Big Inductor = Big money

[NyxOne]

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

[Sydney]

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 )

[NyxOne]

Re: Big Inductor = Big money

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

[djg]

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.

[bolland83]

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.

[Sydney]

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.

[NyxOne]

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.

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.

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...

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

[jim85iroc]

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.

[Brewski]

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 ?

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

[Sydney]

Re: Big Inductor = Big money

...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

[joeybutts]

Re: Big Inductor = Big money

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

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

[johnnyrichards]

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.

[Starkiller4299]

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 ;).

[NyxOne]

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.

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.

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!

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! :D

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! ;)

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.

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!!! :D

Chuck

[jim85iroc]

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.