05-14-13: Richardkrebs
.. if my heavy ET has problems with cantilever flex, bass boost, phase shift and so on; so do the other heavy arms. Rockport, Walker, Kuzma. This because the horizontal effective mass is solely determined by the total weight that is moved sideways at the frequency of interest, since all of these designs are virtually frictionless. Thats correct and thats why the lower mass ET2 has a big advantage over the heavy arms when kept in its standard format. The level of damping of course changes all this. This is not correct. The damping may ameliorate the amplitude of the resonant peak, and result in less bass boost, but the high mass still provides an inertia, a resistance that the cartridge has to work against to track the groove, particularly on eccentric records. It is this inertia that causes the cantilever to flex and increase distortion. |
Oh, it just dawn on me, could the "less smooth" of the Rockport bearing cause by the flex of tiny airhost? If it is, then the airhost actually provide considerable "damping"! |
Dover.
My calculation of weight delta was based on how much weight the air bearing has to carry. Not the horizontal effective mass. You voiced concern that I had taken it outside its load carrying capability. My calculation is correct since the bearing is supporting the weight of the counterweight, it is designed to take the heavier magnesium wand, the full counterweight complement and heavier cartridges.
Re heavy arms. I assume you are saying that ANY heavy arm, and this includes the Rockports, Walker and Kuzma have serious problems with distortion. Further, by implication, you are saying that the owners of these arms are deaf to these distortions.
We will have to agree to disagree on where we should target the horizontal Fr. In Bruce's paper on the oil trough he talks about the effect of Fr being apparent at 3x its frequency. Targeting say the 12 hz you mentioned would mean that it is causing phase and amplitude problems at 36 hz. This is not good. |
Bruce Thigpen:
"The ET-2 with the
damping trough will exhibit almost perfect low frequency phase response."
You don't like the ET-2 set up to have near perfect low frequency phase response?
Thats fine, its a free world, but it means you accept/enjoy DISTORTION.
BTW, as you haven't run an ET2 for heading towards two decades, isn't your credibility suspect? |
05-15-13: Richardkrebs
Dover.
My calculation of weight delta was based on how much weight the air bearing has to carry. Not the horizontal effective mass. You voiced concern that I had taken it outside its load carrying capability. Optimum load capacity. You have added 30g of lead to the mass the bearing has to carry. This has 2 negative effects - it pushes to mass to the extreme and one would redesign the bearing if one were knowingly going to operate the arm at a higher mass level. Secondly the added mass will impact the shearing forces involved - the arm is not frictionless and the bearing is not absolutely rigid - these are some of the reasons why users are hearing different results with higher pressures. As a point on your calculations on FR I led slide the error in your calculations - the bearing has a resonance, the bearing tube has a resonance and the total resonance will be a sum of the resonances inherent in the arm. One really needs to measure the resonances to see whats going on , thats why Bruce does extensive testing. The maths you are using for FR calculations is not the complete story. 05-15-13: Richardkrebs
Re heavy arms. I assume you are saying that ANY heavy arm, and this includes the Rockports, Walker and Kuzma have serious problems with distortion. Further, by implication, you are saying that the owners of these arms are deaf to these distortions. I think you should use the word preferences, when making judgments on other folk, but certainly they may well be. Some folk like fat bottom ends others prefer speed and musical timing. For me music is about timing and nuance - I can certainly hear the slugging of the sound and loss of musical timing when adding too much horizontal effective mass to the ET2 as others in this thread have also found when they removed the decoupling from the I Beam. You may also like to read the comparison of the Kuzma to the Walker in the Absolute Sound mag December 2006 where the reviewer articulates the differences - the Kuzma being dark and solid vs the Walker having more of "the "gestalt" of a live concert, more lifelike presence of instruments, their colors, their dynamics, and the space they play in" of the Walker "fuller, more realistic in tonal color, bigger, bloomier, wider, deeper, more layered in soundstaging, and a bit more authoritative dynamically". 05-15-13: Richardkrebs
Targeting say the 12 hz you mentioned would mean that it is causing phase and amplitude problems at 36 hz. This is not good. Depends how big the amplitude problems are. Some of the heavy arms you have mentioned have additional measured resonances at 100hz & 200hz. In your case you you have reduced the theoretical resonance from 8.08hz to 5.17hz. so yes you have a small residual at 24hz in a standard unmodified arm - but this is outweighed by the amplitude of the resonance being much higher when you added 62g of horizontal effective mass. Furthermore that small secondary resonant peak at 24hz with the standard arm can be dialled down with careful tuning of the counterweight spring. I very much doubt whether many systems are truly flat to 20hz in a real home environment. In your case you have shifted the secondary resonance from 24hz to 15hz, but have increased the amplitude of the 15hz resonance substantially - probably 6-12db higher in amplitude compared to the smaller resonance at 24hz with the arm as standard. |
Chaps...I'm not an ET user nor an Aro user, but I do use both a 12" unipivot + an air bearing linear tracker, so if I could be permitted to offer a humble opinion, hopefully useful to the topic ;)....
In this game, sometimes we tend to think about what we SHOULD hear, rather than what we DO hear...
In principle, the tolerance gap of a air bearing leads us to think that an air bearing will be therefore compromised sonically - ie. because it will never have solid bearing contact. However I hear no lack of 'leading edges' with a linear tracker. So what is going on?
On the topic of 'leading edges', I think a 'square wave' is an appropriate analogy. The leading edge of square wave (rise time/slope, overshoot control...) is determined primarily by the HF component of the signal/tone. In the same way, the perceived 'leading edges' of sound is poor, if the HF harmonic component of music signal is compromised.
A unipivot typically has excellent HFs, owing to absence of 'bearing rattle'. I also hear excellent HF tone & extension with an air bearing tonearm. Go figure...
The explanation I think is that, at groove modulation frequencies, it is not the rigidity of the bearing that is key, but rather the inertia of the tonearm, as 'seen' by the stylus, that is key. From this perspective, a pivoted tonearm rotates freely, ie. has very low (rotational) friction.... and a linear tracker also has low (linear) friction. Both are similar... but from the viewpoint of the stylus in groove, 'inertia' or Effective Mass (at groove modulation frequencies) must be high - adequately high to reproduce LF signals without resonance/loss of power delivery.
Contributes to the discussion I hope.
(Apologies if this is old ground, I haven't managed to read all 700 pgs ;) ) |
05-15-13: John47
Bruce Thigpen:
"The ET-2 with the
damping trough will exhibit almost perfect low frequency phase response."
You don't like the ET-2 set up to have near perfect low frequency phase response?
