If you do decide to explore it, I would suggest the first step of extending Rod Elliott's electrical simulation. Rod only considered the effect of a +/- 25% change of the 8 Ohm resistance of the woofer. For myself, understanding only in general the input/ output characteristics of the first order series crossover network, I couldn't say what kind of transfer function it will have given a tweeter to woofer impedance ratio of say 2:1 or 1:2.
An assumption that I made was that an impedance difference in the range of one-half to double would most likely give the best results, but who knows? Unfortunately I know very little about the series crossover network and off and on have tried to get an exacting description of it without success.
-Pete
Hi,
No expert on the subject but a fully programmable mini DSP crossover is worth
searching on. I assume most expensive DSP crossovers can, just at the cheap
end your limited to standard c/o functions and level controls, with limited or
no EQ functions per driver or parametric EQ per driver.
rgds, sreten.
You can't just add a extra pot (load) in series/parallel with the tweeter. Both CX point and output level will change.
Voltage Divider
Voltage Divider
The point in adding a parallel resistance with the tweeter IS to change the crossover frequency. Rod Elliott's simplified electrical simulation where the impedances of the woofer and tweeter are made unequal shows no change in level while the crossover frequency shifts. Perhaps there was something wrong with his simulation, but I doubt it. When Rod says that the level remains the same, he is referring to the level of the electrical summation of the voltage drops across the simulated loads of the woofer and tweeter.
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True, but consider working with for example a tweeter and a woofer that are both 8 Ohm, and the tweeter is 6 dB more voltage sensitive than the woofer. Then you can make the two drivers have equal sensitivity by putting a fixed resistor of 8 Ohm in-series with the tweeter.
So now the tweeter and its fixed series resistor have a total of 16 Ohm impedance (hopefully) in the crossover region. So connect variable resistance across the input terminals of the tweeter so that the load impedance in the high pass section of the series crossover network can be varied between 16 Ohm and 4 Ohm. That means that the load impedance in the high pass section can be changed to be double to one-half times the impedance of the woofer (8 Ohm).
nonsuchpro- There are many factors going into the decision as what the crossover frequency should be. But I think a different interesting application for a variable passive crossover would be to vary directivity of the speaker system. That is, increasing the crossover frequency, given a suitable woofer, would increase directivity by causing the woofer to beam. Lowering the frequency would result in less directivity. Some listeners like a more dry type of reproduction (very little ambiance) and such listeners would make the speaker system more directive. Other listeners are partial to ambiance even if it means not really a well-defined type of reproduction. Those second type of listeners would reduce directivity of the speaker.
-Pete
Sorry, I don't want to confuse. In my post # 27, I said connect the variable resistance across the input terminals of the tweeter. I SHOULD have said (thinking about what I was writing) connect the variable resistor in parallel with the series connection of the fixed 8 Ohm resistor and the tweeter.
To add a bit more while I'm here, so if the values of inductance and capacitance of the first order series crossover have been solved for woofer Z = tweeter Z = 8 Ohm, then adjusting the variable resistor should allow you to sweep the crossover frequency from above to below the "normal" crossover frequency corresponding to the load in both the high-pass and low-pass sections equal to 8 Ohm.
To add a bit more while I'm here, so if the values of inductance and capacitance of the first order series crossover have been solved for woofer Z = tweeter Z = 8 Ohm, then adjusting the variable resistor should allow you to sweep the crossover frequency from above to below the "normal" crossover frequency corresponding to the load in both the high-pass and low-pass sections equal to 8 Ohm.
Interesting stuff. I mean even something like a modified Wah pot and electronics would be fun to try with this. I was reading this and got an idea... lol The Technology of Wah Pedals
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