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  1. #1
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    Default Big Inductor = Big money

    Hi guys,

    I just realized how much big inductor ( > 1.0 mH, 18ga and lower) can cost and I was wondering if you have any trick to save money for those big coil ?

    I can' justify building set of speaker where the inductor as much or even more than the woofer! Are you ?

    Any trick / suggestion / recommandations / lessons ?

    Thanks,
    Chuck

  2. #2
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    Default Re: Big Inductor = Big money

    I can' justify building set of speaker where the inductor as much or even more than the woofer! Are you ?
    Neither could I - so I went active. ( other reasons too )

  3. #3
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    Default Re: Big Inductor = Big money

    Quote Originally Posted by Sydney View Post
    Neither could I - so I went active. ( other reasons too )
    Ok. I though of this, especially since the miniDSP kit are available at reasonable price, but how do build full HT system around these. More precisely, how can you setup an active system to work with a modern HT receiver. I guess it's fairly doable if you Amp has pre-out and you're willing to build many Amps but otherwise I can't see how it can be made ?

    Thanks for you input,
    Chuck

  4. #4
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    May 2008
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    wisconsin
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    Default Re: Big Inductor = Big money

    Iron core and P core inductors are reasonably priced.

    If you have an A/V receiver, you already have a subwoofer out connection, that negates the need for really big inductors.

  5. #5
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    Jul 2009
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    AZ
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    Default Re: Big Inductor = Big money

    You could wind your own I suppose. I recall seeing somebody here that does that, I just can't remember who.

  6. #6
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    Default Re: Big Inductor = Big money

    Not having access/breakout to line level is a bottleneck:
    In the past I've used a tape mon output but they are fixed vol.
    I built a "passive preamp" and route everything through this, but that isn't applicable to your situation.
    Copper prices continue to climb, and large caps are not inexpensive.
    As just stated some resort to winding their own coils: there is the cost of setup to do this and the means to measure Le to consider.
    Speaker Builder mag has had articles using a variety of approach to winding with wrap counters.

  7. #7
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    Aug 2010
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    Default Re: Big Inductor = Big money

    Quote Originally Posted by djg View Post
    Iron core and P core inductors are reasonably priced.

    If you have an A/V receiver, you already have a subwoofer out connection, that negates the need for really big inductors.
    Iron core can still be pretty pricey if you need low DCR and high mH.

    Most of time they seem to used to compensate BSC... Although I could be wrong.

    Quote Originally Posted by bolland83 View Post
    You could wind your own I suppose. I recall seeing somebody here that does that, I just can't remember who.
    I'm considering this option...

    Quote Originally Posted by Sydney View Post
    Not having access/breakout to line level is a bottleneck:
    In the past I've used a tape mon output but they are fixed vol.
    I built a "passive preamp" and route everything through this, but that isn't applicable to your situation.
    Copper prices continue to climb, and large caps are not inexpensive.
    As just stated some resort to winding their own coils: there is the cost of setup to do this and the means to measure Le to consider.
    Speaker Builder mag has had articles using a variety of approach to winding with wrap counters.
    I've and LCR meter at home so I guess I should try to wind up me own... Seems like alot of trouble to save money, I wonder if it's worth it? How much can saved ???

    Thanks,
    Chuck

  8. #8

    Default Re: Big Inductor = Big money

    I usually go to iron core inductors if I need big ones. They're cheaper, and all the talk about them saturating really isn't a concern at sane power levels.

    For example, a 2mH 14 AWG air-core inductor, PE part number 266-370 is $30 and has a DC resistance of .3 ohms, and apparently won't saturate until around 800 watts.

    A 2mH iron-core inductor, PE part number 266-554 has a lower DC resistance, a power handling limit that's still 250 watts, all for about $8.

  9. #9
    Join Date
    Feb 2010
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    Default Re: Big Inductor = Big money

    Quote Originally Posted by NyxOne View Post
    I can' justify building set of speaker where the inductor as much or even more than the woofer! Are you ?

