My update....
Hi,
I am in the process of processing my wood wand. It will be treated using danish oil to avoid standing waves and will also help to fill up the cavities. I will be coating the arm finally with a fine layer of PU or Teflon on the outside to protect it from UV, moisture, heat, scratch etc...
@Frank / J D : Any suggestions to improve on this ?
I will be getting the head shell section only by Monday.
So, the wait is still on.
Best regards,
Bins.
Hi,
I am in the process of processing my wood wand. It will be treated using danish oil to avoid standing waves and will also help to fill up the cavities. I will be coating the arm finally with a fine layer of PU or Teflon on the outside to protect it from UV, moisture, heat, scratch etc...
@Frank / J D : Any suggestions to improve on this ?
I will be getting the head shell section only by Monday.
So, the wait is still on.Best regards,
Bins.
well, if that was the case then one would want to use extremely damped and non-resonant materials for the arm. Not wood, not metal.
I'd say you don't want resonances, however there is a school of thought about tonearms & turntables that takes the position that there is a circuit made between the stylus, record, platter, bearing, plinth, arm, cartridge, stylus... etc...
Not to mention the other circuit that is frequently there between the sound in the air and the entire TT system...
I guess it depends on what you are trying to accomplish what you should use??
_-_-bear
I'd say you don't want resonances, however there is a school of thought about tonearms & turntables that takes the position that there is a circuit made between the stylus, record, platter, bearing, plinth, arm, cartridge, stylus... etc...
Not to mention the other circuit that is frequently there between the sound in the air and the entire TT system...
I guess it depends on what you are trying to accomplish what you should use??
_-_-bear
Metal is convenient because it is conductive and screens the wires, it's easy to work, and it rigidity pushes the resonances up to a high frequency. That's a good combination of qualities that's difficult to better. It's actually very easy to damp resonances in metal. A little surface damping (such as a single layer of insulating tape) does the trick very nicely.
...after-the-fact damping is all well and fine, but historically few if any commercial metal arms have this idea incorporated, eh?
as far as pushing resonances "up" in frequency, what does "up" in frequency exactly mean to you? ...not only that there is more than a single mode for potential resonances.
I'm not saying that arms are usually wildly resonant, but that different materials yield different sonics, and in my earlier post I suggested that a "dead" plastic coating rather loses the inherent qualities of going to the trouble of using wood for the wand in the first place. I guess if it is for aesthetics, that's a different matter...
the idea I was addressing goes beyond the resonance(s) in an arm wand, and to the transmitted energy both in the arm wand and in the entire system as a loop or loops.
Ymmv.
_-_-bear
as far as pushing resonances "up" in frequency, what does "up" in frequency exactly mean to you? ...not only that there is more than a single mode for potential resonances.
I'm not saying that arms are usually wildly resonant, but that different materials yield different sonics, and in my earlier post I suggested that a "dead" plastic coating rather loses the inherent qualities of going to the trouble of using wood for the wand in the first place. I guess if it is for aesthetics, that's a different matter...
the idea I was addressing goes beyond the resonance(s) in an arm wand, and to the transmitted energy both in the arm wand and in the entire system as a loop or loops.
Ymmv.
_-_-bear
IMHO the reason not to use a metal wand in a Schroeder design is that you have to attenuate the vibrations traveling in the wand, as the wand is not mechanically grounded. In arms with rigid bearings (ball, knife aso) you want to transport the vibrations to the grounded point (the bearing) and here metal is well suited. In the Schroeder the vibrations would travel to the counterweight and be reflected back from there, causing interference.
Just my 25c
Koldby
Just my 25c
Koldby
Hi guys,
Just to clear up a few things about the use of wood for armwands in MY arms.
No, they are not supposed to "sound" pleasant, colored or otherwise identifyable. Wood is not wood, as metal isn't metal. But it is possible to treat(impregnate, coat...) certain woods, so that they exhibit very high internal damping. Achieving the same with metal(wands) requires the application of CLD techniques or lossy fillings(see Bill Firebaughs arms).
Cosmetics play no role in the choice. It's the density(usually between 0,6 and 1,4) that allows to retain the wand's basic dimensions, yet offer a wide range in terms of the eff. mass of the arm.
