Eminent Technology ET-2 Tonearm Owners

Further...
Mono signals of course, do result in horiz groove modulations.

With regard to the high horizontal mass the standard ET2 has a very high horizontal effective mass as standard ( 25g plus the weight of the cartridge ) compared to a pivoted arm.

However the FR64 of course, has Eff Mass of 30-35gms (or more).

Chaps...I'm not an ET user nor an Aro user, but I do use both a 12" unipivot + an air bearing linear tracker, so if I could be permitted to offer a humble opinion, hopefully useful to the topic ;)....

In this game, sometimes we tend to think about what we SHOULD hear, rather than what we DO hear...

In principle, the tolerance gap of a air bearing leads us to think that an air bearing will be therefore compromised sonically - ie. because it will never have solid bearing contact. However I hear no lack of 'leading edges' with a linear tracker. So what is going on?

On the topic of 'leading edges', I think a 'square wave' is an appropriate analogy. The leading edge of square wave (rise time/slope, overshoot control...) is determined primarily by the HF component of the signal/tone. In the same way, the perceived 'leading edges' of sound is poor, if the HF harmonic component of music signal is compromised.

A unipivot typically has excellent HFs, owing to absence of 'bearing rattle'. I also hear excellent HF tone & extension with an air bearing tonearm. Go figure...

The explanation I think is that, at groove modulation frequencies, it is not the rigidity of the bearing that is key, but rather the inertia of the tonearm, as 'seen' by the stylus, that is key. From this perspective, a pivoted tonearm rotates freely, ie. has very low (rotational) friction.... and a linear tracker also has low (linear) friction. Both are similar... but from the viewpoint of the stylus in groove, 'inertia' or Effective Mass (at groove modulation frequencies) must be high - adequately high to reproduce LF signals without resonance/loss of power delivery.

Contributes to the discussion I hope.

(Apologies if this is old ground, I haven't managed to read all 700 pgs ;) )

One is usually coloured/informed by past experience. Coincidentally, I have a couple of FR64S's myself & you reminded me of the Hadcock GH228 that I have gathering dust.

Another recent unipivot, an Apparition 12" superseded the above. A very fine performer, to the extent that I have had little compunction to A/B with the older arms. A very top shelf pivoted tonearm in my humble experience.

Nothing is perfect in this game (audio & life in general ;)) but with my linear tracker (a Trans Fi terminator) I find the combined qualities of genuine low distortion, wide bandwidth, dynamic stability...are overall most persuasive. Are these attributes typical of linear trackers? I can't be sure at this point.

Regarding Effective Mass...with record groove modulations cut at 45deg, as we know, I think it's not entirely useful I think to dwell on Effective Mass in terms of horiz & vert properties.
Cheers.

Richardkrebs has advocated adding 60+g of horizontal mass by adding lead to the bearing spindle and removing the decoupling mechanism of the counterweight. With the ET2 the decoupling of the counterweight is part of the strategy to keep horizontal mass not too high.

I'm not sure if there is any (groove tracking) disadvantage in having Eff Mass too high, ie. Res Freq too low.

Sure, there may be issue with particular TT suspension or TT support resonances, but arguably not detrimental to good record tracking?

Richardkrebs has advocated adding 60+g of horizontal mass by adding lead to the bearing spindle and removing the decoupling mechanism of the counterweight. With the ET2 the decoupling of the counterweight is part of the strategy to keep horizontal mass not too high.

I'm not sure if there is any (groove tracking) disadvantage in having Eff Mass too high, ie. Res Freq too low.

Sure, there may be issue with particular TT suspension or TT support resonances, but arguably not detrimental to good record tracking?

Dover wrote:
A conventional pivoted arm with an effective mass of 14g with a cartridge of 9g will have a total effective mass of 23g.
The standard ET2 has a horizontal effective mass of 34g or 52g with the damping mechanism.
With your addition of lead and removal of the decoupling, and added fluid damping, your altered ET2 has an effective mass of approximately 114g - 4 times the effective mass of a conventional pivoted arm.

Readers should try to imagine waking around with the weight of three adults sitting on their shoulders, and pretending the weight is of no consequence.
This is what the cantilever has to endure with the Krebs alterations to the ET2.

Sorry Dover, with respect, I hear what you are saying but I don't think that this is what a cartr stylus really "sees".

Static Mass is one thing but Effective Mass is something slightly different... the latter is the "inertia" or the reluctance of the tonearm (pivoted or sliding) to move, as seen by the stylus.

ie. At frequencies above Res Freq, the tonearm is effectively an immobile/stationary object or load, as seen by the stylus...which is a good thing, because you want a stable platform to trace the groove, right?

Referring to your analogy, for example, the tonearm should not be "walking around", it should be standing absolutely still... & having 3 adults sitting on your shoulder ;) ...is going to help hold the cartridge steady.

(The only potential problem with ultra low Res Freqs is the danger of coinciding with TT suspension/support/floor modes.)