Guest bolly Posted April 2, 2005 Report Share Posted April 2, 2005 Anyone with a set of 9's... could you do me a quick favour? Unhook the wires on the back of one of them and measure the DC Resistance of each pair of binding posts. I get 4.2ohms for the bottoms and open for the tops, I tried setting the front db switches in different positions to no avail. I pulled each driver on the front and checked them individually, they're fine. BTW, the tops were working perfectly before I put them in the back room. This is freakin' me out. Does anyone know what's going on here? Link to comment Share on other sites More sharing options...
Guest bolly Posted April 2, 2005 Report Share Posted April 2, 2005 Thanks willie1! He gets the same readings as I do, that puts me at ease! Link to comment Share on other sites More sharing options...
Guest Bret Posted April 2, 2005 Report Share Posted April 2, 2005 I get about 12 ohms across the top. But you've seen how bad my caps are. Link to comment Share on other sites More sharing options...
Guest bolly Posted April 2, 2005 Report Share Posted April 2, 2005 Just so I have this straight, your 6uF measured 21.2uF. Do you have another meter that you could confirm this? I'm startin' to get worried again.Greg Link to comment Share on other sites More sharing options...
Guest Bret Posted April 2, 2005 Report Share Posted April 2, 2005 >Do you have another meter that you could confirm this? I'm startin' to get worried again.<Greg, I'm lost. I used a Fluke multimeter for the DCR on the upper cabinets; not the capacitance meter. Hang on. . . you don't want much do you?! ;-)I re-checked and got kinda upset. . . 4.8x . . . only after I put the meter away did I remember I'd turned the UMR down and so had switched-in a resistor.I'm no expert, but I really don't think you should be getting either zero or infinite resistance.Bret Link to comment Share on other sites More sharing options...
Guest bolly Posted April 2, 2005 Report Share Posted April 2, 2005 I just checked the schematic, Would the presence of a capacitor in series with the tweeter, mid, and lower mid cause me to get an open reading on my DVM? I can't find a capacitor to experiment on(check resistance) and I actually had two of them here a couple weeks back. Link to comment Share on other sites More sharing options...
Guest bolly Posted April 2, 2005 Report Share Posted April 2, 2005 I'll bet that the cap in series blocks the DC from the meter and won't complete the cct. I get a reading on the bottoms because thee cap is in parallel. Worried for nothin' Whew! Link to comment Share on other sites More sharing options...
Guest Bret Posted April 2, 2005 Report Share Posted April 2, 2005 >I'll bet that the cap in series blocks the DC from the meter and won't complete the cct.<I know caps block DC (Ken did a daring experiment to prove this, and it worked), but you know, I've never tried to measure the resistance of a capacitor. I wonder if the cap is charged if it makes a difference, or if a leaky cap, would show DCR?You know, I get so discouraged when stuff like this happens. I want to know what the ISSUE is even if I can't explain the physics. Maybe I ought to go take a course or two at the local jr college just so I don't have to spend so much time wondering about things.I don't know what the issue is, but I don't think a cap's not-passing DC is it. I've never put a VOM across a speaker system, any speaker, and had it read open, ever.It may even be something like differences in the way our meters work and maybe you do have nothing to worry about. The caps ought to block the DC, so why do I get a reading? That doesn't explain why I get readings that change with resistor settings and you don't.Interesting.I do suppose you can't tell much of anything from DCR across a passive crossover like these. Maybe someone who knows more than either of us will jump-in here and give us a clue. Apparently they wouldn't have to know a lot to have either one of us beat.Ah, one last question. . . did you unstrap both the + and - straps? I understand that the two crossover elements aren't connected, so theoretically it shouldn't matter. But theoretically I ought to be getting the same reading you are.And here I was having such a laid-back Saturday.Bret Link to comment Share on other sites More sharing options...
Guest bolly Posted April 2, 2005 Report Share Posted April 2, 2005 ...someone will chime and clear this up! Your Saturday, imagine how I felt Bret when I read an open! Agghhhhhh! Bret, if I'm right, your speaks could have shorted caps in em... BTW, I don't have the straps, I ran mine bi-amped with a SPEC-2 and A Yamaha M-80. (currently one 11" is having a re-cone) Link to comment Share on other sites More sharing options...
soundminded Posted April 3, 2005 Report Share Posted April 3, 2005 OK,here's your answer. When you apply an ohmeter to a discharged capacitor, current will flow and then decrease as the capacitor charges up to the voltage of the battery inside the meter. With a small capacitor, this will happen very quickly and then when no current is flowing anymore because the capacitor is charged to the same voltage as the battery in the meter, it will show an open circuit, infinite ohms. Try this with a large electrolytic capacitor and you will see the meter first say zero ohms as a lot of current flows and it will slowly show increasing resistance until it reads infinite ohms. The current flowing at any instant is the difference between the battery voltage and the capacitor voltage at that instant divided by the series resistance in the meter. The rate at which this happens depends on the capacitance value and the value of the series resistor. It's called the RC time constant and is exploited for timing circuits used for triggering SCRs, triacs, even relays to switch. If you have an analog meter, try it and you will see the meter needle first swing to zero ohms and slowly swing back to infinity if the capacitor is large enough. Hope this explains it. Link to comment Share on other sites More sharing options...
Guest bolly Posted April 3, 2005 Report Share Posted April 3, 2005 That's exactly what I was hoping was happening. Link to comment Share on other sites More sharing options...
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