Tweakers' Asylum

Re: Mix up of components...

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In Reply to: Mix up of components... posted by Al Sekela on August 4, 2005 at 16:25:39:

perhaps that's the case ... i should get a 2nd opinion before buying anything.
basically - i have an altec n3000 crossover that i'm trying to smooth out the high end with. someone suggested this: An L-pad has three terminals, 3-2-1, input-output-ground.
Buy a 2�F cap and a 40�H inductor and wire them in series with each other, now wire one lead to 3 (input) and the other lead to 2 (output). This will allow the level to be turned down so it is not 'shouty' and still have all the very high end.
if anyone has any thoughts on this i'd appreciate any input ... thanks again

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milli- versus micro- - Al Sekela 13:41:42 08/05/05 (0)
OK.
milli- is used to indicate a factor of 1/1,000, while micro- means a factor of 1/1,000,000. There are 1000 microhenries in one millihenry.
The combination of a 2 microfarad capacitor in series with a 40 microhenry inductor has a self-resonance frequency of 17.8 KHz. This means it looks like a capacitor up to the resonance frequency, where it is essentially a dead short. It then looks like an inductor at frequencies much above this.
When used to bypass the L-pad, it is giving you full response near the 17.8 KHz resonance frequency, with the attenuation of the L-pad at much lower and much higher frequencies.
When looking for components, pay attention to the parasitic resistances of the inductor and capacitor. These remain in the circuit even at resonance. A very small inductor, for example, may have too much resistance to allow this scheme to work properly.
40�H - djk 23:53:06 08/04/05 (0)
40�H and 2�F in series will lift the HF smoothly up to 18Khz.
JBL uses these exact values in the 4430 studio monitor crossover.
- http://www.jblproservice.com/pdf/Studio Monitor Series/4430LR.pdf (Open in New Window)
Probably meant 0.40mH. Just guessing. (NT) - Kal Rubinson 19:28:19 08/04/05 (0)
mt

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