Natural Sound
- Thread starter PeterA
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That is correct Stephane .. in fact if you have a narrow high backed chair you block reflections from wall behind and if upholstery is rounded you get very little reflections from chair.. your head block most of the direct sound impacting the chair back in any case ( yours is a bit too wide but you solve that to some extent with pillow)
I think the " high back issue" is a bit overated
Phil
This post is from another thread, so I moved it hear. Member Microstrip asked me to make two videos showing the RoadRunner tachometer reading on my turntable when I turn off the motor. One is without the stylus in the groove and one is with the stylus in the groove. The tachometer measures the speed of the platter once per revolution and it is read at the motor controller. The third video is of the platter free spinning to a complete stop.
It is interesting to note that the tachometer display shuts off around 28 RPM. This takes about 23 seconds with the stylus in the groove, 26 seconds without the stylus in the groove, and about 5 min 30 seconds with no thread attached to the platter. When the motor is shut off, the motor and flywheel keep spinning but have more friction and slow down pretty quickly, so with the loose thread attached to the platter, they slow the platter down faster than when it is free spinning.
Changing the thread tension does affect the sound, and if it is too loose, dropping the stylus into the groove will very slightly change the tachometer reading by 0.002 RPM or so. I have the tension set so that dropping the stylus into the groove does not change the speed of the platter, but no tighter. I can also adjust the torque. I increase the torque slightly when the thread is looser. I find that the best sound is when the motor seems to influence the platter the least while still maintaining correct and consistent speed. Too loose and the sound does become slightly less focused and articulate. If the tension is too tight, the sound becomes a bit hard. Bass note decays get shortened and sound less hollow and woody. Same with drums. Overall the sound loses some richness and some weight.
Video with the arm in the armrest:
Video with the stylus in the groove:
EDIT: And here is a video that I posted before of the platter free spinning with no thread attached. You can also see the tachometer reading. Note the video is very long showing the platter rotating until it comes to a complete stop. @hb22 was asking about how long the last rotation takes as a gauge for the the quality of the bearing. He can watch the last couple minutes of this video as the platter slows to a stop.
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So, three things: 1) The platter speed starts dropping significantly immediately once the power is off and 2) Stylus drag increases the rate of slow down by about 10% (3 seconds faster to 28 RPM than with the needle not engaged). 3) The string/motor also applies a lot of drag on the platter but this is likely pretty constant and once motor is active it is unlikely to be an issue.
I am surprised that the stylus has so much effect on your turntable given the mass of the platter. One would have thought that the mass inertia would find this drag insignificant but it rather suggests that the needle drag is a quite significant force. One would expect an even greater effect with a lower mass platter.
I guess for your specific design, what would be interesting would be to know how quickly or slowly the platter speed is adjusted to 33 RPM when there is a high drag situation in the music...it seems clear that a large modulation could significantly lower the speed (maybe by 0.5 to 1 RPM even) and then how quickly your platter can come back up to speed with the high mass and lowish torque (or is it rather a high torque motor?). How long does it take for your turntable to come up to speed from a stop? We could then deduce how long it takes to change speed by 0.5 or 1 RPM, as this might effect tonality of the sound coming after large groove modulations or highly dynamic material.
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If all of that were true, the tachometer reading would change while I was playing music, depending on the modulations. That is not the case. The platter slows down pretty quickly because the motor stops, and so the thread is contending with the mass of the platter on one end and the rapidly slowing motor and heavy flywheel on the other end. The motor causes drag on the platter when it is shut off. This is a condition that never occurs when playing music with the motor running.
Stylus drag is very real. In my case, the platter does not change speed if I lower the stylus when the motor is on. On my old SME turntable the platter slowed down so much that I had to set the speed while playing music. That is not the case with this turntable. I can affect this by changing the tension of the thread. Too loose and the platter will slow down when I lower the stylus. I could tighten the tension, and that would change the results on the videos because then the motor slowing down is even more coupled to the platter. Now there is slippage at the motor pulley. Stylus drag is likely one of the reasons that David’s new turntable has an even more massive platter, though I have not spoken with him about this directly.
I also put up a video showing the results with the timeline strobe on the wall on the opposite side of the room while playing music. I would welcome anyone sharing videos of their turntable doing any of this stuff. But basically I made the videos because microstrip asked for them.
EDIT: another interesting test would simply be to disconnect the thread connection to the motor and then spin the platter by hand up to 33.33 RPM and lower the stylist into a groove. Without the stylist, it takes half an hour for the platter to stop. It would surely be less with the stylist, but I don’t know how much less.