Thats fine, its a free world, but it means you accept/enjoy DISTORTION. No I dont believe Bruce Thigpen does enjoy distortion. On the contrary Bruce Thigpen has cleverly designed an arm that tracks superbly and can be fine tuned via the adjustable VTA, Azimuth, and decoupled counterweight. Bruce Thigpen does not add 60g+ of horizontal effective mass and remove the decoupling of the I Beam. The perfect phase response that Bruce obtains with the damping is achieved by operating the arm within its design parameters. Keeping the horizontal mass as low as possible is part of the design. Adding 30g of lead to the arm and removing the counterweight decoupling will indeed create significant distortion, including an inflated bottom end and phase anomalies, but that is not how Bruce runs the arm. |
Pseudo science from Dover:
"removed their fluid damping and replaced it with electromagnetic damping which has the benefit of not inhibiting movement until the movement happens."
Pseudo science: its identical with fluid damping - there is no damping unless there is movement (same with the dampers, so called shock absorbers, on your car. Drive slowly over a speed hump and the whole vehicle is raised, ie there is no movement, and no damping). |
Dover.
Secondary resonance? You mentioned this twice in your post 05-15-13. The frequency numbers you used were 3x Fr for this. The 3x Fr figure is the multiplier used by BT where he considers the amplitiude and phase anomolies above Fr have fallen to a level that is benign. Think a normal distribution curve. In our industry, we use a 6x Fr multiplier since we operate in a much more conservative environment.
There is no 6-12db increase in amplitude at 3x Fr or even Fr. The arm is damped with an oil trough. See the graph and read the technical notes from BT, posted by Chris on 05-14-13. Note also, Bruce set up the arm with a "deliberately high Q" and low compliance cartridge.
You let slide and error in my calcs because other parts of the arm have their own resonance. Sorry No. See BT's own formula for calculating horizontal Fr. It does not take into account these other structural resonances.
That said these other resonances can have an effect on the shape of the resonance curve but the fundamental determinent is the horizontal mass.
There are 2 possibly 3 structures in a standard ET who's own resonance is low enough to have this impact. The decoupled counterweight, which is deliberate. The relatively compliant gooseneck and the o'rings in the manifold. The o'rings are a maybe since they typically allow movement towards and away from the record, not laterallly.
(Anyone interested in observing how compliant the goose neck is could try this test. Do it at your own risk!
Lift the arm with the lifter and put the stylus guard on. Travel the arm fully inwards and then lightly push the spindle where the wiring plug is against the bearing sleeve. Now lightly pull the cartridge end of the wand towards the outer edge of the record. You can clearly see deflection of the wand. The goose neck is flexing. If you are able to let it go quickly, you will see it momentarially oscillate. If chris did this with the aluminium goose neck he would need to literally bend the wand to get any deflection.)
All three of these structures have been altered (stiffened) or eliminated in my arm since in my opinion they all compromise "leading edge" and have other negative consequences.
The other compponents of the standard arm have, IMO less impact on leading edge performance with the airbearing having none at all. It's resonance is in the 100s of Khz, way outside the audio spectrum. Spock15's experience with his air bearing arm seems to support my view. However it is the cacophony of all of the individual resonances amongst many other factors that makes up the "sound" of the arm. On that front we agree.
|
Spock15
I currently own an ET2, Naim Aro & Hadcock unipivot and have just sold off my Bluenote Borromeo ( Titanium tubed unipivot ).
I hear a crisper articulation of the leading edge with all three unipivots. It's not large. The Aro is better in this regard than the Bluenote & Hadcock. I do agree with you that effective mass, both horizontal and vertical contribute to the "squarewave".
With regard to the high horizontal mass the standard ET2 has a very high horizontal effective mass as standard ( 25g plus the weight of the cartridge ) compared to a pivoted arm.
Richardkrebs has advocated adding 60+g of horizontal mass by adding lead to the bearing spindle and removing the decoupling mechanism of the counterweight. With the ET2 the decoupling of the counterweight is part of the strategy to keep horizontal mass not too high.
Bruce Thigpen has measured, not theorised, actually measured on the ET2 a 6-12db lift in bass response when increasing the horizontal effective mass by 30g ( removing the decoupling ). From what I have actually heard, in a real system, since I have owned an ET2 from the mid 80's, increasing the mass slugs the sound and robs the music of musical pace and timing. Most of the contributors on this thread ( Frogman, Slaw, Ct0517 & myself )have found big improvements when carefully tuning the decoupled counterweight, as predicted by Bruce's testing.
By the way I still own a Dynavector 501 which has a very high horizontal effective mass, and whilst the bass is quite punchy, the musical timing, soundstaging, and resolution is well down on both my Naim Aro and Fidelity Research FR64S ( yes I own 2 of these as well ).
|
One is usually coloured/informed by past experience. Coincidentally, I have a couple of FR64S's myself & you reminded me of the Hadcock GH228 that I have gathering dust.
Another recent unipivot, an Apparition 12" superseded the above. A very fine performer, to the extent that I have had little compunction to A/B with the older arms. A very top shelf pivoted tonearm in my humble experience.
Nothing is perfect in this game (audio & life in general ;)) but with my linear tracker (a Trans Fi terminator) I find the combined qualities of genuine low distortion, wide bandwidth, dynamic stability...are overall most persuasive. Are these attributes typical of linear trackers? I can't be sure at this point.
Regarding Effective Mass...with record groove modulations cut at 45deg, as we know, I think it's not entirely useful I think to dwell on Effective Mass in terms of horiz & vert properties.
Cheers. |
What an extraordinary hobby this is. RK and I share this wonderful aluminum ET2 Gooseneck that he made - I really like it.
At this current (snapshot) in time however;
RK’s tonearm objective is adding more control and damping to his Krebs Arm.
I meanwhile am trying to figure out how to go wireless with my ET 2.5.
Think Free Willy !
Maybe my IT background biases are showing. With that the damping fluid should be coming early next week with the adhesive tape. Look forward to trying it again after all these years.
Welcome to the thread Spock15. Listing what your air bearing and pivot arms are would be nice to those of us reading for reference.
Thekong has provided some excellent perspective between the Rockport and ET2.
Hi TheKong – were you able to find the lead to make the counterweights at those tire shops ?
Look forward to Rugyboogie providing perspective with the Kuzma Airline and ET2 soon – Congrats on getting an ET2 - RB.
Now we need a Swedish fellow or gal :^) to come on here to help provide perspective on the Air Tangent and ET2. Maybe I will look for one (Air Tangent) to close this loop. However no remote control version for me.
As I type this Ottawa to Toronto area of Ontario experienced a 4.8 earthquake – a little shakey. |
As I type this Ottawa to Toronto area of Ontario experienced a 4.8 earthquake – a little shakey. Sort of like my JMW 12 unipivot. :^) |
Further...
