In some hi end crossovers use Copper Foil Inductor, at the same time they use Air Core Inductor, and I have also seen Air Core Inductor Toriode.
Only taking into account the contribution to the sound quality of the system.
Which Inductor should be used for which part of each crossover?
Or what inductor is better for that frequency range?
Or who are the best inductors?
Only taking into account the contribution to the sound quality of the system.
Which Inductor should be used for which part of each crossover?
Or what inductor is better for that frequency range?
Or who are the best inductors?
The best inductor is one that suits your purpose and budget.
Air core inductors do not saturate
Foil coils may have no advantage other than looking cool.
The toroidal inductors have a core, and their advantage is they interact less with other inductors since the magnetic field is self contained.
Iron/ferrite cores can saturate and cause distortion, but if selected properly they don't cause much.
If you wanted a 12mH air core coil with ~0.4 ohm resistance, you would need 9AWG wire on a 4.5" diameter core, 2-1/8" long with ~300 turns The resulting coil would be a 8.25" in diameter and weigh about 21 pounds and cost roughly $250.
For an iron or ferrite core coil of teh same value, you can cut cost by a LOT.
ERSE Super Q 12mH 16 AWG 500W Inductor Crossover Coil
This one gets you close to 0.1 ohm!
Jantzen Audio 12mH 14 AWG C-Coil Toroidal Inductor Crossover Coil
Air core inductors do not saturate
Foil coils may have no advantage other than looking cool.
The toroidal inductors have a core, and their advantage is they interact less with other inductors since the magnetic field is self contained.
Iron/ferrite cores can saturate and cause distortion, but if selected properly they don't cause much.
If you wanted a 12mH air core coil with ~0.4 ohm resistance, you would need 9AWG wire on a 4.5" diameter core, 2-1/8" long with ~300 turns The resulting coil would be a 8.25" in diameter and weigh about 21 pounds and cost roughly $250.
For an iron or ferrite core coil of teh same value, you can cut cost by a LOT.
ERSE Super Q 12mH 16 AWG 500W Inductor Crossover Coil
This one gets you close to 0.1 ohm!
Jantzen Audio 12mH 14 AWG C-Coil Toroidal Inductor Crossover Coil
The toroid's have ridiculously low DCR. Some feel this gives better bass and transient response, however I often end up using the DCR to my advantage to avoid dedicated BSC circuits! 
I reserve foil coils for series in delicate mids and tweets. In the small mH values ( < 1mH), if you need very low DCR and low distortion, large gauge foil is the way to go.
I reserve foil coils for series in delicate mids and tweets. In the small mH values ( < 1mH), if you need very low DCR and low distortion, large gauge foil is the way to go.
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See here page 5-32
http://www.egr.msu.edu/em/research/goali/notes/module5_nonideal_behavior.pdf
The inductors shown are relatively pure inductors far enough below the self resonant peak. Above the peak they act like capacitors.
best inductor is no inductor...i tend to biamp for many reasons, one minor reason not having any inductors between amp and woofer when active crossover is used
otherwise one can not completely avoid inductors, when taking care of midrange breakups and such, so i select air core with thick wire, nothing fancy
otherwise one can not completely avoid inductors, when taking care of midrange breakups and such, so i select air core with thick wire, nothing fancy
Some people imagine that a post quoting them is an argument. To the contrary, I was sharing information for people who might not have understood your post about capacitance and resonance.
I don't have any foil coils to measure, nor do I have a signal generator handy that is reliable to much beyond audio frequencies.
Wouldn't a lower dcr inductor also allow the bass driver to better track the amplifier signal ?
Ron, did you use a calculator program to find these parameters? Can I ask what you used?
Thanks,
Bill
I personally don't have a strong opinion on the audibility between an 0.4 and 0.2 DCR coil, but there are times when high DCR makes the crossover better. By "better" I mean the curve goes the way you want it to more easily. I can't comment on the overall applicability of a coil with 1.4 Ohms! Of course it sounds cheap and bad, but who knows, it may have matched the efficiency of the tweeter.
I believe maybe Wolf has done some listening experiments on this issue.
