Al Klappenberger Posted October 17, 2009 Share Posted October 17, 2009 These days it seems that everybody is experimenting with upgraded midrange (squawker) horns and fancy drivers to replace the K55 / Atlas PD-5VH. I can't complain since my Trachorn is part of the reason people ate thinking about it! Anyhow, I keep getting questions about moving the 400 Hz crossover frequency of my Universal network up to 500 Hz to accommodate better drivers like the Altec 902 or the JBL 2426h I use in my Belles. I hope to illustrate why this is not feasible and also explain why my "Universal" network is actually "universal". The reason for both is the same. Here is the plot of the woofer and squawker channels of my Universal network on a log scale of 20 to 2000 Hz. Notice that the two plots cross at about 3.16 dB. This is my "definition" of the crossover frequency OF THE NETWORK. That is, the frequency point where the attenuation through the two channels is identical. With power equally divided between the two channels you will have half the total power in each. That is 3.01 dB attenuation. Mother nature always wants to take a little off the top. It's kind-of like the interest on your credit card! Anyhow, that happens because of resistive losses in the components. In this network it amounts to about 0.16 dB leaving us with 3.16 dB out each channel. That happens at the little black dot (marker) located at 377 Hz on the plots. That's a nominal 400 Hz crossover. Note that this filter is a first order filter. 6 dB / Octave slope. To make the measurements I have terminated the midrange filter by connecting a 13 Ohm resistor between taps X and 4 on the network. This is where the K55 would be connected. The woofer is simulated by a 1 mHy inductor in series with a 6 Ohm resistor which is the complex impedance of the Klipsch K33 woofer driver. The measurements are taken across the 6 Ohm resistor and the total winding of the 3619 autotransformer. The 1 mHy inductor is part of the woofer filter in this test plot. More about that next! Quote Link to comment Share on other sites More sharing options...
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