Rega tonearm overhang at the published 222 mm mounting distance.
Rega prints 222 mm as the mounting distance from platter centre to arm hole centre on the RB220, RB330, and RB880. That distance is the pivot-to-spindle figure this page calculates from. The same Rega pages print a factory effective length of 236.5 mm, a factory overhang of 14.5 mm, and a factory offset of 21.55 degrees. Those factory numbers are Rega's own alignment. The table is Baerwald, Lofgren B, and Stevenson for 222 mm, which is a different target.
Published mounting distance: 222 mm.
Rega prints this mounting distance directly: platter centre to arm hole centre, 222 mm.
Factory alignment published by Rega for the RB220, RB330, and RB880: 14.5 mm overhang and 21.55 degrees offset, with 236.5 mm effective length. 222 plus 14.5 is 236.5. That factory pair is not the Baerwald column.
- Pivot to spindle
- 222.0 mm
- Effective length
- 236.5 mm
- Factory overhang
- 14.5 mm
- Factory offset
- 21.55 deg
Baerwald, Lofgren B, and Stevenson.
The studio clamps this distance to 150 mm through 400 mm. Null radii stay on the IEC groove. Overhang, offset, and effective length follow the distance.
| Curve | Overhang | Offset | Inner null | Outer null | Effective length |
|---|---|---|---|---|---|
| Baerwald (IEC) | 17.30 mm | 22.99 deg | 66.00 mm | 120.89 mm | 239.30 mm |
| Lofgren B | 17.66 mm | 22.88 deg | 70.16 mm | 116.19 mm | 239.66 mm |
| Stevenson | 15.42 mm | 21.98 deg | 60.33 mm | 117.42 mm | 237.42 mm |
Sources
Questions about this arm
Is 222 mm the Rega effective length?
No. Rega publishes 222 mm as the mounting distance from platter centre to arm hole centre on the RB220, RB330, and RB880. That is the pivot-to-spindle distance. On those same pages Rega also prints an effective length of 236.5 mm, an overhang of 14.5 mm, and an offset of 21.55 degrees. 222 plus 14.5 is 236.5. This page does not claim that every Planar plinth, including arms Rega has not listed here, uses 222 mm. If your arm's sheet prints a different mounting distance, enter it in the field.
Why does the Baerwald column not say 14.5 mm?
14.5 mm and 21.55 degrees are Rega's own published alignment for these arms. Baerwald, Lofgren B, and Stevenson are calculated here from the 222 mm mounting distance and the IEC 60098 groove radii. They are a different target. Use 14.5 mm if you want the factory setup, and the table if you want one of the three curves.
Will the null radii move if I type a different pivot distance?
No. Null radii come from the IEC 60098 inner groove at 60.325 mm and the outer groove at 146.05 mm, which are the radii StrobeHz uses. With those radii the table reads 66.00 mm and 120.89 mm for Baerwald, 70.16 mm and 116.19 mm for Lofgren B, and 60.33 mm and 117.42 mm for Stevenson. Overhang, effective length, and offset angle are the quantities that move when the pivot distance changes.