Mono signals of course, do result in horiz groove modulations. |
With regard to the high horizontal mass the standard ET2 has a very high horizontal effective mass as standard ( 25g plus the weight of the cartridge ) compared to a pivoted arm. However the FR64 of course, has Eff Mass of 30-35gms (or more). |
Richardkrebs has advocated adding 60+g of horizontal mass by adding lead to the bearing spindle and removing the decoupling mechanism of the counterweight. With the ET2 the decoupling of the counterweight is part of the strategy to keep horizontal mass not too high. I'm not sure if there is any (groove tracking) disadvantage in having Eff Mass too high, ie. Res Freq too low. Sure, there may be issue with particular TT suspension or TT support resonances, but arguably not detrimental to good record tracking? |
Richardkrebs has advocated adding 60+g of horizontal mass by adding lead to the bearing spindle and removing the decoupling mechanism of the counterweight. With the ET2 the decoupling of the counterweight is part of the strategy to keep horizontal mass not too high. I'm not sure if there is any (groove tracking) disadvantage in having Eff Mass too high, ie. Res Freq too low. Sure, there may be issue with particular TT suspension or TT support resonances, but arguably not detrimental to good record tracking? |
05-15-13: Richardkrebs
In Bruce's paper on the oil trough he talks about the effect of Fr being apparent at 3x its frequency. Targeting say the 12 hz you mentioned would mean that it is causing phase and amplitude problems at 36 hz. This is not good. 05-16-13: Richardkrebs
Dover.
Secondary resonance? You mentioned this twice in your post 05-15-13. The frequency numbers you used were 3x Fr for this. The 3x Fr figure is the multiplier used by BT where he considers the amplitiude and phase anomolies above Fr have fallen to a level that is benign. Richardkrebs, according to your own posts 05-15-13: Richardkrebs - There is a phase and amplitude problem at 3xFr 05-16-13: Richardkrebs - There isn't a problem at 3xFR Of course I agree with your first statement. The second is wrong. 05-15-13: Richardkrebs
Note also, Bruce set up the arm with a "deliberately high Q" and low compliance cartridge. Richardkrebs your statement is misleading. Bruce added 18g of horizontal effective mass with the damping trough mechanism. You have added 62g of mass to your arm by adding lead and removing the decoupled counterweight. Assuming your example of 9g cartridge and 32g of counterweight plus your added lead of 30g then; The horizontal effective mass of the ET2 with damping trough is Std ET2 - 25+9+18=52g KREBS ET2 - 25+9+32+18+30=114g If you believe that you can increase the horizontal mass of the ET2 from 52g to 114g and get the same results as Bruce Thigpen, then that is where you are wrong. 05-15-13: Richardkrebs
See BT's own formula for calculating horizontal Fr. It does not take into account these other structural resonances.
That said these other resonances can have an effect on the shape of the resonance curve but the fundamental determinent is the horizontal mass. Ok, so you disagree with me, then in the second sentence you agree with me. I'll take the second view. If the fundamental determinant is horizontal effective mass, why do you expect the same results as Bruce Thigpen when you have more than doubled the horizontal mass with your changes to your ET2. The other key issue with running high horizontal mass, far higher than recommended by Bruce Thigpen, is the increased tracking distortion that this causes. I quote from Bruce Thigpen:
If the weight is coupled the system resonant frequency would be extremely low, a resonant frequency at 3Hz with a significant rise in response (6-12dB) results, which would affect tracking slightly because of the asymmetric position of the cantilever, we opt for splitting the horizontal resonance frequency into two points and lowering the "Q" which improves tracking.
More important than tracking, the intent was to reduce the modulation effects of low frequency energy (FM and AM) that increase distortion in the cartridge,
To reiterate, from my listening experience increasing the horizontal mass and removing the decoupling of the counterweight on the ET2 slugs the sound and the distortion can be clearly heard. |
05-17-13: Ct0517
As I type this Ottawa to Toronto area of Ontario experienced a 4.8 earthquake – a little shakey.
Sort of like my JMW 12 unipivot. :^) My local audio shop has been selling VPi’s for some years. In my experience if the arm is wobbling then it is either not set up correctly or perhaps the bearing needs checking. As a matter of interest, the Aro is inherently more stable than the VPI and most unipivots as the bearing is a radius tip sitting in a cup with a defined radius. This provides damping of around 2db, is a true mechanical ground and is self centering. With the VPi the tip is upside down – the cup sits on top of the tip, so it is less stable, and is not a true mechanical ground. Stereophile review ARO – June 1993
Unipivots have traditionally been only marginally stable, but much thought has evidently gone into the ARO's design. Lowering the counterweight to about record level has given the ARO excellent stability. This also lowers the center of gravity to below the pivot point, providing about 6dB of mechanical damping of the stylus. Another 2dB or 3dB seem to come from the bearing cup, which has a sapphire insert. The bearing is the ARO's stroke of genius. In other unipivots, a sharp pin is mounted to the turntable and the arm carries a cup which sits atop the pivot point. The ARO's arm carries the sharp tip, resting this atop a stationary cup: a true mechanical ground I can run an extremely eccentric record or a warped record and the ARO remains incredibly stable – there is no wobble or change of azimuth when disturbed. |
Dover
I do wish you would stop repeating your fundamental error ad nauseum.
BT measured a rise in response of 6-12 db at the resonant frequency. Say 3 to 8 hz. I don't call these frequencies bass.
Bruce measurements show that this rise in response is reduced by 8db with the addition of an oil trough. This in test conditions which used a deliberately high Q and a low compliance cart. The amplitude of resonance decreases the further you move away from Fr. BT suggests that resonance effects frequencies up to 3xFr.
My rigs Fr is just above 5hz, almost 4 times lower than what is normally accepted to be the lower bass, 20hz.
