DIY arm question

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Never really thought the tubular shape had any other purpose than screen and hide the wires. Some of the higher-end Sheu arms, like the Cantus seem to sound good using just a perforated strip of acrylic. No idea how they compare to tubular designs but for diy it certainly seems like a simpler solution.
 
Jerry T. said:

I suspect a tapered tube has something to do with resonance, but could you elaborate please? I would like to now more about this.
Jerry T.

Simply put the nearer the mass to the headshell the more it
adds to the effective mass off the arm. So a tapered section
will outperform a straight section of equal effective mass.

Or put another way a tapered section will weigh more than
a straight section of the same effective mass, it will be stiffer.

TBH I'm not sure resonances would be spread that much,
depends on the sort of taper you use, but you can ease
the impedance change as you hit the bearing end of the
arm.

If the bearing end is a ball you could run the taper into this.

Bit like this ;

:) sreten.
 

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As a thought : With some spray on glue that sets fairly hard I can't see why you couldn't "roll your own" tapered armtube from aluminium foil.

Should be possible. Might make it a foam cored one. KEF used to make foil sandwich foam cores for the B139. Did a quick look in "loudspeaker and headphone handbook" (just jotting down some parts):

...to obtain maximum stiffness the sandwich must be thick, optimum proportions for a given total weight.... (optimum core thickness)/(optimum skin thickness)= 2/[sqrt(g)-1] with g= (1-Ya/Ys)/(1-Da/Ds) Ya= core modulus, Ys= skin modulus, Da=core density, Ds=skin density.....This sandwich will be stiffer than the same total weight of either of the materials separately....berilium is the best (skin material), aluminium the second best...core should have maximum stifness in the thickness direction.....honeycomb Al or impregnated paper (for the core)....expanded polystyrene most practical.....resultant stifness in ratio 1:20:200 for paper:expanded polystyrene:sandwich of 9mm expanded polystyrene with 2 sheets of 0.05mm Al glued with epoxy to both sides.

This is for speaker cones, but there is no reason this could not be used for other purposes.
 
[
True, they are tapered but being designed for clobbering golf
balls they are probably too strong and thus heavy to be ideal
for a tonearm.

QUOTE]

Yeah, and they have a big blob of alluminium or wood that would shurely scratch the record. On a slightly more seious level, i´ve built a few arms,some came out crap a few came out really good, all kinds of design and material, as in comercial arms: some ridicoulus things are fantastic and some really good looking wonders are not that fun. A few simple observations: if You want to do it all go for one point bearing, if lateral ball bearings, rip a standard arm for central pillar and build on that. Materials matter but less so than how You put it together. The best result of my ventures was made of sheet alu, balsawood and two 5mm glasstubes, one point bearing and mated to a GAS sleaping Beauty. Especially good bottom end but too fragile to survive the first party.
 
sreten said:


Simply put the nearer the mass to the headshell the more it
adds to the effective mass off the arm. So a tapered section
will outperform a straight section of equal effective mass.

Or put another way a tapered section will weigh more than
a straight section of the same effective mass, it will be stiffer.

TBH I'm not sure resonances would be spread that much,
depends on the sort of taper you use, but you can ease
the impedance change as you hit the bearing end of the
arm.

If the bearing end is a ball you could run the taper into this.

Bit like this ;

:) sreten.

Ah, i understand about the tapered arm now, but how did they fit the bearing in there?

sreten said:
With a foam core (instead of a former) would be
wise not to forget the wires to start off with.

I'm beginning to warm to the idea (except I have a Rega).

The real issue is how to incorporate the headshell part.

:) sreten.

I'm going to modify the tone arm on my Thorens first, but after that i will definitely try to build my own tone arm. This forum is very inspirational. :D

ingvar ahlberg said:
[
True, they are tapered but being designed for clobbering golf
balls they are probably too strong and thus heavy to be ideal
for a tonearm.

QUOTE]

Yeah, and they have a big blob of alluminium or wood that would shurely scratch the record. On a slightly more seious level, i´ve built a few arms,some came out crap a few came out really good, all kinds of design and material, as in comercial arms: some ridicoulus things are fantastic and some really good looking wonders are not that fun. A few simple observations: if You want to do it all go for one point bearing, if lateral ball bearings, rip a standard arm for central pillar and build on that. Materials matter but less so than how You put it together. The best result of my ventures was made of sheet alu, balsawood and two 5mm glasstubes, one point bearing and mated to a GAS sleaping Beauty. Especially good bottom end but too fragile to survive the first party.

Do you have some pictures or drawings of your projects please?
 
Official Court Jester
Joined 2003
Paid Member
huh,seems that I opened Pandora's box here .....;)
in any case-I have EMT 930st with original arm (exact number is somewhere in papers and 'puter ,but I'm too lazy), and I need good arm for my 401;
too bad for little jewel to sit in box without any use....
what ya ppl think about proper arm (DIY) for that 'table?
my problem is that I don't have too much free time for thinkerin' ...
I have time and energy for slow'n'easy DIYin',but offten not for drawing and calcs.....
is some sort of wood better (huh,so audiofool term-isnt it?) ?
Sreten-do you remember Basis from Subotica,with unipivot arm made from wood here called Grab (what is proper word in EL?) ?
 
Here's a pic of the Cantus which i still think will make an excellent and easy diy project.

The only arm i've ever tried cloning was the Welltempered and it came out surprisingly well considering the effort involved. If i ever do it again it will most likely be a Schroeder.
 

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Official Court Jester
Joined 2003
Paid Member
analog_sa said:
Here's a pic of the Cantus which i still think will make an excellent and easy diy project.

The only arm i've ever tried cloning was the Welltempered and it came out surprisingly well considering the effort involved. If i ever do it again it will most likely be a Schroeder.

Analog-tnk ya for pic;
where I can find some drawings for both arms -cantus and WTA?
I'm curious about WTA long time ago,but I canot find any usefull drawings.
 
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