I\u2019ve built the first prototype (see my last post) of the cross-over and made some distortion and mid-woofer near-field frequency measurements with the focus on the cone break-up behavior.<\/p>\n
The mid-woofer cross-over section is made of a simple 2nd order electrical filter in order to achieve a 4th order LR cross-over slope with a cross-over point at 2000Hz. For the notch filter section a cap shunt over the series coil is used to reduce the cone break-up at 10kHz.<\/p>\n
In order to simplify the cross-over and to get a more accurate notch filter, I choose the cap shunt instead of the LCR notch filter type. A cap shunt connected across the coil and in series with signal path, requires a high quality component in order not to degrade the sound quality.<\/p>\n
Thanks to the relatively low cross-over frequency, the odd-order distortions are low, even at higher listening levels. There isn\u2019t a huge difference in the distortion measurements between using a notch filter or not for the mid-woofer cone break-up.<\/p>\n
Don’t be fooled by the distortion measurements alone, the cone break-up is very audible and a notch filter is a must. The notch filter reduces the break-up with an additional 15dB and the effect is clearly visible in the frequency measurements.<\/p>\n
A brief listening test to the prototype cross-over suggests that some work needs to be done at the tweeter section in order to find the proper balance between the mid and highs and the tweeter level.<\/p>\n
For the mid-woofer cross-over section I want to use a coil with as low internal resistance as possible. I will test and listen to both iron-core and copper-foil coils to determine the best choice for the design.<\/p>\n
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![\"\"](\"https:\/\/www.audioexcite.com\/wp-content\/uploads\/2011\/12\/System-2R-TW-axis-18cm-85db-Filter-v1.0-+-notch.jpg\" "\\"System-2R")
<\/a>![\"\"](\"https:\/\/www.audioexcite.com\/wp-content\/uploads\/2011\/12\/System-2R-TW-axis-18cm-85db-Filter-v1.0-no-notch.jpg\" "\\"System-2R")
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