Do You Swing Long and Large?

LOOK AT MY BIG SWINGER!

Vinyl lovers seem to be gravitating toward longer and longer tonearms. This is surely not only to satisfy our inner Ron Jeremy but to also reduce tracing distortions caused by angular error - in other words, when the cantilever is NOT perfectly tangential to the groove.

A quick lesson in geometry: a tangent to a circle is a line that just touches a circle at one point and where a line drawn at that point to the center of the circle is perpendicular to the line. 

With a pivoted tonearm perfect tangency occurs only at two points across the record's surface. With a longer tonearm, the maximum degree of error from perfect tangency to the groove is minimized.

What a great reason to get that lengthening you've been thinking about, right?!

DO I REALLY WANT TO SWING BIG?

Not so fast, audiophiles. Let's look closely at our fixation with more length.

Most of us slept through high school physics or got the pass to take woodworking shop instead. For some, the following will be new. All else remaining equal between a 9" arm and a 12" arm, the following is true:

  • More length = increased moment of inertia

    • It's much tougher to start and stop quickly when you gotta throw around a longer moving mass. Spindle holes cut out of center and record warps cause extra challenges for longer arms.

  • More length = decreased tonearm rigidity

    • We're talking about infinitesimals that REALLY matter in vinyl playback. When the groove content modulates your cartridge motor, your cartridge motor should absorb ALL of that energy from the groove contents and convert it into electrical energy. If the tonearm gets excited - even in the slightest bit - by the groove content, then that electrical information - MUSIC! - is lost. The arm should only be responding to groove POSITION, not its content.

  • More length = more cost​

    • Duh​

So, the question needs to be asked: are the increased inertial forces, the decreased rigidity and increased costs I will incur from a 12" arm less to give up than I will gain from the lower tracing distortion a longer arm will give me?

The answer depends on whether the designer did a good job of engineering the 12" arm. We cannot expect that a 12" arm identical in design to its 9" younger brother (other than the arm tube length and perhaps the counter weight) will perform as well as the 9" arm when you take the improved tracing error out of the equation. Decreases in rigidity and increases in inertial forces are not correlated in a linear fashion with tonearm length. In other words, increasing arm length by 25% results in MORE than a 25% impact on rigidity and inertial forces that must be accounted for and ameliorated by significantly more engineering and construction effort.

The answer to the question of swinging big also depends upon how you feel about the sound of tracing distortions. 

WHAT DOES TRACING DISTORTION SOUND LIKE?

Tracing distortion doesn't sound anything like the distortion you hear from amps or speakers when you drive them too hard. At lower tracing error levels, some distortions can actually appear to be subjectively pleasing. Slight angular error of the cantilever can cause 2nd and 3rd order distortions (think SET amps) but at the expense of a shrunken soundstage, decreased dynamics and image precision. As the error increases, so do the higher order distortion harmonics and eventually significant IM distortions kick in. Keith Howard did an interesting article on this subject in 2006 for Stereophile.

If you have a WallyTractor Universal you can listen to this form of distortion for yourself:

  1. Align your cartridge using the "New Record Collection" arc option

  2. Find a record in your collection that goes very close to the label. You can use the WallyTractor's pivot to spindle ruler and jig for this. The jig has a little "nipple" on one end that fits perfectly into the record's spindle hole so you can measure the distance from the center of the record to the innermost groove. Try to find a record that gets as close as 56-57mm to the center but at least goes to 60mm.

  3. Listen to the record from the middle of the playing surface, playing close attention to the size of the soundstage, midrange tonality, imaging precision and overall musical clarity. Notice how audible characteristics change as you play the last 2 centimeters of the grooves.

  4. Email to let us know what you found! We love hearing from audiophiles that just had an "a-ha!" moment.

SO YOU WANT TO KNOW WHAT IT WOULD BE LIKE IF YOU HAD A REALLY LONG ONE?

We gotchya! You can hear for yourself what your diminutive shorty would sound like if it were a swinging monster by simply re-aligning your cartridge to the WallyTractor Universal's "New Record Collection" arc for your tonearm's effective length. This isn't the reason we put a second set of arcs on the WallyTractor - READ HERE FOR THAT - but it is a cool side benefit of owning a WallyTractor Universal. 

With this re-alignment, you'll get to hear the benefit of having the lower tracing distortions of a 12" arm in your 9" arm. It's about a 26% to 28% improvement in tracing distortions WITHOUT the potential of having the inertial and rigidity downsides of the longer arm. Be sure to only do this assessment with records that are not cut too closely to the label.

Well, we're not sure we helped you decide whether or not to get that lengthening you are considering, but at least you may feel better informed.

707-210-6345

Santa Rosa, CA 95404

  • WallyTools on Instagram

©2020 by WAM Engineering LLC