    Thanks,
    Chuck
    NyxOne,

    It's painful but I'm justifying by looking at total project cost rather than just the crossover cost. Both the Cranberry Lambics and later this summer the Tripplebochs will have more money spent in crossover parts than they will in drivers but I only spent $10 per woofers and $16 per tweeter so I think I made out alright over all.

    Take it easy
    Jay
    "I like Brewski's threads, they always end up being hybrid beer/speaker threads based on the name of his newest creation." - Greywarden

    Breakfast Stout - HiVi RT2 II/Aurasound NS6
    Imperial Russian Stout - Vifa DX25/Fountek FW146/(2) Fountek FW168s - Built by Fastbike
    Ruination 2.5 way - Vifa DX25/Fountek FW168
    Levitation TM
    - Vifa BC25SG15/Fountek FW168

  10. #10
    Join Date
    Dec 2010
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    WV
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    Default Re: Big Inductor = Big money

    Quote Originally Posted by NyxOne View Post
    ...Seems like alot of trouble to save money, I wonder if it's worth it? How much can saved ???
    LOL: I guess I've heard those questions asked in many DIY situations:
    ( Non Diyer ) Speaker buyers question the rationale of DIY building in the first place...

    Some wind to get a precise Le ( not off the rack )
    Some guys are pretty good at scrounging up/ salvaging and reclaiming magnet wire.
    And you are half way there...

    Found this very old approach on Google books:
    Popular mechanics magazine: written so you can understand it, Volume 34
    page 628
    And
    http://thefuturescience.com/products.html
    http://www.youtube.com/watch?v=jvC2n2_YJhs
    http://community.klipsch.com/forums/t/93570.aspx

  11. #11
    Join Date
    Oct 2008
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    VA
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    Default Re: Big Inductor = Big money

    Dad always told me, you wanna play, you gotta pay.

    In all seriousness, I look at it like Brewski stated.

  12. #12
    Join Date
    Oct 2005
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    Sioux Falls
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    11,765

    Default Re: Big Inductor = Big money

    I've tried winding my own, started a thread last year on it. It is tedious, time consuming work and requires a meter with more precision that the cheapies most of use. If you have a woofer tester, no big deal but if you are using one of the cheap meters, most of them are only 5% to begin with, which is higher than all but the cheapest of the cheap inductors anyways. Additionally, if you do not have a source for magnet wire that is dirt cheap... let's just say counting only the cost of the wire I bought off-the-shelf, a 20awg 0.5mH coil self-wound will save me about 20%. How many do I have to wind before I save the cost of the meter used to measure them? In fact, if I buy 20awg coils from Erse Audio, instead of the Jantzen from PE it is cheaper than winding them, with the wire I bought anyways. Plus the time cost, and the trying my patience cost. I also had to build a winder, which still doesn't work right and cost me (so far) $40 worth of parts.

    DIY inductors for fun, but just like building speakers it is only a real, true value if you value neither your time nor count the cost of tools. I mean, I value my time immensely, and the amount I can get done on other stuff while clicking "submit" on an order page is worth a lot more to me than a custom wound inductor.

    Also, pay close attention to the speaker building buyouts at PE. They often have assembled crossovers that can be bought for next to nothing. Last year they had subwoofer crossovers with two 9.6mh 19awg iron core coils for less than three dollars. I picked up a few of them, and now you are looking at a rapid return on investment of a cheapish meter and a few minutes unwinding to get the appropriate value, plus you will end up with a lot of magnet wire that can be used to wind smaller value air cores.

  13. #13
    Join Date
    Aug 2010
    Location
    SW MI
    Posts
    284

    Default Re: Big Inductor = Big money

    If you have a digital multimeter (which are typically pretty accurate, to within 1% at least) and a signal generator*, then with a simple resistor you can determine the inductance.

    Putting the inductor and resistance in series, the -3dB point of the network (as measured from the middle) is at w= L*R. (w=2*pi*Frequency)

    So.....for instance, if you are trying to make a 1mH inductor, and you have a 1Mohm resistor, set your frequency generator to 1V at (1,000,000*.001)/2pi=159 Hz, and adjust the inductor till you get 0.701 volt output.

