Boron Tube Cantilever Manufacturing Patent

[dlaloum]

I came across this link....

http://www.patentgenius.com/patent/4212838.html

Among other things it talks about the 2k to 10k droop on most cantilever types:

A prior art cantilever for a pickup cartridge is made of a pipe of an aluminum alloy. In order to obtain required strength, the pipe must have a large diameter and a thick wall and consequently is very heavy, so that the effective mass of avibrator is increased. In order to solve these problems, there has been proposed to use a pipe made of titanium because the latter has excellent mechanical strength so that both the diameter and wall thickness may be reduced and consequently the weightmay be reduced. However, even with the titanium pipe sufficient strength and rigidity cannot be attained.

In order to attach a stylus tip, one end of a cantilever is pressed flat, a hole is formed through the flattened portion and the stylus tip is forcibly fitted into this hole. In this case, the cantilever is annealed so that the decrease instrength and rigidity results. In order to solve this problem, the cantilever with the stylus tip is subjected to the oxidation process, but satisfactory strength and rigidity still cannot be attained because the oxidation process results in theincrease in rigidity and Young's modulus only by 10%. Furthermore the control of oxidation of the cantilever is difficult and in the extreme case the cantilever becomes brittle.

Because of these unsatisfactory cantilevers, the conventional pickup cartridges exhibit the so-called drooping phenomenon. That is, their frequency response drops in the range between 2 and 10 KHz below the high resonance frequency f.sub.0(which is in general between 10 and 40 KHz). Thus the flat frequency response curve cannot be obtained. Furthermore their transition characteristics which determine the degree of trackability are not satisfactory.

So far the only company I have found who still seems to be using Boron tube cantilevers is Steinmusic with their Aventurion 6 cartridge - which appears to be a custom modified Benz LP-S with boron tube cantilever (?).

Anyone know of any other currently made boron tube cantilever cartridges?

[Ldg]

Thanks DL. That patent is a process patent, and the part you quoted is the only reference to the mid dip, from a quick read through. It also is just an assertion, with no explanation, which I've heard before and represents a sort of conventional view.

But the part that's missing for me is the explanation of the link between rigidity/mass and transmission loss. I really don't get it. It reminds me of South Park and the underpant gnomes :

Step 1. Colect Underpants
Step 2. ???
Step 3. Profit

Also, the patent is silent about self resonant vibration, which you'd think it would expound ? Being more rigid doesn't prevent vibration, it just moves it to a different frequency.

The process patent is interesting though - thanks again.

[dlaloum]

It filled in a few blanks for me in how the Boron tubes were made... the mention of the 2k to 10k dip was a matter of side interest...

[abelb]

A bit of Googling shows that the Technics EPC-305MC cartridge had a boron pipe. I found some suggestions that the AT OC9ML/II had a boron pipe as well but I don't think that's accurate.
http://www.vinylengine.com/library/technics/epc-305mc.shtml

[steve195527]

During the 80s there seemed to be a glut of vendors marketing cartridges with "boron" cantilevers,think a lot were solid rods though,it seemed to be the "in" material for a few years
What materials are used in the construction is only interesting from a technical or engineering viewpoint,to be honest all I was/am bothered about is how the end product sounded and tracked,and some using exotic materials sounded pretty bad/mediocre,and as ld hinted at some of these materials were only used as a sales gimmick(of sorts)

[dlaloum]

Boron Rod is now one of the top materials...

A substantial % of the top cartridges use Boron cantilevers.

A tube (as opposed to a rod) has a bunch of physical advantages, including lower effective mass, and improved rigidity...

There is a good reason no one uses aluminium rods but the standard is aluminium tube cantilevers...

It seems clear that lots of effort went into improving cantilevers in the 80's and 90's with cartridges released as late as 1998 sporting boron tube cantilevers at the top end...

Then somewhere in the last ten years - poof - no more boron tubes.

Until then they were mentioned by many manufacturers (who used them) as the ultimate...

This included:

Clearaudio
Technics
Van Den Hull
Benz
Notingham
Monster Cable

Googling Boron tube cantilever brings up quite a collection of classic cartridges - all of them high end...

Currently the same companies are all providing cartridges with boron rod cantilevers....

Sales gimmick? or Technology which has become too expensive to use as it gradually lost the manufacturing scale required to keep it going?

The physics behind a boron tube are well understood and make sense... Although that is far more LD's field than mine!

But I would argue that the objective that was #1 for designers right through to the 90's was producing a perfectly neutral cartridge that perfectly reproduced every detail of the original recording.

Starting in the late 90's there was a movement away from neutrality towards euphony...
Euphony can be achieved more economically than neutrality, and is a lot more prone to marketing spin... and of course measurement becomes irrelevant as euphony is a subjective approach not an objective one.

