Foil Coils or plain ole wire?

Collapse
This topic is closed.
X
X
 
  • Time
  • Show
Clear All
new posts
  • JonMarsh
    Mad Max Moderator
    • Aug 2000
    • 15214

    Foil Coils or plain ole wire?

    One of the recurring questions that seems to be of interest to speaker builders is the matter of copper foil coils- does it make a difference, and is it worth the cost?

    Well, first off, I'll be the first one to say, "Well, try it, listen to them in your own projects....see what you think..."

    But some folks have been noticing there aren't any foil coils in the projects I've "published" to date, and wonder if it's something I'd consider, and when.

    Now, a lot of you probably realize that my day job is technical, having something to do with power semiconductors. All true. More to the point, my background is SMPS design (prior to joining Siemens Semiconductors, now known as Infineon). In Switch Mode Power Supplies, we use coils (inductors), and sometimes at fairly high frequencies. How high? Well, some of my past projects, even 10 years ago, were operating in the 500 kHz region Quite a bit higher than CD Audio, in fact, that's almost the bottom of the AM Radio band; and those are square wave converters, with rise and fall times measured in a few nanoseconds. So, for the sake of arguement, let's say I have some familiarity with HF power conversion.

    OK, the arguement for foil inductors is to reduce skin effect. Hmmm, good idea. I worry about that in power conversion, and in fact, usually use custom litz wire conductors or planar foil conductors in high frequency applications for inductors and transformers- generally, above 100 kHz. In fact, I use a simple MathCAD calculation to compare the resistance of the wire with the total impedance at a given frequency due to the combination of resistance and skin effect. That's not hard to estimate for circular conductors at all, like conventional magnet wire. It's a good idea to do, because often, in a given frequency range, it may be more cost effective to use bundled smaller solid conductors, rather than go full tilt boogie to Litz wire.


    So, I've been scratching my head and wondering, should I use foil inductors in some special area's in crossovers, maybe in things like the notch filter for the RD50's, where it's in the series path for the full range signal.

    The typical inductor I use is always air core, and usually wound with 14 or 15AWG wire. Let's use the 14 AWG for an example for skin effect calculations, as it's larger in diameter and more likely to have problems.

    Since I can't run MathCAD on the web, I'm going to past in some screen shots. Since we're talking about audio, we dont' have to worry about the harmonic spectrum of square wave converters- let's just take a stab at this at 10 kHz, OK? Ideally, we don't want any skin effect, because although it's affect is just like inductance, it's a secondary effect which adds into the inductance, and increases losses in the coil, changes the Q of the circuit, and changes the rate of roll off.




    Hmmmm, I think we can say with some safety, that at 10 kHz, and with a wire no thicker than AWG 14, skin effect isn't yet becoming an issue. BTW, if you redo this for 100 kHz, it's another story altogether. So maybe for your ionic super tweeter crossover....

    Now, this is just the top level of the document, the functions definitions are implemented below this, from standard "text book" equations. (I'm not inventing anything here, folks). Here's the gory details for those of you with that interest...





    This jibes with the practice I've had in SMPS, where above 30-50 kHz I generally prefer small gauges or specialty wire. For SMPS converters, it's the actual power loss which is measurable in terms of the heating affect on the inductor.

    Would a foil inductor of the same DCR be audibily better in a 5-10 kHz crossover? I'm not saying it can't be, but at this time, I'm likely to be another guy from Missouri- show me. At a 1.25 kHz crossover, I'm sceptical. :roll:

    Be on the lookout- the better foil inductors have about the same DCR as good wire inductors- but I've seen some advertising a given AWG that don't have as low a resistance- there's something odd going on there. Match the DCR to the application- there's not point using a hot shot inductor in an LCR zobel, when all the more expensive part is going to be doing is making the vendor some more money.

