If bypassing "sounds better," or has increased detail, then it is likely a result of the tweeter output being magnified in the 5–8 kHz range. The output curve will be qualitatively the same for the other early speakers using the same x-o circuit, but with different x-o and peak frequencies. The peak level for the "bypass" condition is reduced by 0.5 dB from its value without the "ESR." The peak of the "flat" curve is reduced by 0.25 dB. When a 0.2-Ohm series resistor is added to the 6-uF capacitor to simulate ESR, the curves look similar except for a slightly reduced Q. Some increase may be needed in highly absorbing rooms, but not that much or in every situation. Bypassing the wiper thus gives a permanent +3.5 dB output increase. At maximum output, the tweeter sees an increase of +3.5 dB from just below 5 kHz to ~8 kHz. At the factory "flat" setting, the response is -3 dB at 5 kHz as it should be. To see the effect of pot rotation we plotted the tweeter crossover transfer function (V tweeter/V input) for the AR-3a. another suggestion, which we address here, is the recently discussed practice of "bypassing" the tweeter pot-moving the rotor lead to the hi side of the pot, setting it at maximum output. Replacements are listed in the Allied Electronics (Richardson TX) catalog for about $23.
One was to purchase new pots, but they are not manufactured in large quantities or widely stocked. Recently there have been discussions on a number of threads relating to the difficulty in replacing Polack 16-Ohm, 25-W potentiometers used in many early AR crossovers (AR2-ax, -4x, -3, -3a, -5 and such).
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