Ideal tonearm length ?

[Daithi]

Presumably a longer tonearm has less tracking error.
So why are so many tonearms so short?
And what is the ideal practical length for a tonearm to minimise tracking error?

[JerryVan]

Presumably a longer tonearm has less tracking error.
So why are so many tonearms so short?

Probably for 2 reasons.
1. After some arbitrary length, you most likely get diminishing returns for each additional inch.
2. Nobody wants a cabinet that's 36" deep.
3. (Bonus reason) Most people were not audiophiles who would even know the difference.

[AudioFeline]

The ideal length would depend on the design of the arm/cart/system.

It would depend on the design of your player...
- If you are using a pivoted arm, then a longer player would give less tracking error.
- If it is a tangential/linear-tracking arm, the added length doesn't make any difference to tracking error, as there is no tracking error.

Other factors:
- most tonearms are 9" long. 12" arms are designed for transcription and audiophile turntables, and give the lower tracking error. They are also heavier arms, so are generally used with MC cartridges (MM carts are more common for 78/disk playing).
- the weight of the arm needs to be matched with the compliance of the cartridge used with it. Low compliance carts work with higher-mass arms, high compliance carts are suited to low-mass arms. The length of the arm influences the mass, and the cart's used. Older tonearms tend to be high-mass, newer arms tend to be low-mass. Weights can be added to the headshell of a low-mass tonearm to make it heavier to be compatible with a low-compliance cartridge.
- Very long tonearms can have difficulty containing resonances within acceptable freq's/levels.

[Daithi]

So what is the ideal length for a hollow non-electric tonearm? As measured from the center of the horn pivot to the center of the soundbox mount?

[Marco Gilardetti]

As said above, in theory the longest the tonearm the less the tracking error, but long tonearms are heavy, wobbly and of course also cumbersome.

The longest Hi-Fi turntables/tonearms that were engineered and industrialised to a reasonable degree featured a 12'' tonearm. In the picture below you can see the Thorens "long base" TD 125, where you should easily notice that the tonearm base is more apart than usual, and also the arm looks oddly longer than what your eyes are accustomed to. There never was much market for these oversized turntables that fit nowhere and were produced in small numbers even in their heyday; they were always very expensive and produced in small numbers, not even to mention their special 12'' tonearms that cost no less than fortune.



When it comes to home-made oddballs crafted by "fantasy" makes, then there's no limit. See this whooping 27'' tonearm extreme turntable that, in my humble opinion, has absolutely no chance to play any better than a well built 12''.

[Daithi]

So what is the ideal length for a hollow non-electric tonearm? As measured from the center of the horn pivot to the center of the soundbox mount?

[Marco Gilardetti]

So what is the ideal length for a hollow non-electric tonearm? As measured from the center of the horn pivot to the center of the soundbox mount?

Since the tracking error is pretty much the last of the problems when it comes to sound fidelity in 78 RPM records, a tonearm longer than 10'' (which, as we said, is what is considered "all right" for Hi-Fi applications) makes absolutely no sense.

Whatever is OK for Hi-Fi, is more than enough for 78 RPMs.

[Daithi]

I have 5 tonearms that range in length from 7 to 8.5 inches. Are all of these lengths unlikely to damage records?

[Marco Gilardetti]

It depends much more by the correct design of the tonearm than by the length of the tonearm itself, which alone doesn't mean much. There are long arms with an awful geometry, and very well engineered arms with consistently low tracking error despite being short. If you provide pictures and/or makes and models, we might be able to tell.

[Daithi]

Lets assume for the purposes of this discussion that all the tonearms are the same design but are different lengths. Sorry for so many questions. Just trying to get my head around it.