|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
66.210.239.98
I am modifying an Empire 298 and I was going to widen the plinth to accommodate an arm board so I can mount tone arms of various lengths. Is this the sole purpose of an arm board or are there other reasons? Can someone post a picture of a TT with out an arm board so I can see what is underneath?
Thanx.
"To Do Is To Be" Socrates
"To Be Is To Do" Plato
"Do Be Do Be Do" Sinatra
Follow Ups:
Q'est que c'est?
Later Gator,
Dave
They are solid cast bronze and each one weighs 25lbs without arm and sits on 3 brass spikes. One can change cartridges, adjust VTA and VTF and even yank on each arm and the pods are going nowhere :^)
all have to resonate at the same frequency.
I have seen this design many times and it seems a better way to go for tonearm isolation from any motor or platter bearing noise.
If the platter is vibrating and the arm pod is rock solid, then we have movement of the LP groove in relation to the stylus tip, and that is not a good thing. So, best to use an outboard pod with a well-secured, well isolated, and mechanially damped turntable.
nt
"To Do Is To Be" Socrates
"To Be Is To Do" Plato
"Do Be Do Be Do" Sinatra
Removable armboards make it easier to mount and/or remove tonearms on the turntable. And while armboards may not completely isolate the tonearm, they might provide it with a certain amount of isolation from vibrations of all kinds.
disrupting the I.V. in his arm.
...regards...tr
nt
nt
"To Do Is To Be" Socrates
"To Be Is To Do" Plato
"Do Be Do Be Do" Sinatra
I am no one to challenge another on the vinyl issue except when it comes to building phono preamps. But as Musikmike said that it was for isolating the arm/cartridge from the table. I can't see how when it is attached directly to the table with screws. I also was told from others it is best to use a different material that what the plinth is made from because all can resonate differently. Then I was told that both the table and arm should resonate at the same frequency. So now I am at a total meltdown from all the theories.
To me, the armboard appears to be nothing more than a place to mount tonearms and if they are changed all that is affected or damaged is the armboard and not the entire plinth. I have seen arms mounted directly to the plinth but I was also told that a good plinth design takes damping into consideration where the arm(s) are going to be mounted.
So, now with all that, who is correct?
Your summation is correct. To allow drilling of a mounting hole of the proper size and location on a drill press.
Just look at it from a manufacturers perspective.
> > So, now with all that, who is correct? < <
Certainly not Mike, unless he was referencing some turntable that I'm not aware of.
tb1
motor and bearing.
For people enjoying "mods" the sound of the cartridge/arm will change with different substances. Wood vs. a polymer, for instance...different woods...different polymers.
Everything impacts on the sound, changing it slightly. For instance, the JMW arm mounted on the arm board made of the same material as the plinth will sound different than one mounted on a wood arm board with a polymer chassis.
In my case, a wood arm board made similar yet veery different than VPI'S armboard. A bit more warmth, for instance. Not earth-shaking difference, yet not too subtle.
******************************
Music. Window or mirror?
the arm-board cannot "separate" itself from vibrations caused by the motor or bearing unless it has some isolation type properties, such as a complaint suspension of some sort. However, any form of compliant isolation would allowed the arm to move independently from the bearing/platter ... which would cause all types of sonic problems.
No, an arm board is a relatively simple device meant for mounting the arm. Type or material and esp. lightness/rigidness of the material is key to it's sound quality.
Hopefully, all vibration control is done before it hits the arm, or ...
tb1
Thanks for the clarification. I make great mud pies, though.
Mmmmm. Mudpies....
******************************
Music. Window or mirror?
It is true that the armboard is never completely isolated from the rest of the turntable but it does not need "compliant suspension" in order to provide a certain amount of protection from vibration(s). A seperate armboard mounted onto (or next to) the main body of a turntable should provide a disruption in the flow of vibrations. And I think that choice of armboard material matters too (For example: a rigidly mounted armboard made of lead or graphite may absorb or neutralize more vibration than a rigidly mounted armboard made of glass or steel).
