BEC Posted March 25, 2004 Share Posted March 25, 2004 Al, The only frequencies I have in the meter are 100 hz, 120 hz, 1khz and 10khz. Here are the Q numbers for those frequencies for three inductors. Parts Express "I" core: 100 hz 7.613 120 hz 8.925 1 khz 22.11 10 khz 8.421 Universal Transformer Iron core 2.5 mH inductor 100 hz 5.283 120 hz 6.193 1 khz 13.33 10 khz 4.232 Solen Air Core 2.4 mh inductor 100 hz 4.124 120 hz 4.945 1 khz 25.47 10 khz 8.883 Looks like the Q of all them is pretty poor at the frequencies where these inductors are used in crossovers. Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted March 26, 2004 Author Share Posted March 26, 2004 Bob, Yep.. That's about what I expected. Down low the DCR is the controling factor and as you go up other losses take over. Try the same test on an air-core wound of Litz wire. You will find the Q peaks a lot higher. In fact, for the values about .3 mHy it peaks nicely at 6000 Hz which is perfect for squawker / tweeter crossovers. I would like to see where the "I core" actually peaks. It seems to me. with the right core material, it could be made to peak at 400 Hz. Al K. Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted March 26, 2004 Author Share Posted March 26, 2004 Bob, I ran the Q on the 2.5 mHy iron core coil in the Klipsch AA netwrok at a range of frequencies. It's best frequency is around 1100 Hz. I don't have any 2.4 mHy Solen air-core coils on hand right now to compare. They are on order. Freq, Q ----, --- 200, 7.2 400, 12.0 600, 13.8 800, 14.8 1000, 15 1200, 15 1400, 14 1600, 13.8 1800, 13.3 2000, 12.8 2500, 11.7 3000, 11 4000, 9.6 6000, 7.8 Al K. Quote Link to comment Share on other sites More sharing options...
BEC Posted March 26, 2004 Share Posted March 26, 2004 Al, Wish I could do more frequencies. That is one good thing you can do with the old GR 1608 with an external source. Bob Quote Link to comment Share on other sites More sharing options...
BEC Posted March 26, 2004 Share Posted March 26, 2004 Al, Here are some Q numbers for 3 Lizt wire inductors. Solen 1.5 mH Litz wire 14 awg. Freq. Q 100 hz 1.968 120 hz 2.362 1 khz 19.25 10 khz 62.48 Solen .51 mH Litz wire 14 awg. Freq. Q 100 hz 1.484 120 hz 1.780 1 khz 14.64 10 khz 57.36 Solen .15 mH Litz wire 18 awg. Freq. Q 100 hz 0.605 120 hz 0.757 1 khz 6.296 10 khz 44.35 Bob Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted March 26, 2004 Author Share Posted March 26, 2004 Bob, That looks about right! Litz definitly moves the high frequency Q up a lot. I really don't understand why. I don't believe the skin effect explanation. It has to be something like some secondayr current moving around the wire instead of down its lingth. If you got one of those Gertz spiral inductors to measure, they are interesting. Their Q peaks way up even higher than Litz. In fact, they peak up too high to be good for crossover networks. Al K. Quote Link to comment Share on other sites More sharing options...
BEC Posted March 27, 2004 Share Posted March 27, 2004 Al, According to my reading, the separate insulated strands break up eddy currents that would form in the conductor. Much the same reason that iron cores are laminated and ferrite cores are composed of ferite "islands". That would supposedly increase the Q dramatically at high frequencies. I have a bit of trouble getting my mind around the idea that eddy currents in the copper conductor could be significant at frequencies as low as audio. On the other hand, the Litz wire inductors are much better inductors (in Q) in my 10 khz test than any others I have tested. Got to be some reason for that and I guess reduced eddy currents is the best explaination I have heard so far. Bob Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted March 27, 2004 Author Share Posted March 27, 2004 Bob, Yes, I assume eddy currents around the wire rather than down its length is the improvement, but I don't understand how they can form! Al K. Quote Link to comment Share on other sites More sharing options...
krustyoldsarge Posted March 27, 2004 Share Posted March 27, 2004 On your advice (given some while back) I replaced the Iron core inductors in my KG-4 crossover with air core and am quite happy with the results. Was definitely challenging stuffing those upgraded parts on that little board! Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted March 27, 2004 Author Share Posted March 27, 2004 Sarge, That is the kind of report that keeps me pushing the air-core inductors. I which to heck I could find a real scientific reason for it! There is so much subjective factor in audio that just becasue 50 people say something sounds better it still doesn't make it so! It sure does make you want to go with the flow though! Al K. Quote Link to comment Share on other sites More sharing options...