    Best regards,

    Jon




    Earth First!
    _______________________________
    We'll screw up the other planets later....
    Last edited by ThomasW; 24 March 2006, 01:02 Friday.
    the AudioWorx
    Natalie P
    M8ta
    Modula Neo DCC
    Modula MT XE
    Modula Xtreme
    Isiris
    Wavecor Ardent

    SMJ
    Minerva Monitor
    Calliope
    Ardent D

    In Development...
    Isiris Mk II updates- in final test stage!
    Obi-Wan
    Saint-Saëns Symphonique/AKA SMJ-40
    Modula PWB
    Calliope CC Supreme
    Natalie P Ultra
    Natalie P Supreme
    Janus BP1 Sub


    Resistance is not futile, it is Volts divided by Amperes...
    Just ask Mr. Ohm....
  • Cdub
    Member
    • Aug 2003
    • 56

    #2
    Wow! Umm, that's way over my head 8O But now at least I know the bottom line for future projects

    Chris

    Comment

    • PMazz
      Senior Member
      • May 2001
      • 861

      #3
      And PE has a new line of lower cost air core and foil inductors. Check em' out.



      Pete
      Birth of a Media Center

      Comment

      • Hank
        Super Senior Member
        • Jul 2002
        • 1345

        #4
        Although the new P.E. foil inductors are available in 16, 14 and 12 gauge, their wire air-core jobs are only available in 20 and 18 gauge. I wonder why. :?
        I've always wondered about the preference for foil inductors and have reconed it like the endless debates about interconnect construction. That's NOT a request to start and interconnect discussion! :LOL:

        Comment

        • Dennis H
          Ultra Senior Member
          • Aug 2002
          • 3791

          #5
          FWIW, North Creek prefers wire....

          Click now and see best headphones, headsets and earbuds in 2024 . Our expert authors review top headphones, headsets and earbuds.


          Inductor FAQ's

          Why does North Creek make wire wound inductors, and not copper foil inductors?

          North Creek has had the ability to make copper foil inductors since 1995, but the fact of the matter is that when properly made, wire wound inductors have much better bass and a smoother midrange than any of the copper foil inductors available today - even those we make here. There are two reasons for this:

          First and foremost, our wire wound inductors are made on a custom built, tension-free winding machine. This winding method minimizes the stretch and mechanical deformation of the copper, so there is no strain on the copper and its conductivity remains at a maximum. All copper foil inductors (and most copper wire inductors) are wound at very high tensions, so both the copper and the insulating film are stretched and remain under tension for the life of the product. Tension is differential stretch, which creates microfractures in both the copper and insulating material. This is about the worst thing one can do to a conductor.

          The second factor is mechanical stability: North Creek inductors are varnish sealed in a vacuum chamber, which bonds each winding to the six surrounding it throughout the entire body of the coil. Most copper wire inductors are varnish dipped, which seals the outer wraps but not the coil body. Copper foil inductors are usually heat sealed, which seals the edges but not the body. Typical copper wire and copper foil inductors will have a number of mechanical resonances that are activated by current flowing through the inductor, and can be heard to "sing along" with the input signal. Because of their unique vacuum impregnation, North Creek inductors do not show any signs of mechanical resonance.

          Copper foil inductors also have long term stability problems. This is because over time, air entering the coil body slowly oxidizes the copper surface and begins to penetrate the foil. This oxidation gradually degrades the conductivity of the copper, and over time the performance of the inductor.

          The only application for copper foil inductors - where high DCR is acceptable and low ACR may be beneficial - is as series inductors in small dome midrange circuits.
          Edit: added quote tags for clarity
          Last edited by Dennis H; 04 January 2005, 13:28 Tuesday.

          Comment

          • JonMarsh
            Mad Max Moderator
            • Aug 2000
            • 15214

            #6
            I'm getting asked about this a lot again lately, so I'm bumping it to the top to make it easier for folks to find...
            the AudioWorx
            Natalie P
            M8ta
            Modula Neo DCC
            Modula MT XE
            Modula Xtreme
            Isiris
            Wavecor Ardent

            SMJ
            Minerva Monitor
            Calliope
            Ardent D

            In Development...
            Isiris Mk II updates- in final test stage!
            Obi-Wan
            Saint-Saëns Symphonique/AKA SMJ-40
            Modula PWB
            Calliope CC Supreme
            Natalie P Ultra
            Natalie P Supreme
            Janus BP1 Sub


            Resistance is not futile, it is Volts divided by Amperes...
            Just ask Mr. Ohm....

