Wood vs. The Rest: Testing Armtube Material

There are lots of talks in the industry on the best armtube material, whether wood is better than Aluminum, or maybe Carbon fiber is the perfect material and so on.
To find out who's right and which material is perfect for hi-fi tonearm armtube, we decided to conduct a little research.
We hope that results of our investigation will help you understand armtube material impact to the tonearm's sound and help choosing tonearm in armtube material perspective.

The Background

Figure 1 shows, why tonearm's sound depends on armtube material (and why turntable sound quality depends on mat material).

Fig. 1. Acoustic vibration spreading through the sound system

Stylus, while moving in the vinyl's groove, not only produces the musical signal, but also oscillates the cartridge itself. The oscillation (shown in red arrows) can be transferred through the armtube, partially reflect from the counterweight, and through the tonearm bearings, tonearm support, chassis, platter bearings, platter, mat and vinyl return back to the stylus. On the other hand, stylus causes vinyl plate vibrations (blue arrows), which, through the mat, platter, platter bearings, chassis, tonearm support, tonearm bearings and armtube, return to the stylus again.
The interference of these two acoustic vibrations can slightly impact the sound quality. Armtube material can suppress these parasitic accoustic vibrations (and of course, tonearm's effective mass depends mainly on armtube material).

The Gear

To carry on with the research, we built the device shown in Figure 2 (you can see its picture in the top-right of the article).

Fig. 2. Armtube testing device scheme

It consists of two acoustic dampers, holding the armtube; at the point A a broadband acoustic signal is fed; at the point B, it is registered using the broadband acoustic receiver and then passed to the spectrum analyzer.

The Wood

We acoustically tested following armtube materials:

  • Western redcedar,
  • Ebony Macassar,
  • Cocobolo,
  • Pernambucco,
  • Pao Ferro,
  • Panzerholtz (Tankwood)
  • Zirocote
  • Wenge.

Also for comparison we carried the same test to Carbon fiber, Fiberglass and Aluminum arms.

The Result

As you can see from the graphs on the right side of an article, woods with closest-to-perfect characteristics are Redcedar, Pernambucco and Panzerholz. They don't have clearly expressed resonant frequencies, and their sound damping characteristics are close to exponential function.
Results of our test are basically same to some audiophile opinion, that tonearms with Redcedar and Pernambucco wands produce very clean, transparent and deep sound. Meanwhile, even if tests show Panzerholtz being nearly perfect material for the arm, audiophile opinions on it are different.

 

  • A
Tool for testing armtube sound properties
  • A
Acoustic characteristics in Perfect conditions
  • A
Cocobolo (Dalbergia retusa) arm
  • A
Acoustic characteristics of Cocobolo arm
  • A
Brazilwood (Caesalpinia echinata), also known as Pernambuco, arm
  • A
Acoustic characteristics of Pernambuco arm
  • A
Wenge (Millettia laurentii) arm
  • A
Acoustic characteristics of Wenge arm
  • A
Zirocote (Cordia dodecandra) arm
  • A
Acoustic characteristics of Zirocote arm
  • A
Western redcedar (Thuja plicata) arm
  • A
Acoustic characteristics of Western Red Cedar arm
  • Macassar ebony (Diospyros celebica) arm
Makassar ebony (Diospyros celebica) arm
  • Acoustic Charakteristics of Macassar Ebony arm
Acoustic characteristics of Makassar ebony arm

Approximate effective mass of Reed tonearm in grams

Armwand Azimuth adjuster Effective lenght
9,5" 10,5" 12"
Cocobolo Yes 14 17 22
No 12 14 17
Pernambucco Yes 14 17 22
No 12 14 17
Wenge Yes 12 14 17
No 10 12 14
Zirocote Yes 14 17 22
No 12 14 17
Western Red Cedar Yes 10 12 14
No 8 10 12