|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
76.171.170.23
In Reply to: Re: disagree, with reservations, complications, & One Overcooked Analogy / long posted by user510 on May 5, 2007 at 14:41:06:
Guess I should have emphasized the way around that is obviously used in some tables, like the Teres armboard shown..As mentioned .."Ultra-overkill massive construction, careful attention to mass-balancing, and then patient testing may be how these all come to terms with ..."
In some cases, though, yes, outboard arm-mounts lack physical integrity, as materials, or based on construction / design.
But beyond the 'lever' issue, presented by that situation, my other point is that :
If the armboard represents any lesser a massed physical presence than the mass of the plinth, it becomes a target for motor resonance proceeding from the greater resisting area (mainland) to the lesser resisting area (peninsula).
Until the armboard region of the system represents at least as imposing a resonance-conducting venue as the plinth, it's a path of least resistance. Isn't it ?
In the case of your Teres armboard, the layered & ultra-rigid approach probably represents an imposing roadblock to resonance. Not so the simpler-construction, simpler-material, outboard armboards we see sometimes. (Besides, w/ DC servo beltdrive, there's way less to fear by way of rumble than with an Idler-coupled design..)
J.
Follow Ups:
I guess the way to proceed would be to arrange a test to measure resonance flow into various armboard schemes, eliminating all the intuitive/instinctive/subjective takes.In the Auditorium plinth pictured I don't think that I see any lack of structural integrity in that particular overhanging armboard. It will be rigid providing the armboard material is of adequate tensile strength. Resonant flow from motor, into plinth, into armboard? Just how much vibration does that Garrard motor emit?
My TD124 motor seems well mannered and quiet, emitting only a soft whir that can just be heard when you put your ear next to it. If I place the probe end of a mechanics stethoscope against the cast chassis in the vicinity of the running motor, I can faintly hear the whir of the motor, just barely. Place the stethoscope onto the plinth next to the cast chassis and nothing is heard.
Another stethoscope anecdote, Teres style.
When I had just mounted the Shelter 501 type 2* cartridge to the 'Expressimo RB250' I noticed some very distinct "needle talk" while playing a record with the amplifier muted. I found this to be interesting so I used a Stethoscope to trace the path of these resonances. With the probe placed to the side of the all acrylic Teres armboard I could distinctly hear the music being tracked through the earpieces. I then followed the resonant path of this "needle talk" with the stethoscope. It traveled out of the RB tonearm into the armboard and down into the acrylic base of the Teres. The further away from the tonearm, the fainter the "music" heard through the ear-piece. This confirmed to me, and other Teres owners, that the cantilever armboard of the Teres was indeed transferring resonances away from the tonearm and into the massive base where it would likely dissipate and die. Possibly the resonance would also flow through the cone footer nearest the armboard mounting joint and into the isolation base. It then struck me as being an efficient armboard in the area of resonance management.Of course there is no similarity of this type between the armboard on the Garrard plinth shown and that of the Teres, which was indeed carefully considered.
-Steve
* The Shelter has a very -stiff- low compliance cantilever and exhibits obvious needle talk.
user510's system
We are talking about reducing resonance by a factor of as much as 4 times. Take a strain gauge and place it against the body of an idler turntable. This will read the mechanical resonance or the physical displacement of the material created by the frequency resonance of the motor and the accoustic feedback from the environment.When you mount a tonearm directly to the plywood plinth there is 4 times more resonant energy communicated to the tonearm than with a decoupled arm board. A directly mounted tonearm board and a rigidly connected cantelever armboard are basically interchangeable. However the cantelevered armboard exhibits less "strain" IF you select the proper materials.
Now you can build a variety of clever tonearm boards. For example, you could build armboards from MDF, Rock Maple, Walnut, Ebony, or Carbon Graphite and you will hear a difference in the sound with each variety of tonearm board. Each of these various materials is actually decoupling the plinth from the tonearm. The materials work differently regarding the frequency resonance and the physical resonance which I would prefer to call "strain."
Mixing material can also help diminish resonance and "strain". I often use acrylic and another material to tune out the resonance.
It is not the mass of the armboard that matters. It is the careful sellection of the material to accomplish the resonance control and strain resistance that matters most in terms of the sound quality of the turntable.
tubesforever's description of the virtues of different materials and cantilevering seem right on the money to me. The armboard depicted here (which is my turntable) is a single piece of cast copper, very heavy. It is secured to the base - which is constructed of all kinds of different woods in various pieces with various voids - via a single heavy allen bolt from the bottom right up through to the armboard.This turntable sounds AMAZING. My previous plinth was no slouch, was 24" wide, and had the 12" arm directly mounted on the armboard. The LignoLab plinth blows it away in every way - more controlled bass, more air, more layering, more PRAT, and just wonderful musical flow pouring out of the speakers.
The plinth was designed for 12" arms, by the way (check the toneimports.com page, or if you can read German, the auditorium-23.de page), so the cantilevered arm board was a conscious design choice. Knowing how these guys design equipment - via listening - I think that, as tubes suggests, they experimented by listening to multiple different materials and constructions until they found the combination that best dealt with resonance.
This post is made possible by the generous support of people like you and our sponsors: