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mboxler

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About mboxler

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  1. Perhaps I don't understand what this means. I believe you demonstrated that the autoformer itself doesn't change phase. But when used with a series capacitor, as @Deang mentions above, won't the inductance of the output taps increase the phase shift of the circuit, creating a 2nd order high pass to the squawker? A capacitor/l-lad circuit will still be first order. Again, I believe the inductance of the T2A is close to half that of the 3636, so the T2A phase shift increase would be greater. Mike
  2. I don't fully understand your predictions, but here are the 3636 and T2A. The 3636 is based on 76mH taps 0-5. The T2A on 44.8mH. Mike 3636.asc T2A.asc
  3. I for one have always wondered if the autoformer's inductance is as irrelevant as some have claimed. The spec sheet for the T2A states that the inductance between taps 0 - 3 is 11.4mH +- 15% (at 1000Hz?). My meter measures 8.5mH on one of my T2A's, taps 0 - 3. I'm sure your equipment is better that mine. What is the inductance across taps 0 - 3 on the 3636? Do you have a T2A to measure? I assume your tests were conducted without a series capacitor, therefore the autoformer's inductance would have no affect on the voltage across the driver. It would be interesting to run similar tests with appropriate series capacitors to see how the shunt inductance affects the frequency curve. Thanks, Mike
  4. Hey Don Can you post the schematic you have (I believe it's 820928, not 82092B???). The latest schematic I have is revision 900102, which appears to be what you have installed? I'm also assuming the rheostats are variable L-Pads. Mike
  5. Although I can't find the AB-3 schematic, I did find a document describing a 162 Hz notch filter across the woofer in the AB-3 crossover. It's composed of a 12mH inductor and a 80uf capacitor, but the series resistor value is missing. I assume the purpose of this filter was to tame this hump?
  6. If the inductance of the T4A, taps 0 - 5, is the same as the T2A, taps 0 - 5, then the inductance of the T4A, taps 0 - 3, should be 18.1mH (45.6mH / 2.512). Sorry, I don't have a T4A to verify this. Mike
  7. Are you guys just wanting is to test the crossovers to make sure everything is working as designed? If so, all you need are some resistors to replace the drivers, a true RMS meter (I use a Fluke 115), and a sine wave generator (I use an app on my phone). I think I have the ES schematic in LTSpice. Using it, I can determine what the voltages across the resistors should be for a certain input voltage at a given frequency. I do this all the time when testing my crossover designs. It isn't perfect, but clearly shows if I have component issue. If the voltages are right, and the speaker sounds bad, then I know my design sucks. Mike
  8. Threads like these kinda bum me out. I can't tell if my capacitors are out of spec because I don't know what the original specs were. Even if I knew the original specs, my DE-5000 LCR meter can't accurately tell me if my capacitors are out of spec.
  9. Seems to me that an lpad, unlike an autoformer, will not result in a consistent voltage drop across the driver at all frequencies. This is because the impedance curve of most drivers is not flat. When the driver impedance increases, the voltage across the driver will also increase. Likewise, the voltage across the driver will drop as impedance decreases. Although the variations may be small, wouldn't this be considered distortion?
  10. I always thought that those straps were made out of gold-plated tin/steel, not brass.
  11. That looks like a B2 crossover. Here's the schematic. Mike
  12. Nice build! Your 3619 autoformer is limited to -3, -6, -9, and -12db, but I see no reason why you can't move the tweeter circuit from tap 5 to tap 4. Looks like the DE10 around 3db hotter than the K77, and the load change on the 13uf capacitor isn't that significant. Mike
  13. I have always based my simulation (LTSpice) on an old post from Bob Crites (RIP). He measured 6.6mH across taps 4-5 of a 3619. Since those taps should equal 29.3% of the total windings, then I came up with 38.38mH across taps 0-4, and 76.76mH across taps 0-5. You probably should recheck my findings 🙂. Mike
  14. Autotransformer types and values: T2A(3110A) -3, -6, -9, -12db T3A(3465-M) -6db T4A(3485) -4db T5A(3496) -6db T7A(3504) -10db T8A(3507) -8db T9A(3540) -3db T10A(3542) -9db T11A -12db Looks like the T9A has only one tap, tap 4, which is -3db. It would be the same as a T2A using tap 4, also -3db.
  15. Better may have been a poor choice of word. In a true 3rd order Butterworth high pass filter, the second capacitor is 3 times larger than the first. 6.8uf is close enough. The 7.5uf would have been fine also, but I assumed you wanted to stay with CSA's. Looking on Al's website, in the Super AA-X section, you'll see how he converts AA to something close to the Universal. Can't make out the second cap value, but I believe it's 6.8uf. Notice also that he doesn't replace the 2.5mH woofer inductor as a part of the conversion. Also, schematic doesn't show the 1.5 amp fast blow fuse. I had it in initially but removed it when I swapped out the woofer inductor. Have fun with your project! What squawker/tweeter are you using? I also made a couple of other tweaks that you may want to try later, but they can be added to the finished crossover easily. Mike
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