Heyo ho hey yo
Putting the finishing touches on the crossover design for my MTM and, as I tend to do, I got a little fancy with it, which has led me to a couple questions that I'm having a hard time finding good info about. It's one of those topics that's hard to search for.
I've attached a screenshot of my crossover schematic which I've designed and optimized using the LSPcad demo using measurements taken with HOLMimpulse and Speaker Workshop (for impedance measurements)
I'm at the step right now where I'm pricing out all the parts to order them so I can build the darn things for real, and this leads me to questions.
A) On resistors:
1) how does one know how much power handling you need? For R1 I'm obviously going to use a 10Watt, as all the power going through the speaker has to go through this resistor, but what about R2 in the notch filter, or R3 in the impedance-compensation circuit? Are there any good rules of thumb for this type of thing? (FYI, the notch filter is centered around 12,000hz)
2) Do I need to worry about wire-wound resistor inductance at all? I was going to use a non-inductive type for R1, but is that an issue at all for the others?
B) On Inductors:
1) What kind of part would one use for a very small inductance value in a crossover? L2 in the notch filter on the high frequency driver calls for a mere 47uH, or .047mH. Parts express only sells one inductor that goes that low, which is an 18guage air-core type, at .05mH. Are there other/better options for this?
C) On Capacitors:
1) I'm aware that electrolytics are frowned upon for passive crossover use, but do their negative aspects affect crossovers different in different types of circuits? For instance, would electrolytics be fine in the impedance compensation circuits (C3 and C5) in both drivers? What about the notch filter? Should I just stick with polys everywhere I can manage? Good thing I have a lot of room for crossover on these bad boys...
Putting the finishing touches on the crossover design for my MTM and, as I tend to do, I got a little fancy with it, which has led me to a couple questions that I'm having a hard time finding good info about. It's one of those topics that's hard to search for.
I've attached a screenshot of my crossover schematic which I've designed and optimized using the LSPcad demo using measurements taken with HOLMimpulse and Speaker Workshop (for impedance measurements)
I'm at the step right now where I'm pricing out all the parts to order them so I can build the darn things for real, and this leads me to questions.
A) On resistors:
1) how does one know how much power handling you need? For R1 I'm obviously going to use a 10Watt, as all the power going through the speaker has to go through this resistor, but what about R2 in the notch filter, or R3 in the impedance-compensation circuit? Are there any good rules of thumb for this type of thing? (FYI, the notch filter is centered around 12,000hz)
2) Do I need to worry about wire-wound resistor inductance at all? I was going to use a non-inductive type for R1, but is that an issue at all for the others?
B) On Inductors:
1) What kind of part would one use for a very small inductance value in a crossover? L2 in the notch filter on the high frequency driver calls for a mere 47uH, or .047mH. Parts express only sells one inductor that goes that low, which is an 18guage air-core type, at .05mH. Are there other/better options for this?
C) On Capacitors:
1) I'm aware that electrolytics are frowned upon for passive crossover use, but do their negative aspects affect crossovers different in different types of circuits? For instance, would electrolytics be fine in the impedance compensation circuits (C3 and C5) in both drivers? What about the notch filter? Should I just stick with polys everywhere I can manage? Good thing I have a lot of room for crossover on these bad boys...
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As for electrolytics capacitors, the real problem is that they change value over time (up to 20%), so if your filter does the work even with a different capacitor value, you are safe. But in your case all the capacitors are of small value and IMHO not worth the trouble of electrolytics.
As for the resistance power, this is a question that I had in mind for some time, and I'm also looking for an answer: when one can use a 5W, 10W 20W resistor?
Ralf
As for the resistance power, this is a question that I had in mind for some time, and I'm also looking for an answer: when one can use a 5W, 10W 20W resistor?
Ralf
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