BEC Posted March 27, 2004 Share Posted March 27, 2004 Al, I think that an impedence plot of the combination of K-33 woofer and various inductors over the range of 20 hz to 500 hz would perhaps show any difference if one exists. Bob Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted March 27, 2004 Author Share Posted March 27, 2004 Bob, I don't know what an impedance plot of an inductor and a woofer would tell you. Remember that a K33 has 1 mHy in series with it already! If there is a difference between ironand air core it may be a matter of figuring out what to measure. I really doubt that impedance is it. Intermodulation aparently isn't it either! Al K. Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted March 27, 2004 Author Share Posted March 27, 2004 Sorry.. double post. It happens every time a second page is started when I post a reply. I think it didn't "take" and hit it again! Al K. Quote Link to comment Share on other sites More sharing options...
Andre_Roy Posted March 29, 2004 Share Posted March 29, 2004 Hey Thanks for the good reading and great info. Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted March 31, 2004 Author Share Posted March 31, 2004 Bob, I ran the Q on the 2.5 mHy iron core coil in the Klipsch AA network at a range of frequencies earlier. I din't have any 2.4 mHy Solen air-core coil on hand at the time. I got some in, so here's the Q numbers with the numbers from the iron core to compare: Freq, Q air Q Iron ----, ----, ------- 200, 7.7, 7.2 400, 14.5, 12.0 600, 20.0, 13.8 800, 23.1, 14.8 1000, 25.0, 15 1200, 25.8, 15 1400, 25.7, 14 1600, 25.0, 13.8 1800, 24.4, 13.3 2000, 23.7, 12.8 2500, 20.6, 11.7 3000, 17.8, 11 4000, 15.7, 9.6 6000, 11.6, 7.8 Al K. Quote Link to comment Share on other sites More sharing options...
BEC Posted March 31, 2004 Share Posted March 31, 2004 Al, At the beginning of this measurement session we have been in, I had just tried to tell the difference between a Universal Transformer 2.5 mH iron core inductor built to PWK's specs, a 2.5 mH 14 awg air coil inductor and a 2.5 mH "I" core inductor by listening tests in a 1979 Lascala using a Type A crossover. I switched out the three inductors a few times and could not tell any difference in sound. I then started measuring to see if I "should" have heard a difference. I really haven't seen a measured number yet that makes me think I should have heard a difference in the frequency range where we use these inductors in crossovers. Bob Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted April 1, 2004 Author Share Posted April 1, 2004 Bob, You are beginning to convert me to your way of thinking. I can't see any good reason to choose air over iron core either! The only argument for air over iron is that there is no question about air core. The iron isn't there! The question becomes wether iron is as good! I considered the larger version "I core" inductor Parts Express sells for the woofer filter in my new Khorn extreme-slope network. It has a lot lower DCR than the Solen I'm using. The question is still up in the air. Al K. Quote Link to comment Share on other sites More sharing options...
BEC Posted April 1, 2004 Share Posted April 1, 2004 Al, I like the Parts Express "I" core also. It is the champ on DCR and is an impressive looking device in case someone wants that type of look. It is also very easy to mount since it is a sort of 2 X 4 (roughly) package with mounting holes. Of course the Universal Transformer 2.5 mH iron core device that I am having built is also very good in the DCR reading (0.279 ohms compared to 0.189 for the PE "I" core) and takes up even less room. I think you would likely have to go to a 12 awg or larger air core inductor to approach the DCR readings of a 16 awg iron core. Bob Quote Link to comment Share on other sites More sharing options...
STL Posted April 1, 2004 Share Posted April 1, 2004 I am glad you guys started this discussion before I bought the parts to build crossovers for my Cerwin-Vega/Cornwall-II hybrid! Speaking of inductors, what do you guys think of the SledgeHammer and Madisound units? Quote Link to comment Share on other sites More sharing options...
BEC Posted April 1, 2004 Share Posted April 1, 2004 STL, Haven't had one of those to test. Send me one and I will tell you all about it. Bob Quote Link to comment Share on other sites More sharing options...
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