There is no rise in bass response in my system. |
'Audio' review of the ET-2. Excellent read with some (if you haven't already read it) surprising, even startling, results. By Edward M Long in 1987, when reviews were a serious affair. As I'm semi literate, Chris has kindly uploaded my jpegs to his site. Thankyou Chris. Go to http://s1173.photobucket.com/user/CT-993/library/?sort=2&page=1 (it works, I've tried it) and you will find 7 pages of review, including v interesting measurements. I did try to post this review here, but that cann't be done presently. Sorry guys if this duplicates an earlier ET-2 post. I haven't read every one of well over 700 posts. |
05-17-13: Richardkrebs
Dover
I do wish you would stop repeating your fundamental error ad nauseum. I am not aware of any errors on my part. Please read my last post. It outlines the errors you have made. Let’s address the fundamentals: The ET2 has a unique patented decoupled counterweight. The decoupled counterweight is damped at its natural resonant frequency of 2-5hz. This decreases the rise in frequency response at the fundamental resonance. ( page 9 of the ET2 manual ). So with your cartridge a standard arm would have a fundamental resonance at 8hz, and the decoupled counterweight reduces the amplitude or size of this resonance. Removing the decoupling as you have done will see an increase in the resonance of 6-12db – as shown in Bruce’s testing, documented on his website. Now you state you have added some 62+g of mass to your ET2 and removed the decoupling. So there are 2 points here: 1. Removing the decoupling increases the fundamental resonance by 6-12db. 2. Increasing the mass has reduced your FR to 5hz. One can see that by adding mass you have placed the fundamental resonance in the same zone as the natural resonance of the decoupled counterweight. This would be a disaster as the 2 resonances will likely sum together to create a large one. You can deduce from this that removing the decoupling not only takes out a fundamental design feature of this arm that provides a flat response in the bass, it actually compounds the problem of the FR peak and makes it doubly worse. Now let’s assume that your system has no response below 30hz, just for arguments sake, not that I’m suggesting it does. The reality is that phase shifts at fundamental resonance ( bass in my language ) will affect the rest of the frequency spectrum. In other words it affects the mid and highs. ET website
If a tonearm/cartridge system has a substantial rise in response below 20 Hz as most do, the phase response at the low end will be shifted and phase shift will occur beginning at 2 to 3 times the resonant frequency down to Fr. The time in which low frequency signals come from the tonearm will be shifted slightly with respect to mid-range frequencies within the audible range and substantially shifted up to several periods at resonance. One can clearly hear these distortions when adding mass to the ET2 and removing the decoupling spring. 05-17-13: Richardkrebs
Bruce measurements show that this rise in response is reduced by 8db with the addition of an oil trough. This in test conditions which used a deliberately high Q and a low compliance cart. The amplitude of resonance decreases the further you move away from Fr. BT suggests that resonance effects frequencies up to 3xFr. This testing is irrelevant in your case because of what you have done to your ET2. The testing was conducted with a standard ET2 with a decoupled counterweight and fluid damping added - the total horizontal effective mass was approx. 54g. You have altered your ET2 by removing the decoupling of the counterweight, which increases FR by 6-12db and increases the horizontal effective mass by 32g. You have also added 30g of lead to your tonearm. Your tonearm weighs approx. 114g compared to the 52g tested by Thigpen. Thigpens test results cannot be applied to support your argument that your arm does not have a rise in response in the bottom end because you have doubled the weight of your arm and removed the decoupling mechanism from the counterweight. What you have not addressed, other than the discussion on the impact of FR, is the tracking distortion that is generated by increasing the mass of the arm, in your case more than doubling it. I quote from Bruce Thigpen: If the weight is coupled the system resonant frequency would be extremely low, a resonant frequency at 3Hz with a significant rise in response (6-12dB) results, which would affect tracking slightly because of the asymmetric position of the cantilever, we opt for splitting the horizontal resonance frequency into two points and lowering the "Q" which improves tracking.
More important than tracking, the intent was to reduce the modulation effects of low frequency energy (FM and AM) that increase distortion in the cartridge, You have doubled the weight as seen by the cantilever. A conventional pivoted arm with an effective mass of 14g with a cartridge of 9g will have a total effective mass of 23g. The standard ET2 has a horizontal effective mass of 34g or 52g with the damping mechanism. With your addition of lead and removal of the decoupling, and added fluid damping, your altered ET2 has an effective mass of approximately 114g - 4 times the effective mass of a conventional pivoted arm. Readers should try to imagine waking around with the weight of three adults sitting on their shoulders, and pretending the weight is of no consequence. This is what the cantilever has to endure with the Krebs alterations to the ET2. |
This is the story of an audiophile called Dorothy and her ET2, a tonearm she has owned for many years.
For the first few years she used a light MM cartridge and used only 2 of the 4 lead weights supplied positioned in the middle of the I beam. “It looks visually balanced better this way to me”, Dorothy said. She did have a quick skim through the ET2 manual but ....oh!..... so many pages ....some really technical “guy” must have written that for sure she thought. Anyway.....how she set it up sounded good to her... so she left it this way for a few years.
Then one day she decided to buy an MC cartridge. She noticed it was quite a bit heavier. Instead of moving the existing weight further out on the ET2 I Beam (as the ET2 manual says to do) - she put on the other two weights she had stored in her drawer all this time; so they could meet up around the middle of the I-beam again. She was after all comfortable with this middle of the I Beam positioning. “It just looks visually better balanced this way” Dorothy said. It sounded good again. She was happy.
Then later on she was reading on the internet about some ET2 owners who just couldn’t stop fiddling with their ET2’s.
"Must be all guys for sure” Dorothy thought to herself.
But she was intrigued about how they were discussing the aspect of loading up the weight on the I-Beam. They were putting more thought into it; putting just enough weight on so that the weight was at the end of the Ibeam – no matter what cartridge. Some of these guys were even crazy enough to change cartridge screw sizes to accomplish this.
“Well” she thought to herself “maybe there was a screw loose somewhere else with some of them?”
But she was intrigued ....she could resist no longer. She tried it and did what was required to get the weight out at the end of that “pirate plank” even though it did just did not look right to her.
Lo and behold more music “sprang” forward ! She said to herself “all these years I was listening to my ET2 and I was loving it; But now... well I love my ET2 even more!”
She felt good about herself.
Does this story have a lesson ?
Yes, Dorothy felt good about herself, but it wasn’t because her favorite songs sounded even better to her.... which they did; no, it wasn’t the main reason. You see Dorothy always knew that she could listen to her favorite songs anywhere; even in the car and they would always put a smile on her face. It was about the music itself after all.
No, what made her feel real good – was that she had learned something and understood more about how her ET2 actually worked. That learning and knowledge is what made her really feel good. She then said to herself “maybe I should read the ET2 manual that guy called Bruce wrote? ”
Right after thinking that another thought came into her head. “If only my boyfriend was as easy to tune as this ET2” |
This is how I test my vinyl setup for Structure Feedback and my ET2 (2.5) Pump for Noise and Vibrations.
I am interested to know what techniques others use. I’d like to learn different ways of doing this.
TEST FOR STRUCTURE FEEDBACK
Some people think that direct sound waves affect our cartridge. Some people put plastic shields around their turntable. If you think that direct air waves really affect your cartridge “trying yelling at your cartridge and see what happens” infamous quote from Audiogon user Halcro.
Can you hear yourself through your speakers when you do this?
Henry – if you see this I hope you don’t mind me quoting you.
My test for structure feedback is to set up the TT on mute and lower the stylus onto the lead in groove. Record not spinning. Unmute the phono and turn to a level that is considered high for your room.
Start jumping up and down right beside your TT. Pretend you are dancing with your spouse. Actually invite her/him in and jump together with no music. Just be prepared she may ask you to boogie to real music later as she gets warmed up. If your setup survives this test you should be good to go.
TESTING THE PUMP for NOISE and VIBRATIONS.
This test should actually be good for any air bearing linear tracker that uses a captured bearing like the ET2 and ET 2.5.
No jumping this time just listening.
Same as the above in regards to muting your phono with a still record and unmuting but with a BIG difference.
1st – DO NOT turn on your pump and lower your stylus onto the lead in groove. Unmute and turn the volume up. Listen to how quiet it is. When finished mute system and raise the ET2. I say raise the ET2 because I don’t know how good your pump and setup is. More on this later.