I do not really know what the rate of platter deceleration means when the platter is connected to a motor that is not spinning. This is never a condition when listening to music and I don’t know if it’s an indication of anything meaningful.
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Thanks, Peter.
Thanks Peter. In fact I am only interested in speed measurements without the string or thread - and It seems me we miss that data on slow down with tonearm down and no string.
BTW - apologies I do not remember any more - how is the speed measured by the tachometer?
Thanks Peter. In fact I am only interested in speed measurements without the string or thread - and It seems me we miss that data on slow down with tonearm down and no string.
BTW - apologies I do not remember any more - how is the speed measured by the tachometer?
From what I have seen, the tacho is far to slow to show you what is happening on the musically relevant time scale. For sure your super heavy platter will be less impacted from stylus drag than a lighter platter but it will also be resistant to speeding back up for the same reason. I don't think the issue can ever be fully solved with mass based on what I am seeing. I guess I am surprised that even with the high mass of your platter that needle drag is still having a rather large effect and it suggests to me that high mass might not be the best solution to the problem and that the opposite, high torque and low mass, might be at least as valid.
I know this issue with SME because a friend of mine had one and we put my Allnic Speednic on it and it was clear that it was not at the right speed when starting with the needle down; however, you could also see the speed subtly fluctuating throughout because of the needle drag. The Allnic is pretty sensitive this way, whereas my Yamaha GT-2000 was completely rock steady regardless of playing a record or not. The Yamaha is interesting because it has some mass in the platter (6KG to be exact...but with an 18KG optional platter) and has reasonable torque being a direct drive. The combination of a very smooth DD mechanism and some flywheel mass (it is also oversized with more weight at the outside) to tackle the problem multidimensionally.
The tachometer measures speed with a sensor on the base of the turntable and a small magnet placed on the platter, so once per revolution. It is the RoadRunner tachometer without speed correction.
I will see if I can add a video without thread of the platter slowing down.
You don't think the impact would be essentially the same as tonearm up or down with the string attached?
This makes sense. Perhaps this is one of the reasons David decided on a strobe readout on his new platter besides just the cool factor. Here is a video showing the tachometer while playing music and then the strobe dash of the Sutherland Timeline up close on the wall directly behind the platter and then far away, on the opposite wall. Note the length of the strobe dash increases the longer the distance from the device. Both the tachometer and the consistency of the dash show steady speed during playback. I also have a video of my friend's Technics SP10 Mk3 in my system with the Timeline. The results were also rock steady. It would be interesting if other people would be willing to share such results.
Video with TimeLine:
That depends on whether or not the motor is on. The difference without motor is 2 seconds (24 vs 26) before the readout ends. Depending on string tension, when the motor is on, there is no measurable or audible difference in speed when lowering the stylus.
High mass thread drive is one approach and smooth motor DD is another approach. In both cases, accurate and consistent speed is maintained if well implemented. Audible differences may be the result of the noise from the motor and then other factors in the turntable design.
I am not able to quantity the energy dissipated in the motor and thread due to friction and self braking - so these numbers are useless for me.
The Sutherland Timeline is a really useful gadget. The only machines I've ever seen that were really speed stable are the Technics. You can play an LP over and over on the SL1200G or SP10 and the Timeline will have the dot in the same place all day long. Its more speed stable than my LP mastering lathe was.
I agree. It’s a great device. But I’ve never gotten a dot read out even on my friends SP 10 mk3. The light is on for a period of time as the platter moves, creating a line and the further the mark is from the spindle, the longer the line. So I refer to it as a dash and it can be a short dash if the turntable is next to a wall and a very long dash if you are measuring it on the other side of the room. For that reason, I usually make two marks on a piece of paper and hold the paper up on the wall to see if the dash drifts out of the space between the two marks or not. It’s a very revealing test and I have posted a bunch of videos showing the results from different turntables, but no one else wants to add videos of other tables to the database. I took the device to a friend’s VPI turntable and the results were so bad so bad that he immediately removed it from the spindle and told me the weight of the device affected the speed of the turntable. With such devices comes risk.
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The platter is probably quartz synchronized. Probably some other direct drive turntables show similar behaviour.
The problem with such gadgets is the same as simple audio measurements such as frequency response - some people will naively associate its information with sound quality.
BTW, did you compare the SL1200G with the new SL1000R? Surely, the sound, not the stability of the mark!
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