ARM/CARTRIDGE MATCHING, TRACKING, AND COMPLIANCE

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You cannot stick any cartridge onto any arm and expect the best results. Arm and cartridge must be carefully matched. Specifically what you’re matching is cartridge compliance with tonearm mass. Compliance (compliant-ness, amount of give, the opposite of stiffness) refers to how much force is required to deflect the cantilever. The cantilever is like a spring topped by the weight of the arm and cartridge body. A low-compliance cartridge is noncompliant and so resists being deflected; it is best matched with a high-mass arm. A high-compliance cartridge is quite elastic and easily deflected and so is best paired with a low-mass arm.

Ideally, the cartridge should be compliant to the audio frequencies so it can accurately trace them, but inert to tracking and warp frequencies, which you don’t want the cartridge to pick up along with the mu sic. Again, ideally the tonearm should be the reverse—inert to audio frequencies (so the arm doesn’t move along with the cartridge) and com pliant to tracking and warp frequencies (so it will promptly follow record irregularities).

If the cantilever “spring” is very stiff (has a low compliance), then it needs the control of a high-mass tonearm; otherwise the spring will throw the arm around. (Obviously you can’t see this happening—it occurs on the scale of micro-resonances.) If the spring is quite soft and floppy (highly compliant), then you need a low-mass arm; otherwise the spring will be crushed. A highly compliant cartridge can more faithfully follow the tiny modulations of the groove than a stiffer one. But on the other hand, the relatively low mass arm it has to be matched up with is less rigid and therefore more resonant—so the potential benefits of improved groove tracing are offset by the problems of arm resonance. Also, a highly compliant cartridge tends to be more vulnerable to groove junk.

The arm/cartridge system’s particular resonant frequency is also determined by the arm/cartridge mass and cantilever compliance. The arm and cartridge are a weight sitting on the spring of the cantilever. Like any weight on any spring, this system has a resonance—at some particular frequency, even a slight amount of energy can cause the system to vibrate, coloring the sound. Either the higher the mass OR the higher the compliance, the lower the arm/cartridge’s resonant frequency. The lower the mass OR compliance, the higher the resonant frequency.

The arm/cartridge match should set that resonance at a frequency where there isn’t much to make it vibrate, and certainly below the audible range, ideally somewhere between 8 and 12 Hz. Below that range, resonance can be excited by rumble and motor noise, while anything above 15 Hz enters into the range of what we can hear and so resonances can be excited by the music on the record.

Tracking ability is the ability of the cartridge (in conjunction with tonearm and table) to maintain the stylus in uninterrupted contact with the groove wall. This differs somewhat from tracing ability, which is how accurately the stylus, when held in proper contact with the groove, retraces the groove’s exact path. Tracing ability is determined largely by stylus footprint.

All cartridges sometimes mistrack, especially at high modulations when the music gets loud. When you consider the conditions that styli have to perform under, it’s remarkable they do so well. The stylus must smoothly hug corner curves as well as track the dips and bumps without bouncing up and out of the groove, all the while traveling at speeds many times the acceleration of gravity. (Superstylus—faster than a speeding bullet....

Listening to mistracking is a little like wearing eyeglasses that aren’t quite correctly aligned—your vision is just slightly out of focus. Even if you’re not consciously aware of it, the overall effect is disturbing. Poor tracking not only sounds bad, it is also a major cause of record and stylus wear.

Tracking at the lower frequencies is most affected by the cartridge compliance; at higher frequencies, it’s most affected by the stylus tip mass. This is the combined mass of the stylus and cantilever plus the compliance of the cantilever suspension. This defines just how much weight is knocking against the groove walls. Because tip mass deter mines the actual pressure exerted against the groove walls, it may be the single most important factor in record wear and damage.

Most higher-compliance cartridges are good trackers—in fact, most competently designed cartridges, providing they’re well set up in a good arm on a good table, track well. A commonly offered example of an excellent tracker is the Shure V15 Type V-MR, though some don’t like its somewhat clinical, even edgy sound quality.

Mistracking can be minimized by adjusting the vertical tracking force, which is the downward pressure exerted by the tonearm on the cartridge and stylus to keep the stylus in the groove. The typical tracking force of 1.5 to 2 grams recommended for many cartridges may seem negligible (and a cartridge manufacturer recommending anything less than this is likely to be a purveyor of “geewhiz” gimmickry). But stop to consider that all of this pressure is focused in one minute location—the stylus point usually ranges from about 0.5 to 1 mil (0.001 inch) in radius. So the pressure at the groove/stylus contact point is measured in literally TONS per square inch.

Too much force will cause excessive record wear and reduce the stylus’s facility to respond to the groove modulations. But on the other hand, too light a tracking weight can be even more damaging than too heavy a force. Underweighted, the stylus can more easily bang around in the groove, hitting against the walls (instead of sliding along them) and actually chipping the vinyl. A mistracking stylus bounces off the walls, regains contact, loses it again, and so on. Even though you may not consciously identify the problem, this distortion is very irritating and fatiguing to listen to as well as extremely damaging to your records. (See later article for a description of how groove wall damage occurs.)

As a general guide in arm/cartridge matching, moving magnets often have high compliance, so they are often best matched with an arm having minimal mass. Moving coils tend to have low compliance (meaning they’re stiff) and may require pairing with an arm of medium to high effective mass. We’d recommend selecting a cartridge to match the arm you’re using, rather than choosing the cartridge first and then selecting the arm accordingly. As much of a difference as a cartridge can make to the music, the arm surpasses its importance in the system hierarchy.

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Updated: Friday, 2016-05-13 19:17 PST