4 ohm speakers
Posted 12 April 2012 - 01:35 PM
Posted 12 April 2012 - 03:05 PM
All of the early AR 12-inch speakers were indeed 4-ohm designs. Reason: Ed Villchur selected the Altec Lansing 755A (Western Electric design) for the midrange-tweeter for the original 1954 AR-1, and the 755A—from 1947 until well into the 1960s—was designed as a 4-ohms speaker. Therefore, the AR 12W flat-side woofer was designed to be compatible with the 755A impedance, and it was designed at 4 ohms. By the way, Henry Kloss wound the first AR-1 voice coils by hand on bronze formers.
Since the AR-3, AR-3a, AR-11, AR-10, AR-9 and other AR 12-inch designs used a version of the original woofer, the speakers were all made for 4 ohms. By this time, of course, many new solid-state amplifiers were capable of the high current necessary to safely drive these 4-ohms speakers, so the low impedance was a good thing to drive these low-efficiency, low-Z speakers. For example, side-by-side comparison of an AR-3/3a to a comparable 8-ohm KLH or the 8-ohm Advent Loudspeaker of that period, the AR speakers needed the 3 dB extra amplifier current—for the same voltage input to the amp—just to keep up with the equivalent sound level. The 4-ohm AR-3/3a had about 3 dB lower efficiency than the equivalent 8-ohm KLH/Advent.
The Fisher TX-300 was woefully inadequate to drive something like the AR-3a. It used germanium transistors, and these simply weren't as reliable as the silicon transistors that followed in later designs. The Fisher also was not safe to operate below 8 ohms, and it would surely self-destruct if driven hard into a difficult load like the AR-3 or AR-3a.
You are right that the Advent provided more punch in the bass than the AR-2ax, but the AR-2ax's bass response—though less extended—was nevertheless somewhat flatter than the Advent.
Posted 12 April 2012 - 08:14 PM
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