The idea of increasing stiffness to raise the first(and all the other) resonance point by using carbon fiber or metals like magnesium, titanium, steel...) may make sense at first glance, but one needs to consider that the high frequency content as imbedded in the record groove is disproportionately high(and not much low frequency energy "dumped" into the arm), hence the EQ(usually RIAA) in the phonostage.
It is actually quite easy to excite most tonearms measurably and audibly.
It's a misconception to think that vibrations traveling down an armtube can all "exit" through a rigid bearing.
It's equally not true, that in my design the vibrations are reflected at (or by)the counterweight. The armwand plus counterweight interface is designed to act as a transmission line.
As a simple procedure to determine the "sound" of an arm I suggest putting it in equilibrum(stylus guard on the cart), then tap it(wand and bearing structure) at various points. Not "scientifically" accurate, but it'll give you a good idea....
All the best,
Frank Schröder
Just to clear up a few things about the use of wood for armwands in MY arms.
No, they are not supposed to "sound" pleasant, colored or otherwise identifyable. Wood is not wood, as metal isn't metal. But it is possible to treat(impregnate, coat...) certain woods, so that they exhibit very high internal damping. Achieving the same with metal(wands) requires the application of CLD techniques or lossy fillings(see Bill Firebaughs arms).
Cosmetics play no role in the choice. It's the density(usually between 0,6 and 1,4) that allows to retain the wand's basic dimensions, yet offer a wide range in terms of the eff. mass of the arm.
The idea of increasing stiffness to raise the first(and all the other) resonance point by using carbon fiber or metals like magnesium, titanium, steel...) may make sense at first glance, but one needs to consider that the high frequency content as imbedded in the record groove is disproportionately high(and not much low frequency energy "dumped" into the arm), hence the EQ(usually RIAA) in the phonostage.
It is actually quite easy to excite most tonearms measurably and audibly.
It's a misconception to think that vibrations traveling down an armtube can all "exit" through a rigid bearing.
It's equally not true, that in my design the vibrations are reflected at (or by)the counterweight. The armwand plus counterweight interface is designed to act as a transmission line.
As a simple procedure to determine the "sound" of an arm I suggest putting it in equilibrum(stylus guard on the cart), then tap it(wand and bearing structure) at various points. Not "scientifically" accurate, but it'll give you a good idea....
All the best,
Frank Schröder
Actually, that's not quite true - I had that misconception for a long while. Records are cut very nearly constant amplitude, but there's a shelf equaliser using the 318us and 75us time constants. So why do we need what we recognise as RIAA? Because we use velocity transducers. Magnetic cartridges have a response that rises at 6dB/octave, so the bulk of RIAA is actually correcting for the velocity response of the cartridge. Weird cartridges (strain gauge, capacitor, piezo) are amplitude transducers so they only need to implement the shelf equaliser - which they commonly do mechanically (and fairly badly).
Nevertheless, your point about deliberately placing damped resonances at a lower frequency is still valid (and interesting) - it's just that they'll only be attenuated by the amount of the shelf equaliser (318/75 = 12.5dB) - which is still a very useful amount.
Bear: "Up" to me means higher. The dimensions and shape determine the distribution of harmonics, once that's fixed, the density and stiffness of the material determine where the fundamental occurs. If there's any inherent damping, that will affect the higher harmonics. I'd like to try an arm made of foamed beryllium...
(Sadly, I have no more idea of how to make such a material than I have of transparent aluminium, but it might be more feasible.)
A highpass filter instituted via Olson's book is exactly what hanging a tonearm from a thread is. It's pretty simple, and was nicely worked out almost 7o years ago.
Hi EC8010,
I'm very much aware of the transfer characteristic of velocity vs. displacement/amplitude transducers. I own and use both types. Nevertheless, thank you for being more specific.
When measuring the lowest torsional mode on many tonearms, you'll find it to be between 300 and 500Hz. Normal modes(the fundamental) can be found from 1,3khz to 2,5kHz (up to 6kHz on the "stiffest" armwands I've measured). The magnitude of these peaks(normal modes always stronger than torsional modes) depends upon the material and the amount of damping(internal or external) off course. But, as you've pointed out, they do fall in the "critical" window between 500Hz and 2122Hz, aka 318µs and 75µs(particularly the much stronger normal modes).
Additionally it should be pointed out that it is unlikely that you'll see torsional modes being exited in a unipivot(or similar) tonearm. Only if the bearing plane is offset quite far from the center of the wand. All sorts of other s#*t going on though...