            Comment

            • Hank
              Super Senior Member
              • Jul 2002
              • 1345

              #7
              Uh-oh, someone's asked about foil inductors again.
              Just don't post anything about interconnect construction. :nono:

              Comment

              • Davey
                Senior Member
                • Jan 2003
                • 355

                #8
                The real reason to use foil coils is so you can unwind them and create these oh so cool speaker wires.



                Davey.

                Comment

                • GrahamT
                  Senior Member
                  • Oct 2004
                  • 378

                  #9
                  Originally posted by Hank
                  Uh-oh, someone's asked about foil inductors again.
                  Just don't post anything about interconnect construction. :nono:
                  ROFL!

                  Jon could be making this stuff up and we would never know the difference. :lol:

                  Comment

                  • JonMarsh
                    Mad Max Moderator
                    • Aug 2000
                    • 15214

                    #10
                    Originally posted by Davey
                    The real reason to use foil coils is so you can unwind them and create these oh so cool speaker wires.



                    Davey.

                    I've often wondered if someone would do this sooner or later.. thing is, if you can leave a good dielectric on so you can space the conductors on top of each other, then it would lower the net series inductance. Doing it the way shown in that link, the net cable inductance is dominated by the conductor separation (area inside the current loop), and the inductance is about the same or higher as for zip cord. Skin effect would be swamped by the net cable inductance. Much higher than for Kimber or Cardas woven designs.

                    Sooner or later, we'll see everything on the 'net...


                    ~Jon
                    the AudioWorx
                    Natalie P
                    M8ta
                    Modula Neo DCC
                    Modula MT XE
                    Modula Xtreme
                    Isiris
                    Wavecor Ardent

                    SMJ
                    Minerva Monitor
                    Calliope
                    Ardent D

                    In Development...
                    Isiris Mk II updates- in final test stage!
                    Obi-Wan
                    Saint-Saëns Symphonique/AKA SMJ-40
                    Modula PWB
                    Calliope CC Supreme
                    Natalie P Ultra
                    Natalie P Supreme
                    Janus BP1 Sub


                    Resistance is not futile, it is Volts divided by Amperes...
                    Just ask Mr. Ohm....

                    Comment

                    • Davey
                      Senior Member
                      • Jan 2003
                      • 355

                      #11
                      Jon,

                      I think increasing inductance was the whole idea. This way they can start to have a low-passing effect and sound different than zip cord. And if it sounds better than zip cord it must be better, right?

                      Davey.

                      Comment

                      • JonMarsh
                        Mad Max Moderator
                        • Aug 2000
                        • 15214

                        #12
                        Exactamundo! Different is always better, right?
                        the AudioWorx
                        Natalie P
                        M8ta
                        Modula Neo DCC
                        Modula MT XE
                        Modula Xtreme
                        Isiris
                        Wavecor Ardent

                        SMJ
                        Minerva Monitor
                        Calliope
                        Ardent D

                        In Development...
                        Isiris Mk II updates- in final test stage!
                        Obi-Wan
                        Saint-Saëns Symphonique/AKA SMJ-40
                        Modula PWB
                        Calliope CC Supreme
                        Natalie P Ultra
                        Natalie P Supreme
                        Janus BP1 Sub


                        Resistance is not futile, it is Volts divided by Amperes...
                        Just ask Mr. Ohm....

