A little inside the dugout discussion...
In order to design effective passive crossovers I need to get some accurate real-life measurements from the speakers, specifically DC Resistance and Inductance. I also need to measure the real parameters of the components going into the crossover because sometimes the tolerance variation between two capacitors, resistors, or inductors can be so great that I will want to do something about it. Also, if I am combining multiple capacitors to get an effective capacitance other than what is offered in the off-the-shelf models or if I want to unwind a stock inductor to get a value other than what is offered in the catalog, I need a means to accurately measure those components. As such, I've owned a high grade handheld LCR meter which measured Inductance (L), Capacitance (C) and Resistance (R) with relatively high precision.
Well, I paid a small fortune for this meter about 25 years ago when they were less common and the Chinese factories were not churning them out by the billions, so it is a tad special to me even though I could buy a new one today of similar accuracy for $50.
Anyway...
When I dug out my LCR Meter and installed a new battery in it, I was disappointed to discover the unit wasn't working properly. Would get a display and it would read out values when I attempted to measure things, but it was wonky. The resistance mode would take a long time to settle, longer than it should, and it would show different values every time I'd measure the same component. Even shorting the leads would result in a "zero" with a residual value which varied greatly between each test - i.e. with shorted leads it would read 0.03 one time, 0.00 another time, and 0.10 the next. That's not a good sign. Things were even more sporadic with the Inductance and Capacitance measurements. This was bothersome.
I decided that even though I could get a new meter for about $50 on Amazon and it would arrive in a day or two, I would attempt to get my trusty old friend back into shape. I made a bold assumption that the many contacts inside the meter were dirty or corroded and disassembled the unit and thoroughly cleansed the switch contacts with Caig DeoxIT D5 and a foam applicator. I also swept the user accessible zero calibration potentiometer about a hundred times, fairly aggressively. Then I separated the two circuit boards and cleaned the pin connectors and sockets with more DeoxIT D5 and foam applicator. After that I very carefully pulled the logic IC from its DIP socket, lightly cleaned the pins before reseating it. Lastly, I removed the protection fuse and used a burnishing tool to clean the socket and used DeoxIT D5 to wash off the ends of the fuse. The final step before reassembling the meter was to lightly spray the contact points with Caig PreservIT P5 contact lubricator and preservation solution. I allowed the disassembled unit to set exposed to the air to allow any residual and excess solutions to evaporate, then I carefully reassembled the unit.
When I fired it up to test things out, I was pleased to see it working as I remember. It was responsive, the controls responded properly, and the readings were what I expected. When measuring the resistance of shorted leads, I got a consistent 0.01 Ohms (which is what I got back in the day, I assume that 1/100 Ohm of resistance is the wire and alligator clips resistance), the inductance mode read exactly what I had handwritten on the four inductors I had in my parts drawer about 15 years ago, and the capacitance mode showed readings exactly in line with printed parameters on every different sized capacitor I tried (well within the rated tolerance). With a speaker driver, the Inductance meter played the 1kHz test tone and settled on a stable reading within about 5 seconds, which feels faster than my memory of the unit back in the day.
So, with about an hour of patiently and deliberately disassembling, cleaning, and reassembling my LCR Meter, it is back as my trusty side-kick I rely on for designing and building crossovers.
In order to design effective passive crossovers I need to get some accurate real-life measurements from the speakers, specifically DC Resistance and Inductance. I also need to measure the real parameters of the components going into the crossover because sometimes the tolerance variation between two capacitors, resistors, or inductors can be so great that I will want to do something about it. Also, if I am combining multiple capacitors to get an effective capacitance other than what is offered in the off-the-shelf models or if I want to unwind a stock inductor to get a value other than what is offered in the catalog, I need a means to accurately measure those components. As such, I've owned a high grade handheld LCR meter which measured Inductance (L), Capacitance (C) and Resistance (R) with relatively high precision.
Well, I paid a small fortune for this meter about 25 years ago when they were less common and the Chinese factories were not churning them out by the billions, so it is a tad special to me even though I could buy a new one today of similar accuracy for $50.
Anyway...
When I dug out my LCR Meter and installed a new battery in it, I was disappointed to discover the unit wasn't working properly. Would get a display and it would read out values when I attempted to measure things, but it was wonky. The resistance mode would take a long time to settle, longer than it should, and it would show different values every time I'd measure the same component. Even shorting the leads would result in a "zero" with a residual value which varied greatly between each test - i.e. with shorted leads it would read 0.03 one time, 0.00 another time, and 0.10 the next. That's not a good sign. Things were even more sporadic with the Inductance and Capacitance measurements. This was bothersome.
I decided that even though I could get a new meter for about $50 on Amazon and it would arrive in a day or two, I would attempt to get my trusty old friend back into shape. I made a bold assumption that the many contacts inside the meter were dirty or corroded and disassembled the unit and thoroughly cleansed the switch contacts with Caig DeoxIT D5 and a foam applicator. I also swept the user accessible zero calibration potentiometer about a hundred times, fairly aggressively. Then I separated the two circuit boards and cleaned the pin connectors and sockets with more DeoxIT D5 and foam applicator. After that I very carefully pulled the logic IC from its DIP socket, lightly cleaned the pins before reseating it. Lastly, I removed the protection fuse and used a burnishing tool to clean the socket and used DeoxIT D5 to wash off the ends of the fuse. The final step before reassembling the meter was to lightly spray the contact points with Caig PreservIT P5 contact lubricator and preservation solution. I allowed the disassembled unit to set exposed to the air to allow any residual and excess solutions to evaporate, then I carefully reassembled the unit.
When I fired it up to test things out, I was pleased to see it working as I remember. It was responsive, the controls responded properly, and the readings were what I expected. When measuring the resistance of shorted leads, I got a consistent 0.01 Ohms (which is what I got back in the day, I assume that 1/100 Ohm of resistance is the wire and alligator clips resistance), the inductance mode read exactly what I had handwritten on the four inductors I had in my parts drawer about 15 years ago, and the capacitance mode showed readings exactly in line with printed parameters on every different sized capacitor I tried (well within the rated tolerance). With a speaker driver, the Inductance meter played the 1kHz test tone and settled on a stable reading within about 5 seconds, which feels faster than my memory of the unit back in the day.
So, with about an hour of patiently and deliberately disassembling, cleaning, and reassembling my LCR Meter, it is back as my trusty side-kick I rely on for designing and building crossovers.
Last edited:
