Acoustic Research LST - Rare, Wonderful "Everyday Monitors"

Edgar Villchur and Henry Kloss founded Acoustic Research in 1954 after validating their industry-changing acoustic suspension cabinet design.  The AR1 was followed, logically, by the AR2, and then the AR3 in 1958.  The components used in these systems: a large, high-compliance 11" paper pulp cone woofer, coated fabric dome midrange, and low Fs dome tweeter - became the foundation of generations of speaker  designs to follow.  In 1970, after much pressure from the music production industry to create a speaker suitable for studio playback environments, AR developed the LST.

The Acoustic Research LST ("Laboratory Standard Transducer") occupies a rare and highly-prized place in the industry. Developed under the leadership of Roy Allison, one of the foremost minds in acoustic engineering, the LST was created not merely as a consumer product, but as a professional-grade reference monitor capable of maintaining spectral accuracy across a wide range of room conditions and listening positions.

The LST is a four-way, ten-driver system housed in a sealed, acoustic suspension cabinet. Each speaker contains four dome tweeters, four dome midranges, and two 11-inch acoustic suspension woofers, all arranged in a uniquely angled and faceted baffle design. This configuration was carefully developed to overcome the limitations of conventional speaker dispersion. By placing drivers on angled panels, the LST achieves a remarkably uniform polar response, minimizing the detrimental effects of room reflections while maintaining excellent off-axis performance. The result is a speaker with a wide and stable soundstage, consistent tonal balance throughout the room, and less dependency on the listener's exact position—a significant breakthrough at the time.

To control all of these components, the crossovers needed to do the usual job of "traffic control" within each frequency pass-band, but in the case of the LST also provide room boundary controls, accessible from a front rotating switch labeled "Spectral Balance". With 6 settings available, the user could tailor the response of all of the pass-bands at the same time, with one turn.  A robust internal autoformer made this possible.  

The cabinets on these speakers are finished in walnut veneer with a heavily braced, non-resonant design, weighing approximately 85 pounds per unit and reflecting the no-compromise build quality typical of AR’s high-end offerings.

Due to its high cost, size, and demanding amplification needs, the LST was not a mass-market product but was embraced by audio professionals, recording studios, and serious audiophiles. Over time, it has become a revered piece of hi-fi history—a symbol of what was technically possible during the golden age of American loudspeaker design.

This pair is absolutely lovely.  Sitting on home-made shapely risers, the speakers can visually recede into a room, or be positioned prominently - demanding attention. The original walnut veneer and Irish linen grille fabric have a timeless aesthetic. These speakers were serviced several years ago by the original owner.  All 8 tweeters were replaced with modern components, but we have seen a number of "resto-mods" over the years, and none quite as appropriate or as good as this one.  Listen with confidence that these modifications were done well. 

Demos are encouraged in Andover, MA.

$1,999/pair (plus applicable sales tax)

* Note, shipping ONLY available by freight. Please inquire!