Audiophile Turntable 101: Acoustic Research AR-XA TESTED!

Objective tests of the legendary AR-XA turntable's stellar performance and shock/room isolation to eliminate rumble and incipient acoustic feedback. Time stamps:
00:00 Intro
04:27 Sub-chassis' ground strap dissipates static charge (reduces pops/ticks)
04:57 Neutral balance tonearm (vs. typical stable balance) maintains a constant tracking force even on dips/warps.
08:54 Hefty platter + low friction bearing = speed regulation, but light enough to be driven by a highly accurate synchronous clock motor
10:36 Neutral balance arm perk: tilted shelf friendly.
13:14 ULTRA low mass, acrylic headshell under 7g w/ wiring: low inertial mass where it matters most, to track difficult/imperfect records
14:13 Very rigid/inflexible "box-construction" headshell prevents microscopic flexing (distortion) despite its low mass. WARNING: delicate attachment threads! *
16:27 AR white paper "Skating Force: Mountain or Molehill?"- R. S. Oakley Jr., Audio magazine, p.40 Mar. 1967 summarized: It's unimportant if using an adequate tracking force from the get go, however a DIY design like a weight suspended by a thread draped over a bent paper clip, attached to the arm, may be added if desired.
https://www.americanradiohistory.com/Archive-Audio/60s/Audio-1967-03.pdf
17:15 Dead accurate speed and very low wow & flutter, including actual stylus drag during the RPM test. [Even with my pulley's oxide and a cheap, aftermarket belt instead of AR's original belt, which were frozen solid and then machined on both sides for precise surface uniformity.]
19:51 Even "flat" LPs have micro warps (bumps/dips). This is why the AR-XA keeps its pivot height MUCH lower than the competition in order to minimize "warp wow". I demo the XA pivot height to that of a $28,000 tonearm using a 1 kHz test tone on the CBS STR-100 test record with an artificial warp.
28:15 Shock/vibration immunity hammer test No. 1.
32:07 Acoustic feedback "howl" immunity even @ MAX vol., ON a speaker with full-range playback, including immunity to "incipient acoustic feedback distortion", preventing boominess and murkiness, found at lower volumes with many other designs
38:35 Ultra low mass headshell/arm: McProud Test success at 33 RPM. [WARNING: May damage the stylus on the competition!]
40:35 Full-size, NAB broadcast quality spindle diameter to minimize groove eccentricity wow.
42:07 Artificially induced 1mm eccentricity audibility demo

THE FOLLOWING TEST MUST BE LISTENED TO WITH LARGE SPEAKERS WITH GOOD, DEEP BASS, IN A QUIET ROOM, OR FULL-SIZE HEADPHONES:

43:38 Floating sub-chassis to kill ROOM rumble, demo. Thanks to the VERY low resonance bounce (~4Hz) and inverted tripod spring isolation.

50:37 NAILING WOOD HAMMER TEST 2, literally ON the XA! It must be mounted on a dead solid surface. WARNING: Do not attempt.

THIS IS A 100% STOCK, UNMODIFIED MODEL!
[Other than replacing the organically decayed rubber belt, grommets, and platter mat.]

 The XA turntable and tonearm work together as an integral SYSTEM. [In theory one can mix and match but it opens a whole new can of worms for things that can potentially go wrong if the two designers had different goals or frames of reference for what is "proper".]

The low rpm clock motor minimizes vibration noise, decoupled from the platter via a rubber belt and has a constant, correct speed regardless of temperature or AC line voltage fluctuations.

 
"Despite being cheap, the AR turned out to be the single most important turntable of all time."

- HiFi News Magazine [the oldest audio magazine in the world and the largest in the UK] May, 2009, p. 41
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*From my AVSforum post, 05/19/19:

". . . many people (including some magazine reviewers) discredited the XA tonearm . . . because they failed to read the instructions and hence ended up harming their headshells. Whereas on a typical headshell (e.g., Technics SL-1200) you can rotate the mounting collar to pull in the headshell into the mount, this exact same procedure applied to the XA can potentially strip the delicate, acrylic threads. On the XA the headshell must be fully inserted and HELD pressed into the fully seated position FIRST, prior to tightening the outer collar.

AR was able to release the lowest mass tonearm of any turntable on the market (at the time) by shaving off EVERY gram possible. Any unnecessary weight in the headshell or its mount are especially problematic because being so far away from the fulcrum they have greater inertial mass. [AR's minimization of inertial mass is why it passes the McProud test, as I demonstrate]. This explains why AR prioritized low mass over ruggedness for the mount.

Considering my XA headshells ($2/ea.) are older than me and have lasted over half a century shows that with proper care and use the design was indeed rugged enough."
Damped arm descent bypass video: https://www.youtube.com/watch?v=GbNvCKCaiVM
12K 203L 07192020, 28.4K 490L 17DL 021221, 36K 601L 26DL 032921,40K 662L27DL 061321

Видео Audiophile Turntable 101: Acoustic Research AR-XA TESTED! канала M. Zillch