Now have a friend turn on your pump and repeat the above procedure and lower the stylus again. Is there any noise in the background now that has been transmitted down the airline into your system that was not there before?
Is it the same level of quietness, or is there now a little more background noise with the pump on. If you are using a regular aquarium type pump and no surge tank you will hear differences. For those with good pumps and a properly setup ET2, ET 2.5 there is no need to raise the stylus or unmute after listening with no pump. Have the friend turn your pump on and off while you have your ear on one of the speakers.
If you are introducing noise with your pump down the airline you are not hearing what the ET2 can do. The sound is being glazed over by air noise vibrations from the pump.
I came across this years ago – maybe 8? by accident. I had an actual small ground hum type noise and could not for the life of me figure out how to solve it. I tried for two days. I could just hear the pump at the time in the other room running faintly. It was a Medo AC110.
Finally after a couple of days of trying to fix the problem, I unplugged the pump and I tried the above test. No more noise. Damn! I substituted my backup Medo pump at the time and all was quiet again. The bad pump was still delivering PSI but had a piston problem sending noise and vibrations down. I also found back then that a long run of air tube coiled up also helps to minimize the vibrations.
I didn’t discover the above problem until I had swapped in cartridge, wires, amps, preamps, speakers first ! That set me on my pump journey the next few years and I ended up with the pump I use now.
So how do you guys test for structure feedback and airline noise/vibrations with an air bearing?
Cheers. |
Holy multi-post Batman ! You guys are making the nice people on the audiogon help desk work overtime. |
Re the 'Audio' review. When you call up the pages on Chris's site, I've been alerted to what can be confusing.
Call up one of the pages, then hit the + button at the bottom right of the page TWICE, and readable it will be. |
'Audio' review: further to my comment about enlarging individual pages on Chris's site.
I've found it better to use View(Toolbar)> Zoom > Zoom In, and Ctrl + or Ctrl- |
Chris.
Brilliant test idea you used for checking the smoothness of the pump air flow.
I smoked my current pump running it at a higher pressure. Will definately be trying your idea out when it's replacement arrives. |
Dover.
- The error you repeat, is saying that my arm exhibits a rise in bass response of 6-12db. I'm pretty sure that most of the readers here would not call 5Hz bass. I can't hear that frequency and my system certainly cannot reproduce it. The arm has always had some method of damping. This reduces the amplitude of resonance at Fr. If you ask BT, he will say that the amplitude falls away to be benign at 3x Fr. Just over 15hz in my case. A frequency which some may call Bass, but one which I doubt my system can reach down to either.
-The change in shape of the resonance curve I refer to is clearly shown in the graph BT published with the oil trough manual. It is not a smooth standard deviation type curve. There are bumps and hollows on the slopes. This is caused by other structures resonating at frequencies near the fundamental.
-BT does not increase the horiz effective mass by 18gm when he adds his oil trough and nor do I with mine. He adds 18gm to the total weight of the arm. The effective mass is increased by the weight of the paddle. Well under 1 gram on mine. This makes my arm around 96 gm when carrying the Shelter, not 114 as you state.
You repeatedly try to paint the weight of my arm as being an outlier in linear arms and that my arm is singular in being so heavy. It is not, as we have seen in this thread. Some fellow posters own these heavier arms. Criticize my arm and you simultaenously criticize theirs.
-BT uses a very elegant method to reduce the FM and AM interfearance in the audio band caused by a high ampltude Fr. He decouples the counterweight which reduces the amplitude at Fr. Other designers use another method, they damp the arms horizontal movement which also significantly reduces the amplitude at Fr. This by using an oil trough, the lead out wires, the air line or a combination of these. It is simply another method of dealing with the problem. Both are valid, both have their advocates and detractors. This is the nature of our hobby.
-Chris has clearly enunciated the improvemmets in the bass articulation when he applied my goose neck design. Could it be that the problems you hear in the bass region when you locked the counterweight were simply due to the compliance of the gooseneck being laid bare, combined with maybe insufficient damping? |
Hi,
I was wondering when someone will add something useful to this thread that is more in line with modifications with results as opposed to a subjective debate?
Regards
Alx |
Dover has repetitiously stated richardkrebs ADVOCATES adding lead mass to ETs
This is incorrect.
Mr Krebs openly told the forum how he sets up HIS arm for his LOW compliance cartridge, and the reasoning behind it.
He (RK) suggested others could try it to educate/inform themslves, adding to the collective knowledge of posters, because IT IS EASILY REVERSED.
RK has not tried to CONVINCE others to follow his setup. |
TEST FOR STRUCTURE FEEDBACK ……. Start jumping up and down right beside your TT……. Hi Ct, The most extremely test of this sort that I have seen was that, while following your initial settings, instead of jumping around the TT, you kick on its stand! :-) It was performed on a Rockport Sirius III at the agent, and yes, it was pretty much silent from the speakers! That stand was actually an OEM pneumatic table by TMC, and I am using a similar one under my Capella II. Unless you kick it hard enough that the whole stand / TT assembly (roughly 400-500 lbs.) moves over the floor, you can hardly hear any thumping from the speaker indeed! Hi Dover, You have mentioned that too high a horizontal effective mass would result in a raised bass response by 6-12db. So, in what frequency range are we talking about (the Fr at below 12Hz?)? I just wonder if the high horizontal effective mass is the only consideration here, and whether other factors, such as the design of the air-bearing, would make a considerable difference in the outcome. In short, does that only apply to the ET design, or also to the Rockport and Kuzma etc? I asked because my Rockport 6000, already has a high horizontal effective mass of 80g (with the lightest counterweight, and excluding the cartridge), but yet MF found it lacking in the bass! The upgraded 7000 and Sirius III arms added even more mass to “cure” this problem! Not meant to be argumentative, just want to learn more! Thanks! |
The most extremely test of this sort that I have seen was that, while following your initial settings, instead of jumping around the TT, you kick on its stand! This is not a test for Structure-Borne Feedback. It merely places a Dynamic (hitting) sound source into a structure. I have never seen a scientic correlation between 'Impact' sound sources and Air or Structure Borne sound sources? It is like the ubiquitous "Boink Test" that some audio reviewers used to do........tapping on the plinths of their turntables to see how 'immune' the turntable is feedback? Chris' test of jumping on the floor around the turntable is a little more viable as it transfers the impact-induced source into Structure-Borne feedback within the floor........ however the form of that feedback is quite different to that which our systems are normally subjected. Any suspended floor system (timber or steel-framed or reinforced concrete) will be subjected to Structure-Borne Feedback because of the stresses and deflections caused by the structural spans.....as well as the materials used in the floor construction. These stresses result in subsonic low-frequency Structure-Borne feedback which passes easily into equipment racks, support stands and into the turntable plinths sitting upon these racks/stands. That's why a wall-mounted turntable shelf is the best way to minimise this. |
These stresses result in subsonic low-frequency Structure-Borne feedback which passes easily into equipment racks, support stands and into the turntable plinths sitting upon these racks/stands. Hi Halcro, Thanks for the information! So, any idea what is the frequency range of these structure-borne feedback? Thanks! |
Hi Thekong,
In a suspended reinforced concrete slab......there can be frequencies from 5-10Hz and higher.
