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Using 8 Ohm Tweeters in an AR-3a


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As I posted earlier I have a badly dented tweeter on one of my ‘new’ AR-3a speakers. I do have an 8 Ohm tweeter from an AR2 that looks identical to the AR3 tweeter but is higher impedance. I’m wondering just what the results of installing the 8 Ohm tweeter would be. The AR-3a factory tweeter setting is 1.75 Ohms (1 to :) which, using DC analysis techniques (ignoring the cap) should give about a 3.9dB reduction in output from full on (at higher frequencies). With 0.5 Ohms (1 to B) and an 8 Ohm driver using the same analysis technique, it looks like the output should be 0.8dB below full on. Adding the 3 dB reduction for an 8 ohm vs 4 Ohm driver, gives a gross match to within 0.1 dB.

I then modeled the system in PSpice including the 6 UFD cap and found that using the 8 Ohm driver (modeled by an 8 Ohm resistor) would shift the crossover curve somewhat. Adding 16.5 UFD (2X33UFD in series) in series with the tweeter gives a pretty good match (within 0.2 dB) from 1 kHz to 100 kHz. I have attached the simulation schematic and probe results.

Has anyone actually tried this? Is the only difference between the drivers the impedance?



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