BEC Posted March 20, 2004 Author Share Posted March 20, 2004 Al, I have always leaned toward HP, Tek, Wavetek, Fluke, and such. That has always kept me in old stuff for test equipment. The B&K 885 caught my attention while searching for something to replace my old GR 1608A. It is the only device of its kind that I could find. Next closest thing would be a bench LCR at many times its cost or a used HP of unknown cal. By the way, I recently got an HP 3325A Synthesizer/Function Generator. You can start the sweep anywhere and sweep to anywhere. First generator I have ever had that could start at 0 (or any other number) and go to exactly 20 khz (or any other number) and repeat that sweep at any rate you select. Amplitude is selectable up to 3 VRMS. Will drive speakers directly for instance. Bob Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted March 20, 2004 Share Posted March 20, 2004 Bob, Yes, the problem of absolute calibration of used instruments is a big concern. I used to work in an instrument cal lab years ago. The buz words were always "tracabiltiy to National bureau of standards"! All I can do is compare them to references I have here and one instrument to another. I have a box here of "standards". I got a bunch of 1% caps and few 0.1% resistors. That's about all I can do. As to sweep generators, I have two of them. Two WaveTeks. I am using them less and less in favor of wideband noise and a two-channel FFT analyzer. Also used. It's an old Scientific Atlanta / Spectral Dynamics SD375 and I love it to pieces. What a boat anchor though! The thing is 8080 computer based and weighs 55 LBS! Al K. Quote Link to comment Share on other sites More sharing options...
BEC Posted March 20, 2004 Author Share Posted March 20, 2004 Al, I also made my living for a couple of decades around cal labs as at first an insrument tech and later instrumentation start-up engineer at various Nuclear Power Plants (and even more sinister nuclear facilities). Tracable to NBS is one of the favorite buzz phrases. Finding a piece of test equipment out of cal might require recalibration off all plant equipment that piece of test equipment calibrated since its last calibration. Finding a lab standard out of cal is a many order of magnitude greater problem. Don't know if it is still done this way, but lab standards went on an escorted trip yearly to a primary cal facility for calibration. They could never be out of the owners custody. Bob Quote Link to comment Share on other sites More sharing options...
Deang Posted March 22, 2004 Share Posted March 22, 2004 Looking at those numbers makes me want to ask something uncomfortable. Considering the substantial differences in Q, and the moderate differences in DCR -- should anyone really ever place an air core in a circuit designed with an iron core? Quote Link to comment Share on other sites More sharing options...
BEC Posted March 22, 2004 Author Share Posted March 22, 2004 Dean, Your question is the reason these figures are posted. Without getting into a discussion of "better or worse", I think we can all agree they are different. I can't hear the difference between an air core and an iron core inductor in the same type A crossover, but my spectrum analyzer can see the difference. One curve "looks" better to me than the other. Bob Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted March 22, 2004 Share Posted March 22, 2004 Bob and Dean, You two got me interested in the iron versus air core inductor debate. I just did a spectrum analyzer intermod comparison between the two. It's posted under "Ods and Mods". Al K. Quote Link to comment Share on other sites More sharing options...
BEC Posted March 24, 2004 Author Share Posted March 24, 2004 Al, You might be interested in the numbers on this Parts Express Iron core 2.5 mH inductor. It is an "I" core design rated at 500 watts. Price is around $12.00 or less in larger quantity. Inductance 2.463 mH DCR 0.189 Q 22.11 ESR 0.711 Z 15.51 Phase 87.38 Bob Quote Link to comment Share on other sites More sharing options...
BEC Posted March 25, 2004 Author Share Posted March 25, 2004 Bump Quote Link to comment Share on other sites More sharing options...
Deang Posted March 30, 2004 Share Posted March 30, 2004 I'm thinking woofer inductors here. Something else that is killing off my brain cells is if you consider the small variations from unit to unit. You know, one wound slightly tighter than the other, one with 1/4 inch more wire -- or the inch we cut off to get a nice looking connection. Then we have the small variations in the winding of the voicecoil itself, differences in AWG and length of internal wiring used, etc, etc... All this stuff between the binding post and voicecoil adds up. I'm starting to think we're a bunch of kooks worrying about this stuff. Any "improvement" that isn't clearly audible is just a waste of time and money. Bass isn't like the treble in that small changes are next to impossible to pick out. I say just use something damn close that looks nice to replace the stock units that look like rust buckets after about 20 years. I like those new Klipsch 2.45mH clones that Bob is using. Quote Link to comment Share on other sites More sharing options...
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