[8thnerve]

Hello all, I was wondering if you could help me find this behemoth of an Inductor.  Would I be better off to just use two 8 Henry inductors instead?  And what is a good choice that is not too ridiculously expensive?

I am trying to make a simple 6db low pass filter at 40Hz for the 2nd voice coil in the Gallo Ref IIIs.

Thanks,

NAthan

[Dan Banquer]

Try www.partsexpress.com They have a section of Erse brand chokes that you might be able to use.
                     d.b.

[Occam]

Hello all, I was wondering if you could help me find this behemoth of an Inductor.  Would I be better off to just use two 8 Henry inductors instead?  And what is a good choice that is not too ridiculously expensive?
I am trying to make a simple 6db low pass filter at 40Hz for the 2nd voice coil in the Gallo Ref IIIs.

Nathan,

I do hope you mean 16 milliiHenrys (16mH), which would seem more appropriate (and cheaper!) for a LPF on a voice coil. You are talking speaker level rather than line level, aren't you? If that voicecoil has a nominal 4 Ohm impedance, it would require a 16mH coil for that 40hz lowpass.

If so, you could look at Madisound, Zalytron or Northcreek for air core or laminate coils. Or, if a masochist, you could wind your own, referring to this website -
http://www.lalena.com/audio/calculator/inductor/

[8thnerve]

Yes, sorry, millihenrys.  I have decided to go with 15 mH instead, but these are very difficult to find.  I have only found Iron core at this size.  Would I be better served to use two 7.5 mH?  Does the DCR of each coil add to the overall DCR?

[8thnerve]

What is the practical advantage of a lower DCR?  Also, what are the practical differences between air core and iron core?

[Occam]

Nathan,

Yes, both DCR and Inductance is additive when connected in series, so you could simply use 2 7.5-8.00mH in series. As to its wisdom, dunno. Higher DCR is going to effect the response (via a change in Qts), but as to its materiallity, again, dunno.

An aircore inductor of that size is going to be rather large, if available at all. Cored inductors, iron, laminated grain oriented steel, ferrite, etc... will be substantially smaller, and have lower DCR(all things being equal). Its also a given that an air core inductior  will have less distortion. Perhaps some of the speaker manufacturers and/or experts will weigh in. Alternatively, you might post the question on the Madisound discussion forum.

[mcgsxr]

Try Solen in Canada, they have that in 10, 12, 14, and maybe 16 gauge.  You can choose heptalitz too, for extra sexy appearance, even though it will likely be inside a cabinet...

http://www.solen.ca

Mark

[_scotty_]

8thnerve,power is lost to the DCR in the inductor when it is in series between the amplfier and the woofer,this also impacts the speakers efficiency.The presence of the series resistance
also affects the the woofers Qts and this must be accounted for in the speaker system alignment. Perhaps the most serious impact the series resistance has is to decouple the amplifier from the load and reduce its control over the woofer. This adversely affects the transient accuracy
of the woofer as the amplifiers dampening factor is reduced. A solid state amplifier can be made to sound a lot like a tube amp simply by inserting
a .5ohm resistor in series between the amplifier and the loudspeaker.
Here is a link to what is possibly a state of the art inductor from Mundorf
http://www.e-speakers.com/products/null-ohm.html
http://www.e-speakers.com/products/n106.html
http://www.e-speakers.com/products/n130.html
These inductors virtually eliminate the problem of series resistance
in this application. They are not inexpensive however.