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Old 23rd January 2006, 08:06 PM   #1
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Default a crossover design component question...

i am reading david weems "great stereo sound speaker manual" and i am learning about designing crossovers...

there are questions i have that are over topics he covers that kind of confuse me...mainly involved with the components used...

i know that the inductance of the value is the most important value of an inductor because it selects what frequency you are crossing over at...what about Inductor DCR? i read that sometimes it doesnt matter, and sometimes it does....what is DCR for an inductor? how do you know what value to use for it? when is it important and when is it not?

also, for capacitors, are there any other values on a capicitor (other than its capacitance) that are important when choosing which ones to use?

finally, what about resistors? is it important that they are non-inductive? anything else i should know about choosing resistors?

thanks to everyone...
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Old 23rd January 2006, 08:45 PM   #2
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DCR is the DC Resistance of an inductor, i.e. the resistance of the wire in the coil. Generally low DCR is preferred, especially for series and higher order crossovers.

For capacitors, the voltage rating is important, and the type of capacitor is important. Generally bipolar electrolytics are best avoided. Use decent quality film or foil capacitors.

Go for non-inductive resistors, the inductance in wire-wounds can cause problems with the crossover frequency, especially with tweeters. Metal film resistors are best, you normally want a 10W rating.
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Old 23rd January 2006, 09:34 PM   #3
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so basically for those inductors, get the lowest DCR i can?

and for the voltage rating of capacitors, how do i know what is preffered?
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Old 23rd January 2006, 09:50 PM   #4
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Yes, you want the lowest DCR you can reasonably get with respect to price and physical size.

Most film and foil caps have fairly high voltage ratings, but you're looking for about 100V or more.
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Old 23rd January 2006, 11:03 PM   #5
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Quote:
Originally posted by jaygeorge1979
so basically for those inductors, get the lowest DCR i can?
jaygeorge1979,

When you're designing your crossover, you treat the inductor DCR as a resistor 'in series' with the inductor. The lower the DCR, the less signal is 'removed' by (or the less power is required to produce the same sound level through) the inductor. For parallel crossovers, this can become apparent in high order crossovers.

For first order series crossovers, a high DCR inductor means that the roll-off for the high-pass plateaus below the crossover point (which can be dangerous for your tweeter). I think I read somewhere that an inductor with a dcr of .8ohm causes the high-pass roll-off to level out at -20dB.
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Old 23rd January 2006, 11:52 PM   #6
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i think u guys have answered all my questions!
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Old 24th January 2006, 02:18 AM   #7
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One point not said is that the coil resistance alters the electrical 'Q' of the speaker.
This usually is not significant. It can, however, make slight changes to the bass response and 'tightness' of the sound.

Lower DCR is better.
Don't use a cheap coil with high DCR.
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