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”AR3a improved”.... one of my favorite speakers
Around 2004 I bought a pair of AR3a from a hifi friend, who has a lot of Acoustic Research speakers as reference for excellent sound.
The following pictures to describe the renovation of the famous 3 way speaker from Acoustic Research
The AR3a
One pair of AR3a in fair condition..but blurry jpg...The speaker box without stuffing material. Solid woodwork inside the box, but frontplate only 22mm in thickness, and that is not a solid woodplate for the units when milling 10 mm down into the plate.
A pair of rare AR3a in birch veneer sold in 2021
Acoustic Research Inc.
Edgar Villchur invented the dome tweeter
and the "acoustic suspension" princip
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The company "AR", was founded in 1952 and incorporated on August 10, 1954 by audio engineer, researcher and audio-electronics teacher mr. Edgar Villchur in Cambridge, Massachusetts, USA.
The acoustic suspension principle based on patent US No. 2,775,309, was granted to Edgar Villchur and assigned to Acoustic Research in 1956. The AR-3 speaker, featuring both the acoustic suspension woofer (patented in 1956) and the new dome tweeter, is displayed at the Smithsonian Institution for its historical significance in audio technology.
Mr. EdgarVillchur continued to research improvements in sound reproduction, turning his attention to the tweeter . Edgar Villchur was granted the patent for his direct-radiating dome tweeter in 1962 (U.S. Patent 3,033,945).
Read more:
http://en.wikipedia.org/wiki/Edgar_Villchur.
Very solid crossover hardwired point to point with real thick 1,3mm copper-wire coils and high quality Sprague capacitors
The original AR3a crossover schematic to the left. A redrawn AR3a crossover right
Two crossovers ready for mounting. The new AR3a crossovers with the original coils and new MKP polypropylene capacitors and three-step turn switches to replace the old rheostats.
Speaker frontplate increased by ½ inch. ~ 12,5mm MDF, and the front edge wooden strip reduced to a thickness of 7 mm. Later new Riopalisander veneer was glued on.
New feets of wood adapted ...height approx. 4 inch
The new crossovers installed...Both speakers ready for unit mounting
A very important point is, that the closed box must be completely airtight when the loudspeaker principle of acoustic suspension is used.
The old AR logo with data and guarantee still there.
New goldplated connectors installed. The old black rheostat print reused....
The old foam surroundings cleaned off. Takes approx. one hour for each unit if done properly. One have to take care not to harm the voicecoil.
The woofer cone treated with a thin layer of ”Dammar” a kind of resin to connect the cone paper fibers, and a thin (very thin) spray layer of black paint.
From Japan:
One of the most powerful 3-way speakers I've ever listened to. You never get tired of that punch in the bass.
It may be a little difficult to understand how, with a fairly simple crossover in the AR3a, such a homogeneous and pleasant-sounding interaction between the three units has been achieved. Acoustic Research really managed to adapt the crossover frequencies and units acoustically to each other, creating a perspective that few other speakers have managed to achieve.
A dark set of AR3a ”improved” in rosewood compared to a standard pair of AR3a in birch veneer. I think I prefer the sound from the new polypropylene capacitors in my modified AR3a “improved” rosewood boxes.
Rgds Kim
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