In a suspended timber-framed floor they could get up to 10-16 Hz but would not normally get as low as the concrete.
Of course....the 'creaking' we can often hear in suspended floor structures as they 'move' whilst we are in bed at nights......are of a far higher frequency.
It's really the very low frequencies doing the damage as Structure-Borne Feedback as they are indicative of 'movement' within the floor structure. |
Dover wrote:
A conventional pivoted arm with an effective mass of 14g with a cartridge of 9g will have a total effective mass of 23g.
The standard ET2 has a horizontal effective mass of 34g or 52g with the damping mechanism.
With your addition of lead and removal of the decoupling, and added fluid damping, your altered ET2 has an effective mass of approximately 114g - 4 times the effective mass of a conventional pivoted arm.
Readers should try to imagine waking around with the weight of three adults sitting on their shoulders, and pretending the weight is of no consequence.
This is what the cantilever has to endure with the Krebs alterations to the ET2. Sorry Dover, with respect, I hear what you are saying but I don't think that this is what a cartr stylus really "sees". Static Mass is one thing but Effective Mass is something slightly different... the latter is the "inertia" or the reluctance of the tonearm (pivoted or sliding) to move, as seen by the stylus. ie. At frequencies above Res Freq, the tonearm is effectively an immobile/stationary object or load, as seen by the stylus...which is a good thing, because you want a stable platform to trace the groove, right? Referring to your analogy, for example, the tonearm should not be "walking around", it should be standing absolutely still... & having 3 adults sitting on your shoulder ;) ...is going to help hold the cartridge steady. (The only potential problem with ultra low Res Freqs is the danger of coinciding with TT suspension/support/floor modes.) |
Hi Halcro,
Thanks for the information again! As I can’t use wall mount in my room, I have never experience its effectiveness!
My room has suspended concrete floor. According to the specification, the pneumatic table could isolate up to 85-90% of the vibration at 5Hz, and 97% at 10 Hz, it has worked out very well for me! I certainly could hear the improvement in background blackness with its use!
Thanks! |
Thekong, hi there, Hi Dover,
You have mentioned that too high a horizontal effective mass would result in a raised bass response by 6-12db. So, in what frequency range are we talking about (the Fr at below 12Hz?)?
I just wonder if the high horizontal effective mass is the only consideration here, and whether other factors, such as the design of the air-bearing, would make a considerable difference in the outcome. In short, does that only apply to the ET design, or also to the Rockport and Kuzma etc?
I asked because my Rockport 6000, already has a high horizontal effective mass of 80g (with the lightest counterweight, and excluding the cartridge), but yet MF found it lacking in the bass! The upgraded 7000 and Sirius III arms added even more mass to “cure” this problem! Just to clarify there are 2 separate issues with the Krebs set up - 1. Removing the decoupling of the counterweight This is where Bruce has tested extensively and posted his results on his website. The removal of the decoupling increases the amplitude of the fundamental resonance by 6-12db. Now if you read the Audio review posted by John47, bottom of page 5, you will see that with the Talisman they measured 2 resonances at 4hz & 9hz. This illustrates how the decoupling system works, by splitting the resonance it actually reduces the peak of the fundamental resonance and results in a flat response in the bottom end. Now Richard is saying that doesn't matter because the resonance is outside the audio band. That statement is not correct because a large resonance at the fundamental frequency will generate signal out of phase that imposes itself on the audible range, negatively impacting timing accuracy, imaging etc. A bass note for example will have harmonics that carry right through to the high frequencies. The preservation of phase at all frequencies is critical to presenting an accurate soundstage, harmonics etc. This is precisely why Frogman, Ct0517, Slaw and myself hear better timing with the counterweight decoupling tuned properly. Frogman has described hearing more bass notes. The other problem generated by the resonance is tracking and tracking distortion - if you have instability at very low frequencies there will be a negative impact on tracking, whether you hear it or not. 2. The other issue is adding significant mass. Now Richard is partially correct when he says that damping with oil, wire, air hoses etc will also help to control resonant peaks at FR. But the real issue is that there are 2 downsides to this approach of high mass - Firstly by carrying this additional mass the cantilever is now pushing a much higher weight. This means that on eccentric records the cantilever deflection will be much higher, and there is increased distortion from the coils moving into a non linear phase. This is one of the primary design considerations Bruce has endeavoured to address by keeping the mass as low as possible. It is wrong to think of this particular issue as a bass problem. The biggest negative is the phase distortion and tracking distortion which impacts the whole range. Secondly in my experience damping tends to slug the sound, as you heard at your friends place. There is a logical explanation for this - by loading up the cantilever it becomes less responsive, less nimble. By loading up the horizontal mass, you are increasing the inertia of the arm, it resists movement, the cartridge cant follow the groove, the cantilever flexes more, more distortion. In a nutshell you might get a more solid bottom end with more mass, but in my experience it comes at a cost - loss of speed and the preservation of accurate phase and time throughout the whole frequency range is compromised. Sometimes in audio less is more. Bottom end extension is not much good if it is muddy and out of phase. High frequency extension can tell you more about how hard a drum is hit than the actual fundamental. From this you can see that having the fundamental in phase with the upper harmonics is critical. In my early days of audio I reckon my Proac Tablettes, which rolled of from 70hz could tell you more about whats happening at 30hz simply because they were very quick compared to many full range speakers - and before the naysayers here get in - I had Proac Studio 3 EBS monitors at the same time. Bearings of course play a role, not just the pressure but the design and airflow etc. An air bearing can be stiffer than one at much higher pressure due to bearing surface area, etc. In the TAS review of the Kuzma/Walker clearly to the arms have different strengths and weaknesses. The Kuzma supposedly is very strong in the bottom end, the Walker appears to be more nimble presents timing better. Pretty hard to work out why these differences occur, because we dont have enough information. In my view given that you have both the Rockport and ET you should enjoy the benefits of both approaches - why anyone would try and convert the ET2 into something that it was never intended to be - a high mass arm - is beyond comprehension. I know at least one reviewer who considers the Kuzma is not as good as the ET2. With regard to Fremers comments on bass response, I dont take much notice. The chances of him getting the ET2 set up correctly are pretty remote, simply because he is time constricted. About the only reviewer that I would trust to ensure that the ET2 is set up correctly would be Martin Colloms due to his technical knowledge and insght, and in the early days of audio reviewers spent many months with gear, not days/weeks. |
Oh dear, Andy Payor doesn't know what he's doing either.