Edits: 03/13/12
> > A seperate armboard mounted onto (or next to) the main body of a turntable should provide a disruption in the flow of vibrations. < <
Take a stethoscope (I've done this a xhundred times) to a turntable in which you can hear either bearing or motor noise (or most likely, both). You will hear that noise reproduced in identical fashion, either placing the steth at the arm-board or at the chassis it's mounted too.
Since this form of noise (bearing/motor) is consistent when revolution/playing, it can NEVER-EVER be disrupted (it must be eliminated at the source, the motor and/or bearing). It will, in fact, remain a constant form of noise throughout the 'table, in which it will certainly damage musical retrieval.
As I stated, in NO WAY SHAPE OR FORM should an armboard be responsible for isolating vibration from internal mechanical devices.
What an armboard should do ... is QUICKLY deal (no ringing) with the mechanical energy that the stylus imparts into the arm. This "energy" needs to be dissipated, not isolated, in very quick fashion, or it too will effect musical delivery.
tb1
Whatever the origin of the noise you are hearing in your stethoscope, it is a sign that the material has been set into vibration by the noisy motor or tt bearing. The energy required to initiate the vibration will dissipate itself as heat in the material(s) of which the plinth and armboard are made. The further away you get from the source of the noise or energy, the less energy/noise there is. Also, when the vibrational energy reaches the interface of two dissimilar materials, some of it will be reflected back from the boundary, and some will be transmitted. If the armboard is made of alu and the plinth is made of wood, some of the energy from the noisy bearing or motor will never get to the armboard. This applies to endogenous sources of vibration. If we are talking about mechanical feedback (e.g., footfalls, etc), then the tt as a whole, including the armboard, might be affected in concert with each other.
The noise that emanates from either the motor and/or bearing will remain a CONSTANT. Therefore the armboard cannot "dissipate" a CONSTANTLY receiving noise, which can only be stopped when the 'table is switched off.
In this case, the armboard will act as a conduit, passing all noise, near it's entirety, towards the stylus.
This is easily demonstrable using a steth.
tb1
Yes, the noise you hear with your stethoscope at the armboard will remain a constant. My point was that it is induced in the armboard by a fraction of the energy that was put into the plinth from the bearing and motor. Most of the energy was dissipated as heat or reflected back into the plinth at the armboard/plinth interface, on its way to the armboard. However, that fraction can vary depending upon the material composition of both the armboard and the plinth. That was my point.
There is a whole school of thought that says the bearing and the arm mounting should be as firmly coupled as possible, with therefore no discrete armboard per se but a continuous structure between the two. My Kenwood L07D is built that way. It is supremely "quiet", which I think indicates that the arm and platter are in near perfect synch when it comes to vibrations. Plus of course the rest of the heavy CLD plinth is there to sink vibrations as much as possible.
> > Most of the energy was dissipated as heat or reflected back into the plinth at the armboard/plinth interface, on its way to the armboard. However, that fraction can vary depending upon the material composition of both the armboard and the plinth. < <
(assuming that the armboard is directly coupled to the plinth, and that no compliant material is used)
Although material composition can and does effect transmission, since motor noise remains a constant, no material I've heard has changed or dissipate it to nearly the degree in which I considered it "isolated" or "dissipated". Even the amplitude remains relatively consistent, in other words, if you put the steth near the motor, then away at the armboard, you're basically going to hear identical motor noise.
I've heard this behavior - consistently - with a variety of 'tables ... many using different materials. In fact, the hardest lightest materials types (which I use and think sounds best for any armboard) tend to transmit noise without any hesitation. Even 'tables that use outboard motor pods (claiming motor noise isolation), if the motor is noisy, that noise will STILL travel and be heard within the turntable.
And yes, you can hear amplitude differences, frequency changes, resonance effects, dissipation, isolation, and a host of "noise" issues ... using a good steth.
Without one, my table wouldn't be nearly as refined.
tb1
Your experiences are inconsistent with wave mechanics as we understand them to operate. You should probably get them written up in Physics Journal. Really, I think you are just splitting hairs for no purpose whatsoever. Nobody is claiming an armboard will fix a noisy motor or bearing, or that a stethoscope isn't a useful tool. But you can't possibly believe that literally, absolutely zero vibrational energy from the motor or bearing is absorbed or reflected on its way to the tonearm mount. That's just not physically possible.
