The Equipment: Audio-Technica AT-605 Audio Insulators, a system for attenuating vibrations at audible and sub-audible frequencies in turntable assemblies.
Dimensions: 1 1/2 inches height clearance required for isolated component. Price: $25. Warranty: "limited," one year parts and labor. Manufacturer: Audio-Technica, Japan; U.S. distributor: Audio-Technica U.S. Inc., 33 Shiawassee Ave., Fairlawn, Ohio 44313.
Comment: Few things are as annoying as a tone arm that skips a groove at the slightest provocation, forcing even the cat to tiptoe across the room. Or a music system that is given to moaning whenever the volume is turned past the whisper level. These forms of undesirable behavior, vibration sensitivity and acoustic feedback, are what the AT-605 is designed to combat.
The system consists of four damped feet that are meant to be placed under a turntable in such a way that its own feet, which are not doing the job, remain free of contact with the supporting surface. The AT-605 feet are adjustable in height, and a spirit level is included to aid in setting the turntable level. The effectiveness of the insulator set depends in part on the turntable with which it is used. That is, it may not improve the isolation of the most sophisticated turntables on the market, but it does seem likely to help a great many whose feet are just adequate.
We tested the system by setting a turntable (with a better-than-average suspension) next to a loudspeaker that had been placed woofer--down on a table. The speaker was driven with a sweep tone essentially from 0 to 100 Hz, and the signal from the turntable pickup (which was placed on a record) measured with and without the AT-605. The actual data depend, of course, more on the other equipment than on the Audio Insulators, but the difference between the two curves is impressive. One peak slightly below 20 Hz was attenuated by nearly 6 dB, and another near 60 Hz by about 3 dB. Further, the system gave 1 dB or so of extra attenuation at all frequencies above about 5 Hz, the lowest frequency at which we could get useful data with this setup. We also noticed, but did not measure, decreased susceptibility to shocks. The device is not a panacea, but can help materially where a problem exists.
There is no reason why the Audio Insulators should be used only on turntables. If acoustic feedback is the difficulty, the speakers can be isolated as well, which should suppress structure-borne vibration by about another 3 dB.
Or, if your tape deck's drive feeds rumble to the turntable, either or both could be isolated from the supporting surface. According to the manufacturer, each of the feet can support up to 9 pounds--or a maximum of 36 pounds for a set--and still retain its damping characteristics. One other nice thing about the AT-605 is that it will not detract from the appearance of your sound system.
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(High Fidelity, Apr. 1977)
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