As always, the cartridge generator doesn't discriminate between the stylus(+cantilever and coil assembly) moving relative to the mounting platform, aka the tonearm, but also the turntable, - or vice versa.
Couple it rigidly, fine. But without proper means to damp the energy fed into the armwand by either the cartridge OR the turntable, you're prone to exiting whatever structural resonances there are. Unless there is some phase related cancellation, but that's another topic.
And the properties of the tonearm wand material are just one of so many other problems to deal with when designing an arm. Ahhh, the fun....
Easy reading:
RIAA equalization - Wikipedia, the free encyclopedia
Magnetic cartridge - Wikipedia, the free encyclopedia
More challenging:
Wapedia - Wiki: Normal mode
Wapedia - Wiki: Normal mode.
Good night,
Frank
I'm very much aware of the transfer characteristic of velocity vs. displacement/amplitude transducers. I own and use both types. Nevertheless, thank you for being more specific.
When measuring the lowest torsional mode on many tonearms, you'll find it to be between 300 and 500Hz. Normal modes(the fundamental) can be found from 1,3khz to 2,5kHz (up to 6kHz on the "stiffest" armwands I've measured). The magnitude of these peaks(normal modes always stronger than torsional modes) depends upon the material and the amount of damping(internal or external) off course. But, as you've pointed out, they do fall in the "critical" window between 500Hz and 2122Hz, aka 318µs and 75µs(particularly the much stronger normal modes).
Additionally it should be pointed out that it is unlikely that you'll see torsional modes being exited in a unipivot(or similar) tonearm. Only if the bearing plane is offset quite far from the center of the wand. All sorts of other s#*t going on though...
As always, the cartridge generator doesn't discriminate between the stylus(+cantilever and coil assembly) moving relative to the mounting platform, aka the tonearm, but also the turntable, - or vice versa.
Couple it rigidly, fine. But without proper means to damp the energy fed into the armwand by either the cartridge OR the turntable, you're prone to exiting whatever structural resonances there are. Unless there is some phase related cancellation, but that's another topic.
And the properties of the tonearm wand material are just one of so many other problems to deal with when designing an arm. Ahhh, the fun....
Easy reading:
RIAA equalization - Wikipedia, the free encyclopedia
Magnetic cartridge - Wikipedia, the free encyclopedia
More challenging:
Wapedia - Wiki: Normal mode
Wapedia - Wiki: Normal mode.
Good night,
Frank
Yes, it is. Frequency is entirely determined by mass and spring constant of the string/magnet system, as well as grounding of the vibrations from the string. First order is easy. WRT to frequency of system osciallation.
Not any thinking at all on my part. Just some reading.
Hi again,
Not exactly the regiment I used for my tests, and their armwands are not treated the same way, BUT, interesting nonetheless:
turntables.lt - research
A very good arm, btw....
Cheerio,
Frank
Not exactly the regiment I used for my tests, and their armwands are not treated the same way, BUT, interesting nonetheless:
turntables.lt - research
A very good arm, btw....
Cheerio,
Frank
That link actually makes me wonder if some of the thoughts I had regarding vibrations, was not that far from the truth:
Reflections from the counterweight has to be dealt with, espeacially if there isn´t a ridig point along the arm tube. And yes a way to do that is to make the arm tube a lossy transmission line.
As far as I can see the rigid bearing CAN (not nessesary does) terminate to a certain degree the vibrations so you can transform the vibrations to heat outside the wand.
Please enlighten me if I am totally wrong here.
Koldby
Reflections from the counterweight has to be dealt with, espeacially if there isn´t a ridig point along the arm tube. And yes a way to do that is to make the arm tube a lossy transmission line.
As far as I can see the rigid bearing CAN (not nessesary does) terminate to a certain degree the vibrations so you can transform the vibrations to heat outside the wand.
Please enlighten me if I am totally wrong here.
Koldby
Maybe I was being too non-specific?
What frequency High Pass are you either calculating or measuring, and for what?
What is highpassing what from where, through what to where?
The arm looks to me like it is capable of response almost to DC...
So I am unclear what your "highpass" reference refers to.
Are you talking about the combined response of a cartridge and arm such that it is "tuned' above ~10Hz. typically - to avoid LF warp artifacts? Or something else?
I thought the subject was transmitted/reflected (resonances) in the audible 'audio' range??
...probably just me being slow and confused?
_-_-bear