    Not 100% accurate, but costs you next to nothing if you have a signal generator, and certainly close enough for our purposes . As JohnnyR points out, I'm not sure it's worth the time investment, but you can certainly 'roll your own' with a modicum of equipment.

    *A clever person might realize that you can use a computer's audio out and a frequency generator program to make a signal generator .

  14. #14
    Join Date
    Aug 2010
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    Canada, Québec
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    229

    Default Re: Big Inductor = Big money

    Quote Originally Posted by jim85iroc View Post
    I usually go to iron core inductors if I need big ones. They're cheaper, and all the talk about them saturating really isn't a concern at sane power levels.

    For example, a 2mH 14 AWG air-core inductor, PE part number 266-370 is $30 and has a DC resistance of .3 ohms, and apparently won't saturate until around 800 watts.

    A 2mH iron-core inductor, PE part number 266-554 has a lower DC resistance, a power handling limit that's still 250 watts, all for about $8.
    Good to know! Anything above 150 watt feels like insanity (at least for me) if we excude subwoofer and PA needs and VERY inefficient speakers.

    Quote Originally Posted by Brewski View Post
    NyxOne,

    It's painful but I'm justifying by looking at total project cost rather than just the crossover cost. Both the Cranberry Lambics and later this summer the Tripplebochs will have more money spent in crossover parts than they will in drivers but I only spent $10 per woofers and $16 per tweeter so I think I made out alright over all.

    Take it easy
    Jay
    I guess your right and it's part of the game!

    Quote Originally Posted by Sydney View Post
    LOL: I guess I've heard those questions asked in many DIY situations:
    ( Non Diyer ) Speaker buyers question the rationale of DIY building in the first place...

    Some wind to get a precise Le ( not off the rack )
    Some guys are pretty good at scrounging up/ salvaging and reclaiming magnet wire.
    And you are half way there...

    Found this very old approach on Google books:
    Popular mechanics magazine: written so you can understand it, Volume 34
    page 628
    And
    http://thefuturescience.com/products.html
    http://www.youtube.com/watch?v=jvC2n2_YJhs
    http://community.klipsch.com/forums/t/93570.aspx
    Thanks for the reference! I might give it a try some day!

    Quote Originally Posted by johnnyrichards View Post
    I've tried winding my own, started a thread last year on it. It is tedious, time consuming work and requires a meter with more precision that the cheapies most of use. If you have a woofer tester, no big deal but if you are using one of the cheap meters, most of them are only 5% to begin with, which is higher than all but the cheapest of the cheap inductors anyways. Additionally, if you do not have a source for magnet wire that is dirt cheap... let's just say counting only the cost of the wire I bought off-the-shelf, a 20awg 0.5mH coil self-wound will save me about 20%. How many do I have to wind before I save the cost of the meter used to measure them? In fact, if I buy 20awg coils from Erse Audio, instead of the Jantzen from PE it is cheaper than winding them, with the wire I bought anyways. Plus the time cost, and the trying my patience cost. I also had to build a winder, which still doesn't work right and cost me (so far) $40 worth of parts.
    That's pretty much the feeling it gave me... and why I'm not winding my own right now! Maybe I'll do it some day but I think it'll be more a question of experimenting then a way of saving money.

    My LCR is as cheap as it get ($20) ... but I also have a WT3 so I've everything to validate the values!

    Quote Originally Posted by johnnyrichards View Post
    DIY inductors for fun, but just like building speakers it is only a real, true value if you value neither your time nor count the cost of tools. I mean, I value my time immensely, and the amount I can get done on other stuff while clicking "submit" on an order page is worth a lot more to me than a custom wound inductor.
    I value my time more then anything else! Time can't be bought, no matter how wealthy your are.

    Quote Originally Posted by johnnyrichards View Post
    Also, pay close attention to the speaker building buyouts at PE.
    Just what I did, I almost bought everything John K (music and design) had to sell! It's not buyout but I've found it here, in PE's "Free Classified" forum.