                        Comment

                        • david teltschik
                          Member
                          • Dec 2004
                          • 30

                          #13
                          I totally agree about the whole theory versus reality when it comes to inductors. The quality of the caps in the upper to midrange circuits are WAY more important! I did come across some rather nice woofer inductors however. Mundorf makes LARGE value inductors in a transformer arrangement with nice/thick wire with Dcr in the range of 0.05 Ohms. I can honestly say that I can hear the difference in a nice woofer. But that's just me. As far as the quality of CFAC inductors....I have found the Janzen coils from PE to be much tigher in the winding, and for use clumbsy DIYers...i can appreciate the thick plasic casing around the outer winding as well. I would have done some damage to the Goertz coils by accident a few times.

                          Comment

                          • David Meek
                            Moderator Emeritus
                            • Aug 2000
                            • 8938

                            #14
                            Jon, I really enjoy puzzling my way through the formulae - thanks for a great thread!

                            Now, being the parent of two teen-agers and a lovable (but VERY inquisitive) dog, I'm wondering how long it'll be before someone trying the exposed copper strips as speaker wire loses one of their prized Quad 989s when their Teacup Poodle noses the two runs together. . . . :B
                            .

                            David - Trigger-happy HTGuide Admin

                            Comment

                            • Al Klappenberge
                              Junior Member
                              • Mar 2005
                              • 6

                              #15
                              Jon,

                              I have done some testing on foil , solid and Litz wire inductors. The results are that the foil inductors have their highest "Q" up too high in frequency. The one I tested (.2 mHy) peaked out at 20 KHz. A Litz wire inductor was better and peaked at 6000 Hz (which was right where I needed it). The soild wire inductors (even heavy wire) had very poor Q except at woofer frequency ranges where DCR is the controlling factor.

                              BTW: the big factor on spiral inductors is that each turn shileds the ones next to it. That forces a phase distribution through the coil that keeps each turn nearly in phase with the adjacent ones. This means very little capacitive current flows. That makes their distributed capacity very low. That's a good feature that is a moot point in a loudspeaker crossover network. I personally think foil inductors are a waste of money!

                              AL K.
                              http://www.s114186177.onlinehome.us/

                              Comment

                              • jeroen_d
                                Junior Member
                                • Nov 2006
                                • 8

                                #16
                                Totally disagree. Apply foil coils, listen to them in A/B tests and you will find that it is the only type of coil that you want to use in future.

                                Regarding to measurements, here are some that are not in line with Jon's calculations. http://www.hifivoice.com/audio/miles...omponents.html
                                Apparently the calculation model should be different, it cannot explain the measurements shown in this link. Skin effects do not seem to be the most important parameter.

                                Alas I don't know if coil vibrations affect the sound quality I subjectively experience, but at least in the following link there are measurements showing that on certain aspects large differences exist within the audio band.
                                See here for measurements performed by Bernd Timmermans http://www.mundorf.com/english/baute...r-GoldFoil.pdf from the German DIY magazine Hobby Hifi.

                                Foil coils do not have to be too expensive if you choose Jantzen cross coils. See http://www.partsexpress.com/pe/pshow...=255-624&DID=7 .

                                Comment

                                • Brian Bunge
                                  Super Senior Member
                                  • Nov 2001
                                  • 1389

                                  #17
                                  What about the issues with the copper corroding that I've experienced with the foil coils? That's enough of an issue for me to not use them.

                                  Comment

                                  • ThomasW
                                    Moderator Emeritus
                                    • Aug 2000
                                    • 10934

                                    #18
                                    Originally posted by jeroen_d
                                    Totally disagree. Apply foil coils, listen to them in A/B tests and you will find that it is the only type of coil that you want to use in future.
                                    Been there done that and couldn't drink the cool-aid.

                                    Some pretty exhaustive component testing was done when the Charlie Hansen was developing the original Avalon Acoustic designs. So there's a reason the kilo-buck Avalon designs use wire inductors instead of foil, and trust me it's not a cost cutting measure.....
                                    Last edited by ThomasW; 30 November 2006, 21:03 Thursday. Reason: correct spelling

                                    IB subwoofer FAQ page


                                    "Complicated equipment and light reflectors and various other items of hardware are enough, to my mind, to prevent the birdie from coming out." ...... Henri Cartier-Bresson

                                    Comment

                                    • Wilk
                                      Senior Member
                                      • Oct 2006
                                      • 104

                                      #19
                                      All those measurements are showing for sure is that some parts are built better/different then others. John's calcualtions are pretty hard to argue with considering its mathcad, and he posted the formulas.

