Hello,

I'm referring to the 4430's 3134 network schematics. The 4435's is rather similar. The more I look at it, the less I don't understand it, honestly:

There's a L102/C3 LP filter that drives the 2135H woofer. So far so good. But there's C8/R2, which resemble a Boucherot cell in an power amplifier's output, but with 100 times the capacitance. What does this series network do?

The HP section is even more complicated. Ok, the HP itself is C11/L2 that drive an L pad. This L pad may be arranged as usual, i.e. a 8 Ω rheostat in series with the tweeter and a about 42 Ω one (according to my own measurements) in parallel with it - which puzzles me, as the other way round should have to be assumed, in order to have a almost constant input impedance, hence a predictable rolloff frequency. In the given arrangement the tweeter sees an almost constant impedance. What's that good for? And why does the 42 Ω rheo give no output in it's fully ccw position?

Then there's a series resonant bypass, consisting of C9, L1 and the 30 Ω rheo and the voice coil's inductance and DC resistance. C9 and L1 alone would have a resonant frequency of 17.8 kHz. But there's the VC inductance. With my newly acquired De Ree DE-5000 LCR meter I measured my pair of 2421A's and got very different results between both - and surprisingly depending on the measurement frequency in the same unit. The readings were about 0.3 and 0.4 resp. @ 100, 120 and 1000 Hz, and 13.2 and 15.2 µH resp. @ 10 kHz. Ok, let's compute with the mean value of 14.2 µH and get a resonant frequency of 15.3 kHz. The Q(uality) factor depends on the rheo's plus the VC's DC resistances. This series resonant circuit bypasses the rheostat even in it's ccw position. But what's the use for the rheo to get open in fully ccw, as said in the underline?

Finally, what's the controls for mids and treble? I guess the rheo is the treble, and the L pad is the mid control. Am I right?

Best regards, and pardon me for causing you quite a headache !

Edit, additional question: Does anyone know the DC resistance values of the involved inductances? Are they air cored?