Introduction

Cartridge alignment is the process of positioning the stylus, the cartridge body, and the tonearm geometry so that the stylus traces the record groove with the least possible tangential error. On any pivoted tonearm, perfect tangency across the whole record is impossible — the arm swings in an arc while the cutting lathe moves in a straight line. What alignment does is pick two points on the record where the stylus is perfectly tangent — the null points — and minimise the error everywhere else.

This sounds like a minor nicety, but it is the single most audible setup parameter after tracking force. Sibilance, inner-groove grit, bass bloom, and a narrow soundstage are all partly determined by alignment. The work on this problem dates to the 1930s and 1940s — Erik Löfgren's 1938 paper and H. G. Baerwald's landmark 1941 Journal of the Audio Engineering Society piece laid the mathematical groundwork that every modern protractor is still built on.

Three named standards dominate the audiophile world: Baerwald (IEC), Löfgren B, and Stevenson. They all use two null points; they just put them in different places. This article explains what each one does, why the differences matter, and how reviewers and the wider community choose between them.

The Three Alignment Standards

All three standards are solutions to the same optimisation problem: given a tonearm's effective length and offset angle, where should the two null points sit to minimise some definition of tracking error?

  • Baerwald (also called IEC, or Löfgren A): Null points at approximately 66.0 mm and 120.9 mm from the spindle. This solution minimises the maximum weighted distortion across the playable area of the record. Peak tracking error is around 1.8°, and distortion is spread fairly evenly. Baerwald is the default on most high-quality protractors and the recommended alignment of many reviewers.
  • Löfgren B: Null points at approximately 70.3 mm and 116.6 mm. This solution minimises the average (RMS) weighted distortion. Distortion is slightly lower on average but slightly higher at the extreme ends of the record than Baerwald.
  • Stevenson: Null points at approximately 60.3 mm and 117.4 mm. Stevenson pushed the inner null point to the IEC-defined inner groove radius (60.3 mm) to minimise distortion at the very end of the side — at the cost of higher distortion at the outer grooves.

All three use essentially the same mathematics. The difference lies purely in which portion of the record each designer decided was most important to optimise.

Related parameters that alignment constrains:

  • Overhang: Distance the stylus extends past the spindle. See what is overhang.
  • Offset angle: The angle at which the cartridge is rotated in the headshell (typically 22–24°). Set automatically by the headshell on most modern arms.
  • Zenith angle: The rotation of the cartridge body itself. Set by eye to make the cartridge sides parallel to the protractor grid lines.

A correctly aligned cartridge has the right overhang and the right zenith — one without the other isn't alignment.

What Happens When Alignment Is Wrong

The consensus across the audiophile press and the measurement community (Audio Science Review, Hi-Fi News test LP measurements, Stereophile's setup columns) is consistent: alignment errors show up first as rising distortion toward the inner grooves — the well-known phenomenon of inner groove distortion.

A few published numbers:

  • A properly aligned cartridge using Baerwald geometry can measure under 1% THD at the inner groove using a good line-contact stylus (Hi-Fi News Test LP track 6, as documented in many reviewer rigs).
  • A misaligned cartridge — overhang off by 3 mm, or zenith off by 3° — can push inner-groove distortion to 3–5% THD or more.
  • Subjectively, reviewers describe misalignment as "sibilant", "edgy on voices", "congested in complex passages", or "bass loses definition". The inner half of the record suffers most.

The choice of alignment standard also audibly matters — though less dramatically than getting any standard roughly right. Listeners who finish every side (classical, long-form jazz, dub) often prefer Stevenson, because it minimises distortion at the very end where the music may still be peaking. Listeners who prefer even performance and mostly hear the middle of sides gravitate toward Baerwald or Löfgren B. There is no single right answer — it's a legitimate taste choice.

How To Align Your Cartridge

The standard method across every credible setup guide:

  1. Choose a standard. Baerwald is the safe default. Stevenson if you prioritise inner-groove performance. Löfgren B if you want lowest average distortion.
  1. Get a two-null-point protractor. Free printable templates are available from the Vinyl Engine library; the Dr Feickert NG and MintLP Best Tractor are common commercial choices. Manufacturer-supplied null gauges (Rega, Technics, Pro-Ject) usually match Baerwald or close to it.
  1. Loosen the cartridge bolts so the body can slide in the headshell slots.
  1. Outer null point: Place the protractor on the spindle. Lower the stylus onto the outer null point. Slide the cartridge forward or back until the stylus sits on the target and the cartridge's sides are parallel to the grid lines.
  1. Inner null point: Move to the inner null point. Check alignment. If it's off, split the difference with the outer point and re-check both.
  1. Tighten bolts gently, re-check both points, and confirm that zenith and overhang are simultaneously correct.

Reviewers routinely remind readers that alignment is iterative. Tightening the bolts can shift the cartridge by a fraction of a millimetre — which is enough to matter. A final check after everything is locked down is not optional.

One underappreciated point from the measurement community: printed protractors must be verified for scale. Print-to-fit settings in PDF readers can shrink a template by 2–3%, which ruins the geometry. Always check the printed scale bar against a ruler before use.

Common Misconceptions About Cartridge Alignment

MYTH

“Baerwald is objectively best.”

Baerwald minimises peak weighted distortion — a specific optimisation criterion. Löfgren B minimises average distortion. Neither is objectively best; they optimise for different things.

MYTH

“If the cartridge bolts are straight, alignment is correct.”

No. The cartridge must be rotated in the headshell to match the alignment standard. "Looks straight" is rarely close enough.

MYTH

“Alignment is a one-time setup.”

It changes whenever you swap cartridges, re-mount the headshell, or disturb the tonearm. Check it periodically.

MYTH

“Manufacturer protractors are wrong.”

Usually they're Baerwald or close to it, and fine for a factory cartridge. They're just less flexible than a two-null universal protractor.

MYTH

“Linear-tracking arms need alignment too.”

They need vertical alignment and azimuth, but not the two-null Baerwald/Stevenson geometry — linear tracking has no offset angle and maintains zero tangential error by design.

FAQ

Which alignment should I use?

Baerwald is the safe default. If you frequently hear the last few tracks of a side, Stevenson reduces distortion there. Löfgren B is a middle ground preferred by some reviewers.

Do I need a protractor, or can I use a ruler?

You need a two-null-point protractor. A ruler alone cannot verify zenith or null-point tangency.

Why does the inner groove always sound worse?

Because linear groove velocity is lowest there and alignment error is often highest. Stevenson-aligned setups reduce this audibly; better stylus profiles (line contact) help further.

Does changing alignment standard change overhang?

Slightly — usually within 1–2 mm. The overhang value is linked to the chosen null points.

How precise does alignment need to be?

Within about 1 mm of overhang and 1–2° of zenith is the working tolerance for good sound. Perfectionists chase tighter tolerances with precision protractors.

What's "offset angle" and do I need to set it?

Offset angle is the cartridge's rotation relative to the headshell. On detachable-headshell arms you may set it; on integrated arms like Rega it's fixed by the headshell shape. Either way, it's part of the broader alignment package.

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