                                      At 10Khz, or any other audible frequency skin effect is not a measureable parameter with any kind of test equipment, unless you are test with High Voltage cables, and alot of power. What you think is skin effect is usually a phase problem between coils due to poor spacing or winding. These types of problems occur in both types of inducters when they are poorly built.

                                      The placement of inductors on a crossover board is a much audible/measureable issue than skin effect. Any difference you hear is most likely to do with this if both parts are of simular quality. Due to the fact that the orientation of the foils is usually different when mounted on board than a coil. (If you use the same board)

                                      Comment

                                      • Brandon B
                                        Super Senior Member
                                        • Jun 2001
                                        • 2193

                                        #20
                                        OK, so am I taking away from this that Jon sees no benefit to the increased cost, not necessarily a detriment to foil inductors (excepting where there is an increase in resistance)?

                                        Your 10 foot pole comment in the other thread made me think there was a negative to using them (other than cost, which is moot for me at this point since it's a sunk one).

                                        BB

                                        Comment

                                        • jeroen_d
                                          Junior Member
                                          • Nov 2006
                                          • 8

                                          #21
                                          Originally posted by Wilk
                                          All those measurements are showing for sure is that some parts are built better/different then others. John's calcualtions are pretty hard to argue with considering its mathcad, and he posted the formulas.

                                          At 10Khz, or any other audible frequency skin effect is not a measureable parameter with any kind of test equipment, unless you are test with High Voltage cables, and alot of power. What you think is skin effect is usually a phase problem between coils due to poor spacing or winding. These types of problems occur in both types of inducters when they are poorly built.

                                          The placement of inductors on a crossover board is a much audible/measureable issue than skin effect. Any difference you hear is most likely to do with this if both parts are of simular quality. Due to the fact that the orientation of the foils is usually different when mounted on board than a coil. (If you use the same board)
                                          I'm not arguing the maths, I'm just saying that skin effect is apparently not such a dominating factor. We agree.

                                          Build quality apparently is also an issue. I agree on that also.

                                          But: these measurements by Marc were not done on a crossover board. Each coil experienced the same circumstances. Also the listening tests were done that way. Show me some measurements of coils that I can buy and also showing that foil measures worse.

                                          Thomas, those things about Avalon are nice and all that. Can you back up with measurements?

                                          Comment

                                          • Paul H
                                            Senior Member
                                            • Feb 2004
                                            • 904

                                            #22
                                            :roll:

                                            Comment

                                            • Wilk
                                              Senior Member
                                              • Oct 2006
                                              • 104

                                              #23
                                              I am not trying to say that foils measure worse. I am simply trying to explain that the testing that you are showing, and has been shown by most MFR's that I have seen is not consistant. Everyone is showing you a different test. Different test show different results, and can be set up to show that either is better at this or that. A better DCR on a inducter is just that DC resistance. The second you get above 1 Hz applied to them everything changes. And the fact that it is better at DC does not help you in speaker crossovers it is just used as a basic gauge for design purposes. The resistve properties of all materials/designs will change at frequency. What matters is the resistive value at the frequencies you are using them at in your design. You won't find that info on any MFR site because it does not help them sell products, and they don't wanna spend the money required for that type of test equipment.

                                              What John is trying to explain is that physics, not electronics puts film at a disadvantage to coils for audio frequencys. DC prefers to travel on a flat plan, therefore you get a better DCR. AC pefers to be on a round conducter.

                                              If they sound better or different to you in a speaker, then by all means use them. This is a function of personal preference though as the specific specifications you are looking at can not possibly have any audible effects on the over all speaker design.

                                              If you can hear a difference by switching 2 high quality, same value inductors, then the placement of the inductor on the crossover assembly is to close to other components.

