Kasey
A system designed and built in early 2019 which was given away to a friend who really liked them. Two notch filters were added to compensate for his room acoustics which, according to calculations, would have had a severe hump in the bass response of the order of about 10dB.. Given his musical preferences, that eventually proved to be unnecessary but the filters were left in anyway.
PHOTO 1
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2
The sides were held in a jig until the glue at their junction set, after which these braces were installed. |
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At the bottom, the input terminals. At the top, the two bypass switches. They are in bypass mode, down, 55hz on the right and 110hz on the left. |
The crossovers. The 55hz notch filter is in the upper right corner; inductor, resistor, capacitor from top to bottom. The 110hz notch filter is top center; resistor, capacitor, inductor from left to right. The L-pad is the pair of resistors to the left of the inductor at the lower right corner. |
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The finished pair. Total cost of materials, about US$700. |
FIGURE 1
Response of each section, in dBV measured across a resistive load equal to the nominal impedance of the drivers at the crossover frequencies. This doesn't show the actual speaker outputs; it's purpose is to show the effect of the notch filters. The brown curve is without the notch filters in and the red curve is with both filters in. |
FIGURE 2
Actual responses. The band above 300hz is measured at 1w1m, gated to reduce the room effects. The woofer section below 300hz is measured near field. Blue, no notch filters applied; red, notch filters applied. The fixed L-pad is applied in the mid-section. None is used for the tweeter. While the 5dB rise above 10khz may be objectionable to a listener younger than 40 years of age, it would be beneficial to one over 40, in this case, well over 65. |
FIGURE 3
The crossover, three way, second order, Butterworth. The notch filters are shown on the left side above the woofer. The bypass switches, SW1 & SW2 are shown to the right of these filters. The fixed L-pad to the mid-range is encircled in green. It attenuates about 4dB. |
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