> > Your experiences are inconsistent with wave mechanics as we understand them to operate. < <
Not at all.
> > You should probably get them written up in Physics Journal. < <
And they say "I'm" condescending?
> > But you can't possibly believe that literally, absolutely zero vibrational energy from the motor or bearing is absorbed or reflected on its way to the tonearm mount. That's just not physically possible. < <
Didn't say that, I'm stating that an armboard, when directly coupled to the plinth, will not (and should not) "isolate" a CONSTANT source of noise to nearly the degree you, and others here, are suggesting.
In other words, your claim that "vibrational energy from the motor or bearing is absorbed or reflected on its way to the tonearm mount" is true, but it is so minimal in practice, as to make this point ... moot.
tb1
Sorry, I wasn't trying to be condescending, just making a little joke.
To be clear, I did not say, nor do I believe, that an armboard can provide sufficient isolation from an excessively noisy motor or bearing. In fact, I explicitly said just the opposite: that an armboard should never be considered a "band-aid" for a noisy motor or bearing, which I think is the point you are trying to make. I can't speak for what others here believe.
But the mechanics of the materials used for armboards are not exactly irrelevant either. The kind of material used for an armboard (or plinth) will determine the degree to which vibrational energy is absorbed or reflected, and can also change the frequency of vibration due to the impedance difference between different types of materials. That is in part why a stainless steel armboard or plinth will have a different sound than one constructed of maple or carbon fiber, and acrylic will sound different still. This is true even in cases where the motor and bearing are extremely quiet.
we are actually arguing (i prefer debating) the same argument.
> > That is in part why a stainless steel armboard or plinth will have a different sound than one constructed of maple or carbon fiber, and acrylic will sound different still. This is true even in cases where the motor and bearing are extremely quiet. < <
Yes, it will, but IMO this has more to do with the armboard ability to quickly dissipate tonearm induced energy, rather than dissipate motor or bearing noise.
In my travels, I've found that bearing noise is nearly impossible to isolate from the arm/platter. Motor noise can be isolated to degrees, depending on the amount of vibration and the quality of it's mount, and a well tuned suspension will very much isolate a large degree of motor noise. There are ways to do it, but simply placing a noisy motor in an outside mount/pod (which many current tables do) does near nothing, the noise will still migrate towards the stylus.
That said, and we both agree, it's best to eliminate (or minimize) bearing and motor noise at the source. One of the very reasons my turntable sounds as good as it does, is based on the above principles.
It took me years to refine.
tb1
Lew is absolutely right on the physics. Some of the vibrational energy will be reflected backward at the material interface, and some will be dissipated (released as heat) on its way through the armboard. Yes, you'll still be able to hear bearing and motor noise with a stethoscope on the armboard, but there is no way it will be at the same amplitude as at the source. These materials are not perfect sound conductors.
Of course armboard or plinth material should not be thought of as a "band-aid" for a noisy motor or bearing either. It's obviously better to have a quiet motor and bearing to begin with, which I imagine is the point Tbone is trying to make.
... I'd be willing to bet that a well-designed armboard (even a solidly mounted one) dissipates or at least breaks up stored vibrational energy TO SOME DEGREE, before it reaches the tonearm. It's too bad you can't measure amplitude differences with your steth.
> > ... I'd be willing to bet that a well-designed armboard (even a solidly mounted one) dissipates or at least breaks up stored vibrational energy TO SOME DEGREE, before it reaches the tonearm. < <
That "SOME DEGREE" of dissipation is meaningless if a CONSTANT source (which is impossible to break-up) of noise is always being channeled towards the stylus.
> > It's too bad you can't measure amplitude differences with your steth. < <
No need to measure, I can hear amplitude.
tb1
When you have two unlike materials coupled to one another, some of the energy from the vibrations (waves) will be transmitted to the new material, others will be reflected backward. The frequency of the vibration will also change as it moves from one material to another. That's why different armboard materials will have different sonic characteristics.
Edits: 03/14/12
Some arms need to be mounted in different spots in relation to the platter.
A separate armboard allows replacement of arm board with different arm location. without rebuilding a whole new plinth
Post a Followup:
FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
This post is made possible by the generous support of people like you and our sponsors: