About 3-Pole Bump Filters ?

Hi All,

(A) Re; Todds' 3-way "bump-circuit for the 2410/2307(HL91) combo .

- I built up a partial working version of the horn circuit that Toddalin is now using . Through that exercise I became aware that this circuit has it's 3-pole hipass arranged as a "bump-circuit" /before initiating its' mid-frequency roll-off . Giskard had previously displayed this in a voltage drive for the orginating L200B and Zilch confirmed the bump was present in that example of the 3-way crossover that Todd had sent him . ( I knew the "bump" worked in my circuit through a couple of different type of measurements . ) The bump does a good job at shoring up the droopy response of the last lower octave for the 2410/2307 combo .
- See the pics below for the "predicted" bump versus the realized bump in Todds 3-way crossover .

(B) Now; A new bump circuit for a 2426H/2307(HL91) combo.

(i) Overview
- With a bunch of Lpads in place & with an extra resistor in line with the compression driver ( to simulate a 16 ohm driver ) / the working circuit impedance that the CLC components "see" , calculates out to be @ 6.3 ohms .

- Here are some component values ( with calculated Fc points )
C1 = 16.5 uF = 1536. hz
L1 = 2.1 mH = 476. hz
C2 = 24 uF = 1056. hz

- This 3 passive elements form 2 measurable resonances , peaking at approx. 900 hz and 700 hz .

- If one looks at the "pole spreads" between the CLC elements one will notice that C1/L1 = about 1.6 octaves
C2/L1 = about 1.1 octave
C1/C2 = only about .73 octave

- I don't know the math, necessary to predict where these 3 components are going to form their resonant points. Intuitively, I wouldn't have "guessed" anywhere near those 2 measured points of 700 & 900 hz.

(ii) A question

- Does anyone have a math formula ( that they can post ) that would accurately predict which two frequency points the resonant pairs are going to peak at ?

Thanks <> Earl K