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In Reply to: Adjusting attenuation of Hiraga x-over passive equalization section posted by JeLL-O on May 22, 2002 at 01:03:49:
Hi Angelo, I built the 16 ohm version Hiragas several years ago, and used them happily for a while. My math is pretty shaky when it comes to the time constants, but it is possible to figure them using the formulae in the original SP article. There is also another way to determine what your crossover is doing. You can feed a constant voltage AC signal from an audio generator to the input, while terminating the driver outputs with the proper resistors- i.e. 16 ohm resistors for a 16 ohm network. Measure and plot the output voltages at various frequencies, and you can see what the network is actually doing as you make changes.Of course, the wild cards are still the drivers' varying sensitivity at different frequencies, plus the patterns of the horns used, so SPL testing in the listening room with the mic at your listening spot is really helpful if possible. I have found it necessary to potentiometers of several times the speaker impedance (50 ohms for 8 ohm driver, 100 ohm for 16 ohm driver) in series with the driver leads to permit final level matching- not the last word in impedance matching, but works well in practice.
Follow Ups:
Steve,The original SP article on the VOT A5 didnt have the formulas. Ill get my hands on an RTA and measure first to confirm what i think im hearing.
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