                                              As far as measurements, It will take me a little time, but I'll see what I can do.

                                              Anyone with more audio expereinces then myself got some MFR they would like included, or specific test they want run.

                                              Comment

                                              • Wilk
                                                Senior Member
                                                • Oct 2006
                                                • 104

                                                #24
                                                Sorry about the double post, but i just remebered one more thing.

                                                The reason that foil cost more than coils. Is based on manufactoring cost, not quality. The cost to create a long, flat piece if copper verus pull a copper wire is signifigantly more expenive to the factory, and the cost is just passed on down.

                                                So don't fall victim to the more expensive has got to be better trap.

                                                Comment

                                                • jeroen_d
                                                  Junior Member
                                                  • Nov 2006
                                                  • 8

                                                  #25
                                                  I will try to not fall victim .

                                                  I also do not know how the measured results can affect the clear sound differences that I hear. Before I heard these foil coils, I was really really sceptical and didn't want to spend money on them. It is just that someone else did, and set up a good A/B test, that convinced me that there are things going on that cannot be explained just by calculations. Just as Jon is, I'm an engineer and have no problem at all to follow his maths.

                                                  Yes, every coil that you measure will give different results. I had a fierce discussion with Marc, following your line that despite his measurements this should not have any effect in the audio frequency range in which these coils were used.
                                                  Until I heard very clearly, this was by no means subtle, what he was talking about. He is also an engineer at the highest level, makes his measurements with the greatest care, and also is not able to make the link between what we hear in this case and what we measure. We do not come further that hypothesize about microphonic behaviour and that the foil performs so well because of the tight mechanical structure.

                                                  Comment

                                                  • Wilk
                                                    Senior Member
                                                    • Oct 2006
                                                    • 104

                                                    #26
                                                    Please don't take anything I said the wrong way. I am not trying to pull into doubt anyones specific measurements, and or experience. I am just saying that this is not as cut and dry as a few test of limited available parameters proving anyone right or wrong. It is entirely possible that your speakers sound better with foils, and that all his measurements are correct. The measurements posted and, or your A, B test are not enough information to determine the correct answer. My point is that there are many factors that you are not looking at, but still willing to say one type is superior to another.

                                                    I make electrical measurements for a living, and have no clue which one is better for use in a crossover.

                                                    One of these is what would be needed to answer this from a purely electrical standpoint.

                                                    Phase/Gain Impedance Analyzer

                                                    My lab doesn't have one, but I get them in from time to time for calibration.

                                                    Comment

                                                    • jeroen_d
                                                      Junior Member
                                                      • Nov 2006
                                                      • 8

                                                      #27
                                                      Well, that would be very useful equipment, but I don't see what's wrong with the HP 4263B LCR that marc uses.

                                                      I think my message didn't entirely come through yet. You're completely right that my preference is based on a too limited set of experiences. On the contrary, people who boldly state that buying foil coils is a waste of money, make these statements also on a limited set of experiences. I only want to put some weight against strong opinions pointing at one direction. Just to make sure that everyone makes his own decisions, not entirely based on opinions or calculations presented by some respected individuals.

                                                      And still, you can measure this way and measure the other way, there still is a missing link to explain what we hear. I cannot relate the measurement results to the difference in tonal balance, having the set of measurements of a certain coil at hand and listening to it. Whether you prefer the one sound or the other, the calculations presented by Jon and the measurements I referred to have not been examined in a scientific way to find out whether they relate to the difference in sound. At least not to my knowledge.

                                                      Comment

                                                      • Wilk
                                                        Senior Member
                                                        • Oct 2006
                                                        • 104

                                                        #28
                                                        The math that John posted is as scientific as it gets. It is right out of any electronics text book that you can find. There is no way to question that without questioning several long standing laws of physics.

