Tweaker's Asylum

Posted by Mart on May 06, 1999 at 01:47:30:

In Reply to: Zobel's attenuation on driver posted by hZ on May 03, 1999 at 01:25:08:

I toke my Morel MDT40 T/S parameters:

Re = 5.45ohm
Le = 0.05mH
fs = 700hz
f1 = 500hz
f2 = 1kHz
Zmin = 6.0ohm
Zmax = 9.9ohm

    +---Cs---+
    |        |
0---+---Rs---+---Re---Le---0
    |        |
    +---Ls---+

where:
Rs = Zmax - Re = 4.45ohm
Cs = 1/(Re*2*Pi*f2) = 29.2uF
Ls = Re/(2*Pi*f1) = 1.735mH

I wired a notch filter but virtually nothing happened, which could be expected due to the small size of the impedence spike & the couple octaves distance away from the XO point. I then wired a Zobel of:

0---Cz---Rz---0

where:
Rz = Zmin = 6.0ohm
Cz = Le/Rz/Re = 1.529uF

And, low & behold, a 2dB boost occurred between 5-10kHz, up & disappeared by installing a Zobel. Mind you, an 8kHz reasonant interplay between the XO cap & the voice-coil inductance was overted by the Zobel. In fact, the response curve resembles a unit Q 2nd-order XO roll-off knee.

Follow Ups:

• Just ran some numbers through Excel ... Mart 23:46:04 5/06/99 (6)
  • OK, so Mathematica says 2 variables were off ... Mart 09:56:09 5/07/99 (5)
    • got Mathematica to retrieve generic Conjugate(notch) values Mart 23:46:29 5/10/99 (4)
      • summary thus far... Mart 12:22:58 5/12/99 (3)
        • circuits in Theil-Small Parameters Mart 05:54:46 5/14/99 (2)
          • Yo JON RISCH Mart 11:48:14 5/14/99 (1)
            • FWIW, I could only reduce the 2 eqs to ... Mart 13:37:21 5/14/99 (0)