The Talking Machine Forum — For All Antique Phonographs & Recordings

Being a physicist, I always tend to mentally dig the scientific reasons why any device works or is more effective than another.

Concerning very loud needles, it is widely acknowledged that the "loud tone effect" descends from the improved thickness of the metal shaft of the needle, which is also shorter in some cases. This gives less flexibility to the groove-needle-diaphragm chain, hence the louder sound.

This makes sense (and is probably the actual reason) but leaves me puzzled concerning those super-loud needles that bear added masses. It may be conjectured that the body of the mass implicitly strengthens the needle's shaft just as in the case of a "thicker" needle, but I have to disagree with this. As it can be seen in drawings or actual images of these needles, the mass is very flattened and positioned towards the tip, as lower as it can go without scratching the record. There is then a negligible "reinforcement" effect on the shaft, if any:





Moreover, I recently came across a type of needle that I never saw before and that confirms that the effect is given preminently by the presence and position of the added mass. The latter is made with a wounded spring (as much as in a low-tone wounded piano string, and possibly with the same or similar machinery) which, being flexible by definition, can't add any stiffness to the needle's shaft:



I really can't understand on which principle this type of needles work. The only serious hypothesis I can conjecture is that the mass may induce a vibrational node point somewhere along the needle-diaphragm path, which in turn, perhaps for a local resonance point induced at the diaphragm, or for the generation of added harmonics, may have the effect of amplifying its vibrations.

Has any historical document, commercial paper or well written article surfaced lately, that can shed any light?

I've sometimes wondered about this too - I can't see how the extra mass can reduce flexural energy-loss along the length of the needle. But it will probably increase record wear, since the groove wall has to accelerate the extra mass.

Perhaps the flat-disc portion of the needle, pressed against the needle chuck, would further reduce any flexibility in the groove-needle-diaphragm chain. Maybe the added contact at the chuck would also magnify the lateral groove pattern. I agree it would probably significantly increase groove wear.
Bob

The added masses are well away from the chuck (actually as far as possible) and don't touch it at all.

The increased wear is true for all loud needles, with or without added masses. X mechanical energy in, X acoustic energy out. The stress excess is paid at the groove's level in any case.

I would tend to think that the inertia presented by the increased weight would tend to have a damping effect on the sound, and definitely increase wear on the record grooves...

Snake-oil, if you ask me...

I think those needles may have simply been a gimmick marketed to gullible people. There were lots of technical scams then. Tone modulators, anyone?

I will add that the "mass-added" needles do look fun...

De Soto Frank wrote:I would tend to think that the inertia presented by the increased weight would tend to have a damping effect on the sound

Yes, perhaps. But perhaps the opposite is true for the very same reason. Orchorsol wrote << since the groove wall has to accelerate the extra mass >> and that sentence really made me ponder.

It is probably correct to affirm that yes, the groove wall accelerates the extra mass. So there is an extra force involved, as F=ma, and a displacement. So we have a work. Where does the energy related to that work go, as it can only be transformed but not destroyed? We can assume that most part of it goes into heat and groove destruction. But not all of it; a percentage of it must surely go into extra kinetic energy, which in turn has to be released *somewhere else*. It is obbvious that it is realeased in the form of extra acoustic energy, but how, and where? My best conjecture is that it is released at the diaphragm, in the form of overshoot.

I personally don't think that added masses were cheats. Needles with added masses were also available in multi-compartment multi-tone assortment needle tins, and when present they were always classified as the loudest of all. Which wouldn't have made sense if any of the other needles' types in the assortment were in fact louder.

I think I have to devise some laboratory experiment under controlled conditions. That is add an extra mass to a known "normal" needle, record the sounds with a digital sampler and analyse the samples graphically on a computer; and see if that sheds any light also on the effectiveness of adding masses. The inverse also should be done, that is removing (by grinding and filing) the mass from an added-mass needle and see what happens. But unfortunately I don't own any added-mass needle.

Marco Gilardetti wrote: I think I have to devise some laboratory experiment under controlled conditions. That is add an extra mass to a known "normal" needle, record the sounds with a digital sampler and analyse the samples graphically on a computer; and see if that sheds any light also on the effectiveness of adding masses. The inverse also should be done, that is removing (by grinding and filing) the mass from an added-mass needle and see what happens. But unfortunately I don't own any added-mass needle.

Marco, please PM me with your address and I'd be very happy to send you some for that purpose.

PM sent, thank you very much!