Perhaps the absence of boron tubes and the design trend towards subjective euphony rather than objective neutrality are linked?

bye for now

David

[steve195527]

Boron Rod is now one of the top materials...

A substantial % of the top cartridges use Boron cantilevers.

A tube (as opposed to a rod) has a bunch of physical advantages, including lower effective mass, and improved rigidity...

There is a good reason no one uses aluminium rods but the standard is aluminium tube cantilevers...

It seems clear that lots of effort went into improving cantilevers in the 80's and 90's with cartridges released as late as 1998 sporting boron tube cantilevers at the top end...

Then somewhere in the last ten years - poof - no more boron tubes.

Until then they were mentioned by many manufacturers (who used them) as the ultimate...

This included:

Clearaudio
Technics
Van Den Hull
Benz
Notingham
Monster Cable

Googling Boron tube cantilever brings up quite a collection of classic cartridges - all of them high end...

Currently the same companies are all providing cartridges with boron rod cantilevers....

Sales gimmick? or Technology which has become too expensive to use as it gradually lost the manufacturing scale required to keep it going?

The physics behind a boron tube are well understood and make sense... Although that is far more LD's field than mine!

But I would argue that the objective that was #1 for designers right through to the 90's was producing a perfectly neutral cartridge that perfectly reproduced every detail of the original recording.

Starting in the late 90's there was a movement away from neutrality towards euphony...
Euphony can be achieved more economically than neutrality, and is a lot more prone to marketing spin... and of course measurement becomes irrelevant as euphony is a subjective approach not an objective one.

Perhaps the absence of boron tubes and the design trend towards subjective euphony rather than objective neutrality are linked?

bye for now

David

doesn't the top linn cartridge use a boron tube cantilever?I don't think there is now more of a trend to euphony rather than neutrality than there has ever been,unless you compare to a master tape how do you know what is accurate and what is just "nice" sounding?Stan Curtis never ever liked using a turntable set up to dem products he designed as he thought them all to give a very poor sound compared to master tapes,which he tended to use when he could

[Hanuman]

Starting in the late 90's there was a movement away from neutrality towards euphony...

I'm not so sure about that either. Some of the stuff I had in the '80s & early 90s was rather coloured, to say the least, but very beautiful to listen to. I think there was a lot of stuff like that around at the time. It might be true that there is now more diversity of products than there ever was, thereby giving more exposure than before to alternative approaches like single-ended amps. I'm not sure that "neutral" and "euphonic" are entirely mutually exclusive actually. A neutral system sounds euphonic if if it does the job well.

Maybe the reason for the extinction of the boron-tubed cartridges is simply that the tooling to produce them has worn out and it's just not economical to re-tool. Or, maybe the licensing has long-expired but the patent is still valid. Or, maybe it turned out to be not such a good idea.

[Ldg]

The physics behind a boron tube are well understood and make sense... Although that is far more LD's field than mine!

IIRC, I already set out my opinion and explained why I reckon any benefits are typically overstated, at least from a theoretical perspective. Perhaps it was simply concluded not worth the hastle/cost after the demise of 4 channel ?

There probably are now alternate composite materials that would allow some pretty interesting novel cantilever structures that would likely surpass boron/other exotic metals. But there's also marketing principles involved here, and boron/borides have an established market position. Whether that is strictly justified is debatable i reckon, from a theoretical perspective.

[steve195527]

Starting in the late 90's there was a movement away from neutrality towards euphony...

I'm not so sure about that either. Some of the stuff I had in the '80s & early 90s was rather coloured, to say the least, but very beautiful to listen to. I think there was a lot of stuff like that around at the time. It might be true that there is now more diversity of products than there ever was, thereby giving more exposure than before to alternative approaches like single-ended amps. I'm not sure that "neutral" and "euphonic" are entirely mutually exclusive actually. A neutral system sounds euphonic if if it does the job well.

Maybe the reason for the extinction of the boron-tubed cartridges is simply that the tooling to produce them has worn out and it's just not economical to re-tool. Or, maybe the licensing has long-expired but the patent is still valid. Or, maybe it turned out to be not such a good idea.

or perhaps with modern techniques cheaper materials give a result just as good or even more probable is that vendors have found by using cheaper materials and tooling and more advertising they can make more profit,most(well a lot) of hi-fi is smoke and mirrors and there are many cases of the Emperors new clothes!

[1200y3]

There are thousands of patents for thousands of reasons, many just crazy or useless. The use of the product in manufacturing is almost always based on cost or practicality. The stylus choice is often chosen just to keep the cartridge quality lower, because after all, the cartridge will outlast the stylus.