Eminent Technology ET-2 Tonearm Owners
11-28-13: RichardkrebsThis seemingly innocuous statement requires careful examination as it continues the flawed thinking espoused earlier in this thread. If the goal were to keep the cartridge still, then one would never reach the end of the record. The record groove is not a straight line; it is a spiral with a decreasing radius that requires the cartridge to move to the center of the record as it plays. Furthermore if the record is not perfectly centered, even by 0.01mm, then the cartridge is required to move in and out from the center approximately 660 times for a standard 33rpm record at Industry Standard or 0dB (20 minutes of music). This means that the arm will reverse direction 1320 times within approximately 20 minutes of music. (Is anyone here still of the view that adding lead mass to an ET2 that is reversing direction 1320 times per side of a record is a good idea?) There are two goals which are in conflict with each other - 1. To ensure that the cartridge maintains a constant relationship with the groove the cartridge will be constantly moving to align itself with the groove. 2. To ensure that the recovery of as much information as possible which would suggest keeping the cartridge as still as possible. On the one hand we want the cartridge to maintain a position that at all times it aligns the cantilever pivot point to the center of the groove. In order to achieve this, the cartridge must be able to move laterally freely and unimpeded whilst playing. Any addition of mass or "apparent" mass by adding lead, stiffening the counterweight spring or adding fluid damping will increase the inertia and will reduce the ability of the cartridge to maintain the correct alignment with the groove instantaneously. The increased inertia will introduce lag to the response time of the cartridge tracing the groove and increase cantilever flex and distortion. Some may not hear this effect, but it is there and is readily apparent in a resolving system with good fundamental timing. If you want to hear the concept proposed by Richardkrebs that the cartridge should remain still here is a link to the Transcriptors Transcriber. This turntable has a fixed arm which tracks linearly by holding the cartridge still while moving the platter underneath. http://www.youtube.com/watch?v=IQ_r0Vk9Ct8 Have a listen. This set up has more WOW (as in pitch variation) than a wind up gramophone on its last legs. This is the sound you will end up with if you add enough lead, fluid damping and/or remove the counterweight spring as has been suggested. As Frogman has confirmed with his experiments - when he decouples the spring and lowers the apparent mass, he gets a quicker and more tuneful bass response. Less weighty but better timing. The use of fluid damping may ameliorate a resonance issue with some particular arm/cartridge combinations, but it comes at the cost of compromising the ability of the cartridge to follow the groove by increasing the resistance to tangential movement - it slugs the sound. A better solution is to ensure that arm/cartridge resonances are minimised such that fluid damping is not required. I would also point out, since someone mentioned the Townsend Rock, I sold several of these when I was an importer/retailer in the 80’s. The use of fluid damping in this TT killed the sound so much, that cartridge differences were nullified. For example, one customer could not hear the difference between a Madrigal Carnegie and a Koetsu Red. I also ran an ET2 on the Townsend Rock for a while, with a Shure V15Vmr and can assure you the sound was much improved in speed, timing, articulation and transparency without fluid damping. Having dealt with Max Townshend directly, I should point out that Max’s reference cartridge, at the time he designed the Rock and the fluid damping mechanism, was the London Decca Gold cartridge, a poorly constructed cartridge with no cantilever and notorious for it’s poor tracking ability. It was in this context that he came up with the trough design. |
Hi Dover, It would seem to me that the constant corrective motion of the arm to compensate for LP production imperfections, either lateral or vertical (warps), would involve some degree of "overshoot" and, thus, generate some stylus/groove misalignment due to inertia and that a properly implemented damping system would reduce this overshoot while having minimal impact on the initial transient response, ie using a minimal amount of the damping fluid such that the paddle only skims the fluid's surface (per Frogman). I would not argue that the use of damping is a sonic tradeoff in practice and would not be desirable in a world of perfect LPs and ultra-stable resonance-free cartridges, but perhaps it is a desirable solution in our real world of neither? Dave |
