana Event Website
Laminated cores are vastly superior IMO for reduction in eddy currents and hysteresis, ie low distortion. My only application for cored inductors though would be for woofer low pass, where a 20AWG coil is still providing a fairly high DCR, so only a good coil for a low budget 3-way in which case the coil distortion may be a secondary consideration anyway.
I don't use 20AWG much at all anymore. I used them in the recent small 3-ways because I had them, and they were shunts in mid/high networks.
18AWG Lam-core have about the same DCR as 14AWG air-core, so there can be a cost and size advantage.
When I did the coil-rig a few years back, the slam of Lam-core was liked by most, but the emphasis once recognized sounded a bit artificial to me after a while. The P-core did not sound good by comparison. Nobody voted for the foils by a show of hands in preference. Standard air-core also were liked.
InDIYana Event Website
High mH with small gage wire is really asking for trouble. Easier to wind with new wire imo.
I thought that I had seen a technical report that ferrite core inductors not only saturated below their rating, but also had either distortion or hysteris measurements that were unacceptable compared to laminate core inductors. Haven't used them since!
Powder cores have pretty bad saturation profiles, it starts almost immediately when power is applied. I'm not sure what the composition of the buyout coils is. I think I have some floating around, maybe I'll do some destructive testing.
Those PE buyouts are the ones I wrote about a few years ago. I used one on an Usher 8955 and ran into trouble almost immediately. I have also used them as the shunt coil on midrange crossovers with no audible issues, but now consider them a lesson-learned and will never use them in a series position again.
^ Good feedback.
So as SHUNTS, they are OK but not as series sound shaping devices?
Generalizations like that can be quite problematic. Series or parallel, the component is in the signal path and all the same principles apply. Main difference is the series component being used for a low pass filter on a woofer has a much higher current demand than the component placed in a mid-range circuit, which will be the biggest difference driving factor there.
For insight of power dissipation of components in any circuit, if you're using VituixCAD, simply select view -> power dissipation.
This can be done in XSIM as well.
Not in a way that makes sense for music input, Xsim simply simulates flat spectrum 20Hz-20kHz, very "worst case" and not realistic of normal operation with music signal at high frequency especially.
Egomaniacs can be quite problematic as well.
Low saturation thresholds.
Now that I have seen the availability of large spools of magnet wire, the idea of buying the buyout bobbin inductors just for the wire doesn't seem to make sense. For those who wind their own inductors, how significant is the cost savings vs buying PE/ERSE/Jantzen?
Related:
https://purifi-audio.com/2020/04/28/dist/
This inductance business is far more complex than I thought after reading that Purfi link.
But what I came away with is that air cores are best where transient response is what you are after like midwoofers, mids and tweeters and laminated steel cores are fine and have less memory than the rest of the cored options - and best suited to low pass series or shunts in woofers and subwoofers.
Do I have this right?
I read the article and saw the term flux... Which made me think of the flux capacitor in Back to the Future... Which made me think of Christopher Lloyd's hair... And then I forgot why I was reading the article. 😁
That guy is a freaking hoot!
My take away was the "gritty" or "poping" sound produced by the ferris core material. I wonder how this compares to the "gritty" sound produced by non-polar electroytics placed in series with a tweeter (DA)? Sounds like an energy storage and release problem, where the delayed release of energy back into the circuit is unrelated to the original waveform. I have some "P" core inductors on the woofer circuits in my "Dual Exhaust" speakers. When I get these speakers finished, I will do some experiments to see if I can get the inductors to "pop" at high power levels.
Yeah, not sure grit and pop are from the construction of the coil - unless it is from saturation induced odd order distortion. We talk about not being able to measure what we hear, but I would assume we can measure audible grit and pop from a coil. An o-scope would definitely show how the waveform is changed.
IMO no reason to make your own inductors for cost savings unless you like that activity. If you go to large diameter wire or Litz wire you might find some savings by devaluing your time.
I wind my own air cores for mids and tweeters to get the values I want without waiting for delivery and unwinding. I get plastic bobbins on Ebay (search Inductor bobbin) and use inductor calculators to measure and cut the wire before winding.
http://www.colomar.com/Shavano/inductor_info.html
http://www.pronine.ca/multind.htm
https://www.diyaudioandvideo.com/Calculator/AirCoreInductorDesigner/
Ebay search "wire coil frame" brings up more results.
I'm too damn lazy to wind my own inductors, but if guy's enjoy it I say have fun.
Or just order "custom" coils from Meniscus. I think he will wind you any value you'd like.
I've wound a few pairs of smaller valued air cores for tweeter shunts. These days, in general, I'm too lazy and my time doing other things out weighs saving a few bucks on inductors.