Posted by Wayne Parham on December 01, 2003 at 15:24:51

In Reply to: 2Pi Tower Update: APT80 Tweeters posted by garman on December 01, 2003 at 13:31:23:

A first-order crossover adjacent to a third-order crossover has 180^o phase shift. So swap the wires on the tweeter. The Zobel on your midwoofer makes your coil act as a first-order filter.

Without a Zobel, a series coil acts as (much) less than first-order and it isn't a crossover at all. It is a stepped attenuator, with a nearly flat response curve having 3-6dB attenuation above a the frequency where voice coil inductance becomes significant compared to series coil inductance. There is no electrical rolloff as is expected of a crossover because voice coil reactance rises proportionally to series coil reactance making them form a voltage divider that is nearly linear with respect to frequency. Typically phase shift on such an arrangement is less than 20^o rather than the 90^o shift at the asymptote of a first order filter.

So anyway, the Zobel makes your series coil become a first-order filter. Being adjacent to a third-order filter causes a 180^o shift. So swap the wires and see what happens.

• Modeling effects of XOver - garman 11:21:12 12/02/03 (4)
  • Re: Modeling effects of XOver - Wayne Parham 15:37:35 12/02/03 (3)
    • Re: Sounds like school - garman 11:10:58 12/03/03 (2)
      • Re: Sounds like school - Wayne Parham 17:54:17 12/03/03 (0)
      • Re: Sounds like school - Adrian Mack 15:06:32 12/03/03 (0)