Recommendation for a crossover choke

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murphythecat8

murphythecat8

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Joined 2011
hi
I need two 0.47mH chokes. They need to be aircore and decently low DCR. I have a small budget. Any recommendation?

for your information, my crossover is:
For the Tweeter the resistors are 4R7 in series and 6R8 in parallel. Choke is 0.47mH and Capacitor is 1.5uF.

For the Midrange the RC across the driver is 12 Ohm and 4.7uF. The crossover Capacitor and Inductor for the Lowpass are 2.2uF and 0.5mH.

thanks
 
S

ScottG

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Joined 2003
murphythecat8 said:
really? so what type of resistor to use?
Click to expand...

..the resistance of the coil itself. ;)

I think for inductors (beyond it's own resistance) it's about mechanical damping - solution there is just "pot" the thing in some higher temp. wax (..or resin, but I'd prefer the wax).



-resistors (beyond resistance) can and do sound different depending on the application, again likely a mechanical damping effect.
 
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murphythecat8

murphythecat8

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Joined 2011
Okay, I thought you mean that the resistors in my crossover need to be of high quality? Is that also the case, like in the tube amp, where the cathode ressitor must be different then the plate resistors, ect

can you help me to find good chokes: they need to be aircore and decently low DCR. Theres too much choice at newark, I have no idea which to pick really....
 
wintermute

wintermute

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Ah that is actually a common misconception. In fact the DCR in shunt coils on tweeters IS important. The lower the better. The reason being that it is the LOW frequencies that you want to be shunted off (as you don't want them distorting and intermodulating your tweeter), so if the DCR is high then those low frequencies can't pass so easily and the coil does not do it's job as well as intended. This post http://www.diyaudio.com/forums/mult...eble-but-without-sibilance-2.html#post2605112 has the reasoning behind this.

Tony.
 
P

pdul

Member
Joined 2009
Ah that is actually a common misconception. In fact the DCR in shunt coils on tweeters IS important. The lower the better. The reason being that it is the LOW frequencies that you want to be shunted off (as you don't want them distorting and intermodulating your tweeter), so if the DCR is high then those low frequencies can't pass so easily and the coil does not do it's job as well as intended. This post http://www.diyaudio.com/forums/multi...ml#post2605112 has the reasoning behind this.
Click to expand...
Yes but within reason. The guy said low budget, and combined with the fact, that its already filtered thru a 1,5uf cap. It has to be a very expensive choke to make any percieved difference.
 
wintermute

wintermute

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I wouldn't call ~$17 a very expensive choke :) esepcially since it has a DCR of 0.16ohms which is decently low.... yes you could go with the 20ga one at $5.00 but it has a DCR of 0.47 ohms, which I would think will start to make a difference. But obviously there is a point of diminishing returns :)

Attached is the sim from my crossover for my mtm's. The shunt coil is in a 3rd order network, and is 180uH and had dcr of 87 milli ohms. If I increase the DCR to 470milli ohms I get the blue curve. It may not look that significant but the is 10db more energy getting through to the tweeter at 100Hz with the higher dcr coil. That is what Simon, and Lynn in the thread I linked to are saying is really bad. In a second order (electrical) network the difference may be greater.

Tony.
 

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wintermute

wintermute

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Actually after looking at the values of components in the crossover in the first post, I wonder whether they are correct. The lpad resistors seem to be pretty close together in value, and 1.5uF is an awfully small value!! What is your intended crossover frequency?

Tony.
 
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