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#127467 - 07/16/01 09:00 PM Crossovers  
sparky  Offline
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Joined: Oct 2000
Posts: 5,303
http://electrical-contractor.net/ubb/Forum15/HTML/000009.html

ok, this seems the to be the simple one.

what makes it tic ?


Tools for Electricians:

#127468 - 07/17/01 07:17 AM Re: Crossovers  
Redsy  Offline
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Joined: Mar 2001
Posts: 2,056
Bucks County PA
Forgive my elementary explanation, there is probably more to it than this but---

The reactance of the capacitor which decreases with an increase in frequency, will allow only higher frequencies to pass through to the tweeter.

The reactance of the inductor, which increases with increased frequencies, will only pass low frequencies to the woofer.

As far as the 2nd order network, the parallel inductor and capacitor would appear to filter even further, allowing only selected frequencies to reach the woofer & tweeter?

If you're looking for math, baby, don't come looking for me.


#127469 - 07/17/01 04:26 PM Re: Crossovers  
sparky  Offline
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Joined: Oct 2000
Posts: 5,303
Redsy, i probably would'nt understand the math anyway.. the frequency vs. capacitive/inductive reactance has my attention....how does that work?

[Linked Image]


#127470 - 07/17/01 06:08 PM Re: Crossovers  
Redsy  Offline
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Joined: Mar 2001
Posts: 2,056
Bucks County PA
sparky,

The impedance of a capacitive or inductive ckt. depends on the reactance of the ckt., which is related to the frequency of the current flowing.
Inductive reactance (XL) = 2 x 3.14 x Hz. x inductance (in henrys). therefore, as frequency increases, so does impedance (in ohms reactance).
Capacitive reactance (XC) = 1 divided by 2 x 3.14 Hz. x capacitance (in farads). therefore, as frequency increases, impedance(in ohms) decreases.
The drawing shows a sort of low-pass filter(woofer) which is mostly inductive, limiting high frequencies.
The tweeter section is a high-pass circuit, allowing only high frequencies, due to the capacitive nature of the ckt.
Or so I think. My terminology may be off. Someone make corrections as required.


#127471 - 07/18/01 11:16 PM Re: Crossovers  
Scott35  Offline

Broom Pusher and
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Joined: Oct 2000
Posts: 2,707
Anaheim, CA. USA
Sparky,

Sorry to you [and the rest of the group] for throwing these things out with no explanation of what makes them tick or why it's so cool to have them tick in the first place.

The items that Redsy is addressing, along with why these filters [and all other AC filters] work is the term "Resonance"

Resonance in Electricity [or any Electromagnetic Radiation, such as Radio waves or Light waves], is very much the same thing that Sound Resonance is.
All things have a "Resonant Frequency". In Sound, if we match the Resonant Frequency of, say for instance a Crystal Champagne glass, we could cause it to shatter. [remember that old Audio tape commercial with the lady singer shattering the glass??].

Anyhow, the Resonant frequency of the glass is the frequency which it naturaly vibrates, like if you were to tap it with your finger. Match it and you make it shake. Shake it at a high amplitude and it shatters.

Well, the Inductors, Capacitors and Resistors in these filters have Resonant properties which, depending on their values, can be figured to Resonate at a certain Hz.
By figuring the frequency you want to pass through them, then finding the value [size] which equals the Resonant Frequency you want, they will "Shake" at those frequencies - which allows the desired frequencies to pass easily, but block others.

So to sum it up, the key on AC filters is Resonance! Shake those puppies at a desired Hz to pass that Hz! [that's the technical explanation [Linked Image]].

BTW: The Impedance Equalizer included on one Xover is to make the power amp see a more steady Impedance over the complete spread of the frequency spectrum. A Loudspeaker's voicecoil will not always have the rated Z through the spectrum of frequencies it operates on, which throws the total Q of everything to heck in a hand basket [technically speaking].

Scott SET


Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!

#127472 - 07/19/01 03:59 AM Re: Crossovers  
sparky  Offline
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Joined: Oct 2000
Posts: 5,303
as Spock would say,
fasinating....


#127473 - 03/09/06 01:08 AM Re: Crossovers  
Scott35  Offline

Broom Pusher and
Member
Joined: Oct 2000
Posts: 2,707
Anaheim, CA. USA
***BUMP***

Scott35


Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!


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