Dave MacKay Posted March 31, 2023 Share Posted March 31, 2023 2 hours ago, Deang said: What matters is the impedance at the crossover point. This is derived by combining the driver response, in the box, with the network - which is massaged until you get the acoustic response you want. You will not be able to make any sense out of any of this using any of the online calculators, which don’t account for the reactance between the parts, or the out of network acoustic response. Thanks. You're right about not being able to make any sense of this! I've been going through Dickason's Loudspeaker Design Cookbook, but have been finding it hard slogging. Do you have any suggestions about learning materials/resources? Quote Link to comment Share on other sites More sharing options...
Deang Posted March 31, 2023 Share Posted March 31, 2023 Hours on the phone with Al, Bob, DJK, Warren and Max Potter. Many posts from Gil, and many others. I’m mathematically declined, so the books don’t always help me. Quote Link to comment Share on other sites More sharing options...
henry4841 Posted March 31, 2023 Share Posted March 31, 2023 What you are not taking into account is the autotransformer which has inductance in your equation. I had much the same thoughts as you when I saw a 2.5mh inductor in the A and AA crossover networks. PWK knew what he was doing when he used a 2.5mh inductor. 1 Quote Link to comment Share on other sites More sharing options...
mboxler Posted April 1, 2023 Share Posted April 1, 2023 On 3/30/2023 at 1:47 PM, Dave MacKay said: Like @mboxler, I'm confused too. I've been trying to understand how the 1st order filters used in the woofer section of the A and AA networks work. The filter consists of just a 2.5 mH inductor. When I calculate the crossover frequency into the K-33E (which is rated at 4 ohms), I get a crossover frequency of 250 Hz, not the 400 Hz that I was expecting. Even if the K-33E was 8 ohms, the filter would crossover at 510 Hz, not 400 Hz. I know that driver impedance isn't constant, and that it varies with signal frequency. When I vary the woofer impedance based on a curve that @Trey Cannon posted sometime ago, I find that the crossover frequency varies between 220 Hz and 1210 Hz in the frequency range applicable to the woofer. I had hoped for a nice clean drop-off starting at a specific frequency, but that doesn't seem to be how the filter works. i thought that higher impedance = higher crossover frequency = more attenuation = lower SPL but that's not what my REW measurements show. I must be failing to understand something. What am I missing? As I understand it, there's a lot going on regarding the impedance of a K-33E in a Klipschorn... Voice coil DCR Voice coil inductance The loading of the horn itself Other things??? Bottom line, the impedance at 400hz ends up being around 6 ohms @ 28 degrees. That's equal to a 1.1mh inductor with 5.2 ohm DCR. At 800hz, it's 8 ohms @ 40 degrees, which equates to a 2mh inductor with 6.2 ohm DCR. It's a moving target that I assume shows up in your REW measurement. Mike 1 1 Quote Link to comment Share on other sites More sharing options...
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