He's just added distortion by incresing the weight of his arm.
The world according to Dover. |
Thekong. The answer to your question regarding frequencies impacted by horizontal Fr is shown in the attached graph. From memory your Horiziontal Fr was around 5hz with the A-90. So substitute 5 for 1 on the x axis and scale up from there. At 15 Hz (3) the rise in response is almost zero. This is what BT was talking about when he mentions 3xFr. It could be that the perceived improvement in bass performance of subsequent Rockport arms has more to do with the wand, gooseneck and counterweight arm stiffness, rather than total weight. Different bearings make virtually no difference to this graph since it is the mass that the cartridge has to push sideways that counts. The flavour of different arm bearings, however, is another matter entirely. The various curves are showing different values of Q (damping) Note the level of damping makes virtually no difference at frequencies of 3x Fr and above. This does not mean that we can ignore the amplitude at resonance, since it is shaking the arm and this has an impact in the audio spectrum. FM and AM modulation. Bruce reduces this amplitude by decoupling the counterweight. It is an elegant, brilliant solution. Others damp the resonance as I have done. The oil trough, way less elegant, is also a very effective way of doing this. Both methods reduce FM and AM artefacts. http://s1173.photobucket.com/user/CT-993/media/ResonanceGraph_zpsdd78e0f4.png.html?sort=2&o=7What this means, as Spock15 says, at 3xFr and above the arm appears to be solid to the cartridge. We want the cantilever to move not the arm. Now look at frequencies below Fr. At say 0.25 Fr we get transmissibility of 1. What this means is that, with the compliance of the cartridge used, the whole arm moves sideways. The cantilever does not deflect. This is important for eccentric record issues. In other words stay above a horizontal Fr of 3hz. (4x 0.75hz) ) 0.75 Hz being the frequency seen with an eccentric record ay 45rpm. Putting this another way. BT uses at 30cu cartridge in his manual to calculate horizontal Fr. The arm weight he uses is 30gm plus 7gm for the cartridge. We have to assume that he is ok with this combination and that he is not worried about cantilever deflection on eccentric records. When using a 10cu cartridge we can increase the horizontal mass of the arm to 111 gm and have the same peace of mind about cantilever deflection with eccentric records. The cartridge is 3x stiffer so we can push around 3x the weight. It is that simple. Forces on the record groove wall are another thing. We use a stiff cartridge this is the price we pay. Don't play heavily eccentric records. Ha_ha_he_man. What I hear with a heavy linear arm is this... The music takes on mass. Individual notes are solid. This is not to be confused with "heavy" in the derogatory sense. A live struck triangle has this mass. One can imagine walking up to the sound of it and holding it. It would have mass and a textured surface. This is very hard to reproduce and I do not hear this effect with light linear arms when carrying low compliance cartridges. |
Thank you all for the detailed explanation!
|
05-19-13: Ha_ha_he_man
Hi,
I was wondering when someone will add something useful to this thread that is more in line with modifications with results as opposed to a subjective debate?
Regards
Alx
Ha_ha_he_man Alx – Much is covered at the beginning of the thread. Based on my 10 years now with the ET2 and ET2.5. The recently discussed aluminum gooseneck is very nice but it is unique and costs a lot to make (labor wise). A few hundred dollars. I received only a few emails of interest so far. I am willing to pursue reproductions if more interest is shown. The biggest mods in my 10 years with the ET2 and ET2.5 has been the quality pump, wiring loom and the leaf spring mod. For those reading who do not own this tonearm. The ET2 is like a race car. It can be tuned for our rooms/gear which represent the different tracks. For a plug and play audiophile this can represent disaster. A bad nightmare. If you are plug and play and your dealer sets up your cartridge for you or a friend does it – stay away. It must be obvious by now to anyone reading here that if your are using an ET2 or Et2.5; you need to be thinking about what you are doing. If not mistakes will happen; the poor cartridge is always the victim; even though we feel bad ourselves about it. So many adjustments can be made. RichardKrebs
This is very hard to reproduce and I do not hear this effect with light linear arms when carrying low compliance cartridges. Richard your arm started life as an ET 2.0. We have already discussed here how for a really low compliance cartridges the ET 2.5 works best with the double or triple leaf spring. 05-16-13: Dover
Spock15
I currently own an ET2, Naim Aro & Hadcock unipivot and have just sold off my Bluenote Borromeo ( Titanium tubed unipivot ). Congratulations Dover on reacquiring an ET2. Frogman introduced the leaf spring mod to us early on in this thread. One is able tune this tonearm with different leaf springs (single, double, triple) corresponding to the stiffness of the cantilever being used, and the reactions of the resonances in each of our rooms; and to stay within BT’s decoupled design. Based on my direct experience I encourage both Richard and Dover to order some loose leaf springs and a Two I Beams from Bruce to make up a double and triple I-Beam setup. I look forward to impressions of a low compliance cartridge with the double and triple leaf spring. I have already mentioned here I base my vinyl tuning on what I hear with master tape dubs at 15 IPS. I start the LP then 10 seconds later the tape. I toggle between the two. I don’t have any issues with my XV1 when I use the double and triple spring in my room. I believe you can have your cake and eat it too with the double and triple leaf springs and to stay within Bruce’ genius design. Chris,
The thicker spring results in a higher resonance frequency. Thanks
brucet Chris,
You always want the horizontal natural frequency of the counterweight to be less than the cartridge/arm resonance, this is the case 98% of the time.
The natural frequency of the I-beam/leaf spring depends on the thickness of the spring, the amount of weight, and where the weight is on the beam. The natural frequency goes down as the weight moves further out on the beam which is where we want it to be.
brucet Cheers |
Welcome to the thread Ha_ha_he_man.
Not a bad moniker :^) |
CT0517
Based on my direct experience I encourage both Richard and Dover to order some loose leaf springs and a Two I Beams from Bruce to make up a double and triple I-Beam setup.
I look forward to impressions of a low compliance cartridge with the double and triple leaf spring. I modify my recommendation. It applies to Dover only. RK you have come down too far a path with your Krebs arm. You are truly enjoying it. I would never ask you to do something unless you are curious yourself. If you did pursue it you would need to implement a wiring scheme similar to Frogmans - to be the least intrusive on the ET2 based on your plinth design. Dover is about to reacquaint himself with an ET2 and a sound that is very .. well I really like the word that Spock15 used alot ....persuasive. I am sure his system must have changed in the years that have passed. Cheers |
Richard/John47 thanks for making me curious about the damping trough again. Arrived the in mail one kit from Bruce. This kit reminds me of my flu shot ?I don’t like needles and syringes. But it went on real smoothI think Frogman still has his paddle lifted not touching ? I think SLAW is however still liquified ? Added 1 CC per Bruce’ instructions – paddle just touching. Its been over 8 years for me in using one. Will report back later ... so far pretty good ! Cheers |
Thekong – The answer to your question regarding frequencies impacted by horizontal Fr from Richardkrebs are mostly wrong. It is important that they are addressed. Impact of Fundamental Resonance: 05-20-13: Richardkrebs
Thekong.