Best,
Erik
I believe maybe Wolf has done some listening experiments on this issue.
Best,
Erik
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The toroid's have ridiculously low DCR. Some feel this gives better bass and transient response, however I often end up using the DCR to my advantage to avoid dedicated BSC circuits!
I reserve foil coils for series in delicate mids and tweets. In the small mH values ( < 1mH), if you need very low DCR and low distortion, large gauge foil is the way to go.
Hi Erick
What is DCR? and what is dedicated BSC circuit?
Hi Damilan,
DCR = DC resistance. All wires have resistance. Coils are just wires wrapped in loops so they must have it as well. While coils are inductive, which is measured in Henries, they also have a simple resistive value that is because of the long lengths of wire, and the wire's gauge. Any coil including voicecoils has this property. When you shop for inductors at Parts Express you'll see DCR listed for every coil. You can think of it as a "virtual" resistor in series with the "ideal" inductor.
BSC = Baffle Step Compensation circuit. A circuit used to account for the challenge of the baffle step messing up a driver's frequency response. When I say "dedicated" I mean a separate coil/resistor just to solve this problem. I try to cheat with the low pass filter whenever I can instead. A coil made with thinner wire will have a higher DCR, and assist in this.
More here:
Loudspeaker Diffraction Loss and Baffle Step Compensation Circuits
Best,
Erik
DCR = DC resistance. All wires have resistance. Coils are just wires wrapped in loops so they must have it as well. While coils are inductive, which is measured in Henries, they also have a simple resistive value that is because of the long lengths of wire, and the wire's gauge. Any coil including voicecoils has this property. When you shop for inductors at Parts Express you'll see DCR listed for every coil. You can think of it as a "virtual" resistor in series with the "ideal" inductor.
BSC = Baffle Step Compensation circuit. A circuit used to account for the challenge of the baffle step messing up a driver's frequency response. When I say "dedicated" I mean a separate coil/resistor just to solve this problem. I try to cheat with the low pass filter whenever I can instead. A coil made with thinner wire will have a higher DCR, and assist in this.
More here:
Loudspeaker Diffraction Loss and Baffle Step Compensation Circuits
Best,
Erik
I used a 'wheeler formula' calculator I wrote in Excel. The top three below are inputs (in bold). Interesting?
The calculator attempts to make 6a=9b=10c in the formula:
L (uH) = 0.8 * a^2 * n^2 / (6*a + 9*b + 10*c )
where
a = average radius of windings
b = length of the coil
c = difference between the outer and inner radii of the coil.
all dimensions in inches.
----------------------------------------------------------------
AWG 9.00
Insulation Build 1.030
Number of Turns 292
L 12066.94 uH
Layers 16.2111
Turns per layer 18.0123
a 3.1843 19.11
b 2.1229 19.11
c 1.9106 19.11
Wire diameter 0.11786 in, including insul
Core Diameter 4.4580 inches
Coil length 2.1229 inches
Coil Diameter 8.2792 inches
Wire Length 5842.21 inches
Wire Length 486.85 feet
ohms/inch 0.0001
resistance 0.386 ohms
weight 20.59 lb
How would higher DCR make the crossover "better"? It matters in two aspects - altering the efficiency of the woofer when used in series and adjusting the transfer function knee/phase when in parallel. The lower you can go, the better it is for a woofer as every db counts, especially on 2-way systems.
You say you use it for BSC purposes, how exactly? A dedicated BSC circuit actis quite differently to an inductor with its resistance as its not bypassing it. While an inductor might be increased in value to obtain the desired BSC, its DCR does not make it a BSC circuit, by any means.
1.4ohms inductor may have its use and that`s why its produced. One example is when you need to adjust its resistance in order to shape the knee of a high pass crossover. Its also a way to change the tweeter phase angle relative to the woofer phase. Another use is in commercial designs where a budget is set and every penny counts - going from 0R6 to 1R2 would not produce significant output decline and if you pad the tweeter enough, the only noticeable figure would be the sensitivity, which in these days is inflated by about anyone anyways and power is available. But pricewise the cost savings could be reasonable enough.
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