                                                        The whole waste of money thing is an opinion {agreed}

                                                        Comment

                                                        • jeroen_d
                                                          Junior Member
                                                          • Nov 2006
                                                          • 8

                                                          #29
                                                          Please point out where I questioned the math. I only question the model on which the calculations are based. I do not question any law of physics, but the calculation model used by jon is solely directed towards the skin effect. The calculation model does not take into account the forces on individual windings caused by the electromagnetic field which in turn is caused by the AC current through the windings. The model does not worry about the effects measured by Bernd Timmermans. How can you explain otherwise the differences between the calculations and measurements?

                                                          Comment

                                                          • JSG
                                                            Junior Member
                                                            • May 2005
                                                            • 12

                                                            #30
                                                            Can't resist throwing in my $0.02 here.

                                                            Any wound coil with a relatively large number of layers (which includes most, if not all, audio frequency air core coils) will exhibit proximity effect losses. Proximity effect losses are eddy current losses that occur in addition to skin effect losses whereever a conductor carrying AC current is close to another conductor.

                                                            For multilayer coils of round wire, proximity effects usually dominate skin effects as one approaches the skin depth of the wire, sometimes by 10x or more.

                                                            For ribbon conductors, the picture is cloudier. It turns out that a wound ribbon coil shows edge effects that begin to occur at much lower frequency than suggested by the thin dimension of the ribbon, and that the wide dimension of the ribbon dominates the losses.

                                                            How this affects the sound, I'm not qualified to comment on. However, I would expect that the AC resistance of foil-wound inductors may get suprisingly high at surpisingly low frequencies. This is the case with ferrite core inductors, at least, and is predictable.

                                                            I have not looked thoroughly at the capacitance of coils yet.

                                                            John

                                                            Comment

                                                            • jdybnis
                                                              Senior Member
                                                              • Dec 2004
                                                              • 399

                                                              #31
                                                              On the topic of coils. Jantzen Audio published some quantitative specs of their iron core inductors.





                                                              Jon mentioned one reason he never uses iron cores is manufactures didn't publish enough info to tell if some inductor was suitable for a given application. I can't interpret the graphs, but do they suit the bill?
                                                              -Josh

                                                              Comment

                                                              • ThomasW
                                                                Moderator Emeritus
                                                                • Aug 2000
                                                                • 10934

                                                                #32
                                                                Jon doesn't use iron/steel cores for anything because they saturate and ring.

                                                                People are using some of the better steel laminated units to cut costs when building some of Jon's designs. Iron core or bobbin should be avoided.

                                                                IB subwoofer FAQ page


                                                                "Complicated equipment and light reflectors and various other items of hardware are enough, to my mind, to prevent the birdie from coming out." ...... Henri Cartier-Bresson

                                                                Comment

                                                                • Habs4life
                                                                  Member
                                                                  • Apr 2006
                                                                  • 85

                                                                  #33
                                                                  Originally posted by ThomasW
                                                                  Jon doesn't use iron/steel cores for anything because they saturate and ring.

                                                                  People are using some of the better steel laminated units to cut costs when building some of Jon's designs. Iron core or bobbin should be avoided.
                                                                  When the saturation point is reached does the inductance value change?

                                                                  Comment

                                                                  • mmoeller
                                                                    Senior Member
                                                                    • May 2006
                                                                    • 138

                                                                    #34
                                                                    I hear your gonna need a special licsense to get foil caps, cause the stuff inside can be used to make Methamphetamines...That's prolly all they're good for anyway..

                                                                    :rofl:

                                                                    Comment

                                                                    Working...
                                                                    😀
                                                                    😂
                                                                    🥰
                                                                    😘
                                                                    🤢
                                                                    😎
                                                                    😞
                                                                    😡
                                                                    👍
                                                                    👎
                                                                    Searching...Please wait.
                                                                    An unexpected error was returned: 'Your submission could not be processed because you have logged in since the previous page was loaded.

                                                                    Please push the back button and reload the previous window.'
                                                                    An unexpected error was returned: 'Your submission could not be processed because the token has expired.

                                                                    Please push the back button and reload the previous window.'
                                                                    An internal error has occurred and the module cannot be displayed.
                                                                    There are no results that meet this criteria.
                                                                    Search Result for "|||"