Acoustic Research 3a Improved (1974–c. 1977)
The AR-3a Improved is the AR-3a with a new dome midrange driver. It was introduced in 1974 and produced through about 1977. The crossover points are 575 Hz and 4 kHz. The cabinet is finished in oiled walnut veneer with a brown cloth grille.
The controls on the front baffle are what set the 3a Improved apart from the earlier AR-3a. There are separate 3-position level switches for the midrange and tweeter, so you can trim the upper drivers to suit the room. Specs that survive in period literature list frequency response as 45-20,000 Hz ±3.5 dB, impedance of 8 ohms (4 ohms minimum), and recommended amplifier power of 15 to 100 watts. The cabinet measures 24 × 14 × 11-1/2 inches (H×W×D).
Documentation on this model is thinner than on the better-known AR-3a. No original price has surfaced, and the surviving spec sheets don't agree with each other. One lists weight at 53 lbs each, another at approximately 80 lbs shipping weight, which may simply be net versus packed weight. One Australian dealer's spec sheet lists nominal impedance as 4 ohms rather than 8. The 8-ohm figure appears in multiple sources and is more likely correct. Studio Sound (October 1974, p.26) was covering the hi-fi scene in this period, though no dedicated review of the 3a Improved appears in the surviving record.
The 3a Improved is the later, slightly refined take on one of the most influential speakers ever made. It uses the same acoustic suspension formula, with more flexible driver-level adjustment than the original offered.
- System: 3-way, acoustic suspension
- Drivers: 12" woofer, 2-1/2" dome midrange, 3/4" dome tweeter
- Crossover: 575 Hz, 4 kHz
- Frequency response: 45–20,000 Hz ±3.5 dB
- Impedance: 8 ohms (4 ohms minimum)
- Recommended amplifier power: 15–100 watts
- Controls: 3-position midrange switch, 3-position tweeter switch
- Dimensions: 24" × 14" × 11-1/2" (H×W×D)
- Finish: Oiled walnut veneer, brown grille cloth
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