Tonearm Concept

Tonearm is mechanical, acoustical and electronic system. The set of parameters of this system determine characteristics of tonearm. Tonearm "sound" depends on how many parameters were taken into account while designing it. Main parameters of tonearm are:

1. Effective length,

2. Effective mass,

3. Moment of inertia,

4. Acoustical damping of armwand

5. Wiring impedance.

1. Effective length. Effective length of Reed can be from 9" to 12".

2. Effective mass. Effective mass of tonearm is very important when matching cartridge. Cartridge compatibility with tonearm is determined by Tonearm Resonant Frequency. It should be 10 Hz (-4 Hz + 6 Hz); it may vary from 8 Hz to 12 Hz. Tonearm Resonant Frequency can be calculated using following formula:


frez - resonant frequency of tonearm

mef - effective mass of tonearm

mc - weight of cartridge

ms - mass of the screws, nuts, spacers, washers, shims

c - compliance of the cartridge.

Since effective mass of different Reed models can be from 8 g to 25 g. Reed tonearm can be matched with almost any cartridge you have.

3. Moment of inertia. Tonearm moment of inertia It consists of two parts:

a) Cartridge moment of inertia Ic

b) Counterweight moment of inertia Iw.


Because Iw should be (and usually it is) at least 10 times less than Ic, we will use only for approximate calculation.

Cartridge moment of inertia Ic is calculated using the following formula:

(Ic)=(mc+(mef /2))*lef 2

mc - cartridge weight

mef - tonearm effective mass

lef - tonearm effective length

Best result is achieved when Ic is less than 20000 g*cm2.

If LP is perfectly flat, then  Ic does not have any influence. Ic becomes important when LP is not brand new or is not flat for some other reason. In such cases cartridge and tonearm is moving up and down while playing a record. Even if swinging amplitude is around +/- 0.5 mm, tonearm with high Ic may not be able to catch up with LP swing. This causes instant VTF, VTA and SRA changes which lead to sound distortions. To reduce LP swinging, clamps are used.

For more information about distortions, refer to our websites Research page.

4. Acoustical damping of armwand. Stylus, while moving in the vinyl’s groove, produces not just the musical signal, but also oscillates the cartridge. The oscillation can be transferred through the armwand, 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, which, through the mat, platter, platter bearings, chassis, tonearm support, tonearm bearings and armwand, return to the stylus again.

The interference of these two acoustic vibrations can slightly impact the sound quality. Acoustical oscillation damping can be done in two ways:

a) vibrations transferring to the floor. This is the most widespread method. The most common solution is to build a tonearm that should carry away these vibrations as quickly as possible and via mechanical connection transfer them to the floor. Designers/manufactures/increasing the weight of a platter so that it can suppress vibrations and at the same time soft suspension allows much less vibrations to get to the stylus. It can be done quite easily in heavy decks but there are always some vibration that would come back to stylus eventually. The amplitude is not too big but considering the size of the groove they still might introduce some distortion.

b) choosing right armwand material. Reed tonearm armwands are made of different kinds of wood, so it’s sound damping characteristics are close to exponential function. This method was chosen after a lot of tests of different armtube materials and bearing setups. More about choosing armwand material can be found in our website's Research page.

5. Wiring impedance. It is very important to harmonize cartridge output impedance, wiring impedance and preamplifier input impedance.  Cable (made by Stereo-Lux Musikanlagen) used in Reed tonearms has no soldering points and is harmonized perfectly.

After a lot of tests and listening to customer feedback we found out that tonearm adjustment is important not just for mounting tonearm for the first time, but also after changing cartridge or even LP.

That’s why we offer you Reed tonearm, whose sound performance can be compared to other well known world brands and have user friendly and precise adjusters (azimuth, VTA).