    I should mention that I'm Canadian and as one, anything that is cheap for you (USA citizen) is not for us, we get to pay extras for the shipping, which is free most of the time for you, custom fees, taxes, etc.

    Eg : My WT3 cost over 150$... that's 50% more then it cost you guys! Anyway, I'm not complaining, it's just the way it is! :P

    Thanks for your inputs and advices!!!

    Chuck

  15. #15

    Default Re: Big Inductor = Big money

    Another option that I've used at times when the inductor cost really does exceed driver cost, is to go to an MTM arrangement instead of a TM arrangement. The lower impedance will cut the inductor value in half (give or take), which will make it much cheaper.

    The first pair of speakers I built used the "NSB" woofers, which were so cheap that it was cheaper for me to build an MTM than a TM... excluding enclosure costs of course.

  16. #16
    Join Date
    Feb 2006
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    Berkeley, CA
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    Default Re: Big Inductor = Big money

    Quote Originally Posted by johnnyrichards View Post
    if you do not have a source for magnet wire that is dirt cheap... let's just say counting only the cost of the wire I bought off-the-shelf, a 20awg 0.5mH coil self-wound will save me about 20%.
    Even "custom" values are often less expensive (in materials) just buying one size larger and unwinding. But . . . you can have them *now*, without waiting (or shipping cost) . . . and it's so easy to change the value to "tweek" the design . . .

    Quote Originally Posted by johnnyrichards View Post
    DIY inductors for fun, but just like building speakers it is only a real, true value if you value neither your time nor count the cost of tools.
    Duh . . .

    Quote Originally Posted by johnnyrichards View Post
    Also, pay close attention to the speaker building buyouts at PE. They often have assembled crossovers that can be bought for next to nothing. Last year they had subwoofer crossovers with two 9.6mh 19awg iron core coils for less than three dollars. I picked up a few of them, and now you are looking at a rapid return on investment of a cheapish meter and a few minutes unwinding to get the appropriate value, plus you will end up with a lot of magnet wire that can be used to wind smaller value air cores.
    Yep . . . I bought three of those, and am now kicking myself for not having bought more. A lot more . . .

  17. #17
    Join Date
    May 2008
    Location
    Fort Wayne, Indiana
    Posts
    745

    Default Re: Big Inductor = Big money

    FYI, I looked into winding my own a few months ago and found a local source with decent prices on wire. Compared to the PE perfect layer inductors, I figured I'd have about half the cost in wire. That obviously wouldn't include any time/cost of building a winding machine and the time involved in making them.

  18. #18
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    Default Re: Big Inductor = Big money

    I might give it a try some day!
    F.F.R.
    Google Books:
    Inductance calculations: working formulas and tables By Frederick W. Grover
    http://www.nessengr.com/techdata/brooks/brooks.html

  19. #19
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    Default Re: Big Inductor = Big money

    Quote Originally Posted by 1100xxben View Post
    FYI, I looked into winding my own a few months ago and found a local source with decent prices on wire. Compared to the PE perfect layer inductors, I figured I'd have about half the cost in wire. That obviously wouldn't include any time/cost of building a winding machine and the time involved in making them.
    Winding a perfect lay is very difficult IMHO. That is what I had in mind when I decided to try this gig out I will be happy if I can duplicate the cheap 20awg inductors from Erse and Jantzen.

  20. #20
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    Canada, Québec
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    Default Re: Big Inductor = Big money

    Quote Originally Posted by jim85iroc View Post
    Another option that I've used at times when the inductor cost really does exceed driver cost, is to go to an MTM arrangement instead of a TM arrangement. The lower impedance will cut the inductor value in half (give or take), which will make it much cheaper.

    The first pair of speakers I built used the "NSB" woofers, which were so cheap that it was cheaper for me to build an MTM than a TM... excluding enclosure costs of course.
    Ahhhh!!! now were talking! That's the kind of info I was looking for! I guess one could save money just by buying the 4 ohm version of a woofer!

    Thanks a lot,
    Chuck

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