How important is low W & F performance anyway?

Measure meaningful metrics and listen…

the ear / brain is the hard part

there is also

bright shiny heavy hardware attraction ( fishing lure effect ) …

@elliottbnewcombjr 

Ability to achieve such low numbers (if true) gives us a feeling the maker has the ability of precision manufacturing, i.e. nearly friction free tonearm , quality decisions regarding din connectors and cables

Not sure if you are commenting in general, but if your comments are directed at the Holbo I think they are pretty accurate.

The tangential tonearm rides on a 10-micron layer of air and seems totally friction free. It is connected to the deck by 4 Litz wires and a very fine air tube. These hang from the arm before looping up to the deck - there is a long slot in the deck for clearance.

With the arm set at zero tracking force, there is no friction between it and the raising device.  An adjustment screw allows the arm bearing rod to be levelled horizontally, and the arm responds immediately to tiny adjustments.  It tends to centre because of the very slight pull of the Litz wires and air tube.

The Garrard was made well before Computer Numerically Controlled (CNC) machining was even dreamt of.  It has no feedback mechanism to govern speed, but it is continuously braked by an adjustable eddy current brake operating magnetically on a aluminium disk rotating at about 1000-rpm on the motor shaft. A big knob at the front of the deck controls the position of the magnet and therefore the amount of braking effect, and provides fine adjustment of the average speed. This is easily seen under incandescent lighting  on the strobe patterns cast into the rim of the platter - a two Pound Sterling option when the table was new.

The motor has four shaded poles, so it is not quite synchronous, instead slipping slightly with the braking effect and stylus drag.  Personally I think stylus drag is tiny compared to the eddy current brake, which could explain why these decks are valued for their 'drive' when playing heavily modulated passages.

I don't think the Holbo has any feedback mechanism to fine control its speed, either.  Unlike the Garrard, it is not designed for end-users to disassemble . There are separate trim pots for 33 and 45-rpm, but they need a small screwdriver and are round the back and fiddly.  Definitely a set-once and forget proposition.

The round-section 'belt' is far smaller than I expected and stretchier. Nevertheless it gets the 5-kg platter to speed in about 4 seconds while providing good isolation between the platter and the motor.

@richardbrand 

I was making a generality, that while these speed variations may not matter audibly, we are impressed by the implied perfection.

My Thorens TD124: I just remembered the 1st time I put the 9.5 lb cast iron platter, and it’s bearing shaft back into the bearing housing.

The tolerance of the housing and bearing shaft were so fine that an air spring was created, it took several minutes for the air to get out and the platter/shaft to descend fully. I’ve never forgotten that precision.

@richardbrand The review of the Holbo and your experience with the Garrard further confirms my suspicions about whether high specifications equates to good listening experiences, although in both cases with your tables the issue is absolute speed accuracy rather than W&F.   The W&F numbers for both tables are typical of belt/idler drive, but speed accuracy is more problematic.  The Holbo has a DC motor which has a negative torque/speed curve;  no matter how accurately you control the voltage to the motor, it will slow under load unlike an AC synch motor which holds synchronous speed under load until the cogging torque is exceeded and the motor stalls (speed is either 100% or zero).  There are more sophisticated power supplies that have negative output impedance to match the DC motor's internal impedance that can compensate, but they also need temperature compensation or they will behave differently when cold/warm.  It is also belt drive which is susceptible to belt creep (addressed by the RR tach with feedback, but only for AC synch motors).

Likewise the Garrard uses an AC induction motor which has a similar negative torque/speed curve which is why the eddy brake is effective in controlling speed.  Lenco tables also used induction motors (although the idler was employed in a rather unique configuration) and are known for "pace" and "attack".  Unfortunately, they are not known for great speed accuracy.  A common misconception about the Lencos is that they have a high torque motor.  While it is true they consume a lot of power (typically ~20W) they are very inefficient (<10%) so they produce rather low torque given the power consumption.

To my original point, these engineering deficiencies don't seem to detract from the user's perception or enjoyment.  And as others have commented, it is the sum of the parts or the system level that has the most affect on sound.

I think that we are not really asking the right question. Personally, unless a TTs W&F is really bad, I don't notice it as speed error per se. (Perceptible pitch changes in say piano's decay would be considered to be really bad)   But as the TT's figures improve, what I do hear is a solidifying of the sound along with improvements in attack and a lengthening in decay time. A subtle improvement in focus, to use a visual analogy. It becomes easier to hear, see,  into the music. 

Further W&F figures aren't that relevant as they are virtually all measured during steady state operation, a test tone for example. Music is not steady state so it places dynamic loading on the drive thru stylus drag. How it responds to this is much more important. 

Years ago I owned a Goldmund Studio, in an attempt to improve it, I built a regulated power supply based around a LM317 3 pin regulator chip. The change was disappointing. I scoped the supply voltage while playing a record and noticed that it was being modulated in sync with the beat of the music. ( music was muted)  This was a revelation leading me to come up with two explanations.

1) The output impedance of the LM317 supply was high, making it a bad choice for this application 

2) Much more importantly.... the stylus drag was slowing the platter. The JVC motor's feedback loop was sensing this and drawing current in sync with the music's beat in an attempt to hold speed steady. 

I don't recall how heavy the platter was. Certainly it was, for a DD, a fairly high inertia design. 

So how does a TT measure when playing a dynamic piece of music. Now that is a real test of its speed accuracy. (If we hear changes in pitch, the TT is basically broken.) What we are looking for is stability and focus of the music itself. Solidity of the notes, just like the real thing.

Cheers.