The answer to your question regarding frequencies impacted by horizontal Fr is shown in the attached graph. From memory your Horiziontal Fr was around 5hz with the A-90. So substitute 5 for 1 on the x axis and scale up from there. At 15 Hz (3) the rise in response is almost zero. This is what BT was talking about when he mentions 3xFr. This statement is not correct. I quote from Richardkrebs earlier post 05-15-13: Richardkrebs
In Bruce's paper on the oil trough he talks about the effect of Fr being apparent at 3x its frequency. Targeting say the 12 hz you mentioned would mean that it is causing phase and amplitude problems at 36 hz. This is not good. . As you can see Richardkrebs appears to be confused. On the 15/3 he cites Bruce Thigpen as saying that there are phase and amplitude problems at 3 times Fundamental Resonance, then on 20/5 he cites Bruce Thigpen as saying the rise in response is almost zero. Neither of these statements are correct. What Bruce Thigpen actually says on his website is that on an undamped standard ET with decoupled counterweight there is a resonant peak at 3 times the fundamental resonant frequency, and that this is reduced with fluid damping on a standard ET with decoupled counterweight. The other mistake that Richardkrebs continues to make is to use as a reference a graph for a single harmonic oscillator that plucked from Wikipedia. Wikipedia - http://en.wikipedia.org/wiki/Harmonic_oscillatorRichardkrebs - http://s1173.photobucket.com/user/CT-993/media/ResonanceGraph_zpsdd78e0f4.png.html?sort=2&o=7This graph does not represent the forces on the cantilever because the cantilever and cartridge is not a single harmonic oscillator. A cartridge tracking a record groove has a fulcrum point at both ends – the stylus in the groove, about which the cantilever pivots, and the cartridge end of the cantilever which has a suspension. Forces are exerted on BOTH ends of the cantilever. The graph represents a pendulum with only one fulcrum point at one end only. The mathematics that Richardkrebs uses does not apply. 05-20-13: Richardkrebs
Now look at frequencies below Fr. At say 0.25 Fr we get transmissibility of 1. What this means is that, with the compliance of the cartridge used, the whole arm moves sideways. The cantilever does not deflect. This is important for eccentric record issues. . This assertion is wrong on several fronts. The cantilever deflects. Firstly – the record grooves are cut at 45 degrees. The cantilever deflects. For a moving coil cartridge the cantilever deflection moves the moving coils within a magnetic field. That is how sound is reproduced from a record player. This video shows how RCA Living Stereo stereo playback is achieved. http://www.youtube.com/watch?v=Jq2sjGFvNnM If there is no deflection of the cantilever then Richardkrebs system cannot be producing any sound that resembles music. Secondly, the statement defies physics. I quote Bruce Thigpen directly: Bruce Thigpen
“the cartridge will "see" .55Hz mounted in any tonearm, more so in one with higher horizontal inertia. I don't think Kuzma means the stylus does not deflect at all at .55Hz, that would defy physics.” Furthermore, Richardkrebs assumption with regard to Bruce Thigpens views on eccentric records are not supported by what Bruce Thigpen actually says in the ET2 manual. 05-20-13: Richardkrebs
BT uses at 30cu cartridge in his manual to calculate horizontal Fr. The arm weight he uses is 30gm plus 7gm for the cartridge. We have to assume that he is ok with this combination and that he is not worried about cantilever deflection on eccentric records. This assumption again is just plain wrong. I quote from Bruce Thigpen’s ET website: ET2 Manual page 47 :
“if you like to play severely eccentric records, ones with run out greater than 1/8th of an inch, then we suggest you use a low mass pivoted arm.” In summary, Bruce Thigpen is very much of the view that the horizontal effective mass should be kept as low as possible, and the decoupling employed to minimsie fundamental resonant peaks at FR and 3xFR. He has also expressed his view that increasing mass increases distortion, and I quote Bruce Thigpen - Bruce Thigpen:
If the weight is coupled the system resonant frequency would be extremely low, a resonant frequency at 3Hz with a significant rise in response (6-12dB) results, which would affect tracking slightly because of the asymmetric position of the cantilever, we opt for splitting the horizontal resonance frequency into two points and lowering the "Q" which improves tracking.
More important than tracking, the intent was to reduce the modulation effects of low frequency energy (FM and AM) that increase distortion in the cartridge, Thekong , I trust this clarifies the queries you raised. |
Utter Nonsense Dover, and I quote you
"What Bruce Thigpen actually says on his website .......... there is a resonant peak at 3 times the fundamental resonant frequency, and that this is reduced with fluid damping on a standard ET with decoupled counterweight."
It would have been useful if you had done engineering.
The peak is at the resonant frequency, not 3x Fr. |
John47,
my name is Dover, not Utter Nonsense Dover. I have in fact studied engineering and English as well at university.
Please see below the difference between “a” and “the”
"a" [uh; when stressed ey]
indefinite article
3.another; one typically resembling: a Cicero in eloquence; a Jonah.
"the" [stressed th ee; unstressed before a consonant th uh; unstressed before a vowel th ee]
definite article
1. (used, especially before a noun, with a specifying or particularizing effect, as opposed to the indefinite or generalizing force of the indefinite article a or an ): the book you gave me; Come into the house.
2. (used to mark a proper noun, natural phenomenon, ship, building, time, point of the compass, branch of endeavor, or field of study as something well-known or unique): the sun; the Alps; the Queen Elizabeth; the past; the West.
So, in the context of a “resonant peak” “a” does not represent “the”. |
Do you know what PSI and Pump type your ET2 or ET2.5 was designed for ?
3.6 PSI - Original Takatsuki and ET-2 or 2.5
5.0- 7 PSI - WISA 300 air pump and ET-2 or 2.5 with high pressure manifolds
>10 PSI - users with shop compressors and ET-2 or 2.5 high pressure manifolds
Note, if the pressure readings are higher than those listed above, the manifold could be clogged, if the pressure readings are lower, this suggests that the pump may not be performing correctly.
(Taken from Bruce's website) |
What other thread allows us to learn about fine wine from downunder and good English ?
Well I did enjoy that youtube video Dover. Not surprising that not much has changed with the actual record since 1958 when the film was made. I could say they don’t make records as good anymore....anyone disagree?
In 1958 - I was just a thought in my parents eyes till four years later. Does anyone listen to music in a shirt and tie anymore?
At the 4:40 mark is an excellent example imo of a speaker setup. Nearfield and eliminating room problems by taking the room out of the picture. I love those speakers spikes. We can learn lots from these films.
The fellow talking reminds me of my Grade 8 science teacher. The guy in the film does show a bit of a smile at the end however. My science teacher in middle school was a German fellow that never smiled. |
