Posted by Paul C. on August 09, 2001 at 22:27:32

In Reply to: Re: Capacitors posted by Wayne Parham on August 09, 2001 at 21:29:22:

Wayne: I had written you about active crossovers recently... what kind of caps are best for this purpose... more likely to be close to marked value, etc? Are 5% resistors close enough?

As you know, I was looking at xover freq in 800 hz range, for a two way system. So, my questions are:

Is 12 db/oct rolloffs enough, or should I go for 18 or 24 db/oct?

If I cascade two 12 db/oct filters, the Fx point will be -6 db instead of -3 db. Should I overlap the hi pass and low pass a little more?

I had sent you active filter topologies I had gotten from two different sources... one from a Radio Shack op amp book, where all C = C and all R = R. Values were computed from Fx = 1/(2piRC). The second was the same topology, but values were not equal, and it was described as "Butterworth". I am more the KISS type, and was leaning toward the former equal value circuit.

As op amps, resistors and caps are cheap these days, I am leaning toward 24db/oct. (I remember as a kid paying $1.50 for a diode for a "crystal radio". Oh, I could pick up two stations with mine!)

Suggestions?

• Re: Capacitors - Wayne Parham 08:23:48 08/10/01 (5)
  • Active Filters - Paul C. 23:26:42 08/11/01 (3)
    • Re: Active Filters - Wayne Parham 00:16:19 08/12/01 (2)
      • Sallen Key modeling formula - Wayne Parham 00:38:04 08/12/01 (1)
        • Thanks Wayne! - Paul C. 17:46:32 08/12/01 (0)
  • Re: Capacitors - AlexB 14:23:07 08/11/01 (0)